Berlin,Technische Universität
HYBRID LAMINAR FLOW TECHNOLOGY (HYLTEC) Partner: EADS Airbus (D) (Coordinator), Apparatebau Gauting Task1 Operational flight tests, lab tests, manufacturing issues Task2 Laminar flow retrofit studies high drag HLFC via suction causes laminar flow therefore lower drag HYLTEC topics: Consequences
Spiral Laminar Flow: A revolution in understanding?
Greenaway, Alan
Blood Flow Spiral laminar flow #12;Spiral flow in the Aorta (MRI) Computational Fluid Dynamics 0 10 20Spiral Laminar Flow: A revolution in understanding? Reintroduction of natural blood flow Laminar Flow through Runoff (3months) Proximal Anastomosis SLF TM Graft Distal Anastomosis Post-op Angios
Fluvial and submarine morphodynamics of laminar and near-laminar flows: a synthesis
Lajeunesse, Eric
Fluvial and submarine morphodynamics of laminar and near-laminar flows: a synthesis ERIC LAJEUNESSE of purely laminar or nearly laminar flow with an erodible bed. This paper provides a survey and synthesis of a wide range of laminar or near-laminar flow analogues of morphologies observed in the field. Laminar
FREE CONVECTIVE LAMINAR FLOW WITHIN THE TROMBE WALL CHANNEL
Akbari, H.
2011-01-01
Foreign FREE CONVECTIVE LAMINAR FLOW WITHIN THE TROMBE WALLEnergy. -i- FREE CONVECTIVE LAMINAR FLOW WITHIN THE TROMBEABSTRACT Free convective laminar heat transfer between the
Some Observations Regarding Steady Laminar Flows Past Bluff Bodies
Fornberg, Bengt
Some Observations Regarding Steady Laminar Flows Past Bluff Bodies Bengt Fornberg Department, 2013. February 4, 2014 Abstract Steady laminar flows past simple objects, such as a cylinder
Laminar Flow Control Flight Experiment Design
Tucker, Aaron 1975-
2012-11-29
Demonstration of spanwise-periodic discrete roughness element laminar flow control (DRE LFC) technology at operationally relevant flight regimes requires extremely stable flow conditions in flight. A balance must be struck ...
FORMATION OF ROLL WAVES IN LAMINAR SHEET FLOW
Julien, Pierre Y.
FORMATION OF ROLL WAVES IN LAMINAR SHEET FLOW by Pierre Y. Julien and David M. Hartley January 1985 . . . . . . . . . . . . . . . . . . . . . . . . . 1 I1. THEORY ON THE STABILITY OF LAMINAR SHEET FLOW . . . . . . . . . 3 2.1 Steady uniform laminar of the Coefficients fj and y for Laminar Sheet Flow . . . . . . . . . . . . . . 26 APPENDIX I1 .Experimental Data
The Time-Dependent NavierStokes Equations Laminar Flows
John, Volker
Chapter 6 The Time-Dependent NavierStokes Equations Laminar Flows Remark 6.1. Motivation to distinguish between laminar and turbulent flows. It does not exist an exact definition of these terms. From the point of view of simulations, a flow is considered to be laminar, if on reasonable grids all flow
CFD analysis of laminar oscillating flows
Booten, C. W. Charles W.); Konecni, S.; Smith, B. L.; Martin, R. A.
2001-01-01
This paper describes a numerical simulations of oscillating flow in a constricted duct and compares the results with experimental and theoretical data. The numerical simulations were performed using the computational fluid dynamics (CFD) code CFX4.2. The numerical model simulates an experimental oscillating flow facility that was designed to test the properties and characteristics of oscillating flow in tapered ducts, also known as jet pumps. Jet pumps are useful devices in thermoacoustic machinery because they produce a secondary pressure that can counteract an unwanted effect called streaming, and significantly enhance engine efficiency. The simulations revealed that CFX could accurately model velocity, shear stress and pressure variations in laminar oscillating flow. The numerical results were compared to experimental data and theoretical predictions with varying success. The least accurate numerical results were obtained when laminar flow approached transition to turbulent flow.
Numerical Simulation of Laminar Reacting Flows with Complex Chemistry
Bell, John B.
Numerical Simulation of Laminar Reacting Flows with Complex Chemistry M S Day and J B Bell Lawrence Simulation of Laminar Reacting Flows 2 1. Introduction Detailed modelling of time-dependent reacting ows
Aerodynamic Design for Swept-wing Laminar Flow
Belisle, Michael Joseph
2013-11-08
(SARGE), a natural laminar flow and passive laminar flow control wing glove flight experiment funded by the NASA Environmentally Responsible Aviation initiative. The experiment seeks to raise the technology readiness level of the spanwise...
Laminar Entrained Flow Reactor (Fact Sheet)
Not Available
2014-02-01
The Laminar Entrained Flow Reactor (LEFR) is a modular, lab scale, single-user reactor for the study of catalytic fast pyrolysis (CFP). This system can be employed to study a variety of reactor conditions for both in situ and ex situ CFP.
Transverse Diffusion of Laminar Flow Profiles To Produce Capillary Nanoreactors
Krylov, Sergey
Transverse Diffusion of Laminar Flow Profiles To Produce Capillary Nanoreactors Victor Okhonin, Xin We introduce transverse diffusion of laminar flow profiles (TDLFP), the first generic method the capillary by pressure as a series of consecutive plugs. Due to the laminar nature of flow inside
AIAA 2004-2311 Toward Practical Laminar Flow Control--
AIAA 2004-2311 Toward Practical Laminar Flow Control-- Remaining Challenges William S. Saric rights reserved. 1 American Institute of Aeronautics and Astronautics #12;Toward Practical Laminar Flow Arizona State University Tempe AZ 85287-6106 ABSTRACT Different laminar flow control strategies
Optimized Natural-Laminar-Flow Airfoils and D. W. Zingg
Zingg, David W.
Optimized Natural-Laminar-Flow Airfoils J. Driver and D. W. Zingg University of Toronto Institute-Krylov aerodynamic shape optimization algorithm has been modified to incorporate the prediction of laminar natural-laminar-flow airfoils. In particular, the optimization algorithm is able to design an airfoil
Numerical Simulation of Laminar Reacting Flows with Complex Chemistry
Bell, John B.
Numerical Simulation of Laminar Reacting Flows with Complex Chemistry M S Day and J B Bell Lawrence: 47.40.Fw, 82.40.Py Submitted to: Combust. Theory Modelling #12;Numerical Simulation of Laminar
Laminar: Practical Fine-Grained Decentralized Information Flow Control
Witchel, Emmett
Laminar: Practical Fine-Grained Decentralized Information Flow Control Indrajit Roy Donald E-grained program data structures. This paper describes Laminar, the first system to implement de- centralized the labeled data in lexically scoped secu- rity regions. Laminar enforces the security policies specified
Demonstration of a plasma mirror based on a laminar flow water film
Panasenko, Dmitriy
2012-01-01
Benjamin, “Wave Formation in Laminar Flow down an Inclineda plasma mirror based on a laminar flow water film. DmitriyA plasma mirror based on a laminar water film with low flow
Young, Angela Chien-hsin
2008-01-01
M. Mitsumata, et al. (2000). "Laminar shear stress inhibitsdisturbed flow and steady laminar flow." Physiol Genomics 9(of endothelial growth arrest by laminar shear stress." Proc
Inductively coupled plasma torch with laminar flow cooling
Rayson, Gary D. (Las Cruces, NM); Shen, Yang (Las Cruces, NM)
1991-04-30
An improved inductively coupled gas plasma torch. The torch includes inner and outer quartz sleeves and tubular insert snugly fitted between the sleeves. The insert includes outwardly opening longitudinal channels. Gas flowing through the channels of the insert emerges in a laminar flow along the inside surface of the outer sleeve, in the zone of plasma heating. The laminar flow cools the outer sleeve and enables the torch to operate at lower electrical power and gas consumption levels additionally, the laminar flow reduces noise levels in spectroscopic measurements of the gaseous plasma.
Laminar-Turbulent Transition: Calculation of Minimum Critical Reynolds Number in Channel Flow
Laminar-Turbulent Transition: Calculation of Minimum Critical Reynolds Number in Channel Flow) for laminar-turbulent transition in pipe and channel flows. For pipe flow, the minimum critical Reynolds laminar to turbulent flow Rc2 Rc from turbulent to laminar flow Rc(min) minimum Rc Re Reynolds number = UH
Kenis, Paul J. A.
Laminar Flow-Based Electrochemical Microreactor for Efficient Regeneration of Nicotinamide the more widespread use of biocatalysis.2 Here, we utilize multistream laminar flow in a microreactor the occurrence of laminar flow in microscale channels: Multistream laminar flow enables focusing of a reagent
Elongational-flow-induced scission of DNA nanotubes in laminar flow Rizal F. Hariadi*
Winfree, Erik
-induced scission are pro- foundly affected by the fluid flow and the polymer bond strengths. In this paper, laminarElongational-flow-induced scission of DNA nanotubes in laminar flow Rizal F. Hariadi* Department libraries in shotgun ge- nome sequencing 24 . The fluid-flow-induced mechanical shearing of prion fibrils
Bubble transport in three-dimensional laminar gravity-driven flow mathematical formulation
Pilon, Laurent
Bubble transport in three-dimensional laminar gravity-driven flow mathematical formulation, growth and shrinkage in three-dimensional flows. The flow is assumed to be laminar for the sake
Distinct large-scale turbulent-laminar states in transitional pipe flow
Barkley, Dwight
) When fluid flows through a channel, pipe, or duct, there are two basic forms of motion: smooth laminarDistinct large-scale turbulent-laminar states in transitional pipe flow David Moxey1 and Dwight alternat- ing turbulent-laminar flow states on long length scales in subcri- tical shear flows (12
Active Control of Instabilities in Laminar BoundaryLayer Flow--Part I: An Overview
Erlebacher, Gordon
Active Control of Instabilities in Laminar BoundaryLayer Flow-- Part I: An Overview Ronald D laminar flow in a region of the flow in which the natural instabilities, if left unattended, lead have been restricted to maintaining laminar flow through use of a technique termed ``wave cancellation
Interpolation between DarcyWeisbach and Darcy for laminar and turbulent flows
Walter, M.Todd
Interpolation between DarcyWeisbach and Darcy for laminar and turbulent flows W.L. Hogarth a, *, J the square of the velocity is proportional to the hydraulic gradient and if the flow is laminar, whichWeisbach; Porous media; Open channels; Turbulent flow; Laminar flow 1. Introduction Grassed waterways
Laminar flow cells for single-molecule studies of DNA-protein interactions
Cai, Long
Laminar flow cells for single-molecule studies of DNA-protein interactions Laurence R Brewer1 in which the interactions of proteins with DNA have been studied within the confines of laminar flow cells
Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam
Maschke, A.W.
1984-04-16
A charged particle accelerating assembly provided with a predetermined ratio of parametric structural characteristics and with related operating voltages applied to each of its linearly spaced focusing and accelerating quadrupoles, thereby to maintain a particle beam traversing the electrostatic fields of the quadrupoles in the assembly in an essentially laminar flow through the assembly.
Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam
Maschke, Alfred W. (East Moriches, NY)
1985-01-01
A charged particle accelerating assembly provided with a predetermined ratio of parametric structural characteristics and with related operating voltages applied to each of its linearly spaced focusing and accelerating quadrupoles, thereby to maintain a particle beam traversing the electrostatic fields of the quadrupoles in the assembly in an essentially laminar flow throughout the assembly.
Numerical simulation of laminar reacting flows with complex chemistry
Day, M.S.
2011-01-01
of two-dimensional axisymmetric laminar diff usion flames byof a confined axisymmetric laminar diffusion flame using aalgorithms for premixed laminar steady-state flames. Comb.
Analysis of Thermal Dispersion in an Array of Parallel Plates with Fully-Developed Laminar Flow
Fleck, Norman A.
basic heat transfer problems are addressed, each for steady fully-developed laminar fluid flow: (a1 Analysis of Thermal Dispersion in an Array of Parallel Plates with Fully-Developed Laminar Flow dispersion, parallel plate array, fully-developed laminar flow, Peclet number #12;2 Notation a molecular
The antiinflammatory effect of laminar flow: The role of PPAR , epoxyeicosatrienoic acids,
Hammock, Bruce D.
The antiinflammatory effect of laminar flow: The role of PPAR , epoxyeicosatrienoic acids Contributed by Bruce D. Hammock, September 16, 2005 We previously reported that laminar flow activates. Inclusion of AUDA in the perfusing media enhanced, but overexpression of sEH reduced, the laminar flow
Interpolation between DarcyWeisbach and Darcy for laminar and turbulent flows
Interpolation between DarcyWeisbach and Darcy for laminar and turbulent flows W.L. Hogarth a,*, J is laminar, which is the usual case, the velocity is proportional to the hydraulic gradient. This last result: Darcy; DarcyWeisbach; Porous media; Open channels; Turbulent flow; Laminar flow 1. Introduction Grassed
Pressure-Driven Laminar Flow in Tangential Microchannels: an Elastomeric Microfluidic
Kenis, Paul J. A.
Pressure-Driven Laminar Flow in Tangential Microchannels: an Elastomeric Microfluidic Switch Rustem, Massachusetts 02138 This paper describes laminar fluid flow through a three- dimensional elastomeric pressure and changing this aspect ratio. Second, the flow direction of an indi- vidual laminar stream
Laminar Flow of a Sheared Vortex Crystal: Scars in Flat Geometry M.-Carmen Miguel,1
Miguel-Lopez, Carmen
Laminar Flow of a Sheared Vortex Crystal: Scars in Flat Geometry M.-Carmen Miguel,1 Adil Mughal,2 November 2010; published 15 June 2011) We consider the laminar flow of a vortex crystal in the Corbino disk geometry. Laminar flow can be induced by thermal fluctuations melting the crystal, but also by shear stress
Three-dimensionality of sand ripples under steady laminar shear flow
Three-dimensionality of sand ripples under steady laminar shear flow V. Langlois and A. Valance laminar shear flow using a process-based stability approach. The hydrodynamics of the problem is solved under steady laminar shear flow, J. Geophys. Res., 110, F04S09, doi:10.1029/2004JF000278. 1
Unsteady laminar flow and convective heat transfer in a sharp 180 bend
Chung, Yongmann M.
Unsteady laminar flow and convective heat transfer in a sharp 180° bend Yongmann M. Chung a , Paul Unsteady laminar flow and heat transfer in a sharp 180° bend is studied numerically to investigate to be strong. Ó 2002 Elsevier Science Inc. All rights reserved. Keywords: Laminar; Unsteady; Heat transfer
Polymer Brushes Patterned with Micrometer-Scale Chemical Gradients Using Laminar Co-Flow
Braun, Paul
Polymer Brushes Patterned with Micrometer-Scale Chemical Gradients Using Laminar Co-Flow Hyung as narrow as 5 m was created by controlling these parameters. The chemical gradient by laminar co validates the numerical procedures established in this study. Flow of multiple laminar streams of reactive
Computational Study of Turbulent Laminar Patterns in Couette Flow Dwight Barkley*
Barkley, Dwight
Computational Study of Turbulent Laminar Patterns in Couette Flow Dwight Barkley* Mathematics, 91403 Orsay, France (Received 29 March 2004; published 7 January 2005) Turbulent-laminar patterns near--undergoes a discontinuous transition from laminar flow to turbulence as the Reynolds number is increased. Because of its
Gyrotactic trapping in laminar and turbulent Kolmogorov flow
Francesco Santamaria; Filippo De Lillo; Massimo Cencini; Guido Boffetta
2014-10-07
Phytoplankton patchiness, namely the heterogeneous distribution of microalgae over multiple spatial scales, dramatically impacts marine ecology. A spectacular example of such heterogeneity occurs in thin phytoplankton layers (TPLs), where large numbers of photosynthetic microorganisms are found within a small depth interval. Some species of motile phytoplankton can form TPLs by gyrotactic trapping due to the interplay of their particular swimming style (directed motion biased against gravity) and the transport by a flow with shear along the direction of gravity. Here we consider gyrotactic swimmers in numerical simulations of the Kolmogorov shear flow, both in laminar and turbulent regimes. In the laminar case, we show that the swimmer motion is integrable and the formation of TPLs can be fully characterized by means of dynamical systems tools. We then study the effects of rotational Brownian motion or turbulent fluctuations (appearing when the Reynolds number is large enough) on TPLs. In both cases we show that TPLs become transient, and we characterize their persistence.
Coherent Synchrotron Radiation for Laminar Flows
Bjoern S. Schmekel; Richard V. E. Lovelace
2006-11-16
We investigate the effect of shear in the flow of charged particle equilibria that are unstable to the Coherent Synchrotron Radiation (CSR) instability. Shear may act to quench this instability because it acts to limit the size of the region with a fixed phase relation between emitters. The results are important for the understanding of astrophysical sources of coherent radiation where shear in the flow is likely.
A Study of mixing in computer simulated laminar flow systems
McFarland, Allison Anne
1984-01-01
1984 Major Subject: Chemical Engineering A STUDY OF MIXING IN COMPUTER SIMULATED LAMINAR FLOW SYSTEMS A Thesis by ALLISON ANNE MCFARLAND Approved as to style and content by: Gary B. Tatterson (Chairman) ries J. Glover (Member) A. Ted Watson...: Dr. Gary B. Tatterson Mixing is a process that reduces nonuniformities or gradients in composition, properties, or temperature of material in bulk. It is a basic part of many chemical engineering processes, yet the theoretical understanding...
Flores, Leona Marie
2010-01-01
laminar flow in a circular cylindrical tube, with the assumptions that blood is an incompressible Newtonian fluid, the flowLaminar Shear Flow Experiments A parallel-plate flow system was used to impose fluid
Polymer Effects on Heat Transport in Laminar Boundary Layer Flow
Roberto Benzi; Emily S. C. Ching; Vivien W. S. Chu
2011-04-27
We consider a laminar Blasius boundary-layer flow above a slightly heated horizontal plate and study the effect of polymer additives on the heat transport. We show that the action of the polymers can be understood as a space-dependent effective viscosity that first increases from the zero-shear value then decreases exponentially back to the zero-shear value as one moves away from the boundary. We find that with such an effective viscosity, both the horizontal and vertical velocities near the plate are decreased thus leading to an increase in the friction drag and a decrease in the heat transport in the flow.
Laminar Flame Speeds of Nano-Aluminum/Methane Hybrid Mixtures
Sikes, Travis
2014-12-12
An existing flame speed bomb, which uses optical techniques to measure laminar flame speed, was employed to study the fundamental phenomena of flame propagation through a uniformly dispersed aerosol. In a previous thesis ...
Pressure-Driven Laminar Flow in Tangential Microchannels: an Elastomeric Microfluidic
Gardel, Margaret
, Massachusetts 02138 This paper describes laminar fluid flow through a three- dimensional elastomericPressure-Driven Laminar Flow in Tangential Microchannels: an Elastomeric Microfluidic Switch Rustem-to-face (typically at a 90° angle), with the fluid flows in tangential contact. There are two ways to control fluid
A viscous instability in axially symmetric laminar shear flows
Shakura, Nikolai
2015-01-01
A viscous instability in shearing laminar axisymmetric hydrodynamic flows around a gravitating center is described. In the linearized hydrodynamic equations written in the Boussinesq approximation with microscopic molecular transport coefficients, the instability arises when the viscous dissipation is taken into account in the energy equation. Using the local WKB approximation, we derive a third-order algebraic dispersion equation with two modes representing the modified Rayleigh modes R+ and R-, and the third X-mode. We show that in thin accretion flows the viscosity destabilizes one of the Rayleigh modes in a wide range of wavenumbers, while the X-mode always remains stable. In Keplerian flows, the instability increment is found to be a few Keplerian rotational periods at wavelengths with $kr\\sim 10-50$. This instability may cause turbulence in astrophysical accretion discs even in the absence of magnetic field.
Formation of Two-Dimensional Sand Ripples under Laminar Shear Flow Vincent Langlois and Alexandre sand bed patterns under a laminar and steady shear flow. Several issues are addressed here: (i fluid is investigated theoretically. The sand transport is described taking into account both the local
Journal of Power Sources 128 (2004) 5460 Microfluidic fuel cell based on laminar flow
Kenis, Paul J. A.
2004-01-01
Journal of Power Sources 128 (2004) 5460 Microfluidic fuel cell based on laminar flow Eric R compartments. While these PEM-type fuel cell designs have great promise to become the power source of choice a novel microfluidic fuel cell concept that utilizes the occurrence of multi-stream laminar flow
AIR-BREATHING LAMINAR FLOW BASED MICROFLUIDIC FUEL CELL Ranga S. Jayashree1
Kenis, Paul J. A.
AIR-BREATHING LAMINAR FLOW BASED MICROFLUIDIC FUEL CELL Ranga S. Jayashree1 , Lajos Gancs2 , Eric R of the laminar flow-based microfluidic fuel cell. A 5-mm thick graphite plate (anode, fuel cell grade graphite bipolar plate purchased from Fuel Cell Stores.com) was cleaned by sonication in large portions of Milli
Ford, Ian
The laminar flow tube reactor as a quantitative tool for nucleation studies: Experimental results, United Kingdom Received 24 March 2000; accepted 2 June 2000 A laminar flow tube reactor was designed
Computations of Laminar Flow Control on Swept Wings as a Companion to Flight Test Research
Rhodes, Richard G.
2010-01-14
The high cost of energy has resulted in a renewed interest in the study of reducing skin-friction drag in aeronautical applications. Laminar Flow Control (LFC) refers to any technique which alters the basic-state flow-field ...
Hagen, Stephen J.
Laminar-Flow Fluid Mixer for Fast Fluorescence Kinetics Studies Suzette A. Pabit and Stephen J i.d.) at a speed 20 cm/s, under laminar flow conditions (Re 14). Construction from a fused silica studies of fast protein and nucleic acid interactions and folding. We have constructed a laminar coaxial
The relative contributions of radial and laminar optic flow to the perception of linear self-motion
Jenkin, Michael R. M.
The relative contributions of radial and laminar optic flow to the perception of linear self seen location too early. In this article we assess how the radial and laminar components the relative amounts of radial and laminar flow visible. They were then presented with visual motion compatible
Kenis, Paul J. A.
Experimental and theoretical scaling laws for transverse diffusive broadening in two-phase laminar in pressure-driven laminar flow in microchannels at high Pe´clet numbers. Confocal fluorescent microscopy, such as described in this letter, is required for the rational use of laminar flows for performing spatially
Erosion of a granular bed driven by laminar fluid flow
A. E. Lobkovsky; A. V. Orpe; R. Molloy; A. Kudrolli; D. H. Rothman
2008-05-01
Motivated by examples of erosive incision of channels in sand, we investigate the motion of individual grains in a granular bed driven by a laminar fluid to give us new insights into the relationship between hydrodynamic stress and surface granular flow. A closed cell of rectangular cross-section is partially filled with glass beads and a constant fluid flux $Q$ flows through the cell. The refractive indices of the fluid and the glass beads are matched and the cell is illuminated with a laser sheet, allowing us to image individual beads. The bed erodes to a rest height $h_r$ which depends on $Q$. The Shields threshold criterion assumes that the non-dimensional ratio $\\theta$ of the viscous stress on the bed to the hydrostatic pressure difference across a grain is sufficient to predict the granular flux. Furthermore, the Shields criterion states that the granular flux is non-zero only for $\\theta >\\theta_c$. We find that the Shields criterion describes the observed relationship $h_r \\propto Q^{1/2}$ when the bed height is offset by approximately half a grain diameter. Introducing this offset in the estimation of $\\theta$ yields a collapse of the measured Einstein number $q^*$ to a power-law function of $\\theta - \\theta_c$ with exponent $1.75 \\pm 0.25$. The dynamics of the bed height relaxation are well described by the power law relationship between the granular flux and the bed stress.
Erlebacher, Gordon
Active Control of Instabilities in Laminar BoundaryLayer Flow -- Part II: Use of Sensors growth and stabilize the instabilities within the laminar boundary layer. This scenario is shown in Fig
WENO schemes on arbitrary unstructured meshes for laminar, transitional and turbulent flows
Tsoutsanis, Panagiotis, E-mail: panagiotis.tsoutsanis@cranfield.ac.uk; Antoniadis, Antonios Foivos, E-mail: a.f.antoniadis@cranfield.ac.uk; Drikakis, Dimitris, E-mail: d.drikakis@cranfield.ac.uk
2014-01-01
This paper presents the development and implementation of weighted-essentially-non-oscillatory (WENO) schemes for viscous flows on arbitrary unstructured grids. WENO schemes up to fifth-order accurate have been implemented in conjunction with hybrid and non-hybrid unstructured grids. The schemes are investigated with reference to numerical and experimental results for the Taylor–Green vortex, as well as for laminar and turbulent flows around a sphere, and the turbulent shock-wave boundary layer interaction flow problem. The results show that the accuracy of the schemes depends on the arbitrariness of shape and orientation of the unstructured mesh elements, as well as the compactness of directional stencils. The WENO schemes provide a more accurate numerical framework compared to second-order and third-order total variation diminishing (TVD) methods, however, the fifth-order version of the schemes is computationally too expensive to make the schemes practically usable. On the other hand, the third-order variant offers an excellent numerical framework in terms of accuracy and computational cost compared to the fifth-order WENO and second-order TVD schemes. Parallelisation of the CFD code (henceforth labelled as UCNS3D), where the schemes have been implemented, shows that the present methods offer very good scalable performance.
Kenis, Paul J. A.
and proceed in parallel laminar flow, without turbulent mixing. Using laminar flows of reagents is the basis Capillaries Using Multiphase Laminar Flow Patterning Paul J. A. Kenis, Rustem F. Ismagilov, George M. Whitesides* The reaction of species in solutions flowing laminarly (without turbulent mix- ing) inside
The Effects of Frost Growth on Finned Tube Heat Exchangers under Laminar Flow
Kondepudi, Sekhar
1988-01-01
A study on the effects of frost growth on the performance of finned tube heat exchangers under laminar flow has been conducted. The study was both experimental and analytical. The experimental part of the investigation ...
Rheology of sediment transported by a laminar flow
M. Houssais; C. P. Ortiz; D. J. Durian; D. J. Jerolmack
2015-09-28
Understanding the dynamics of fluid-driven sediment transport remains challenging, as it is an intermediate region between a granular material and a fluid flow. Boyer \\textit{et al.}\\citep{Boyer2011} proposed a local rheology unifying dense dry-granular and viscous-suspension flows, but it has been validated only for neutrally-buoyant particles in a confined system. Here we generalize the Boyer \\textit{et al.}\\citep{Boyer2011} model to account for the weight of a particle by addition of a pressure $P_0$, and test the ability of this model to describe sediment transport in an idealized laboratory river. We subject a bed of settling plastic particles to a laminar-shear flow from above, and use Refractive-Index-Matching to track particles' motion and determine local rheology --- from the fluid-granular interface to deep in the granular bed. Data from all experiments collapse onto a single curve of friction $\\mu$ as a function of the viscous number $I_v$ over the range $10^{-5} \\leq I_v \\leq 1$, validating the local rheology model. For $I_v < 10^{-5}$, however, data do not collapse. Instead of undergoing a jamming transition with $\\mu \\rightarrow \\mu_s$ as expected, particles transition to a creeping regime where we observe a continuous decay of the friction coefficient $\\mu \\leq \\mu_s$ as $I_v$ decreases. The rheology of this creep regime cannot be described by the local model, and more work is needed to determine whether a non-local rheology model can be modified to account for our findings.
Copyright 2009 by ASME Laminar fully developed flow in streamwise-periodic
Bahrami, Majid
1 Copyright ©2009 by ASME ABSTRACT Laminar fully developed flow in streamwise-sections [1-5]. It has been experimentally and numerically observed that the entrance lengths of fluid flow theoretical works for such ducts often focus on the periodically fully-developed fluid flow and heat transfer
A unifying method for sizing throttling valves under laminar or transitional flow conditions
Baumann, H.D. (H.D. Baumann Assoc., Ltd., Portsmouth, NH (United States))
1993-03-01
The mass flow passing through a given valve will decrease in Reynolds number ranges below approximately 10,000 due to the transition from fully developed turbulent to laminar flow. The objective of this study is to provide a uniform prediction method to establish, with reasonable accuracy, the ratio between the turbulent and transitional or laminar flow rate passing through a given valve, taking into account the valve's hydraulic diameter and the initial turbulent velocity head loss coefficient. Experimental data from prior research tends to support a proposed unified sizing method that is applicable for all single-stage valves regardless of size or type.
Physica A 385 (2007) 4658 Accumulating particles at the boundaries of a laminar flow
Schindler, Michael
2007-01-01
Physica A 385 (2007) 4658 Accumulating particles at the boundaries of a laminar flow Michael in stationary flows through channels of variable width at small Reynolds number. The combined influence for the particle density. It is shown that for extended spherical particles the shape of the fluid domain gives
On projected NewtonKrylov solvers for instationary laminar reacting gas flows
Vuik, Kees
deposition (CVD) [8] and flows with combustion [19] requires the simultaneous solution of many strongly and considerations apply to laminar combustion as well. Assuming continuum flow, the mathematical model consists for advection, diffusion and reaction, equations (1) are very stiff. In that case, most commercial CFD codes
Manufacturing all-polymer laminar flow-based fuel cells A.S. Hollinger, P.J.A. Kenis*
Kenis, Paul J. A.
Manufacturing all-polymer laminar flow-based fuel cells A.S. Hollinger, P.J.A. Kenis* Department, Urbana, IL 61801, USA h i g h l i g h t s Manufactured a lightweight, all-polymer direct methanol April 2013 Keywords: Manufacturing Polymer Laminar flow Microfluidic Fuel cell Stack a b s t r a c
Spraying Powder Materials by the High-Enthalpy Laminar Plasma Flow
Khutsishvili, M.; Kikvadze, L.
2008-03-19
One of the most promising engineering solutions of the problem of spraying powder materials is the proposed method of plasma spraying by the laminar plasma jet. Laminar plasma flow is characterized by small jet angle divergence; the powder particles are penetrated and accelerated mainly in the axial direction. The molten powder particles are transported almost to the surface of a treated work-piece inside the laminar plasma flow in an atmosphere of the plasma-forming gas with the acceleration on the entire transfer area, which leads to an increase in the particles velocity, a decrease of their oxidability, an increase in the powder deposition efficiency, density, adhesion strength with the surface to be coated.
Dispersion of swimming algae in laminar and turbulent channel flows: theory and simulations
Croze, O A; Ahmed, M; Bees, M A; Brandt, L
2012-01-01
Algal swimming is often biased by environmental cues, e.g. gravitational and viscous torques drive cells towards downwelling fluid (gyrotaxis). In view of biotechnological applications, it is important to understand how such biased swimming affects cell dispersion in a flow. Here, we study the dispersion of gyrotactic swimming algae in laminar and turbulent channel flows. By direct numerical simulation (DNS) of cell motion within upwelling and downwelling channel flows, we evaluate time-dependent measures of dispersion for increasing values of the flow Peclet (Reynolds) numbers, Pe (Re). Furthermore, we derive an analytical `swimming Taylor-Aris dispersion' theory, using flow-dependent transport parameters given by existing microscopic models. In the laminar regime, DNS results and analytical predictions compare very well, providing the first confirmation that cells' response to flow is best described by the generalized-Taylor-dispersion microscopic model. We predict that cells drift along a channel faster th...
A Power-Law Formulation of Laminar Flow in Short Pipes Max Sherman
A Power-Law Formulation of Laminar Flow in Short Pipes Max Sherman Indoor Environment Program ABSTRACT This report develops a theoretical description of the hydrodynamic relationship based on a power pipes can be described with a simple power law dependence on pressure, but that the exponent
On the notion of laminar and weakly turbulent elementary fluid flows: a simple mathematical model
Gianluca Argentini
2006-08-28
An elementary analytical fluid flow is composed by a geometric domain, a list of analytical constraints and by the function which depends on the physical properties, as Reynolds number, of the considered fluid. For this object, notions of laminar or weakly turbulent behavior are described using a simple mathematical model.
Characterization of Limiting Factors in Laminar Flow-Based Membraneless Microfuel Cells
Kenis, Paul J. A.
are underway to develop and optimize microscale fuel cells as high-energy-density power source alternatives, where fuel and oxidant are oxidized and re- duced, respectively, is essential for fuel cell optimization reports the analysis of a microflu- idic fuel cell based on laminar flow using an external reference
Membraneless Hydrogen Bromine Laminar Flow Battery for Large-Scale Energy Storage
Poonen, Bjorn
Membraneless Hydrogen Bromine Laminar Flow Battery for Large-Scale Energy Storage by William Allan and examined for its potential to provide low cost energy storage using the rapid reaction kinetics of hydrogen by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . David E. Hardt Chairman, Department Committee on Graduate Theses #12;2 #12;Membraneless Hydrogen Bromine
Beebe, David J.
destination for loaded fluid and balances the pressure applied to each branch for laminar flow patterningPipette-friendly laminar flow patterning for cell-based assays Erwin Berthier, Jay Warrick, Ben Laminar flow patterning (LFP) is a characteristic method of microfluidic systems that allows two (or more
Wesfreid, José Eduardo
1997-01-01
in a laminar boundary layer flow P. Petitjeans, J. E. Wesfreid, J. C. Attiach Abstract A new technique the effects of stretching on a controlled vorticity sheet coming from a laminar boundary layer flow on a flat. A diffuser keeps the flow laminar with a minimum of perturbation. The key elements of the channel
Kenis, Paul J. A.
A three-dimensional numerical model of a micro laminar flow fuel cell with a bridge: Membraneless fuel cell Laminar flow fuel cell Numerical model Convection-diffusion equations Electrode kinetics equations COMSOL a b s t r a c t The operation of a laminar flow fuel cell (LFFC) involves complex interplay
Laminar and turbulent nozzle-jet flows and their acoustic near-field
Bühler, Stefan; Obrist, Dominik; Kleiser, Leonhard
2014-08-15
We investigate numerically the effects of nozzle-exit flow conditions on the jet-flow development and the near-field sound at a diameter-based Reynolds number of Re{sub D} = 18?100 and Mach number Ma = 0.9. Our computational setup features the inclusion of a cylindrical nozzle which allows to establish a physical nozzle-exit flow and therefore well-defined initial jet-flow conditions. Within the nozzle, the flow is modeled by a potential flow core and a laminar, transitional, or developing turbulent boundary layer. The goal is to document and to compare the effects of the different jet inflows on the jet flow development and the sound radiation. For laminar and transitional boundary layers, transition to turbulence in the jet shear layer is governed by the development of Kelvin-Helmholtz instabilities. With the turbulent nozzle boundary layer, the jet flow development is characterized by a rapid changeover to a turbulent free shear layer within about one nozzle diameter. Sound pressure levels are strongly enhanced for laminar and transitional exit conditions compared to the turbulent case. However, a frequency and frequency-wavenumber analysis of the near-field pressure indicates that the dominant sound radiation characteristics remain largely unaffected. By applying a recently developed scaling procedure, we obtain a close match of the scaled near-field sound spectra for all nozzle-exit turbulence levels and also a reasonable agreement with experimental far-field data.
Formation of a laminar electron flow for 300 GHz high-power pulsed gyrotron
Yamaguchi, Yuusuke; Tatematsu, Yoshinori; Saito, Teruo; Ikeda, Ryosuke; Mudiganti, Jagadish C.; Ogawa, Isamu; Idehara, Toshitaka [Research Center for Development of Far-Infrared Region, University of Fukui, 3-9-1 Bunkyo, Fukui-shi 910-8507 (Japan)
2012-11-15
This paper describes the design of a triode magnetron injection gun for use in a 200 kW, 300 GHz gyrotron. As power and frequency increase, the performance of the gyrotron becomes quite sensitive to the quality of the electron beam. Formation of a laminar electron flow is essential for the realization of a high quality beam with a small velocity spread. In this study, a new method is developed for a quantitative evaluation of the laminarity and is applied to optimize the electrode design. The laminarity depends not only on conventional design parameters such as the cathode slant angle but also on the spatial distribution of the electric field along the beam trajectory. In the optimized design, the velocity pitch factors, {alpha}, larger than 1.2 are obtained at 65 kV, 10 A with spreads, {Delta}{alpha}, less than 5%.
Dynamical Slowdown of Polymers in Laminar and Random Flows
Antonio Celani; Alberto Puliafito; Dario Vincenzi
2006-09-22
The influence of an external flow on the relaxation dynamics of a single polymer is investigated theoretically and numerically. We show that a pronounced dynamical slowdown occurs in the vicinity of the coil-stretch transition, especially when the dependence on polymer conformation of the drag is accounted for. For the elongational flow, relaxation times are exceedingly larger than the Zimm relaxation time, resulting in the observation of conformation hysteresis. For random smooth flows hysteresis is not present. Yet, relaxation dynamics is significantly slowed down because of the large variety of accessible polymer configurations. The implications of these results for the modeling of dilute polymer solutions in turbulent flows are addressed.
Laminar channel flow over a (long)wavy surface
McCready, Mark J.
, if you use it, this notice remain visible to other users. There is no charge for copying of studies have suggested that regime transitions from stratified to slug and/or annular flow occur when then stratified flow becomes unstable to long waves. The plot above shows a number of different models, most based
Cioncolini, Andrea; Santini, Lorenzo [Department of Nuclear Engineering, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy)
2006-03-01
An experimental study was carried out to investigate the transition from laminar to turbulent flow in helically coiled pipes. Twelve coils have been tested, with ratios of coil diameter to tube diameter ranging from 6.9 to 369, and the interaction between turbulence emergence and coil curvature has been analyzed from direct observation of the experimental friction factor profiles. The experimental data compare favorably with existing results and reveal new features that apparently were not observed in previous research. (author)
Laminar flame and acoustic waves in two-dimensional flow
Zaytsev, M. L., E-mail: mlzaytsev@gmail.com; Akkerman, V. B., E-mail: slava.akkerman@gmail.com [Russian Academy of Sciences, Nuclear Safety Institute (Russian Federation)
2011-03-15
The complete system of fluid dynamics equations describing the development of instability of a reaction front in a two-dimensional flow in reversed time are reduced to a closed system of equations of front dynamics by using Lagrangian variables and integrals of motion. The system can be used to analyze processes behind the front without solving the complete system of fluid dynamics and chemical kinetics equations. It is demonstrated how the gas density disturbances induced by the moving front can be described in the adiabatic approximation.
Demonstration of a plasma mirror based on a laminar flow water film
Panasenko, Dmitriy; Shu, Anthony; Gonsalves, Anthony; Nakamura, Kei; Matlis, Nicholas; Toth, Csaba; Leemans, Wim
2011-07-22
A plasma mirror based on a laminar water film with low flow speed 0.5-2 cm/s has been developed and characterized, for use as an ultrahigh intensity optical reflector. The use of flowing water as atarget surface automatically results in each laser pulse seeing a new interaction surface and avoids the need for mechanical scanning of the target surface. In addition, the breakdown of water does notproduce contaminating debris that can be deleterious to vacuum chamber conditions and optics, such as is the case when using conventional solid targets. The mirror exhibits 70percent reflectivity, whilemaintaining high-quality of the reflected spot.
Demonstration of a plasma mirror based on a laminar flow water film
Panasenko, Dmitriy; Shu, Anthony J.; Gonsalves, Anthony; Nakamura, Kei; Matlis, Nicholas H.; Toth, Csaba; Leemans, Wim P. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)
2010-08-15
A plasma mirror based on a laminar water film with low flow speed (0.5-2 cm/s) has been developed and characterized, for use as an ultrahigh intensity optical reflector. The use of flowing water as a target surface automatically results in each laser pulse seeing a new interaction surface and avoids the need for mechanical scanning of the target surface. In addition, the breakdown of water does not produce contaminating debris that can be deleterious to vacuum chamber conditions and optics, such as is the case when using conventional solid targets. The mirror exhibits 70% reflectivity, while maintaining high-quality of the reflected spot.
Heat transport by laminar boundary layer flow with polymers
Roberto Benzi; Emily S. C. Ching.; Vivien W. S. Chu
2011-04-23
Motivated by recent experimental observations, we consider a steady-state Prandtl-Blasius boundary layer flow with polymers above a slightly heated horizontal plate and study how the heat transport might be affected by the polymers. We discuss how a set of equations can be derived for the problem and how these equations can be solved numerically by an iterative scheme. By carrying out such a scheme, we find that the effect of the polymers is equivalent to producing a space-dependent effective viscosity that first increases from the zero-shear value at the plate then decreases rapidly back to the zero-shear value far from the plate. We further show that such an effective viscosity leads to an enhancement in the drag, which in turn leads to a reduction in heat transport.
Accumulating Particles at the Boundaries of a Laminar Flow
Michael Schindler; Peter Talkner; Marcin Kostur; Peter Hanggi
2007-06-25
The accumulation of small particles is analyzed in stationary flows through channels of variable width at small Reynolds number. The combined influence of pressure, viscous drag and thermal fluctuations is described by means of a Fokker-Planck equation for the particle density. It is shown that in the limit of vanishing particle size a uniform particle distribution is always approached in the long time limit. For extended spherical particles, conditions are specified that lead to inhomogeneous densities and consequently to particle accumulation and depletion. Hereby the boundary conditions for the particle density play a decisive role: The centers of spherical particles must keep the minimal distance of their radius from the fluid boundaries. The normal components of the forces acting on the sphere then may assume finite values which are diffusively transported into the bulk of the fluid.
Mechanical and statistical study of the laminar hole formation in transitional plane Couette flow
Rolland, Joran
2015-01-01
This article is concerned with the numerical study and modelling of two aspects the formation of laminar holes in transitional turbulence of plane Couette flow (PCF). On the one hand, we consider quenches: sudden decreases of the Reynolds number R which force the formation of holes. The Reynolds number is decreased from featureless turbulence to the range of existence of the oblique laminar-turbulent bands [Rg;Rt]. The successive stages of the quench are studied by means of visualisations and measurements of kinetic energy and turbulent fraction. The behaviour of the kinetic energy is explained using a kinetic energy budget: it shows that viscosity causes quasi modal decay until lift-up equals it and creates a new balance. Moreover, the budget confirms that the physical mechanisms at play are independent of the way the quench is performed. On the other hand we consider the natural formation of laminar holes in the bands, near Rg. The Direct Numerical simulations (DNS) show that holes in the turbulent bands pr...
Jameson, Antony
High-order accurate simulation of low-Mach laminar flow past two side-by-side cylinders using applications on simulating laminar flow past two side-by-side cylinders at various spacings. The high-by-side cylinders Investigations of the fluid flow and vortex dynamics about sim- ple configurations of two
Convective Heat Transfer Augmentation by Flexible fins in Laminar Channel Pulsating flow
Joshi, Rakshitha U; Bhardwaj, Rajneesh
2015-01-01
Fluid-structure interaction (FSI) of thin flexible fins coupled with convective heat transfer has applications in energy harvesting and in understanding functioning of several biological systems. We numerically investigate FSI of the thin flexible fins involving large-scale flow-induced deformation as a potential heat transfer enhancement technique. An in-house, strongly-coupled fluid-structure interaction (FSI) solver is employed in which flow and structure solvers are based on sharp-interface immersed boundary and finite element method, respectively. We consider twin flexible fins in a heated channel with laminar pulsating cross flow. The vortex ring past the fin sweep higher sources of vorticity generated on the channel walls out into the downstream - promoting the mixing of the fluid. The moving fin assists in convective mixing, augmenting convection in bulk and at the walls; and thereby reducing thermal boundary layer thickness and improving heat transfer at the channel walls. The thermal augmentation is...
Super Stability of Laminar Vortex Flow in Superfluid 3He-B
V. B. Eltsov; R. de Graaf; P. J. Heikkinen; J. J. Hosio; R. Hanninen; M. Krusius; V. S. L'vov
2010-05-04
Vortex flow remains laminar up to large Reynolds numbers (Re~1000) in a cylinder filled with 3He-B. This is inferred from NMR measurements and numerical vortex filament calculations where we study the spin up and spin down responses of the superfluid component, after a sudden change in rotation velocity. In normal fluids and in superfluid 4He these responses are turbulent. In 3He-B the vortex core radius is much larger which reduces both surface pinning and vortex reconnections, the phenomena, which enhance vortex bending and the creation of turbulent tangles. Thus the origin for the greater stability of vortex flow in 3He-B is a quantum phenomenon. Only large flow perturbations are found to make the responses turbulent, such as the walls of a cubic container or the presence of invasive measuring probes inside the container.
Laminar-turbulent patterning in wall-bounded shear flows: a Galerkin model
Seshasayanan, K
2015-01-01
On its way to turbulence, plane Couette flow - the flow between counter-translating parallel plates - displays a puzzling steady oblique laminar-turbulent pattern. We approach this problem via Galerkin modelling of the Navier-Stokes equations. The wall-normal dependence of the hydrodynamic field is treated by means of expansions on functional bases fitting the boundary conditions exactly. This yields a set of partial differential equations for the spatiotemporal dynamics in the plane of the flow. Truncating this set beyond lowest nontrivial order is numerically shown to produce the expected pattern, therefore improving over what was obtained at cruder effective wall-normal resolution. Perspectives opened by the approach are discussed.
Luo, Xiaoyu
Effect of tube spacing on the vortex shedding characteristics of laminar flow past an inline tube the tubes. Complex flow dynamic phenomena such as reattachment of shear layers, in- duced separation, vortex Accepted 27 October 2008 Available online 14 November 2008 a b s t r a c t The effect of tube spacing
Stochastic analysis of the time evolution of Laminar-Turbulent bands of plane Couette flow
Rolland, Joran
2015-01-01
This article is concerned with the time evolution of the oblique laminar-turbulent bands of transitional plane Couette flow under the influence of turbulent noise. Our study is focused on the amplitude of modulation of turbulence. In order to guide the numerical study of the flow, we first perform an analytical and numerical analysis of a Stochastic Ginzburg-Landau equation for a complex order parameter. The modulus of this order parameter models the amplitude of modulation of turbulence. Firstly, we compute the autocorrelation function of said modulus once the band is established. Secondly, we perform a calculation of average and fluctuations around the exponential growth of the order parameter. This type of analysis is similar to the Stochastic Structural Stability Theory. We then perform numerical simulations of the Navier-Stokes equations in order to confront these predictions with the actual behaviour of the bands. Computation of the autocorrelation function of the modulation of turbulence shows quantita...
Bahrami, Majid
Chapter 1 x Introduction 7 1.12 For low-speed (laminar) flow in a tube of radius ro, the velocity u is the length of the pipe and C is a dimensionless constant which has the theoretical laminar-flow value of (1
Kenis, Paul J. A.
MEMBRANELESS FUEL CELL BASED ON LAMINAR FLOW Eric R. Choban, Piotr Waszczuk, Larry J. Markoski in this area focus on downscaling of existing fuel cell technology such as the well-known proton exchange membrane (PEM) fuel cells. Here we study a novel concept for fuel cells: the use of laminar flow instead
Fleifil, M.; Annaswamy, A.M.; Ghoneim, A.F.; Ghoneim, Z.A.
1996-09-01
Combustion instability is a resonance phenomenon that arises due to the coupling between the system acoustics and the unsteady heat release. The constructive feedback between the two processes, which is known to occur as a certain phase relationship between the pressure and the unsteady heat release rate is satisfied, depends on many parameters among which is the acoustic mode, the flame holder characteristics, and the dominant burning pattern. In this paper, the authors construct an analytical model to describe the dynamic response of a laminar premixed flame stabilized on the rim of a tube to velocity oscillation. They consider uniform and nonuniform velocity perturbations superimposed on a pipe flow velocity profile. The model results show that the magnitude of heat release perturbation and its phase with respect to the dynamic perturbation dependent primarily on the flame Strohal number, representing the ratio of the dominant frequency times the tube radius to the laminar burning velocity. In terms of this number, high-frequency perturbations pass through the flame while low frequencies lead to a strong response. The phase with respect to the velocity perturbation behaves in the opposite way. Results of this model are shown to agree with experimental observations and to be useful in determining how the combustion excited model is selected among all the acoustic unstable modes. The model is then used to obtain a time-domain differential equation describing the relationship between the velocity perturbation and the heat release response over the entire frequency range.
Mayer, Michael
Membraneless Vanadium Redox Fuel Cell Using Laminar Flow Rosaria Ferrigno, Abraham D. Stroock This communication describes a small redox fuel cell fabricated using a design that omits the membrane normally used this concept by operating a millimeter-scale redox fuel cell that uses the redox couples V(V)/V(IV) (cathodic
Numerical simulation of laminar plasma dynamos in a cylindrical von Karman flow
Khalzov, I. V.; Brown, B. P.; Schnack, D. D.; Forest, C. B. [University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States); Ebrahimi, F. [University of New Hampshire, 8 College Road, Durham, New Hampshire 03824 (United States)
2011-03-15
The results of a numerical study of the magnetic dynamo effect in cylindrical von Karman plasma flow are presented with parameters relevant to the Madison Plasma Couette Experiment. This experiment is designed to investigate a broad class of phenomena in flowing plasmas. In a plasma, the magnetic Prandtl number Pm can be of order unity (i.e., the fluid Reynolds number Re is comparable to the magnetic Reynolds number Rm). This is in contrast to liquid metal experiments, where Pm is small (so, Re>>Rm) and the flows are always turbulent. We explore dynamo action through simulations using the extended magnetohydrodynamic NIMROD code for an isothermal and compressible plasma model. We also study two-fluid effects in simulations by including the Hall term in Ohm's law. We find that the counter-rotating von Karman flow results in sustained dynamo action and the self-generation of magnetic field when the magnetic Reynolds number exceeds a critical value. For the plasma parameters of the experiment, this field saturates at an amplitude corresponding to a new stable equilibrium (a laminar dynamo). We show that compressibility in the plasma results in an increase of the critical magnetic Reynolds number, while inclusion of the Hall term in Ohm's law changes the amplitude of the saturated dynamo field but not the critical value for the onset of dynamo action.
On the laminar to turbulent flow transition in diabatic helically coiled pipe flow
Cioncolini, Andrea; Santini, Lorenzo [Department of Nuclear Engineering, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy)
2006-07-15
Recently the authors experimentally investigated the turbulence emergence process in adiabatic coiled pipe flow. The results of such an investigation compared favorably with existing experimental evidence and revealed as well some new and striking features of the turbulence emergence process in coiled pipes that were not observed in previous research. The objective of the present investigation is to confirm such findings with diabatic flow through coiled pipes. (author)
Characterization and reduction of flow separation in jet pumps for laminar oscillatory flows
Timmer, Michael A G; Bühler, Simon; Wilcox, Douglas; van der Meer, Theo H
2016-01-01
A computational fluid dynamics model is used to predict the oscillatory flow through tapered cylindrical tube sections (jet pumps). The asymmetric shape of jet pumps results in a time-averaged pressure drop that can be used to suppress Gedeon streaming in closed-loop thermoacoustic devices. However, previous work has shown that flow separation in the diverging flow direction counteracts the time-averaged pressure drop. In this work, the characteristics of flow separation in jet pumps are identified and coupled with the observed jet pump performance. Furthermore, it is shown that the onset of flow separation can be shifted to larger displacement amplitudes by designs that have a smoother transition between the small opening and the tapered surface of the jet pump. These design alterations also reduce the duration of separated flow, resulting in more effective and robust jet pumps. To make the proposed jet pump designs more compact without reducing their performance, the minimum big opening radius that can be i...
Microfluidics: Kinetics of Hybridized DNA With Fluid Flow Variations...
Office of Scientific and Technical Information (OSTI)
Conference: Microfluidics: Kinetics of Hybridized DNA With Fluid Flow Variations. Citation Details In-Document Search Title: Microfluidics: Kinetics of Hybridized DNA With Fluid...
LAMINAR: PRACTICAL FINE-GRAINED DECENTRALIZED INFORMATION
Witchel, Emmett
LAMINAR: PRACTICAL FINE-GRAINED DECENTRALIZED INFORMATION FLOW CONTROL (DIFC) Indrajit Roy, Donald} {} Information flow in a lattice #12;In this talk: Laminar A practical way to provide end-to-end security guarantees. #12;Outline Comparison with current DIFC systems Laminar: programming model Design: PL + OS
Punjabi, Sangeeta B.; Sahasrabudhe, S. N.; Das, A. K.; Joshi, N. K.; Mangalvedekar, H. A.; Kothari, D. C.
2014-01-15
This paper provides 2D comparative study of results obtained using laminar and turbulent flow model for RF (radio frequency) Inductively Coupled Plasma (ICP) torch. The study was done for the RF-ICP torch operating at 50?kW DC power and 3?MHz frequency located at BARC. The numerical modeling for this RF-ICP torch is done using ANSYS software with the developed User Defined Function. A comparative study is done between laminar and turbulent flow model to investigate how temperature and flow fields change when using different operating conditions such as (a) swirl and no swirl velocity for sheath gas flow rate, (b) variation in sheath gas flow rate, and (c) variation in plasma gas flow rate. These studies will be useful for different material processing applications.
Anisotropic flow in transport+hydrodynamics hybrid approaches
Hannah Petersen
2014-11-26
This contribution to the focus issue covers anisotropic flow in hybrid approaches. The historical development of hybrid approaches and their impact on the interpretation of flow measurements is reviewed. The major ingredients of a hybrid approach and the transition criteria between transport and hydrodynamics are discussed. The results for anisotropic flow in (event-by-event) hybrid approaches are presented. Some hybrid approaches rely on hadronic transport for the late stages for the reaction (so called afterburner) and others employ transport approaches for the early non equilibrium evolution. In addition, there are 'full' hybrid calculations where a fluid evolution is dynamically embedded in a transport simulation. After demonstrating the success of hybrid approaches at high RHIC and LHC energies, existing hybrid caluclations for collective flow observables at lower beam energies are discussed and remaining challenges outlined.
Hybrid anodes for redox flow batteries
Wang, Wei; Xiao, Jie; Wei, Xiaoliang; Liu, Jun; Sprenkle, Vincent L.
2015-12-15
RFBs having solid hybrid electrodes can address at least the problems of active material consumption, electrode passivation, and metal electrode dendrite growth that can be characteristic of traditional batteries, especially those operating at high current densities. The RFBs each have a first half cell containing a first redox couple dissolved in a solution or contained in a suspension. The solution or suspension can flow from a reservoir to the first half cell. A second half cell contains the solid hybrid electrode, which has a first electrode connected to a second electrode, thereby resulting in an equipotential between the first and second electrodes. The first and second half cells are separated by a separator or membrane.
Hybrid anodes for redox flow batteries
Wang, Wei; Xiao, Jie; Wei, Xiaoliang; Liu, Jun; Sprenkle, Vincent L.
2015-12-22
RFBs having solid hybrid electrodes can address at least the problems of active material consumption, electrode passivation, and metal electrode dendrite growth that can be characteristic of traditional batteries, especially those operating at high current densities. The RFBs each have a first half cell containing a first redox couple dissolved in a solution or contained in a suspension. The solution or suspension can flow from a reservoir to the first half cell. A second half cell contains the solid hybrid electrode, which has a first electrode connected to a second electrode, thereby resulting in an equipotential between the first and second electrodes. The first and second half cells are separated by a separator or membrane.
Bazán, Fermín S. V.
Estimation of the local heat-transfer coefficient in the laminar flow regime in coiled tubes February 2014 Keywords: Heat-transfer enhancement Coiled tubes Local convective heat-flux estimation. Although many authors have investigated the forced convective heat transfer in coiled tubes, most of them
Kenis, Paul J. A.
Air-Breathing Laminar Flow-Based Microfluidic Fuel Cell Ranga S. Jayashree, Lajos Gancs, Eric R-based microfluidic fuel cell. Micro fuel cells have long been recognized as promising high energy density power sources for portable applications. Many advances in micro fuel cell development have been made, ranging
Linear and nonlinear instability in vertical counter-current laminar gas-liquid flows
Schmidt, Patrick; Lucquiaud, Mathieu; Valluri, Prashant
2015-01-01
We consider the genesis and dynamics of interfacial instability in gas-liquid flows, using as a model the two-dimensional channel flow of a thin falling film sheared by counter-current gas. The methodology is linear stability theory (Orr-Sommerfeld analysis) together with direct numerical simulation of the two-phase flow in the case of nonlinear disturbances. We investigate the influence of three main flow parameters (density contrast between liquid and gas, film thickness, pressure drop applied to drive the gas stream) on the interfacial dynamics. Energy budget analyses based on the Orr-Sommerfeld theory reveal various coexisting unstable modes (interfacial, shear, internal) in the case of high density contrasts, which results in mode coalescence and mode competition, but only one dynamically relevant unstable internal mode for low density contrast. The same linear stability approach provides a quantitative prediction for the onset of (partial) liquid flow reversal in terms of the gas and liquid flow rates. ...
A new friction factor correlation for laminar, single-phase flows through rock fractures
Nazridoust, K. (Clarkson Univ., Potsdam, NY); Ahmadi, G. (Clarkson Univ., Potsdam, NY); Smith, D.H.
2006-09-30
Single-phase flow through fractured media occurs in various situations, such as transport of dissolved contaminants through geological strata, sequestration of carbon dioxide in depleted gas reservoirs, and in primary oil recovery. In the present study, fluid flows through a rock fracture were simulated. The fracture geometry was obtained from the CT scans of a rock fracture produced by the Brazilian method in a sandstone sample. A post-processing code using a CAD package was developed and used to generate the three-dimensional fracture from the CT scan data. Several sections along the fracture were considered and the GambitTM code was used to generate unstructured grids for flow simulations. FLUENTTM was used to analyze the flow conditions through the fracture section for different flow rates. Because of the small aperture of the fractures, the gravitational effects could be neglected. It was confirmed that the pressure drop was dominated by the smallest aperture passages of the fracture. The accuracy of parallel plate models for estimating the pressure drops through fractures was studied. It was shown that the parallel plate flow model with the use of an appropriate effective fracture aperture and inclusion of the tortuosity factor could provide reasonable estimates for pressure drops in the fracture. On the basis of the CFD simulation data, a new expression for the friction factor for flows through fractures was developed. The new model predictions were compared with the simulation results and favorable agreement was found. It was shown that when the length of the fracture and the mean and standard deviation of the fracture are known, the pressure loss as a function of the flow rate could be estimated. These findings may prove useful for design of lab experiments, computational studied of flows through real rock fractures, or inclusions in simulators for large-scale flows in highly fractured rocks.
Mikkelsen, Clark Douglas
1972-01-01
for the steady, isothermal, originally Poiseuillean flow of an incompressible, Newtonian fluid around a rigid sphere fixed on the axis of an infinitely-long, circular cylinder. Similarities in the flow fields of Cases 1 ~ 2, and 3 were indicated as were..., vorticity, and velocity fields for the steady, isothermal, originally Poiseuillean flow of an incompressible, Newtonian fluid around a rigid sphere f fixed on the axis of an infinitely-long, circular cylinder. t The above definitions for Case 1, 2, and 3...
Error estimation and anisotropic mesh refinement for 3d laminar aerodynamic flow simulations
Hartmann, Ralf
Leichta,b , Ralf Hartmann,a,b aInstitute of Aerodynamics and Flow Technology, DLR (German Aerospace Center.Leicht@dlr.de (Tobias Leicht), Ralf.Hartmann@dlr.de (Ralf Hartmann) Preprint submitted to Journal of Computational
Resistive MHD Simulations of Laminar Round Jets with Application to Magnetic Nozzle Flows
Araya, Daniel
2012-02-14
This thesis investigates fundamental flows of resistive magnetohydrodynamics (MHD) by a new numerical tool based on the gas-kinetic method. The motivation for this work stems from the need to analyze the mechanisms of plasma detachment...
Laminar and transitional liquid metal duct flow near a magnetic point dipole
Tympel, Saskia; Schumacher, Jörg
2013-01-01
The flow transformation and the generation of vortex structures by a strong magnetic dipole field in a liquid metal duct flow is studied by means of three-dimensional direct numerical simulations. The dipole is considered as the paradigm for a magnetic obstacle which will deviate the streamlines due to Lorentz forces acting on the fluid elements. The duct is of square cross-section. The dipole is located above the top wall and is centered in spanwise direction. Our model uses the quasi-static approximation which is applicable in the limit of small magnetic Reynolds numbers. The analysis covers the stationary flow regime at small hydrodynamic Reynolds numbers $Re$ as well as the transitional time-dependent regime at higher values which may generate a turbulent flow in the wake of the magnetic obstacle. We present a systematic study of these two basic flow regimes and their dependence on $Re$ and on the Hartmann number $Ha$, a measure of the strength of the magnetic dipole field. Furthermore, three orientations...
Pore-scale lattice Boltzmann simulation of laminar and turbulent flow through a sphere pack
Fattahia, Ehsan; Wohlmuth, Barbara; Rüde, Ulrich; Manhart, Michael; Helmig, Rainer
2015-01-01
The lattice Boltzmann method can be used to simulate flow through porous media with full geometrical resolution. With such a direct numerical simulation, it becomes possible to study fundamental effects which are difficult to assess either by developing macroscopic mathematical models or experiments. We first evaluate the lattice Boltzmann method with various boundary handling of the solid-wall and various collision operators to assess their suitability for large scale direct numerical simulation of porous media flow. A periodic pressure drop boundary condition is used to mimic the pressure driven flow through the simple sphere pack in a periodic domain. The evaluation of the method is done in the Darcy regime and the results are compared to a semi-analytic solution. Taking into account computational cost and accuracy, we choose the most efficient combination of the solid boundary condition and collision operator. We apply this method to perform simulations for a wide range of Reynolds numbers from Stokes flo...
Unsteady laminar pipe flow of a Carbopol gel. Part I: experiment
Antoine Poumaere; Miguel Moyers-Gonzalez; Cathy Castelain; Teodor Burghelea
2013-01-21
A experimental study of low Reynolds numbers unsteady pipe flows of a yield stress shear thinning fluid (Carbopol- 980) is presented. The investigation of the solid-fluid transition in a rheometric flow in the presence and in the ab- sence of the wall slip reveals a coupling between the irreversible deformation states and the wall slip phenomenon. Particularly, the presence of wall slip nearly suppresses the scaling of the deformation power deficit associated to the rheological hysteresis with the rate at which the material is forced. The irreversible solid-fluid transition and the wall slip behaviour emerge in the same range of the applied stresses and thus, the two phenomena appear to be coupled to each other. In-situ measurements of the flow fields performed during an increasing/decreasing stepped pressure ramp reveal three distinct flow regimes: solid (pluglike), solid-fluid and fluid. The deformation power deficit associated with the hysteresis observed during the increasing/decreasing branches of the pressure ramps reveals a dependence on the rate at which the unsteady flow is driven consistent with that observed during the rheological measurements in the presence of slip. The dependence of the slip velocity on the wall shear stresses reveals a Navier-type slip behaviour only within the fluid flow regime, which indicates that the wall slip phenomenon is directly coupled to the solid-fluid transition. A universal scaling of the slip velocity with the wall velocity gradients is found and the slip length is independent on the characteristic time of forcing t0. The paper closes with a discussion of the main findings, their possible impact on our current understanding of the yielding and slip behaviour of Carbopol gels. Several steps worth being pursued by future experimental/theoretical studies are proposed.
TURBULENT-LAMINAR PATTERNS IN PLANE COUETTE Dwight Barkley
Barkley, Dwight
@limsi.fr Abstract Regular patterns of turbulent and laminar fluid motion arise in plane Couette flow near the lowest and is the kinematic viscosity of the fluid. See figure 1. For all val- ues of ¡£¢ , laminar Couette flow at an angle to the streamwise direction. Fluid flows exhibiting coexisting turbulent and laminar regions have
Dynamical Instability of Laminar Axisymmetric Flow of Perfect Fluid with Stratification
V. V. Zhuravlev; N. I. Shakura
2007-09-12
The instability of non-homoentropic axisymmetric flow of perfect fluid with respect to non-axisymmetric infinitesimal perturbations was investigated by numerical integration of hydrodynamical differential equations in two-dimensional approximation. The non-trivial influence of entropy gradient on unstable sound and surface gravity waves was revealed. In particular, both decrease and growth of entropy against the direction of effective gravitational acceleration $g_{eff}$ give rise to growing surface gravity modes which are stable with the same parameters in the case of homoentropic flow. At the same time increment of sound modes either grows monotonically while the rate of entropy decrease against $g_{eff}$ gets higher or vanishes at some values of positive and negative entropy gradient in the basic flow. The calculations have showed also that growing internal gravity modes appear only in the flow unstable to axisymmetric perturbations. At last, the analysis of boundary problem with free boundaries uncovered that's incorrect to set the entropy distribution according to polytropic law with polytropic index different from adiabatic value, since in this case perturbations don't satisfy the free boundary conditions.
Potential Hydraulic Modelling Errors Associated with Rheological Data Extrapolation in Laminar Flow
Shadday, Martin A., Jr.
1997-03-20
The potential errors associated with the modelling of flows of non-Newtonian slurries through pipes, due to inadequate rheological models and extrapolation outside of the ranges of data bases, are demonstrated. The behaviors of both dilatant and pseudoplastic fluids with yield stresses, and the errors associated with treating them as Bingham plastics, are investigated.
Numerical simulation of laminar plasma dynamos in a cylindrical von K\\'arm\\'an flow
Khalzov, I V; Ebrahimi, F; Schnack, D D; Forest, C B; 10.1063/1.3559472
2011-01-01
The results of a numerical study of the magnetic dynamo effect in cylindrical von K\\'arm\\'an plasma flow are presented with parameters relevant to the Madison Plasma Couette Experiment. This experiment is designed to investigate a broad class of phenomena in flowing plasmas. In a plasma, the magnetic Prandtl number Pm can be of order unity (i.e., the fluid Reynolds number Re is comparable to the magnetic Reynolds number Rm). This is in contrast to liquid metal experiments, where Pm is small (so, Re>>Rm) and the flows are always turbulent. We explore dynamo action through simulations using the extended magnetohydrodynamic NIMROD code for an isothermal and compressible plasma model.We also study two-fluid effects in simulations by including the Hall term in Ohm's law. We find that the counter-rotating von K\\'arm\\'an flow results in sustained dynamo action and the self-generation of magnetic field when the magnetic Reynolds number exceeds a critical value. For the plasma parameters of the experiment, this field ...
CFD Investigations of a Transonic Swept-Wing Laminar Flow Control Flight Experiment
Neale, Tyler P.
2011-08-08
wing glove was identified. Next, a full CFD analysis of the aircraft was performed to determine any adverse effects on the wing flow-field from the aircraft engines. This required an accurate CAD model of the selected aircraft. Proper modeling...
Kuang, C.; Chen, M.; McMurry, P. H.; Wang, J.
2011-10-01
This paper describes simple modifications to thermally diffusive laminar flow ultrafine condensation particle counters (UCPCs) that allow detection of {approx}1 nm condensation nuclei with much higher efficiencies than have been previously reported. These nondestructive modifications were applied to a commercial butanol based UCPC (TSI 3025A) and to a diethylene glycol-based UCPC (UMN DEG-UCPC). Size and charge dependent detection efficiencies using the modified UCPCs (BNL 3025A and BNL DEGUCPC) were measured with high resolution mobility classified aerosols composed of NaCl, W, molecular ion standards of tetraalkyl ammonium bromide, and neutralizer-generated ions. With negatively charged NaCl aerosol, the BNL 3025A and BNL DEGUCPC achieved detection efficiencies of 37% (90x increase over TSI 3025A) at 1.68 nm mobility diameter (1.39 nm geometric diameter) and 23% (8x increase over UMN DEG-UCPC) at 1.19 nm mobility diameter (0.89 nm geometric diameter), respectively. Operating conditions for both UCPCs were identified that allowed negatively charged NaCl and W particles, but not negative ions of exactly the same mobility size, to be efficiently detected. This serendipitous material dependence, which is not fundamentally understood, suggests that vapor condensation might sometimes allow for the discrimination between air 'ions' and charged 'particles.' As a detector in a scanning mobility particle spectrometer (SMPS), a UCPC with this strong material dependence would allow for more accurate measurements of sub-2 nm aerosol size distributions due to the reduced interference from neutralizer-generated ions and atmospheric ions, and provide increased sensitivity for the determination of nucleation rates and initial particle growth rates.
Seshadri, K; Lu, T; Herbinet, O; Humer, S; Niemann, U; Pitz, W J; Law, C K
2008-01-09
Methyl decanoate is a large methyl ester that can be used as a surrogate for biodiesel. In this experimental and computational study, the combustion of methyl decanoate is investigated in nonpremixed, nonuniform flows. Experiments are performed employing the counterflow configuration with a fuel stream made up of vaporized methyl decanoate and nitrogen, and an oxidizer stream of air. The mass fraction of fuel in the fuel stream is measured as a function of the strain rate at extinction, and critical conditions of ignition are measured in terms of the temperature of the oxidizer stream as a function of the strain rate. It is not possible to use a fully detailed mechanism for methyl decanoate to simulate the counterflow flames because the number of species and reactions is too large to employ with current flame codes and computer resources. Therefore a skeletal mechanism was deduced from a detailed mechanism of 8555 elementary reactions and 3036 species using 'directed relation graph' method. This skeletal mechanism has only 713 elementary reactions and 125 species. Critical conditions of ignition were calculated using this skeletal mechanism and are found to agree well with experimental data. The predicted strain rate at extinction is found to be lower than the measurements. In general, the methyl decanoate mechanism provides a realistic kinetic tool for simulation of biodiesel fuels.
Fifteen Lectures on Laminar and Turbulent Combustion
Peters, Norbert
Fifteen Lectures on Laminar and Turbulent Combustion N. Peters RWTH Aachen Ercoftac Summer School in Combustion Systems 1 Lecture 2: Calculation of Adiabatic Flame Temperatures and Chemical Equilibria 20: Laminar Diffusion Flames: Different Flow Geometries 156 Lecture 11: Turbulent Combustion: Introduction
Su, Susan Shan
2007-01-01
suggesting that laminar fluid flow may deactivate the cellbe responsive to a laminar fluid flow field, few have beencell response to laminar fluid flow the roundness ratio (see
Eiamsa-ard, Smith [Department of Mechanical Engineering, Faculty of Engineering, Mahanakorn University of Technology, Bangkok 10530 (Thailand); Seemawute, Panida [Department of Civil Engineering, Faculty of Engineering, Mahanakorn University of Technology, Bangkok 10530 (Thailand); Wongcharee, Khwanchit [Department of Chemical Engineering, Faculty of Engineering, Mahanakorn University of Technology, Bangkok 10530 (Thailand)
2010-09-15
Effects of peripherally-cut twisted tape insert on heat transfer, friction loss and thermal performance factor characteristics in a round tube were investigated. Nine different peripherally-cut twisted tapes with constant twist ratio (y/W = 3.0) and different three tape depth ratios (DR = d/W = 0.11, 0.22 and 0.33), each with three different tape width ratios (WR = w/W = 0.11, 0.22 and 0.33) were tested. Besides, one typical twisted tape was also tested for comparison. The measurement of heat transfer rate was conducted under uniform heat flux condition while that of friction factor was performed under isothermal condition. Tests were performed with Reynolds number in a range from 1000 to 20,000, using water as a working fluid. The experimental results revealed that both heat transfer rate and friction factor in the tube equipped with the peripherally-cut twisted tapes were significantly higher than those in the tube fitted with the typical twisted tape and plain tube, especially in the laminar flow regime. The higher turbulence intensity of fluid in the vicinity of the tube wall generated by the peripherally-cut twisted tape compared to that induced by the typical twisted tape is referred as the main reason for achieved results. The obtained results also demonstrated that as the depth ratio increased and width ratio decreased, the heat transfer enhancement increased. Over the range investigated, the peripherally-cut twisted tape enhanced heat transfer rates in term of Nusselt numbers up to 2.6 times (turbulent regime) and 12.8 times (laminar regime) of that in the plain tube. These corresponded to the maximum performance factors of 1.29 (turbulent regime) and 4.88 (laminar regime). (author)
McKinley, Kathryn S.
Control Using Laminar 1 DONALD E. PORTER, Stony Brook University 2 MICHAEL D. BOND, Ohio State University. This article describes Laminar, the first 12 system to implement DIFC using a unified set of abstractions with secrecy and integrity labels and access the 14 labeled data in security methods. Laminar enforces
A New Hybrid Redox Flow Battery with Multiple Redox Couples
Wang, Wei; Li, Liyu; Nie, Zimin; Chen, Baowei; Luo, Qingtao; Shao, Yuyan; Wei, Xiaoliang; Chen, Feng; Xia, Guanguang; Yang, Zhenguo
2012-05-19
A redox flow battery using V{sup 4+}/V{sup 5+} vs. V{sup 2+}/V{sup 3+} and Fe{sup 2+}/Fe{sup 3+} vs. V{sup 2+}/V{sup 3+} redox couples in chloric/sulphuric mixed acid supporting electrolyte was investigated for potential stationary energy storage applications. The Fe/V hybrid redox flow cell using mixed reactant solutions operated within a voltage window of 0.5-1.7 V demonstrated stable cycling over 100 cycles with energy efficiency {approx}80% and no capacity fading at room temperature. A 66% improvement in the energy density of the Fe/V hybrid cell was achieved compared with the previous reported Fe/V cell using only Fe{sup 2+}/Fe{sup 3+} vs. V{sup 2+}/V{sup 3+} redox couples.
Efficient numerical methods for the instationary solution of laminar reacting gas
Vuik, Kees
Efficient numerical methods for the instationary solution of laminar reacting gas flow problems Universiteit Delft Efficient numerical methods for the instationary solution of laminar reacting gas flow of laminar reacting gas flow problems Sander van Veldhuizen Production processes of high-purity, high
Preconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda
Zhang, Jun
kinetics models or turbulent reacting flows. In this work we are interested in a simple model of laminar structure more accurately, we use the vorticityvelocity formulation of the fluid flow equations [1, 3Preconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda Samir Karaa
Rothstein, Jonathan
Laminar drag reduction in microchannels using ultrahydrophobic surfaces Jia Ou, Blair Perot for the laminar flow of water through microchannels using hydrophobic surfaces with well-defined micron flow is laminar and not turbulent, there are currently few demon- strated methods for significantly
The effects of laminar mixing on reaction fronts and patterns I. Introduction
Solomon, Tom
The effects of laminar mixing on reaction fronts and patterns I. Introduction A wide variety scales that are often smaller than a micron. For small Re, the flow is laminar; in this situation
Sivashanmugam, P.; Suresh, S. [Department of Chemical Engineering, National Institute of Technology, Tiruchirappalli 620 015, Tamil Nadu (India)
2007-02-15
Experimental investigation of heat transfer and friction factor characteristics of circular tube fitted with full-length helical screw element of different twist ratio, and helical screw inserts with spacer length 100, 200, 300 and 400mm have been studied with uniform heat flux under laminar flow condition. The experimental data obtained are verified with those obtained from plain tube published data. The effect of spacer length on heat transfer augmentation and friction factor, and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The decrease in Nusselt number for the helical twist with spacer length is within 10% for each subsequent 100mm increase in spacer length. The decrease in friction factor is nearly two times lower than the full length helical twist at low Reynolds number, and four times lower than the full length helical twist at high Reynolds number for all twist ratio. The regularly spaced helical screw inserts can safely be used for heat transfer augmentation without much increase in pressure drop than full length helical screw inserts. (author)
Hybrid Wind Power Balance Control Strategy using Thermal Power, Hydro Power and Flow Batteries
MacDonald, Mark
Hybrid Wind Power Balance Control Strategy using Thermal Power, Hydro Power and Flow Batteries the con- trolled use of hybrid flow battery, thermal and hydro power plant system, to support wind power on range of thermal and hydro power plant reaction times. This work suggests that power and energy
Chen, Binjiao; Wang, Xin; Zeng, Ruolang; Zhang, Yinping; Di, Hongfa [Department of Building Science, Tsinghua University, Beijing 100084 (China); Wang, Xichun; Niu, Jianlei [Department of Building Service Engineering, The Hong Kong Polytechnic University, Hong Kong (China); Li, Yi [Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong (China)
2008-09-15
By contrast with the conventional heat transfer fluid (water), the microencapsulated phase change material (MPCM) suspension, with a small temperature difference between storing and releasing heat, is of much larger apparent specific heat and much higher thermal energy storage capacity. It has been suggested to serve as a dual-functional medium for thermal energy transport and/or storage. The heat transfer characteristics of a kind of MPCM suspension, formed by microencapsulating industrial-grade 1-bromohexadecane (C{sub 16}H{sub 33}Br) as phase change material, were experimentally studied for laminar flow in a circular tube under constant heat flux. A new expression of Ste is put forward in the paper, according to the physical definition of Stefan number. The results in the experiments show: (a) the dimensionless internal wall temperature of the MPCM suspension is lower than pure water, and the decrease can be up to 30% of that of water; (b) the heat transfer enhancement ratio can be 1.42 times of that of water at x{sup +} = 4.2 x 10{sup -2} for 15.8 wt% MPCM suspension, which is not as much as in some references; and (c) the pump consumption of the MPCM suspension system decrease greatly for the larger heat transfer rate compared with water, due to phase change, the decrease can be up to 67.5% of that of water at q = 750 W (15.8 wt%). The kind of MPCM suspension has good application feasibility in practice. (author)
PERSISTENTLY LAMINAR TANGLES MARK BRITTENHAM
Brittenham, Mark
PERSISTENTLY LAMINAR TANGLES MARK BRITTENHAM University of North Texas Department of Mathematics laminar. Being persisently laminar immediately implies, for example that every knot K obtained by tangle be generalized to provide many more examples of persistently laminar tangles. 1. The lamination Oertel
PERSISTENTLY LAMINAR TANGLES MARK BRITTENHAM
Brittenham, Mark
PERSISTENTLY LAMINAR TANGLES MARK BRITTENHAM University of North Texas Department of Mathematics is persistent for K. We call such a tangle persistently laminar. Being persisently laminar immediately implies that the construction of the lamination L #12;can be generalized to provide many more examples of persistently laminar
Natural versus forced convection in laminar starting plumes Michael C. Rogers and Stephen W. Morris
Morris, Stephen W.
fluid from a small, submerged outlet. The plumes were laminar and spanned a wide range of plume, the most important fac- tor determining jet or plume behaviour and evolution is whether the flow is laminar orNatural versus forced convection in laminar starting plumes Michael C. Rogers and Stephen W. Morris
Soot formation in high pressure laminar diffusion flames Ahmet E. Karatas *, mer L. Glder
Gülder, Ömer L.
Review Soot formation in high pressure laminar diffusion flames Ahmet E. Karatas¸ *, Ömer L. Gülder online 30 June 2012 Keywords: High pressure soot formation High pressure combustion Laminar diffusion laminar co-flow diffusion flames burning at elevated pressures. First, a brief review of soot formation
Structure of Laminar Sooting Inverse Diffusion Flames
Mikofski, Mark A
2007-01-01
Combust. Structure of Laminar Sooting Inverse Diffusion2002, p. 252. Structure of Laminar Sooting Inverse Diffusion219-226. Structure of Laminar Sooting Inverse Diffusion
The effects of surface instabilities on laminar film condensation
Gerstmann, Joseph
1965-01-01
Heat transfer rates for laminar film condensation of Freon-1l3 were measured on the underside of horizontal surfaces, inclined surfaces, and vertical surfaces. Several distinct regimes of flow were observed. On the underside ...
Aalborg Universitet Power flow analysis for droop controlled LV hybrid AC-DC microgrids with virtual
Vasquez, Juan Carlos
Aalborg Universitet Power flow analysis for droop controlled LV hybrid AC-DC microgrids controlled LV hybrid AC-DC microgrids with virtual impedance. In Proceedings of the IEEE Power & Energy Interlinking converter PV WT IBS DC microgrid DC microgrid AC microgrid AC Load Figure 1. Structure
Analysis of the laminar flamelet concept for nonpremixed laminar flames
Claramunt, K.; Consul, R.; Carbonell, D.; Perez-Segarra, C.D.
2006-06-15
The goal of this paper is to investigate the application of the laminar flamelet concept to the multidimensional numerical simulation of nonpremixed laminar flames. The performance of steady and unsteady flamelets is analyzed. The deduction of the mathematical formulation of flamelet modeling is exposed and some commonly used simplifications are examined. Different models for the scalar dissipation rate dependence on the mixture fraction variable are analyzed. Moreover, different criteria to evaluate the Lagrangian-type flamelet lifetime for unsteady flamelets are investigated. Inclusion of phenomena such as differential diffusion with constant Lewis number for each species and radiation heat transfer are also studied. A confined co-flow axisymmetric nonpremixed methane/air laminar flame experimentally investigated by McEnally and Pfefferle (Combust. Sci. Technol. 116-117 (1996) 183-209) and numerically investigated by Bennett, McEnally, Pfefferle, and Smooke (Combust. Flame 123 (2000) 522-546), Consul, Perez-Segarra, Claramunt, Cadafalch, and Oliva (Combust. Theory Modelling 7 (3) (2003) 525-544), and Claramunt, Consul, Perez-Segarra, and Oliva (Combust. Flame 137 (2004) 444-457) has been used as a test case. Results obtained using the flamelet concept have been compared to data obtained from the full resolution of the complete transport equations using primitive variables. Finite-volume techniques over staggered grids are used to discretize the governing equations. A parallel multiblock algorithm based on domain decomposition techniques running with loosely coupled computers has been used. To assess the quality of the numerical solutions presented in this paper, a verification process based on the generalized Richardson extrapolation technique and on the grid convergence index (GCI) has been applied. (author)
GAS-PARTICLE FLOW IN THE ENTRY REGION OF A CURVED PIPE
Yeung, Woon-Shing
2011-01-01
=Equilibrium Fluid Dynamics-«Laminar Flow ?ver a Flat Plate.fluid is assumed to be incompressible and the flow nonseparating and laminar.
Gülder, Ömer L.
Formation of Liquid Methane-Water Mixture during Combustion of a Laminar Methane Jet in laminar jet flames of methane at elevated pressures in a high-pressure combustion chamber, we have MPa, after the laminar methane jet flame had been stabilized on a co-flow circular nozzle-type burner
Soot formation in laminar ethane diffusion flames at pressures from 0.2 to 3.3 MPa
Gülder, Ömer L.
Soot formation in laminar ethane diffusion flames at pressures from 0.2 to 3.3 MPa Paul M formation and the structure of the temperature field were studied in co-flow ethane-air laminar diffusion; Laminar ethane diffusion flame; Pressure depen- dence of soot formation; Temperature of high
Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow
Marchese, Francis
Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow Flow
Flow visualisation in inclined louvered fins
T'Joen, C.; De Paepe, M. [Department of Flow, Heat and Combustion Mechanics, Ghent University-UGent, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); Jacobi, A. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801 (United States)
2009-04-15
In this study the flow within an interrupted fin design, the inclined louvered fin, is investigated experimentally through visualisation. The inclined louvered fin is a hybrid of the offset strip fin and standard louvered fin, aimed at improved performance at low Reynolds numbers for compact heat exchangers. The flow behaviour is studied in six geometrically different configurations over a range of Reynolds numbers and quantified using the concept of 'fin angle alignment factor'. The transition from steady laminar to unsteady flow was studied in detail. The fin geometry had a very large impact on the transitional flow behaviour, especially on vortex shedding. (author)
Chandrasekar, M.; Suresh, S. [Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli 620015 (India); Chandra Bose, A. [Nanomaterials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli 620015 (India)
2010-02-15
In this paper, fully developed laminar flow convective heat transfer and friction factor characteristics of Al{sub 2}O{sub 3}/water nanofluid flowing through a uniformly heated horizontal tube with and without wire coil inserts is presented. For this purpose, Al{sub 2}O{sub 3} nanoparticles of 43 nm size were synthesized, characterized and dispersed in distilled water to form stable suspension containing 0.1% volume concentration of nanoparticles. The Nusselt number in the fully developed region were measured and found to increase by 12.24% at Re = 2275 for plain tube with nanofluid compared to distilled water. Two wire coil inserts made of stainless steel with pitch ratios 2 and 3 were used which increased the Nusselt numbers by 15.91% and 21.53% respectively at Re = 2275 with nanofluid compared to distilled water. The better heat transfer performance of nanofluid with wire coil insert is attributed to the effects of dispersion or back-mixing which flattens the temperature distribution and make the temperature gradient between the fluid and wall steeper. The measured pressure loss with the use of nanofluids is almost equal to that of the distilled water. The empirical correlations developed for Nusselt number and friction factor in terms of Reynolds/Peclet number, pitch ratio and volume concentration fits with the experimental data within {+-}15%. (author)
A LEAN METHANE PREMIXED LAMINAR FLAME DOPED WITH COMPONENTS OF DIESEL FUEL
Boyer, Edmond
A LEAN METHANE PREMIXED LAMINAR FLAME DOPED WITH COMPONENTS OF DIESEL FUEL PART I: N-BUTYLBENZENE E better understand the chemistry involved during the combustion of components of diesel fuel flow rate analyses. Keywords: Premixed laminar flame, methane, n-butylbenzene, modelling, diesel fuel
Impinging laminar jets at moderate Reynolds numbers and separation distances Jeffrey M. Bergthorson,
Impinging laminar jets at moderate Reynolds numbers and separation distances Jeffrey M. Bergthorson an experimental and numerical study of impinging, incompressible, axisym- metric, laminar jets, where the jet axis velocities along the centerline of the flow field. The jet-nozzle pressure drop is measured simultaneously
A Hybrid Multiscale Framework for Subsurface Flow and Transport Simulations
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Scheibe, Timothy D.; Yang, Xiaofan; Chen, Xingyuan; Hammond, Glenn E.
2015-06-01
Extensive research efforts have been invested in reducing model errors to improve the predictive ability of biogeochemical earth and environmental system simulators, with applications ranging from contaminant transport and remediation to impacts of biogeochemical elemental cycling (e.g., carbon and nitrogen) on local ecosystems and regional to global climate. While the bulk of this research has focused on improving model parameterizations in the face of observational limitations, the more challenging type of model error/uncertainty to identify and quantify is model structural error which arises from incorrect mathematical representations of (or failure to consider) important physical, chemical, or biological processes, properties, ormore »system states in model formulations. While improved process understanding can be achieved through scientific study, such understanding is usually developed at small scales. Process-based numerical models are typically designed for a particular characteristic length and time scale. For application-relevant scales, it is generally necessary to introduce approximations and empirical parameterizations to describe complex systems or processes. This single-scale approach has been the best available to date because of limited understanding of process coupling combined with practical limitations on system characterization and computation. While computational power is increasing significantly and our understanding of biological and environmental processes at fundamental scales is accelerating, using this information to advance our knowledge of the larger system behavior requires the development of multiscale simulators. Accordingly there has been much recent interest in novel multiscale methods in which microscale and macroscale models are explicitly coupled in a single hybrid multiscale simulation. A limited number of hybrid multiscale simulations have been developed for biogeochemical earth systems, but they mostly utilize application-specific and sometimes ad-hoc approaches for model coupling. We are developing a generalized approach to hierarchical model coupling designed for high-performance computational systems, based on the Swift computing workflow framework. In this presentation we will describe the generalized approach and provide two use cases: 1) simulation of a mixing-controlled biogeochemical reaction coupling pore- and continuum-scale models, and 2) simulation of biogeochemical impacts of groundwater – river water interactions coupling fine- and coarse-grid model representations. This generalized framework can be customized for use with any pair of linked models (microscale and macroscale) with minimal intrusiveness to the at-scale simulators. It combines a set of python scripts with the Swift workflow environment to execute a complex multiscale simulation utilizing an approach similar to the well-known Heterogeneous Multiscale Method. User customization is facilitated through user-provided input and output file templates and processing function scripts, and execution within a high-performance computing environment is handled by Swift, such that minimal to no user modification of at-scale codes is required.« less
A Hybrid Multiscale Framework for Subsurface Flow and Transport Simulations
Scheibe, Timothy D.; Yang, Xiaofan; Chen, Xingyuan; Hammond, Glenn E.
2015-01-01
Extensive research efforts have been invested in reducing model errors to improve the predictive ability of biogeochemical earth and environmental system simulators, with applications ranging from contaminant transport and remediation to impacts of biogeochemical elemental cycling (e.g., carbon and nitrogen) on local ecosystems and regional to global climate. While the bulk of this research has focused on improving model parameterizations in the face of observational limitations, the more challenging type of model error/uncertainty to identify and quantify is model structural error which arises from incorrect mathematical representations of (or failure to consider) important physical, chemical, or biological processes, properties, or system states in model formulations. While improved process understanding can be achieved through scientific study, such understanding is usually developed at small scales. Process-based numerical models are typically designed for a particular characteristic length and time scale. For application-relevant scales, it is generally necessary to introduce approximations and empirical parameterizations to describe complex systems or processes. This single-scale approach has been the best available to date because of limited understanding of process coupling combined with practical limitations on system characterization and computation. While computational power is increasing significantly and our understanding of biological and environmental processes at fundamental scales is accelerating, using this information to advance our knowledge of the larger system behavior requires the development of multiscale simulators. Accordingly there has been much recent interest in novel multiscale methods in which microscale and macroscale models are explicitly coupled in a single hybrid multiscale simulation. A limited number of hybrid multiscale simulations have been developed for biogeochemical earth systems, but they mostly utilize application-specific and sometimes ad-hoc approaches for model coupling. We are developing a generalized approach to hierarchical model coupling designed for high-performance computational systems, based on the Swift computing workflow framework. In this presentation we will describe the generalized approach and provide two use cases: 1) simulation of a mixing-controlled biogeochemical reaction coupling pore- and continuum-scale models, and 2) simulation of biogeochemical impacts of groundwater – river water interactions coupling fine- and coarse-grid model representations. This generalized framework can be customized for use with any pair of linked models (microscale and macroscale) with minimal intrusiveness to the at-scale simulators. It combines a set of python scripts with the Swift workflow environment to execute a complex multiscale simulation utilizing an approach similar to the well-known Heterogeneous Multiscale Method. User customization is facilitated through user-provided input and output file templates and processing function scripts, and execution within a high-performance computing environment is handled by Swift, such that minimal to no user modification of at-scale codes is required.
Moses, Elisha
The Dynamics and Interaction of Laminar Thermal Plumes This article has been downloaded from LETTERS Europhys. Lett., 14-(1))pp. 55-60 (1991) 1 January 1991 The Dynamics and Interaction of Laminar tension, capillarity, PACS. 47.25Q- Convection and heat transfer. PACS. 47.15 - Laminar flows (inc
Clement, Prabhakar
Pipe Flow System Design Holly Guest #12;Problem · An engineer is asked to compute the flow rate · Flow type: Turbulent or Laminar flow · Flow rate · Frictional head loss · Optimal diameters if a pump · = - ( . + . ) · f = friction factor · = relative roughness = · = Reynolds Number = · Laminar flow: 2000
Flame Height Measurement of Laminar Inverse Diffusion Flames
Mikofski, Mark A.; Williams, Timothy C.; Shaddix, Christopher R.; Blevins, Linda G.
2006-01-01
Flame Height Measurement of Laminar Inverse Diffusion Flamesinverse diffusion flame, laminar, flame height, OH, laserair and methane-air laminar inverse diffusion flames were
Laminar circuit organization and response modulation in mouse visual cortex
Olivas, Nicholas D; Quintanar-Zilinskas, Victor; Nenadic, Zoran; Xu, Xiangmin
2012-01-01
Callaway, E. M. (2000). Laminar sources of synap- tic inputSvoboda, K. , et al. (2011). Laminar analysis of excitatoryand Svoboda, K. (2005). Laminar and columnar organization of
Numerical Methods for Incompressible Viscous Flow
Frey, Pascal
. The simplest viscous flow problems involve just one fluid in the laminar regime. The governing equations in nature and technological devices are turbulent. The tran- sition from laminar to turbulent flow phenomena, laminar or turbulent viscous flow is coupled with other processes, such as heat tra
Dynamics on the Laminar-Turbulent Boundary and the Origin of the Maximum Drag Reduction Asymptote
Graham, Michael D.
Dynamical trajectories on the boundary in state space between laminar and turbulent plane channel flow—edge states—are computed for Newtonian and viscoelastic fluids. Viscoelasticity has a negligible effect on the properties ...
Elsheikh, Ahmed H., E-mail: aelsheikh@ices.utexas.edu [Institute for Computational Engineering and Sciences (ICES), University of Texas at Austin, TX (United States); Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Wheeler, Mary F. [Institute for Computational Engineering and Sciences (ICES), University of Texas at Austin, TX (United States)] [Institute for Computational Engineering and Sciences (ICES), University of Texas at Austin, TX (United States); Hoteit, Ibrahim [Department of Earth Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia)] [Department of Earth Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia)
2014-02-01
A Hybrid Nested Sampling (HNS) algorithm is proposed for efficient Bayesian model calibration and prior model selection. The proposed algorithm combines, Nested Sampling (NS) algorithm, Hybrid Monte Carlo (HMC) sampling and gradient estimation using Stochastic Ensemble Method (SEM). NS is an efficient sampling algorithm that can be used for Bayesian calibration and estimating the Bayesian evidence for prior model selection. Nested sampling has the advantage of computational feasibility. Within the nested sampling algorithm, a constrained sampling step is performed. For this step, we utilize HMC to reduce the correlation between successive sampled states. HMC relies on the gradient of the logarithm of the posterior distribution, which we estimate using a stochastic ensemble method based on an ensemble of directional derivatives. SEM only requires forward model runs and the simulator is then used as a black box and no adjoint code is needed. The developed HNS algorithm is successfully applied for Bayesian calibration and prior model selection of several nonlinear subsurface flow problems.
Instability 1) All flows become unstable above a certain Reynolds number.
Weijgaert, Rien van de
show flow in a boundary layer · Below Recrit the flow is laminar and adjacent fluid layers side past) At low Reynolds numbers flows are laminar. 3) For high Reynolds numbers flows are turbulent. 4) The transition occurs anywhere between R ~ 2000 and 106 , depending on the flow. 5) For laminar flow problems
Instability 1) All flows become unstable above a certain Reynolds number.
Weijgaert, Rien van de
· Photographs show flow in a boundary layer · Below Recrit the flow is laminar and adjacent fluid layers side) At low Reynolds numbers flows are laminar. 3) For high Reynolds numbers flows are turbulent. 4) The transition occurs anywhere between R ~ 2000 and 106 , depending on the flow. 5) For laminar flow problems
NEUROSYSTEMS Functional and laminar dissociations between muscarinic
NEUROSYSTEMS Functional and laminar dissociations between muscarinic and nicotinic cholinergic was already greatest in the absence of pharmacological stimulation. Our results indicate that laminar position of receptors across the six layers of cortex, stimulating nAChR and mAChR with laminar specificity might offer
Room Temperature, Hybrid Sodium-Based Flow Batteries with Multi-Electron Transfer Redox Reactions
Shamie, Jack S.; Liu, Caihong; Shaw, Leon L.; Sprenkle, Vincent L.
2015-06-11
We introduce a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane for grid-scale energy storage. Such HNFBs can operate at ambient temperature, allow catholytes to have multiple electron transfer redox reactions per active ion, offer wide selection of catholyte chemistries with multiple active ions to couple with the highly negative Na alloy anode, and enable the use of both aqueous and non-aqueous catholytes. Further, the molten Na alloy anode permits the decoupled design of power and energy since a large volume of the molten Na alloy can be used with a limited ion-exchange membrane size. In this proof-of-concept study, the feasibility of multielectron transfer redox reactions per active ion and multiple active ions for catholytes has been demonstrated. The critical barriers to mature this new HNFBs have also been explored.
Hopf bifurcations to quasi-periodic solutions for the two-dimensional plane Poiseuille flow
Barcelona, Universitat de
the branch of periodic flows which are born at the Hopf bifurcation of the laminar flow. It is known that topics in fluid mechanics. Poiseuille as well as Taylor Couette flow are test problems where of their geometry. The dynamics of plane Poiseuille flow departs from the laminar flow. The stability of the laminar
A hybrid stochastic-deconvolution model for large-eddy simulation of particle-laden flow
Micha?ek, W. R., E-mail: w.michalek@tue.nl [Department of Mechanical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Kuerten, J. G. M. [Department of Mechanical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands) [Department of Mechanical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Faculty EEMCS, University of Twente, 7500 AE Enschede (Netherlands); Zeegers, J. C. H.; Liew, R. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)] [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Pozorski, J. [Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Gdansk (Poland)] [Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Gdansk (Poland); Geurts, B. J. [Faculty EEMCS, University of Twente, 7500 AE Enschede (Netherlands) [Faculty EEMCS, University of Twente, 7500 AE Enschede (Netherlands); Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)
2013-12-15
We develop a hybrid model for large-eddy simulation of particle-laden turbulent flow, which is a combination of the approximate deconvolution model for the resolved scales and a stochastic model for the sub-grid scales. The stochastic model incorporates a priori results of direct numerical simulation of turbulent channel flow, which showed that the parameters in the stochastic model are quite independent of Reynolds and Stokes number. In order to correctly predict the flux of particles towards the walls an extra term should be included in the stochastic model, which corresponds to the term related to the well-mixed condition in Langevin models for particle dispersion in inhomogeneous turbulent flow. The model predictions are compared with results of direct numerical simulation of channel flow at a frictional Reynolds number of 950. The inclusion of the stochastic forcing is shown to yield a significant improvement over the approximate deconvolution model for the particles alone when combined with a Stokes dependent weight-factor for the well-mixed term.
Kandlikar, Satish
, the effect of structured roughness elements on incompress- ible laminar fluid flow is analyzedA numerical study on the effects of 2d structured sinusoidal elements on fluid flow and heat flow Structured roughness elements Laminar flow a b s t r a c t Better understanding of laminar flow
Cirpka, Olaf Arie
allows the coupling of a laminar single-phase free flow and a two-phase porous-medium flow under non be necessary Coupling Situation coupling exists for laminar free flow (Mostaf et al. 2011) boundary layer DuMux in use for Darcy flow and laminar Stokes flow no RANS solver in DuMux or DUNE PDELab Open
Cheng, Wai K.
The effects of charge motion and laminar flame speeds on combustion and exhaust temperature have been studied by using an air jet in the intake flow to produce an adjustable swirl or tumble motion, and by replacing the ...
Room Temperature, Hybrid Sodium-Based Flow Batteries with Multi-Electron Transfer Redox Reactions
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Shamie, Jack S.; Liu, Caihong; Shaw, Leon L.; Sprenkle, Vincent L.
2015-06-11
We introduce a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane for grid-scale energy storage. Such HNFBs can operate at ambient temperature, allow catholytes to have multiple electron transfer redox reactions per active ion, offer wide selection of catholyte chemistries with multiple active ions to couple with the highly negative Na alloy anode, and enable the use of both aqueous and non-aqueous catholytes. Further, the molten Na alloy anode permits the decoupled design of power and energy since a large volumemore »of the molten Na alloy can be used with a limited ion-exchange membrane size. In this proof-of-concept study, the feasibility of multielectron transfer redox reactions per active ion and multiple active ions for catholytes has been demonstrated. The critical barriers to mature this new HNFBs have also been explored.« less
Research Report Spikes, synchrony, and attentive learning by laminar
Rucci, Michele
Research Report Spikes, synchrony, and attentive learning by laminar thalamocortical circuits dynamics, spike-timing-dependent plasticity (STDP), and acetylcholine modulation; detailed laminar thalamic and beta frequency domains. In particular, the model predicts how laminar circuits of multiple cortical
DEPARTMENT OF ENGINEERING SCIENCE High Pressure Laminar Burning
DEPARTMENT OF ENGINEERING SCIENCE High Pressure Laminar Burning Velocity Measurements S. P data Cellularity Real residuals Results Future plans High Pressure Laminar Burning Velocity temperature 725 K High Pressure Laminar Burning Velocity Measurements October 27, 2008 Page 3 #12;System
Power law and composite power law friction factor correlations for laminar and turbulent gasliquid
Joseph, Daniel D.
new unpublished, and data for gas and heavy oil from PDVSA-Intevep. Dimensionless pressure gradients oil are compiled and processed for power law and composite power law friction factor correlations reduce to the power laws for laminar flow when the Reynolds number is low and to turbulent flow when
Kallinderis, Yannis; Vitsas, Panagiotis A.; Menounou, Penelope
2012-07-15
A low-order flow/acoustics interaction method for the prediction of sound propagation and diffraction in unsteady subsonic compressible flow using adaptive 3-D hybrid grids is investigated. The total field is decomposed into the flow field described by the Euler equations, and the acoustics part described by the Nonlinear Perturbation Equations. The method is shown capable of predicting monopole sound propagation, while employment of acoustics-guided adapted grid refinement improves the accuracy of capturing the acoustic field. Interaction of sound with solid boundaries is also examined in terms of reflection, and diffraction. Sound propagation through an unsteady flow field is examined using static and dynamic flow/acoustics coupling demonstrating the importance of the latter.
Methods for Numerical Flow Simulation Rolf Rannacher
models of laminar hemodynamical flows. We discuss space and time dis- cretization with emphasis as flow control and model calibration. We concen- trate on laminar flows in which all relevant spatial-Stokes equations The continuum mechanical model of the flow of a viscous Newtonian fluid is the system
Chaotic self-sustaining structure embeded in turbulent-laminar interface
Teramura, Toshiki
2015-01-01
An iterface structure between turbulence and laminar flow is investigated in two-dimensional channel flow. This spatially localized structure not only sustains itself, but also converts laminar state into turbulence actively. In other words, this coherent structure has a functionality to generate inhomogeneity by its inner dynamics. The dynamics of this functional coherent structure is isolated using the filtered simulation, and a physical perspective of its dynamics is summarized in a phenomenological model called an "ejection-jet" cycle, which includes multiscale interaction process.
Chaotic self-sustaining structure embeded in turbulent-laminar interface
Toshiki Teramura; Sadayoshi Toh
2015-03-16
An iterface structure between turbulence and laminar flow is investigated in two-dimensional channel flow. This spatially localized structure not only sustains itself, but also converts laminar state into turbulence actively. In other words, this coherent structure has a functionality to generate inhomogeneity by its inner dynamics. The dynamics of this functional coherent structure is isolated using the filtered simulation, and a physical perspective of its dynamics is summarized in a phenomenological model called an "ejection-jet" cycle, which includes multiscale interaction process.
Development of a diffraction imaging flow cytometer
, of the laminar flow and the sheath fluid usually has a large curvature and refrac- tive index difference. Often morphology of a particle. We present a jet-in-fluid design of flow chamber for acquisition of clear diffraction images in a laminar flow. Diffraction images of polystyrene spheres of different diameters were
Hybrid models of transport in crowded environments
Battiato, Ilenia
2010-01-01
6.2.5 Hybrid algorithm . . . . . . . . . . . . . . .88 Chapter 5 Hybrid Model for Reactive Flow in a5.3.1 Hybrid validation . . . . . . . . . . . . . . . vii
Solution of Laminar Diffusion Flames Using a Parallel Adaptive Mesh Refinement Algorithm
Groth, Clinton P. T.
scheme to resolve fine-scale features of laminar flames is demonstrated. I. Introduction Combustion associated with our understanding of and ability to predict combustion phenomena. Over the last 10-15 years, the application of computational fluid dynamics (CFD) methods to reactive flows has yielded an improved
Roles for Wnts and their receptors in topographic mapping and laminar termination
Richman, Alisha
2011-01-01
Zhang Y, Meister M, Sanes JR. Laminar restriction of retinalsemaphorin signaling controls laminar stratification in thesignaling in tectal laminar formation. CSH Meeting on Axon
Wesfreid, José Eduardo
2013-01-01
, but of an assemblage of small-scale longitudinal vortices, separated from laminar flow by sharp fronts. For reviews undisturbed stable laminar Poiseuille flow up to Re = 5772 (Orszag 1971), but experiments show transition, surrounded by laminar ones. The inhomogeneity of flow friction generates a coupling between
Laminar flame speeds of moist syngas mixtures
Das, Apurba K. [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States); Kumar, Kamal; Sung, Chih-Jen [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)
2011-02-15
This work experimentally investigates the effect of the presence of water vapor on the laminar flame speeds of moist syngas/air mixtures using the counterflow twin-flame configuration. The experimental results presented here are for fuel lean syngas mixtures with molar percentage of hydrogen in the hydrogen and carbon monoxide mixture varying from 5% to 100%, for an unburned mixture temperature of 323 K, and under atmospheric pressure. At a given equivalence ratio, the effect of varying amount of water vapor addition on the measured laminar flame speed is demonstrated. The experimental laminar flame speeds are also compared with computed values using chemical kinetic mechanisms reported in the literature. It is found that laminar flame speed varies non-monotonically with addition of water for the carbon monoxide rich mixtures. It first increases with increasing amount of water addition, reaches a maximum value, and then decreases. An integrated reaction path analysis is further conducted to understand the controlling mechanism responsible for the non-monotonic variation in laminar flame speed due to water addition. On the other hand, for higher values of H{sub 2}/CO ratio the laminar flame speed monotonically decreases with increasing water addition. It is shown that the competition between the chemical and thermal effects of water addition leads to the observed response. Furthermore, reaction rate sensitivity analysis as well as binary diffusion coefficient sensitivity analysis are conducted to identify the possible sources of discrepancy between the experimental and predicted values. The sensitivity results indicate that the reaction rate constant of H{sub 2}+OH = H{sub 2}O+H is worth revisiting and refinement of binary diffusion coefficient data of N{sub 2}-H{sub 2}O, N{sub 2}-H{sub 2}, and H{sub 2}-H{sub 2}O pairs can be considered. (author)
Meseguer, Alvaro
or intermittency, i.e., spatiotemporal coexistence between laminar and turbulent regions in a fluid flow. Ca laminar flows have also been identified. DOI: 10.1103/PhysRevE.80.046315 PACS number s : 47.20.Lz, 47 explanation of the mecha- nisms that mediate between laminar and fully disordered fluid motion. One
The Timetable of Laminar Neurogenesis Contributes to the Specification of
Polleux, Franck
The Timetable of Laminar Neurogenesis Contributes to the Specification of Cortical Areas in Mouse on either side of the 17-18 border suggesting that there might be different timetables of laminar compute the timetable of laminar histogenesis from birthdating experiments. Here we report the results
Starting laminar plumes: Comparison of laboratory and numerical modeling
van Keken, Peter
Starting laminar plumes: Comparison of laboratory and numerical modeling Judith Vatteville Institut, France (davaille@fast.u-psud.fr) [1] A detailed comparison of starting laminar plumes in viscous fluids. Davaille (2009), Starting laminar plumes: Comparison of laboratory and numerical modeling, Geochem. Geophys
Persistently laminar branched surfaces Ying-Qing Wu
Wu, Ying-Qing
Persistently laminar branched surfaces Ying-Qing Wu Abstract We define sink marks for branched that a non 2-bridge Mon- tesinos knot K has a persistently laminar branched surface unless it is equivalent that there are many persistently laminar tangles. 1 Introduction Essential lamination plays an important role
PARTIALLY SATURATED FLOW IN A COMPOSITE POROELASTIC MEDIUM
. This includes the Barenblatt-Biot double- diffusion model of elastic deformation and laminar flow in a fissured's law for laminar flow and of the momentum balance equations with Hooke's law for elastic deformation and consideration of the effects of dilation of the structure on the flow in both of the components. The fluid
The impact of small-scale turbulence on laminar magnetic reconnection
Watson, P. G.; Oughton, S.; Craig, I. J. D. [School of Physics, University of Sydney, NSW 2006 (Australia); Department of Mathematics, University of Waikato, Private Bag 3105, Hamilton (New Zealand)
2007-03-15
Initial states in incompressible two-dimensional magnetohydrodynamics that are known to lead to strong current sheets and (laminar) magnetic reconnection are modified by the addition of small-scale turbulent perturbations of various energies. The evolution of these states is computed with the aim of ascertaining the influence of the turbulence on the underlying laminar solution. Two main questions are addressed here: (1) What effect does small-scale turbulence have on the energy dissipation rate of the underlying solution? (2) What is the threshold turbulent perturbation level above which the original laminar reconnective dynamics is no longer recognizable. The simulations show that while the laminar dynamics persist the dissipation rates are largely unaffected by the turbulence, other than modest increases attributable to the additional small length scales present in the new initial condition. The solutions themselves are also remarkably insensitive to small-scale turbulent perturbations unless the perturbations are large enough to undermine the integrity of the underlying cellular flow pattern. Indeed, even initial states that lead to the evolution of small-scale microscopic sheets can survive the addition of modest turbulence. The role of a large-scale organizing background magnetic field is also addressed.
MAGNETIC TRANSPORT ON THE SOLAR ATMOSPHERE BY LAMINAR AND TURBULENT AMBIPOLAR DIFFUSION
Hiraki, Y. [National Institute for Fusion Science (NIFS), Toki, Gifu (Japan); Krishan, V. [Raman Research Institute, Bangalore 560 080 (India); Masuda, S., E-mail: hiraki.yasutaka@nifs.ac.j [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Aichi (Japan)
2010-09-10
The lower solar atmosphere consists of partially ionized turbulent plasmas harboring velocity field, magnetic field, and current density fluctuations. The correlations among these small-scale fluctuations give rise to large-scale flows and magnetic fields which decisively affect all transport processes. The three-fluid system consisting of electrons, ions, and neutral particles supports nonideal effects such as the Hall effect and ambipolar diffusion. Here, we study magnetic transport by the laminar- and turbulent-scale ambipolar diffusion processes using a simple model of the magnetic induction equation. Based on a linear analysis of the induction equation, we perform a one-dimensional numerical simulation to study the laminar ambipolar effect on medium-scale magnetic field structures. The nonlinearity of the laminar ambipolar diffusion creates magnetic structures with sharp gradients in the scale of hundreds of kilometers. We expect that these can be amenable to processes such as magnetic reconnection and energy release therefrom for heating and flaring of the solar plasma. Analyzing the characteristic timescales of these processes, we find that the turbulent diffusion timescale is smaller by several orders of magnitude than the laminar diffusion timescale. The effect of the modeled turbulent ambipolar diffusion on the obtained field structures is briefly discussed.
Yin, Chung-Yuan
2009-01-01
Size Measurements in Laminar Premixed Ethylene Flames withof soot aggregate sampled from a laminar acetyleneSize Measurements in Laminar Premixed Ethylene Flames with
Elliptic Flow from a Hybrid CGC, Full 3D Hydro and Hadronic Cascade Model
Tetsufumi Hirano; Ulrich W. Heinz; Dmitri Kharzeev; Roy Lacey; Yasushi Nara
2007-03-27
We investigate the robustness of the discovery of the perfect fluid through comparison of hydrodynamic calculations with the elliptic flow coefficient v_2 at midrapidity in Au+Au collisions at sqrt{s_{NN}}=200 GeV. Employing the Glauber model for initial entropy density distributions, the centrality dependence of v_2 is reasonably reproduced by using an ideal fluid description of the early QGP stage followed by a hadronic cascade in the late hadronic stage. On the other hand, initial conditions based on the Colour Glass Condensate model are found to generate larger elliptic flow due to larger initial eccentricity epsilon. We further predict v_2/epsilon at a fixed impact parameter as a function of collision energy sqrt{s_{NN}} up to the LHC energy.
Cooperative phenomena in laminar fluids: Observation of streamlines
Fink, Martin A.; Kretschmer, M.; Hoefner, H.; Konopka, U.; Morfill, G.E.; Ratynskaia, S. [Max Planck Institute for extraterrestrial Physics, Giessenbachstrasse, 85741 Garching (Germany); Fortov, V.; Petrov, O.; Usachev, A.; Zobnin, A. [Institute for High Energy Density, Russian Academy of Sciences, ul. Izhorskaya 13/19, 125412 Moscow (Russian Federation)
2005-10-31
Complex plasmas are an ideal model system to investigate laminar fluids as they allow to study fluids at the kinetic level. At this level we are able to identify streamlines particle by particle. This gives us the ability to research the behaviour of these streamlines as well as the behaviour of each individual particle of the streamline.We carried out our experiments in a modified GEC-RF-Reference cell. We trapped the particles within two glass rings and forced them to form a circular flow by using several stripe electrodes. In this flow the particles behave like an ideal fluid and form streamlines. By putting an obstacle into the flow we reduce the cross-section. To pass through this constricted cross-section some streamlines have to reconnect. After the obstacle the streamlines split up again. An analysis how streamlines split up and reconnect as result of external pressure on the fluid in our system is presented here.Streamlines also occur if two clouds of particles penetrate each other. We call this 'Lane formation'. Results from our PK-4 experiment are presented here also.
A Hybrid Two Component Accretion Flow Surrounding Supermassive Black Holes in AGN
Liu, B F; Qiao, E; Yuan, W
2015-01-01
It is commonly believed that the optical/UV and X-ray emissions in luminous AGN are produced in an accretion disk and an embedded hot corona respectively. The inverse Compton scattering of disk photons by hot electrons in the corona can effectively cool the coronal gas if the mass supply is predominantly via a cool disk like flow as in BHXRBs. Thus, the application of such a model to AGNs fails to produce their observed X-ray emission. As a consequence, a fraction of disk accretion energy is usually assumed to be transferred to the corona. To avoid this assumption, we propose that gas in a vertically extended distribution is supplied to a supermassive black hole by the gravitational capture of interstellar medium or stellar wind material. In this picture, the gas partially condenses to an underlying cool disk as it flows toward the black hole, releasing accretion energy as X-ray emission and supplying mass for the disk accretion. Detailed numerical calculations reveal that the X-ray luminosity can reach a few...
TOWARDS A UNIFIED THEORY OF NEOCORTEX: Laminar Cortical Circuits for Vision and Cognition
Grossberg, Stephen
TOWARDS A UNIFIED THEORY OF NEOCORTEX: Laminar Cortical Circuits for Vision and Cognition Stephen laminar neocortical circuits give rise to biological intelligence. These circuits embody two new and revolutionary computational paradigms: Complementary Computing and Laminar Computing. Circuit properties include
Controlling chaos in a fluid flow past a movable cylinder Juan C. Vallejo a
Rey Juan Carlos, Universidad
mechanisms are not yet well known. This paper analyzes the fluid flow past a cylinder in a laminar regime of an in- compressible, viscid, time-dependent fluid flow past a cylinder in the laminar vortex sheddingControlling chaos in a fluid flow past a movable cylinder Juan C. Vallejo a , Inees P. Mari
Under consideration for publication in J. Fluid Mech. 1 Edges in Models of Shear Flow
Lebovitz, Norman
Under consideration for publication in J. Fluid Mech. 1 Edges in Models of Shear Flow Norman)). The latter problem is ap- proached theoretically by considering first a laminar shear flow (plane Couette of the laminar flow. This places particular importance on understanding the nature of the boundary of the basin
Integral methods for flow in a conical centrifuge Digby D. Symons n
Symons, Digby
Available online 13 April 2011 Keywords:: Centrifugation Films Fluid mechanics Laminar flow Mathematical. Both papers consider a Newtonian viscous, laminar flow where the film thickness h is much smaller thanIntegral methods for flow in a conical centrifuge Digby D. Symons n University of Cambridge
DETAILED CHEMISTRY MODELING OF LAMINAR DIFFUSION FLAMES ON PARALLEL COMPUTERS
. The gasjet diffusion flame is the basic element of many combustion systems, such as gas turbines, ramspeed, threedimensional, turbulent reacting systems, gasjet laminar diffusion flames constitute a problem jets, and industrial furnaces. Furthermore, the fundamental understand ing of laminar diffusion flames
HYBRID LIMIT CYCLES AND HYBRID POINCARE-BENDIXSON
Johansson, Karl Henrik
HYBRID LIMIT CYCLES AND HYBRID POINCAR´E-BENDIXSON Slobodan N. Simi´c Department of Electrical regular hybrid systems with no branching (Simi´c et al., 2000a). The first one provides a condition for asymptotic stability of hybrid closed orbits in terms of contraction-expansion rates of resets and flows
Characterization of Fuego for laminar and turbulent natural convection heat transfer.
Francis, Nicholas Donald, Jr. (,; .)
2005-08-01
A computational fluid dynamics (CFD) analysis is conducted for internal natural convection heat transfer using the low Mach number code Fuego. The flow conditions under investigation are primarily laminar, transitional, or low-intensity level turbulent flows. In the case of turbulent boundary layers at low-level turbulence or transitional Reynolds numbers, the use of standard wall functions no longer applies, in general, for wall-bounded flows. One must integrate all the way to the wall in order to account for gradients in the dependent variables in the viscous sublayer. Fuego provides two turbulence models in which resolution of the near-wall region is appropriate. These models are the v2-f turbulence model and a Launder-Sharma, low-Reynolds number turbulence model. Two standard geometries are considered: the annulus formed between horizontal concentric cylinders and a square enclosure. Each geometry emphasizes wall shear flow and complexities associated with turbulent or near turbulent boundary layers in contact with a motionless core fluid. Overall, the Fuego simulations for both laminar and turbulent flows compared well to measured data, for both geometries under investigation, and to a widely accepted commercial CFD code (FLUENT).
Ando, Yasutaka; Tobe, Shogo [Ashikaga Institute of Technology, 268-1 Omae, Ashikaga, Tochigi 326-8558 (Japan); Tahara, Hirokazu [Osaka Institute of Technology, 5-16-1 Omiya, Asahi-Ku, Osaka 535-8585 (Japan)
2008-02-21
In this study, to provide continuous plasma atmosphere on the substrate surface in the case of atmospheric thermal plasma CVD, TiO{sub 2} film deposition by thermal plasma CVD using laminar plasma jet was carried out. For comparison, the film deposition using turbulence plasma jet was conducted as well. Consequently, transition of the plasma jet from laminar to turbulent occurred on the condition of over 3.5 1/min in Ar working gas flow rate and the plasma jet became turbulent on the condition of over 10 1/min. In the case of the turbulent plasma jet use, anatase rich titanium oxide film could be obtained though plasma jet could not contact with the surface of the substrate continuously even on the condition that feedstock material was injected into the plasma jet. On the other hand,, in the case of laminar gas flow rate, the plasma jet could contact with the substrate continuously without melt down of the substrate during film deposition. Besides, titanium oxide film could be obtained even in the case of the laminar plasma jet use. From these results, this technique was thought to have high potential for atmospheric thermal plasma CVD.
DEVELOPING FLOW AND HEAT TRANSFER IN STRONGLY CURVED DUCTS OF RECTANGULAR CROSS-SECTION
Yee, G.
2010-01-01
123. HUMPHREY, J.A.C. , "Flow in Ducts with Curvature andViscous Flow in Curved Ducts of Rectangular Cross-Sections,"Laminar Flow in a Square Duct of Strong Curvature,1I J.
Prigozhin, Leonid
flow velocity. i. Dispersion Model We consider laminar flow of a fluid in an infinite straight tube- sociating air of high temperatures," Phys. Fluids, 5, 380 (1962). SOLUTE DISPERSION IN A PULSATING FLOW L. B. In the present paper, the Taylor--Aris theory is extended to the case of laminar flows with periodically varying
Pressure Drop of Fully Developed, Laminar Flow in Rough Microtubes
Bahrami, Majid
in fabrication methods in microelectromechanical systems MEMS have generated significant interest in the area Mem. ASME e-mail: majid@mhtlab.uwaterloo.ca M. M. Yovanovich Distinguished Professor Emeritus Fellow ASME J. R. Culham1 Associate Professor Mem. ASME Microelectronics Heat Transfer Laboratory, Department
Designing a more nonlinearly stable laminar flow via boundary manipulation
Rabin, S. M. E.; Caulfield, C. P.; Kerswell, R. R.
2013-12-04
referees which have led to a substantially improved discussion. SMER is supported by a doctoral training award from EPSRC. This work was performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (http...
CE 576 Environmental Flows Spring 2012
Rehmann, Chris
.1. Conservation of mass 1.2. Conservation of momentum 2. Channel flows 2.1. Laminar flow 2.1.1. Flow in a tubeCE 576 Environmental Flows Spring 2012 Course information Instructor: Prof. Chris Rehmann rehmann in environmental fluid mechanics Prerequisites: Elementary fluid mechanics, calculus, differential equations
Experimental and numerical study of laminar forced convection heat transfer for a dimpled heat sink
Park, Do Seo
2009-05-15
of the copper plate. The outer surface of the test section consisted of fiberglass to reduce heat loss to the outside surroundings. The blower was turned on and air was forced through the test setup. The flow rate through the test section was controlled... STUDY OF LAMINAR FORCED CONVECTION HEAT TRANSFER FOR A DIMPLED HEAT SINK A Thesis by DO SEO PARK Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER...
Conceptual design for a laminar-flying-wing aircraft
Saeed, Tariq Issam
2012-06-12
The laminar-flying-wing aircraft appears to be an attractive long-term prospect for reducing the environmental impact of commercial aviation. In assessing its potential, a relatively straightforward initial step is the conceptual design of a...
Adaptive Finite Element Discretization of Flow Problems for Goal-Oriented Model Reduction
. The emphasis is on laminar viscous incompressible flows governed by the Navier-Stokes equations. But also computation in a laminar viscous fluid modeled by the sta- tionary Navier-Stokes equations for velocity vAdaptive Finite Element Discretization of Flow Problems for Goal-Oriented Model Reduction Rolf
Kudrolli, Arshad
Onset of erosion of a granular bed in a channel driven by fluid flow Anyu Hong, Mingjiang Tao); 10.1063/1.4863989 Simulations of granular bed erosion due to laminar shear flow near the critical.1063/1.2213641 Onset of erosion and avalanche for an inclined granular bed sheared by a continuous laminar flow Phys
Muradoglu, Metin
and pollution are directly related to the conversion of chemical energy into thermal energy via combustion Available online 10 September 2014 Keywords: PDF methods Consistent hybrid method Turbulent combustion Bluff rights reserved. 1. Introduction Turbulent combustion continues to be a key technology in energy
Generalized correlation for foam flow in tubes
Cotter, Carol Lynnette
1996-01-01
with respect to foam in the laminar flow region. A semi-automated system to collect pressure drop-flow rate data for gas in liquid foams was constructed in which foam is created by a foam generator and the pressure drop resulting from the foam flow is measured...
Rohmer, Damien; Sitek, Arkadiusz; Gullberg, Grant T.
2006-01-01
Visualization of Fiber and Laminar Structure in the NormalY, McCulloch AD, Covell JW. Laminar fiber architecture andfunction of human myocardial laminar sheets in vivo. Magn
A New Type of Steady and Stable, Laminar, Premixed Flame in Ultra-Lean, Hydrogen-Air Combustion
Grcar, Joseph F
2008-01-01
for Modeling Steady, Laminar, One-Dimensional PremixedType of Steady and Stable, Laminar, Premixed Flame in Ultra-to support another kind of laminar ?ame that is steady and
Montclair, Sani
2012-01-01
Hybrid Identity; Family, Photography and History in Colonialintersectional politics of hybrid identity is the primarycreated a distinctively hybrid culture, one where language,
Type I Planet Migration in Nearly Laminar Disks
H. Li; S. H. Lubow; S. Li; D. N. C. Lin
2008-12-02
We describe 2D hydrodynamic simulations of the migration of low-mass planets ($\\leq 30 M_{\\oplus}$) in nearly laminar disks (viscosity parameter $\\alpha laminar disks. For $\\alpha \\ga 10^{-3}$, density feedback effects are washed out and Type I migration persists. The critical masses are in good agreement with the analytic model of Rafikov (2002). In addition, for $\\alpha \\la 10^{-4}$ steep density gradients produce a vortex instability, resulting in a small time-varying eccentricity in the planet's orbit and a slight outward migration. Migration in nearly laminar disks may be sufficiently slow to reconcile the timescales of migration theory with those of giant planet formation in the core accretion model.
C. Peralta; A. Melatos; M. Giacobello; A. Ooi
2006-07-08
We investigate the global transition from a turbulent state of superfluid vorticity to a laminar state, and vice versa, in the outer core of a neutron star. By solving numerically the hydrodynamic Hall-Vinen-Bekarevich-Khalatnikov equations for a rotating superfluid in a differentially rotating spherical shell, we find that the meridional counterflow driven by Ekman pumping exceeds the Donnelly-Glaberson threshold throughout most of the outer core, exciting unstable Kelvin waves which disrupt the rectilinear vortex array, creating a vortex tangle. In the turbulent state, the torque exerted on the crust oscillates, and the crust-core coupling is weaker than in the laminar state. This leads to a new scenario for the rotational glitches observed in radio pulsars: a vortex tangle is sustained in the differentially rotating outer core by the meridional counterflow, a sudden spin-up event brings the crust and core into corotation, the vortex tangle relaxes back to a rectilinear vortex array, then the crust spins down electromagnetically until enough meridional counterflow builds up to reform a vortex tangle. The turbulent-laminar transition can occur uniformly or in patches; the associated time-scales are estimated from vortex filament theory. We calculate numerically the global structure of the flow with and without an inviscid superfluid component, for Hall-Vinen and Gorter-Mellink forms of the mutual friction. We also calculate the post-glitch evolution of the angular velocity of the crust and its time derivative, and compare the results with radio pulse timing data, predicting a correlation between glitch activity and Reynolds number.
Advances on Matroid Secretary Problems: Free Order Model and Laminar Case
Jaillet, Patrick
Advances on Matroid Secretary Problems: Free Order Model and Laminar Case Patrick Jaillet Jos´e A are interviewed. Furthermore, we consider the classical matroid secretary problem for the special case of laminar
Advances on Matroid Secretary Problems: Free Order Model and Laminar Case
Jaillet, Patrick
Advances on Matroid Secretary Problems: Free Order Model and Laminar Case Patrick Jaillet1 , Jos are interviewed. Furthermore, we consider the classical matroid secretary problem for the special case of laminar
Laminar and Columnar Distribution of Geniculo-cortical Fibers in the Macaque Monkey
Hubel, David
Laminar and Columnar Distribution of Geniculo-cortical Fibers in the Macaque Monkey DAVID H-Heimer modiikation of the Nauta method. We hoped to correlate the laminar distribution of axon terminals
Interactions between Soot and CH* in a Laminar Boundary Layer Type Diffusion Flame in Microgravity
Fuentes, Andres; Legros, Guillaume; Claverie, Alain; Joulain, Pierre; Vantelon, Jean-Pierre; Torero, Jose L
A three-dimensional laminar non-buoyant diffusion flame was studied with the objective of improving the understanding of the soot production. The flame originated from a porous ethylene burner discharging into a laminar ...
A laminar cortical model of stereopsis and three-dimensional surface perception
Grossberg, Stephen
A laminar cortical model of stereopsis and three-dimensional surface perception Stephen Grossberg University 677 Beacon Street, Boston, MA 02215, USA Running title: Laminar cortical model of depth perception;1 Abstract A laminar cortical model of stereopsis and later stages of 3D surface perception is developed
A multi-level local defect correction technique for laminar flame simulation
Eindhoven, Technische Universiteit
A multi-level local defect correction technique for laminar flame simulation J.H.M. ten Thije to solve the low-Mach number approximation of the conservation laws for laminar flames. Elements of our, describing expansion of the gas mixture due to combustion. Boundary value problems for laminar flames
Context-Sensitive Binding by the Laminar Circuits of V1 and V2
Grossberg, Stephen
Context-Sensitive Binding by the Laminar Circuits of V1 and V2: A Unified Model of Perceptual A detailed neural model is presented of how the laminar circuits of visual cortical areas V1 and V2 implement specific laminar circuits allow the responses of visual cortical neurons to be determined not only
A Flamelet Description of Premixed Laminar Flames and the Relation with Flame Stretch
Eindhoven, Technische Universiteit
1 A Flamelet Description of Premixed Laminar Flames and the Relation with Flame Stretch L.P.H. de of Mathematics and Computing Science, PO Box 513, 5600MB Eindhoven, The Netherlands ABSTRACT A laminar flamelet description is derived for premixed laminar flames. The full set of 3D instationary combustion equations
Near-limit laminar burning velocities of microgravity premixed hydrogen flames
Qiao, Li
Near-limit laminar burning velocities of microgravity premixed hydrogen flames with chemically of chemically-passive fire suppressants on laminar premixed hydrogen flames were investigated by combined use that provides at least 450 ms of 10À2 g. Near-limit laminar burning velocities were measured for outwardly
Crawford, Doug
How laminar frontal cortex and basal ganglia circuits interact to control planned and reactive reactive behaviors are insufficient. This paper proposes a new model, called TELOS, to explain how laminar). In amphibians and all land vertebrates, the BG interact with a laminar structure, the optic tectum (OT), or its
Under consideration for publication in J. Fluid Mech. 1 Averaging method for nonlinear laminar
Lautrup, Benny
Under consideration for publication in J. Fluid Mech. 1 Averaging method for nonlinear laminar Copenhagen Ã?, Denmark (Received October 10, 2002) We study laminar Ekman boundary layers in rotating systems method to describe laminar and turbulent boundary layers in rotating fluids. They used a self
ContextSensitive Binding by the Laminar Circuits of V1 and V2
Grossberg, Stephen
ContextSensitive Binding by the Laminar Circuits of V1 and V2: Unified Model Perceptual Grouping is presented how laminar circuits visual cortical areas implement contextsensitive binding processes such perceptual grouping and attention. model proposes how specific laminar circuits allow responses visual
Stereopsis and 3D Surface Perception by Spiking Neurons in Laminar Cortical Circuits
Grossberg, Stephen
Stereopsis and 3D Surface Perception by Spiking Neurons in Laminar Cortical Circuits: A Method, USA Running title: Spiking laminar cortical model of depth perception Neural Networks, in pressNAPSE program of DARPA (HR0011-09-C- 0001). #12;2 Abstract A laminar cortical model of stereopsis and 3D surface
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames
Gülder, Ömer L.
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames Marc 26 March 2011 Keywords: High-pressure Zero-gravity Laminar ethylene diffusion flames Soot modeling were studied numeri- cally in coflow ethyleneair laminar diffusion flames between 0.5 and 5 atm
A comparison of computational and experimental lift-off heights of coflow laminar diffusion flames
Long, Marshall B.
A comparison of computational and experimental lift-off heights of coflow laminar diffusion flames*), and excited-state OH (denoted OH*) are imaged in coflow laminar diffusion flames. Measurements are made both was performed, which indicates that the lift-off height is sensitive to the laminar flame speed
Wang, Zhi Jian "ZJ"
1 American Institute of Aeronautics and Astronautics Effects of Surface Roughness on Laminar Engineering and CFD Center, Iowa State University, Ames, IA 50011 Laminar separation bubbles (LSBs) are often of surface roughness on laminar separation and turbulent transition can provide insights into the design
Estimation of population ring rates and current source densities from laminar electrode
Einevoll, Gaute T.
Estimation of population ring rates and current source densities from laminar electrode recordings Neuroscience, 2007-2008 #12;1 Introduction Recordings of extracellular potentials with laminar electrodes, i), Schroeder et al. (2001), Ulbert et al. (2001), Buzsaki (2004), Einevoll et al. (2007). The laminar
E ective boundary conditions for laminar ows over periodic rough boundaries
Achdou, Yves
E#27;ective boundary conditions for laminar #29;ows over periodic rough boundaries Yves Achdou #3 are proposed for a laminar #29;ow over a rough wall with periodic roughness elements. These e#27;ective is such an approach ? In this paper, we wish to answer these questions for laminar #29;ows over periodic rough walls
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames
Groth, Clinton P. T.
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames Marc xxxx Keywords: High-pressure Zero-gravity Laminar ethylene diffusion flames Soot modeling a b s t r a c in coflow ethyleneair laminar diffusion flames between 0.5 and 5 atm. Computations were per- formed
Compressible laminar streaks with wall suction Pierre Ricco, Daniel Shah, and Peter D. Hicks
Matthews, Adrian
Compressible laminar streaks with wall suction Pierre Ricco, Daniel Shah, and Peter D. Hicks laminar streaks with wall suction Pierre Ricco,1 Daniel Shah,2 and Peter D. Hicks3 1 Department May 2013) The response of a compressible laminar boundary layer subject to free-stream vor- tical
Laminar Cortical Dynamics of Cognitive and Motor Working Memory, Sequence Learning and Performance
Grossberg, Stephen
Laminar Cortical Dynamics of Cognitive and Motor Working Memory, Sequence Learning and Performance cells, cerebral cortex, laminar computing * Authors are listed in alphabetical order. 1 Supported share the same type of circuit design. It proposes how the laminar circuits of lateral prefrontal cortex
Flame Enhancement and Quenching in Fluid Flows Natalia Vladimirova
Kiselev, Alex
Flame Enhancement and Quenching in Fluid Flows Natalia Vladimirova , Peter Constantin , Alexander scale of the flow and laminar front thickness. For cellular flow, we obtain v U1/4 . We also study speed of the flame can be significantly altered by the fluid flow. Specifically, moderately intense
RICH METHANE PREMIXED LAMINAR FLAMES DOPED BY LIGHT UNSATURATED HYDROCARBONS
Paris-Sud XI, Université de
RICH METHANE PREMIXED LAMINAR FLAMES DOPED BY LIGHT UNSATURATED HYDROCARBONS PART I: ALLENE developed in our laboratory for the reactions of C3-C4 unsaturated hydrocarbons. The main reaction pathways2007 #12;3 INTRODUCTION Soots and polyaromatic hydrocarbons (PAH), which are present in the exhaust gas
Membrane-less hydrogen bromine flow battery
Braff, W A; Buie, C R
2014-01-01
In order for the widely discussed benefits of flow batteries for electrochemical energy storage to be applied at large scale, the cost of the electrochemical stack must come down substantially. One promising avenue for reducing stack cost is to increase the system power density while maintaining efficiency, enabling smaller stacks. Here we report on a membrane-less, hydrogen bromine laminar flow battery as a potential high power density solution. The membrane-less design enables power densities of 0.795 W cm$^{-2}$ at room temperature and atmospheric pressure, with a round-trip voltage efficiency of 92\\% at 25\\% of peak power. Theoretical solutions are also presented to guide the design of future laminar flow batteries. The high power density achieved by the hydrogen bromine laminar flow battery, along with the potential for rechargeable operation, will translate into smaller, inexpensive systems that could revolutionize the fields of large-scale energy storage and portable power systems.
Fullerton, Tracy
2012-02-14
Laminar, two-dimensional, constant-property numerical simulations of flat tube heat exchanger devices operating in flow regimes in which self-sustained oscillations occur were performed. The unsteady flow regimes were ...
IS THE MAGNETIC FIELD IN THE HELIOSHEATH LAMINAR OR A TURBULENT SEA OF BUBBLES?
Opher, M. [Astronomy Department, Boston University, Boston, MA (United States); Drake, J. F. [Department of Physics and the Institute for Physical Science and Technology, University of Maryland, College Park, MD (United States); Swisdak, M.; Schoeffler, K. M. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD (United States); Richardson, J. D. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA (United States); Decker, R. B. [John Hopkins Applied Physics Laboratory, Laurel, MD (United States); Toth, G., E-mail: mopher@bu.edu [University of Michigan, Ann Arbor, MI (United States)
2011-06-10
All current global models of the heliosphere are based on the assumption that the magnetic field in the heliosheath, in the region close to the heliopause (HP), is laminar. We argue that in that region the heliospheric magnetic field is not laminar but instead consists of magnetic bubbles. We refer to it as the bubble-dominated heliosheath region. Recently, we proposed that the annihilation of the 'sectored' magnetic field within the heliosheath as it is compressed on its approach to the HP produces anomalous cosmic rays and also energetic electrons. As a product of the annihilation of the sectored magnetic field, densely packed magnetic islands (which further interact to form magnetic bubbles) are produced. These magnetic islands/bubbles will be convected with ambient flows as the sector region is carried to higher latitudes filling the heliosheath. We further argue that the magnetic islands/bubbles will develop upstream within the heliosheath. As a result, the magnetic field in the heliosheath sector region will be disordered well upstream of the HP. We present a three-dimensional MHD simulation with very high numerical resolution that captures the north-south boundaries of the sector region. We show that due to the high pressure of the interstellar magnetic field a north-south asymmetry develops such that the disordered sectored region fills a large portion of the northern part of the heliosphere with a smaller extension in the southern hemisphere. We suggest that this scenario is supported by the following changes that occurred around 2008 and from 2009.16 onward: (1) the sudden decrease in the intensity of low energy electrons (0.02-1.5 MeV) detected by Voyager 2, (2) a sharp reduction in the intensity of fluctuations of the radial flow, and (3) the dramatic differences in intensity trends between galactic cosmic ray electrons (3.8-59 MeV) at Voyager 1 and 2. We argue that these observations are a consequence of Voyager 2 leaving the sector region of disordered field during these periods and crossing into a region of unipolar laminar field.
Drouilhet, S. M.
1999-07-29
This paper is intended as an introduction to some of the control challenges faced by developers of high penetration wind-diesel systems, with a focus on the management of power flows in order to achieve precise regulation of frequency and voltage in the face of rapidly varying wind power input and load conditions. The control algorithms presented herein are being implemented in the National Renewable Energy Laboratory (NREL) high penetration wind-diesel system controller that will be installed in the village of Wales, Alaska, in early 2000.
Design Study for a Laminar-Flying-Wing Aircraft
Saeed, T. I.; Graham, W. R.
2015-05-20
, compared to 14.6) over a conventional competitor designed, using the same methods, for the same mission. Both weight ratio and engine efficiency could be improved by reducing aspect ratio, but at the cost of an aero- dynamic efficiency penalty... , Nashville, TN. †Research Student, Department of Engineering. Current post: Research Associate, Department of Aero- nautics, Imperial College, London. ‡Senior Lecturer, Department of Engineering, Member AIAA. 1 of 34 Laminar-Flying-Wing Aircraft, Saeed...
Topological Charge and the Laminar Structure of the QCD Vacuum
H. B. Thacker
2006-11-30
Monte Carlo studies of pure glue SU(3) gauge theory using the overlap-based topological charge operator have revealed a laminar structure in the QCD vacuum consisting of extended, thin, coherent, locally 3-dimensional sheets of topological charge embedded in 4D space, with opposite sign sheets interleaved. In this talk I discuss the interpretation of these Monte Carlo results in terms of our current theoretical understanding of theta-dependence and topological structure in asymptotically free gauge theories.
Laminar shocks in high power laser plasma interactions
Cairns, R. A. [University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom)] [University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Bingham, R.; Norreys, P.; Trines, R. [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX (United Kingdom)] [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX (United Kingdom)
2014-02-15
We propose a theory to describe laminar ion sound structures in a collisionless plasma. Reflection of a small fraction of the upstream ions converts the well known ion acoustic soliton into a structure with a steep potential gradient upstream and with downstream oscillations. The theory provides a simple interpretation of results dating back more than forty years but, more importantly, is shown to provide an explanation for recent observations on laser produced plasmas relevant to inertial fusion and to ion acceleration.
Type I planet migration in nearly laminar disks
Li, Hui; Li, Shengtai; Lubow, S H; Lin, D
2008-01-01
We describe two-dimensional hydrodynamic simulations of the migration of low-mass planets ({<=}30 M{sub {circle_plus}}) in nearly laminar disks (viscosity parameter {alpha} < 10{sup -3}) over timescales of several thousand orbit periods. We consider disk masses of 1, 2, and 5 times the minimum mass solar nebula, disk thickness parameters of H/r = 0.035 and 0.05, and a variety of {alpha} values and planet masses. Disk self-gravity is fully included. Previous analytic work has suggested that Type I planet migration can be halted in disks of sufficiently low turbulent viscosity, for {alpha} {approx} 10{sup -4}. The halting is due to a feedback effect of breaking density waves that results in a slight mass redistribution and consequently an increased outward torque contribution. The simulations confirm the existence of a critical mass (M{sub {alpha}} {approx} 10M{sub {circle_plus}}) beyond which migration halts in nearly laminar disks. For {alpha} {approx}> 10{sup -3}, density feedback effects are washed out and Type I migration persists. The critical masses are in good agreement with the analytic model of Rafikov. In addition, for {alpha} {approx}> 10{sup -4} steep density gradients produce a vortex instability, resulting in a small time-varying eccentricity in the planet's orbit and a slight outward migration. Migration in nearly laminar disks may be sufficiently slow to reconcile the timescales of migration theory with those of giant planet formation in the core accretion model.
Curl-Noise for Procedural Fluid Flow Robert Bridson
Bridson, Robert
Curl-Noise for Procedural Fluid Flow Robert Bridson University of British Columbia Jim Hourihan), exactly respects solid boundaries (not allowing fluid to flow through arbitrarily-specified surfaces, without manually adding many vortices, this approach is restricted to fairly laminar flow, and matching
REVIEW ARTICLE Planar laser induced fluorescence in aqueous flows
Crimaldi, John P.
REVIEW ARTICLE Planar laser induced fluorescence in aqueous flows J. P. Crimaldi Received: 14 for measuring scalar concentra- tions in fluid flows. A fluorescent dye is used as a scalar proxy, and local Osbourne Reynolds performed his famous experiments on laminar and turbulent flow in round pipes (Reynolds
Laminar boundary layers in convective heat transport
Christian Seis
2012-12-12
We study Rayleigh-Benard convection in the high-Rayleigh-number and high-Prandtl-number regime, i.e., we consider a fluid in a container that is exposed to strong heating of the bottom and cooling of the top plate in the absence of inertia effects. While the dynamics in the bulk are characterized by a chaotic convective heat flow, the boundary layers at the horizontal container plates are essentially conducting and thus the fluid is motionless. Consequently, the average temperature exhibits a linear profile in the boundary layers. In this article, we rigorously investigate the average temperature and oscillations in the boundary layer via local bounds on the temperature field. Moreover, we deduce that the temperature profile is indeed essentially linear close to the horizontal container plates. Our results are uniform in the system parameters (e.g. the Rayleigh number) up to logarithmic correction terms. An important tool in our analysis is a new Hardy-type estimate for the convecting velocity field, which can be used to control the fluid motion in the layer. The bounds on the temperature field are derived with the help of local maximal regularity estimates for convection-diffusion equations.
Laminar boundary layers in convective heat transport
Seis, Christian
2012-01-01
We study Rayleigh-Benard convection in the high-Rayleigh-number and high-Prandtl-number regime, i.e., we consider a fluid in a container that is exposed to strong heating of the bottom and cooling of the top plate in the absence of inertia effects. While the dynamics in the bulk are characterized by a chaotic convective heat flow, the boundary layers at the horizontal container plates are essentially conducting and thus the fluid is motionless. Consequently, the average temperature exhibits a linear profile in the boundary layers. In this article, we rigorously investigate the average temperature and oscillations in the boundary layer via local bounds on the temperature field. Moreover, we deduce that the temperature profile is indeed essentially linear close to the horizontal container plates. Our results are uniform in the system parameters (e.g. the Rayleigh number) up to logarithmic correction terms. An important tool in our analysis is a new Hardy-type estimate for the convecting velocity field, which ca...
Popov, Pavel P., E-mail: ppopov@uci.edu; Pope, Stephen B.
2014-01-15
This work addresses the issue of particle mass consistency in Large Eddy Simulation/Probability Density Function (LES/PDF) methods for turbulent reactive flows. Numerical schemes for the implicit and explicit enforcement of particle mass consistency (PMC) are introduced, and their performance is examined in a representative LES/PDF application, namely the Sandia–Sydney Bluff-Body flame HM1. A new combination of interpolation schemes for velocity and scalar fields is found to better satisfy PMC than multilinear and fourth-order Lagrangian interpolation. A second-order accurate time-stepping scheme for stochastic differential equations (SDE) is found to improve PMC relative to Euler time stepping, which is the first time that a second-order scheme is found to be beneficial, when compared to a first-order scheme, in an LES/PDF application. An explicit corrective velocity scheme for PMC enforcement is introduced, and its parameters optimized to enforce a specified PMC criterion with minimal corrective velocity magnitudes.
Membrane-less hydrogen bromine flow battery William A. Braff1
Bazant, Martin Z.
refined and optimized over several decades. More recently, a laminar flow fuel cell based on borohydride batteries [23, 27], as well as methanol [25], formic acid [24], and hydrogen fuel cells [29]. However, none
Flow-induced mechanotransduction in cell-cell junctions of endothelial cells
Rabodzey, Aleksandr
2006-01-01
Endothelial cells show an unexpected behavior shortly after the onset of laminar flow: their crawling speed decreases ~40% within the first 30 min, but only in a confluent monolayer of endothelial cells, not in subconfluent ...
Roles for Wnts and their receptors in topographic mapping and laminar termination
Richman, Alisha
2011-01-01
tectum may be assigned termination sites on a "first come,Mapping and Laminar Termination A dissertation submitted inTermination ..
Chen, Kui; Fan, Wendong; Wang, Xing; Ke, Xiao [Division of Cardiology, First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080 (China)] [Division of Cardiology, First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080 (China); Wu, Guifu, E-mail: eecpchina@yahoo.com.cn [Key Laboratory on Assisted Circulation, Ministry of Health, Guangzhou 510080 (China)] [Key Laboratory on Assisted Circulation, Ministry of Health, Guangzhou 510080 (China); Hu, Chengheng, E-mail: huchenghengpci@yahoo.com.cn [Division of Cardiology, First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080 (China)] [Division of Cardiology, First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080 (China)
2012-10-12
Highlights: Black-Right-Pointing-Pointer Laminar shear stress upregulates miR-101 expression in vascular endothelial cells. Black-Right-Pointing-Pointer miR-101 represses mTOR expression through a specific 3 Prime UTR binding site. Black-Right-Pointing-Pointer Overexpression of miR-101 inhibits G1/S transition and endothelial cell proliferation. Black-Right-Pointing-Pointer Blockade of miR-101 attenuates the suppressive effect of laminar flow on mTOR expression. -- Abstract: Shear stress associated with blood flow plays an important role in regulating gene expression and cell function in endothelial cells (ECs). MicroRNAs (miRNAs) are highly conserved, small non-coding RNAs that negatively regulate the expression of target genes by binding to the mRNA 3 Prime -untranslated region (3 Prime UTR) at the posttranscriptional level involved in diverse cellular processes. This study demonstrates that microRNA-101 in response to laminar shear stress (LSS) is involved in the flow regulation of gene expression in ECs. qRT-PCR analysis showed that miR-101 expression was significantly upregulated in human umbilical vein endothelial cells (HUVECs) exposed to 12 dyn/cm{sup 2} laminar shear stress for 12 h. We found that transfection of miR-101 significantly decreased the luciferase activity of plasmid reporter containing the 3 Prime UTR of mammalian target of rapamycin (mTOR) gene. Western analysis revealed that the protein level of mTOR was significantly reduced in ECs transfected with miR-101. Furthermore, miR-101 overexpression induced cell cycle arrest at the G1/S transition and suppressed endothelial cell proliferation. Finally, transfection of miR-101 inhibitors attenuated the suppressive effects of LSS on mTOR expression, which identified the efficacy of loss-of-function of miR-101 in laminar flow-treated ECs. In conclusion, we have demonstrated that upregulation of miR-101 in response to LSS contributes to the suppressive effects of LSS on mTOR expression and EC proliferation. These studies advance our understanding of the posttranscriptional mechanisms by which shear stress modulates endothelial homeostasis.
A lean methane premixed laminar flame doped with components of diesel fuel. I. n-Butylbenzene
Pousse, E.; Glaude, P.A.; Fournet, R.; Battin-Leclerc, F. [Departement de Chimie-Physique des Reactions, Nancy Universite, CNRS, ENSIC, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)
2009-05-15
To better understand the chemistry involved in the combustion of components of diesel fuel, the structure of a laminar lean premixed methane flame doped with n-butylbenzene has been investigated. The inlet gases contained 7.1% (molar) methane, 36.8% oxygen, and 0.96% n-butylbenzene corresponding to an equivalence ratio of 0.74 and a ratio C{sub 10}H{sub 14}/CH{sub 4} of 13.5%. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as diluent, with a gas velocity at the burner of 49.2 cm/s at 333 K. Quantified species included the usual methane C{sub 0}-C{sub 2} combustion products, but also 16 C{sub 3}-C{sub 5} hydrocarbons, and 7 C{sub 1}-C{sub 3} oxygenated compounds, as well as 20 aromatic products. A new mechanism for the oxidation of n-butylbenzene is proposed whose predictions are in satisfactory agreement with measured species profiles in flames and flow reactor experiments. The main reaction pathways of consumption of n-butylbenzene have been derived from flow rate analyses. (author)
Buoyancy effects on conjugate heat transfer due to a laminar impinging jet: Preliminary results
Altieri, G.; De Luca, V.; Ruocco, G.
1999-07-01
A numerical analysis for fluid flow and conjugate conduction/convection heat transfer from a laminar, planar gas jet impingement (JI) on a finite thickness, discretely heated substrate is performed, which includes the effect of buoyancy. The competition between transfer of heat by conduction in the plate and by convection in the fluid is examined. A combination of assisting or opposing mixed convection is modeled, and the related flow field as well as local heat transfer rate is studied as a function of the mixed convection parameter, the Richardson number, for a given geometry and a thermal-fluid base-case. Preliminary evaluations of the heat transfer rate are presented as local Nusselt number distributions, for nonbuoyant, assisted and opposed impinging jets, along the impinged substrate. The complex, non-monotonic progresses of these results justify the inclusion of the conduction mechanism in the substrate, in order to correctly quantify the driving parameters for the heat transfer control. The presented calculations are in fair accordance with existing literature which is limited to pure fluid jet impingement. The inclusion of the conduction mechanism confirms the absence of the conjugate effect when an opposing cooling jet configuration is realized.
The Numerical Simulation Of A Transitional Flow In The VKI-GENOA Turbine Cascade
Yershov, Sergiy; Yakovlev, Viktor; Gryzun, Maria
2015-01-01
This study presents a numerical simulation of a 3D viscous flow in the VKI-Genoa cascade that takes into account the laminar-turbulent transition. The numerical simulation is performed using the Reynolds-averaged Navier-Stokes equations and the two-equation k-omega SST turbulence model. The algebraic Production Term Modification model is used for modeling the laminar-turbulent transition. Computations of both fully turbulent and transitional flows are carried out. The contours of the Mach number, the turbulence kinetic energy, the entropy function, as well as limiting streamlines are presented. The analysis of the numerical results demonstrates the influence of the laminar-turbulent transition on the secondary flow pattern. The comparison between the present computational results and the existing experimental and numerical data shows that the proposed approach reflects sufficiently the physics of the laminar-turbulent transition in turbine cascades.
Applications of Laminar Weak-Link Mechanisms for Ultraprecision Synchrotron Radiation Instruments
Shu, D.; Toellner, T. S.; Alp, E. E.; Maser, J.; Ilavsky, J.; Shastri, S. D.; Lee, P. L.; Narayanan, S.; Long, G. G. [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States)
2007-01-19
Unlike traditional kinematic flexure mechanisms, laminar overconstrained weak-link mechanisms provide much higher structure stiffness and stability. Using a laminar structure configured and manufactured by chemical etching and lithography techniques, we are able to design and build linear and rotary weak-link mechanisms with ultrahigh positioning sensitivity and stability for synchrotron radiation applications. Applications of laminar rotary weak-link mechanism include: high-energy-resolution monochromators for inelastic x-ray scattering and x-ray analyzers for ultra-small-angle scattering and powder-diffraction experiments. Applications of laminar linear weak-link mechanism include high-stiffness piezo-driven stages with subnanometer resolution for an x-ray microscope. In this paper, we summarize the recent designs and applications of the laminar weak-link mechanisms at the Advanced Photon Source.
Meeks, Meghyn
2015-05-08
of this research were to 1) develop new interspecific hybrid bluegrasses and optimize a seed germination technique, 2) use flow cytometry and molecular markers for the characterization of hybrid progeny, and 3) evaluate the growth response and performance of hybrid...
Bell, John B.
Lawrence Berkeley National Laboratory report LBNL-725E 1 A New Type of Steady and Stable, Laminar-air mixtures are found to support another kind of laminar flame that is steady and stable beside flat flames;Nomenclature fuel equivalence ratio 1 Introduction There is growing evidence that a new type of laminar
Grossberg, Stephen
1 Running as fast as it can: How spiking dynamics form object groupings in the laminar circuits laminar cortical circuits Submitted: July 6, 2009 Revised: January 5, 2010 Technical Report CAS/CNS-0009 timing across many interacting cells. Some models have demonstrated spiking dynamics in recurrent laminar
CH(A-X) and OH(A-X) Optical Emission in an Axisymmetric Laminar Diffusion Flame
Long, Marshall B.
CH(A-X) and OH(A-X) Optical Emission in an Axisymmetric Laminar Diffusion Flame J. LUQUE, J. B an axisymmetric laminar diffusion flame [K. T. Walsh, M. B. Long, M. A. Tanoff, and M. D. Smooke, Twenty axisymmetric laminar methane/air diffusion flame studied here has been exten- sively characterized both
Morphodynamic modeling of erodible laminar channels Olivier Devauchelle, Christophe Josserand in time. It is also shown, through a simplified stability analysis, that a laminar river can generate reflects the meandering and braiding tendencies of laminar rivers indicated by F. Métivier and P. Meunier J
On 2-coverings and 2-packings of laminar families J. Cheriyan T. Jordan y R. Ravi z
Cheriyan, Joseph
On 2-coverings and 2-packings of laminar families J. Cheriyan T. Jordan y R. Ravi z January 24: laminar family of subsets, 1-covers, 2-covers, 1-packings, 2-packings, NP-hard, approximation algorithm grant CCR{9625297. 1 #12;1 Introduction Coverings and packings of laminar families by edges Let H
Gülder, Ömer L.
Effects of gravity and pressure on laminar coflow methaneair diffusion flames at pressures from 1 characteristics and flame structure of coflow methaneair laminar diffusion flames between 1 and 60 atm were these effects through the numerical analysis of laminar diffusion flames at pressures ranging from 1 to 60 atm
Bahrami, Majid
rise due to gravity. Assuming laminar flow and noting that 'z L, the pipe length, we get f 4 4 3 128 LQ is 30 cm higher than the surface of tank 2. (a) Estimate the flow rate in m3/h. Is the flow laminar? (b448 Solutions Manual x Fluid Mechanics, Fifth Edition f 1 2Thus h z z 0 by definition. Therefore
Cirpka, Olaf Arie
of the medium under the influence of atmospheric processes, such as laminar/turbulent free flow and solar radia temperature distribution Outlook Following issues need to be addressed in detail: If given relationships
Lu, Wei; Kelley, A. P.; Law, C. K.
2011-01-01
The non-premixed ignition temperature of n-butanol (CH{sub 3}CH{sub 2}CH{sub 2}CH{sub 2}OH), iso-butanol ((CH{sub 3}){sub 2}CHCH{sub 2}OH) and methyl butanoate (CH{sub 3}CH{sub 2}CH{sub 2}COOCH{sub 3}) was measured in a liquid pool assembly by heated oxidizer in a stagnation flow for system pressures of 1 and 3 atm. In addition, the stretch-corrected laminar flame speeds of mixtures of air–n-butanol/iso-butanol/methyl butanoate were determined from the outwardly propagating spherical flame at initial pressures of up to 2 atm, for an extensive range of equivalence ratio. The ignition temperature and laminar flame speeds of n-butanol and methyl butanoate were computationally simulated with three recently developed kinetic mechanisms in the literature. Dominant reaction pathways to ignition and flame propagation were identified and discussed through a chemical explosive mode analysis (CEMA) and sensitivity analysis. The detailed models were further reduced through a series of systematic strategies. The reduced mechanisms provided excellent agreement in both homogeneous and diffusive combustion environments and greatly improved the computation efficiency.
Kiselev, Alex
Flame Enhancement and Quenching in Fluid Flows Natalia Vladimirovay scale of the flow and laminar front thickness. For cellular flow, we o* *btain v ~ U1=4. We also study(T).* * (1) altered by the fluid flow. Specifically, moderately intense@t o levels of turbulence
Vibration of Wires in Liquid Argon Due to Fluid Flow Kirk T McDonald (kirkmcd@princeton.edu)
McDonald, Kirk
Vibration of Wires in Liquid Argon Due to Fluid Flow Kirk T McDonald (kirkmcd. But in these regions, the Reynolds number of the flow is 56/23 = 2.4, in which case the flow is laminar, not turbulent, and there is no excitation of wire vibration. So, I conclude that wire vibration due to fluid flow is negligible (unless
Weiss, M.; Zarzalis, N. [Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Karlsruhe (Germany); Suntz, R. [Institute for Chemical Technology, University of Karlsruhe (TH), Karlsruhe (Germany)
2008-09-15
Effects of turbulent flame stretch on mean local laminar burning velocity of flamelets, u{sub n}, were investigated experimentally in an explosion vessel at normal temperature and pressure. In this context, the wrinkling, A{sub t}/A{sub l}, and the burning velocity, u{sub t}, of turbulent flames were measured simultaneously. With the flamelet assumption the mean local laminar burning velocity of flamelets, u{sub n}=u{sub t} x (A{sub t}/A{sub l}){sup -1}, was calculated for different turbulence intensities. The results were compared to the influence of stretch on spherically expanding laminar flames. For spherically expanding laminar flames the stretched laminar burning velocity, u{sub n}, varied linearly with the Karlovitz stretch factor, yielding Markstein numbers that depend on the mixture composition. Six different mixtures with positive and negative Markstein numbers were investigated. The measurements of the mean local laminar burning velocity of turbulent flamelets were used to derive an efficiency parameter, I, which reflects the impact of the Markstein number and turbulent flame stretch - expressed by the turbulent Karlovitz stretch factor - on the local laminar burning velocity of flamelets. The results showed that the efficiency is reduced with increasing turbulence intensity and the reduction can be correlated to unsteady effects. (author)
Effects of multi-component diffusion and heat release on laminar diffusion flame liftoff
Li, Zhiliang; Chen, Ruey-Hung [Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816-2450 (United States); Phuoc, Tran X. [National Energy Technology Laboratory, Department of Energy, P.O. Box 10940, MS 84-340, Pittsburgh, PA 15261 (United States)
2010-08-15
Numerical simulations were conducted of the liftoff and stabilization phenomena of laminar jet diffusion flames of inert-diluted C{sub 3}H{sub 8} and CH{sub 4} fuels. Both non-reacting and reacting jets were investigated, including multi-component diffusivities and heat release effects (buoyancy and gas expansion). The role of Schmidt number for non-reacting jets was investigated, with no conclusive Schmidt number criterion for liftoff previously arrived at in similarity solutions. The cold-flow simulation for He-diluted CH{sub 4} fuel does not predict flame liftoff; however, adding heat release reaction lead to the prediction of liftoff, which is consistent with experimental observations. Including reaction was also found to improve liftoff height prediction for C{sub 3}H{sub 8} flames, with the flame base location differing from that in the similarity solution - the intersection of the stoichiometric and iso-velocity (equal to 1-D flame speed) is not necessary for flame stabilization (and thus liftoff). Possible mechanisms other than that proposed for similarity solution may better help to explain the stabilization and liftoff phenomena. (author)
Choi, B.C.; Kim, K.N.; Chung, S.H.
2009-02-15
Characteristics of laminar lifted flames have been investigated experimentally by varying the initial temperature of coflow air over 800 K in the non-premixed jets of propane diluted with nitrogen. The result showed that the lifted flame with the initial temperature below 860 K maintained the typical tribrachial structure at the leading edge, which was stabilized by the balance mechanism between the propagation speed of tribrachial flame and the local flow velocity. For the temperature above 860 K, the flame was autoignited without having any external ignition source. The autoignited lifted flames were categorized in two regimes. In the case with tribrachial edge structure, the liftoff height increased nonlinearly with jet velocity. Especially, for the critical condition near blowout, the lifted flame showed a repetitive behavior of extinction and reignition. In such a case, the autoignition was controlled by the non-adiabatic ignition delay time considering heat loss such that the autoignition height was correlated with the square of the adiabatic ignition delay time. In the case with mild combustion regime at excessively diluted conditions, the liftoff height increased linearly with jet velocity and was correlated well with the square of the adiabatic ignition delay time. (author)
Rich methane laminar flames doped with light unsaturated hydrocarbons. Part III : cyclopentene
Gueniche, Hadj-Ali; Fournet, René; Battin-Leclerc, Frédérique
2008-01-01
In line with the studies presented in the parts I and II of this paper, the structure of a laminar rich premixed methane flame doped with cyclopentene has been investigated. The gases of this flame contains 15.3% (molar) of methane, 26.7% of oxygen and 2.4% cyclopentene corresponding to an equivalence ratio of 1.79 and a ratio C5H8 / CH4 of 16 %. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The temperature ranged from 627 K close to the burner up to 2027 K. Quantified species included usual methane C0-C2 combustion products, but also propyne, allene, propene, propane, 1-butene, 1,3-butadiene, 1,2-butadiene, vinylacetylene, diacetylene, cyclopentadiene, 1,3-pentadiene, benzene and toluene. A new mechanism for the oxidation of cyclopentene has been proposed. The main reaction pathways of consumption of cyclopentene and of formation of benzene and toluene have been derived from flow rate analyses.
Bell, Geoffrey C. (Pleasant Hill, CA); Feustel, Helmut E. (Albany, CA); Dickerhoff, Darryl J. (Berkeley, CA)
2002-01-01
A fume hood is provided having an adequate level of safety while reducing the amount of air exhausted from the hood. A displacement flow fume hood works on the principal of a displacement flow which displaces the volume currently present in the hood using a push-pull system. The displacement flow includes a plurality of air supplies which provide fresh air, preferably having laminar flow, to the fume hood. The displacement flow fume hood also includes an air exhaust which pulls air from the work chamber in a minimally turbulent manner. As the displacement flow produces a substantially consistent and minimally turbulent flow in the hood, inconsistent flow patterns associated with contaminant escape from the hood are minimized. The displacement flow fume hood largely reduces the need to exhaust large amounts of air from the hood. It has been shown that exhaust air flow reductions of up to 70% are possible without a decrease in the hood's containment performance. The fume hood also includes a number of structural adaptations which facilitate consistent and minimally turbulent flow within a fume hood.
M. Bahrami ENSC 283 Tutorial # 6 1 ENSC 283 Week # 10, Tutorial # 6 Plane Couette Flow
Bahrami, Majid
of thickness . Gravity tends to make the fluid drain down the belt. Assume that the flow is laminar, steady velocity of the fluid film Step 2: Calculations Since the flow is assumed to be uniform, the only velocity enough belt speed) there are portions of the fluid that flow downward (as indicated by / 0
2. Some simple models of fluid flow: exact solutions of the N-S equation
Read, Peter L.
2. Some simple models of fluid flow: exact solutions of the N-S equation To construct mathematical. Boundary conditions: fluid comes to rest at the walls z = ±h (`no-slip' condition, since flow is viscous flow remains rectilinear (`laminar'). If Re Recrit, turbulence usually sets in: We say
Nonexistence of Coherent Structures in Two-Dimensional Inviscid Channel Flow
Kalisch, Henrik
Abstract Two-dimensional inviscid channel flow of an incompressible fluid is considered. It is shown to the study of transition from laminar flow to turbulence [25]. It follows from the result of this note that this kind of steady flow cannot exist in an inviscid fluid. Imagine a fluid contained in a horizontal
Flow rate analysis of a surface tension driven passive micropump{{ Erwin Berthiera
Beebe, David J.
, causing fluid flow. The behavior of the input drop occurs in two characteristic phases. An analytical value of Re = rU0L0/g # 1, meaning that the flow is very laminar, allowing the use of the Washburn lawFlow rate analysis of a surface tension driven passive micropump{{ Erwin Berthiera and David J
Turbulent transition in a truncated 1D model for shear flow
Dawes, Jon
to a `turbulent' state (i) takes place more abruptly, with a boundary between laminar and `turbulent' flow at fixed Reynolds number are found to be consistent with exponential distributions. Keywords: fluid flowTurbulent transition in a truncated 1D model for shear flow By J. H. P. Dawes and W. J. Giles
Local entropy generation for saturated two-phase flow Remi Revellin a,*, Stephane Lips a
Khandekar, Sameer
promoted. Bejan [1] studied entropy generation through heat and fluid flow of a single-phase fluid. He- and Y-shaped assemblies of ducts, channels and streams. They assumed a laminar and fully developed flow the porous medium approach based on extended Darcy equation for fluid flow, and two-equation model for heat
Bernal, Javier
the boundaries of fractal drums. I. INTRODUCTION The problem of calculating fluid flow through and around complex of Monte Carlo method. Stokes equation for laminar flow in a long tube of uniform cross sectionProbabilistic computation of Poiseuille flow velocity fields F. Y. Hunt, J. F. Douglas, and J
Hu, Hui
of complex thermal-flow phenomena: Renewable Energy, wind energy, wind turbine aeromechanics. Bio-flows and micro-scale heat transfer. Icing physics, aircraft icing, power line icing and wind turbine icing. Low-speed aerodynamics, laminar boundary layer separation, transition and flow control. Wind
Low Magnetic Reynolds Number Hypersonic MHD Flow Using High Order WENO Schemes
Zha, Gecheng
diffusion scheme for 3D Navier-Stokes equa- tions. We present results for hypersonic laminar flows around diffusion E-CUSP (LDE) scheme with a fifth order WENO scheme was developed to resolve flow fields with shockLow Magnetic Reynolds Number Hypersonic MHD Flow Using High Order WENO Schemes Jaejin Lee , Manuel
Boulanger, Joan [Gas Turbine Laboratory, Institute for Aerospace Research, Ottawa, Ontario (Canada)
2010-04-15
At very low Froude number, buoyancy instabilities of round laminar jet diffusion flames disappear (except for small tip oscillations referred to as flickering) and those flames look stable and smooth. This study examines the contributions of the different phenomena in the flow dynamics that may explain this effect. It is observed that, at ultra-low Froude/Reynolds numbers, the material influenced by buoyancy is the plume of the flame and not the flame itself (reaction zone) that is short. Therefore, the vorticity creation zone does not profit from the reaction neighbourhood promoting a sharp gradient of density. Expansion and stretch are also important as they push vorticity creation terms more inside the flame and closer to the burner rim compared to moderate Froude flames. In these latter, the vorticity is continuously created around the flame reaction zone, along its developed height and closer to the vertical direction (in average). (author)
Athirathnam, Rajesh
1999-01-01
as in the case of tomographic reconstruction of bubbles. In the present work great strides have been made to alleviate both the problems by using a Hybrid model of Algebraic Reconstruction Technique (ART), Simplex Method and Genetic Algorithm (GA). The work done...
Newman, D. L.; Goldman, M. V.; Sen, N. [Center for Integrated Plasma Studies, University of Colorado at Boulder, Boulder, Colorado 80309 (United States); Andersson, L.; Ergun, R. E. [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado 80309 (United States)
2008-07-15
A series of one-dimensional Vlasov simulations [Newman et al., Phys. Plasmas 15, 072902 (2008), this issue] show that a sufficiently dense and hot suprathermal electron population can stabilize strong laminar double layers over long periods while regulating their strength and velocity. When suprathermals are less dense or absent, the double layers tend to be sporadic and turbulent. A detailed comparison of the laminar and turbulent regimes reveals that the disruption of the laminar state can be triggered by kinetically modified Buneman instabilities on the low-potential side of the double layer, and by density perturbations that develop into nonlinear coherent shocklike structures on the high-potential side. These findings suggest that the suprathermal electrons may be responsible for suppressing both of these routes to disruption of the laminar state.
Sooting Behaviour Dynamics of a Non-Bouyant Laminar Diffusion Flame
Fuentes, Andres; Legros, Guillaume; Rouvreau, Sebastien; Joulain, Pierre; Vantelon, Jean-Pierre; Torero, Jose L; Fernandez-Pello, Carlos
2007-01-01
Local soot concentrations in non-buoyant laminar diffusion flames have been demonstrated to be the outcome of two competitive processes, soot formation and soot oxidation. It was first believed that soot formation was the controlling mechanism...
Legros, Guillaume; Joulain, Pierre; Jean-Pierre, Vantelon; Fuentes, Andres; Bertheau, Denis; Torero, Jose L
2005-05-03
A methodology for the estimation of the soot volume fraction in a three-dimensional laminar diffusion flame is presented. All experiments are conducted in microgravity and have as objective producing quantitative data ...
Laminar burning velocities and flame instabilities of butanol isomers-air mixtures
Gu, Xiaolei; Huang, Zuohua; Wu, Si; Li, Qianqian [State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049 (China)
2010-12-15
Laminar burning velocities and flame instabilities of the butanol-air premixed flames and its isomers are investigated using the spherically expanding flame with central ignition at initial temperature of 428 K and initial pressures of 0.10 MPa, 0.25 MPa, 0.50 MPa and 0.75 MPa. Laminar burning velocities and sensitivity factor of n-butanol-air mixtures are computed using a newly developed kinetic mechanism. Unstretched laminar burning velocity, adiabatic temperature, Lewis number, Markstein length, critical flame radius and Peclet number are obtained over a wide range of equivalence ratios. Effect of molecular structure on laminar burning velocity of the isomers of butanol is analyzed from the aspect of C-H bond dissociation energy. Study indicates that although adiabatic flame temperatures of the isomers of butanol are the same, laminar burning velocities give an obvious difference among the isomers of butanol. This indicates that molecular structure has a large influence on laminar burning velocities of the isomers of butanol. Branching (-CH3) will decrease laminar burning velocity. Hydroxyl functional group (-OH) attaching to the terminal carbon atoms gives higher laminar burning velocity compared to that attaching to the inner carbon atoms. Calculated dissociation bond energies show that terminal C-H bonds have larger bond energies than that of inner C-H bonds. n-Butanol, no branching and with hydroxyl functional group (-OH) attaching to the terminal carbon atom, gives the largest laminar burning velocity. tert-Butanol, with highly branching and hydroxyl functional group (-OH) attaching to the inner carbon atom, gives the lowest laminar burning velocity. Laminar burning velocities of iso-butanol and sec-butanol are between those of n-butanol and tert-butanol. The instant of transition to cellularity is experimentally determined for the isomers of butanol and subsequently interpreted on the basis of hydrodynamic and diffusion-thermal instabilities. Little effect on flame instability is observed for the isomers of butanol. Critical flame radii are the same for the isomers of butanol. Peclet number decreases with the increase in equivalence ratio. (author)
Flamelet mathematical models for non-premixed laminar combustion
Carbonell, D.; Perez-Segarra, C.D.; Oliva, A.; Coelho, P.J.
2009-02-15
Detailed numerical calculations based on the solution of the full transport equations have been compared with flamelet calculations in order to analyse the flamelet concept for laminar diffusion flames. The goal of this work is to study the interactive (Lagrangian Flamelet Model and Interactive Steady Flamelet Model), and non-interactive (Steady Flamelet Model and Enthalpy Defect Flamelet Model) flamelet models considering both differential diffusion and non-differential diffusion situations, and adiabatic and non-adiabatic conditions. Moreover, a new procedure has been employed to obtain enthalpy defects in the flamelet library, the application of which has been found to be encouraging. The effect of using in-situ, local or stoichiometric scalar dissipation rate conditions, and also the effect of using local or stoichiometric conditions to evaluate the flamelet-like time has been analysed. To improve slow species predictions using the non-interactive models, their transport equations are solved with the reaction terms calculated from the flamelet library, also considering local or stoichiometric conditions in the so-called Extended Flamelet Models. (author)
Rom-Kedar, Vered
flows Phys. Fluids 23, 016603 (2011); 10.1063/1.3531716 Development and characterization of a laminar of immiscible impurities in a two-dimensional flow Phys. Fluids 10, 342 (1998); 10.1063/1.869526 This articleNew Lagrangian diagnostics for characterizing fluid flow mixing Ruty Mundel, Erick Fredj, Hezi
Experimental investigation of ice slurry flow pressure drop in horizontal tubes
Grozdek, Marino; Khodabandeh, Rahmatollah; Lundqvist, Per [Royal Institute of Technology, Department of Energy Technology, Division of Applied Thermodynamics and Refrigeration, Brinellvaegen 68, 10044 Stockholm (Sweden)
2009-01-15
Pressure drop behaviour of ice slurry based on ethanol-water mixture in circular horizontal tubes has been experimentally investigated. The secondary fluid was prepared by mixing ethyl alcohol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 C). The pressure drop tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 30% depending on test conditions. Results from flow tests reveal much higher pressure drop for higher ice concentrations and higher velocities in comparison to the single phase flow. However for ice concentrations of 15% and higher, certain velocity exists at which ice slurry pressure drop is same or even lower than for single phase flow. It seems that higher ice concentration delay flow pattern transition moment (from laminar to turbulent) toward higher velocities. In addition experimental results for pressure drop were compared to the analytical results, based on Poiseulle and Buckingham-Reiner models for laminar flow, Blasius, Darby and Melson, Dodge and Metzner, Steffe and Tomita for turbulent region and general correlation of Kitanovski which is valid for both flow regimes. For laminar flow and low buoyancy numbers Buckingham-Reiner method gives good agreement with experimental results while for turbulent flow best fit is provided with Dodge-Metzner and Tomita methods. Furthermore, for transport purposes it has been shown that ice mass fraction of 20% offers best ratio of ice slurry transport capability and required pumping power. (author)
C. A. Meyer; E. S. Swanson
2015-03-04
A review of the theoretical and experimental status of hybrid hadrons is presented. The states $\\pi_1(1400)$, $\\pi_1(1600)$, and $\\pi_1(2015)$ are thoroughly reviewed, along with experimental results from GAMS, VES, Obelix, COMPASS, KEK, CLEO, Crystal Barrel, CLAS, and BNL. Theoretical lattice results on the gluelump spectrum, adiabatic potentials, heavy and light hybrids, and transition matrix elements are discussed. These are compared with bag, string, flux tube, and constituent gluon models. Strong and electromagnetic decay models are described and compared to lattice gauge theory results. We conclude that while good evidence for the existence of a light isovector exotic meson exists, its confirmation as a hybrid meson awaits discovery of its iso-partners. We also conclude that lattice gauge theory rules out a number of hybrid models and provides a reference to judge the success of others.
Arun Sehrawat; Daniel Zemann; Berthold-Georg Englert
2010-09-25
We present a hybrid model of the unitary-evolution-based quantum computation model and the measurement-based quantum computation model. In the hybrid model part of a quantum circuit is simulated by unitary evolution and the rest by measurements on star graph states, thereby combining the advantages of the two standard quantum computation models. In the hybrid model, a complicated unitary gate under simulation is decomposed in terms of a sequence of single-qubit operations, the controlled-Z gates, and multi-qubit rotations around the z-axis. Every single-qubit- and the controlled-Z gate are realized by a respective unitary evolution, and every multi-qubit rotation is executed by a single measurement on a required star graph state. The classical information processing in our model only needs an information flow vector and propagation matrices. We provide the implementation of multi-control gates in the hybrid model. They are very useful for implementing Grover's search algorithm, which is studied as an illustrating example.
Flow Forcing Techniques for Numerical Simulation of Combustion Instabilities
Nicoud, Franck
Flow Forcing Techniques for Numerical Simulation of Combustion Instabilities A. KAUFMANN* and F of combustion instabilities in gas turbine combustors require the knowledge of flame transfer functions. Those flame) and for one case where a CFD code is necessary (a laminar Bunsen-type flame). © 2002
Bandaru, Vinodh; Krasnov, Dmitry; Schumacher, Jörg
2015-01-01
A conservative coupled finite difference-boundary element computational procedure for the simulation of turbulent magnetohydrodynamic flow in a straight rectangular duct at finite magnetic Reynolds number is presented. The flow is assumed to be periodic in the streamwise direction and is driven by a mean pressure gradient. The duct walls are considered to be electrically insulating. The co-evolution of the velocity and magnetic fields as described respectively by the Navier-Stokes and the magnetic induction equations, together with the coupling of the magnetic field between the conducting domain and the non-conducting exterior is solved using the magnetic field formulation. The aim is to simulate localized magnetic fields interacting with turbulent duct flow. Detailed verification of the implementation of the numerical scheme is conducted in the limiting case of low magnetic Reynolds number by comparing with the results obtained using a quasistatic approach that has no coupling with the exterior. The rigorous...
378 Solutions Manual x Fluid Mechanics, Fifth Edition where heat flow, J/s
Bahrami, Majid
378 Solutions Manual x Fluid Mechanics, Fifth Edition where heat flow, J/s A surface area, m Q 2 'T Ans. L V VV U PU § ·' : 3 3 3 3 ¨ ¸ © ¹ 5.18 Under laminar conditions, the volume flow Q through temperature difference, K The dimensionless form of h, called the Stanton number, is a combination of h, fluid
A STUDY OF COMPUTATIONAL FLUID DYNAMICS APPLIED TO ROOM AIR FLOW
for supplying me a copy of his three-dimensional, laminar, constant density fluid flow computer program, whichi A STUDY OF COMPUTATIONAL FLUID DYNAMICS APPLIED TO ROOM AIR FLOW By JAMES W. WEATHERS Bachelor of the requirements for the Degree of MASTER OF SCIENCE May, 1992 #12;ii A STUDY OF COMPUTATIONAL FLUID DYNAMICS
Thiffeault, Jean-Luc
the last eight years, a number of authors have investigated how efficient laminar fluid mixing can be achieved by engineering fluid flows with a favourable topology. The idea of applying topological tools is independent of the dynamical equations satisfied by the fluid. Topology of a fluid flow may be encoded
Nguyen, H.L.; Wey, Mingjyh.
1990-01-01
Two dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.
The lengths distribution of laminar phases for type-I intermittency in the presence of noise
A. E. Hramov; A. A. Koronovskii; M. K. Kurovskaja; A. A. Ovchinnikov; S. Boccaletti
2008-01-26
We consider a type of intermittent behavior that occurs as the result of the interplay between dynamical mechanisms giving rise to type-I intermittency and random dynamics. We analytically deduce the laws for the distribution of the laminar phases, with the law for the mean length of the laminar phases versus the critical parameter deduced earlier [PRE 62 (2000) 6304] being the corollary fact of the developed theory. We find a very good agreement between the theoretical predictions and the data obtained by means of both the experimental study and numerical calculations. We discuss also how this mechanism is expected to take place in other relevant physical circumstances.
Stability and angular-momentum transport of fluid flows between corotating cylinders
Avila, Marc
2012-01-01
Turbulent transport of angular momentum is a necessary process to explain accretion in astrophysical disks. Although the hydrodynamic stability of disk-like flows has been tested in experiments, results are contradictory and suggest either laminar or turbulent flow. Direct numerical simulations reported here show that currently investigated laboratory flows are hydrodynamically unstable and become turbulent at low Reynolds numbers. The underlying instabilities stem from the axial boundary conditions, affect the flow globally and enhance angular-momentum transport.
Law Jr., C.G.
2010-01-01
Industrial and Engineering Chemistry, 24, 726-736 (1932). C.Industrial and Engineering Chemistry, C. S. Lin, R. W.Industrial and Engineering Chemistry, H. Reichart, "Die
Chen, X.
Microfluidic devices could find applications in many areas, such as BioMEMs, miniature fuel cells and microfluidic cooling of electronic circuitry. One of the important considerations of microfluidic device in analytical ...
A comparative study of the LBE and GKS methods for 2D near incompressible laminar flows
Xu, Kun
a , Hongwei Liu b , Li-Shi Luo c,*, Kun Xu b a National Laboratory of Coal Combustion, Huazhong University. Introduction In general, kinetic methods for computational fluid dynamics (CFD) are derived from the Boltzmann equation, as opposed to conventional CFD methods based on direct discretizations of the Navier
LAMINAR FLOW BASED MICROREACTOR FOR EFFICIENT REGENERATION OF NICOTINAMIDE COFACTORS FOR BIOCATALYIS
Kenis, Paul J. A.
experiments as well as the microreactor characterization experiments using the ferri/ferrocyanide redox couple
Simulation of three-dimensional laminar flow and heat transfer in an array of parallel microchannels
Mlcak, Justin Dale
2009-05-15
ranges from 50 to 400. A constant heat flux of 90 W/cm2 is applied to the northern face of the computational domain, which simulates thermal energy generation from an integrated circuit. A simplified model is validated against analytical fully developed...
Study of Laminar Flow Forced Convection Heat Transfer Behavior of a Phase Change Material Fluid
Ravi, Gurunarayana
2010-01-14
takes into account the melting point and latent heat of fusion of the PCM as shown in Eq. (14) and (15). () ( ) ( ) b sl m p m f 1 2 Cp Cp c Cp 1 c Cp for T T== +? (19) () ( m emf 1 21 cL Cp 1 c Cp for T < T < T (T...
Membraneless hydrogen bromine laminar flow battery for large-scale energy storage
Braff, William Allan
2014-01-01
Electrochemical energy storage systems have been considered for a range of potential large-scale energy storage applications. These applications vary widely, both in the order of magnitude of energy storage that is required ...
Computational Evaluation of a Transonic Laminar-Flow Wing Glove Design
Roberts, Matthew William
2012-07-16
Langley Research Center, and the NASA Dryden Flight Research Center. Upon completion of a wing glove design, a thorough computational evaluation was necessary to determine if the design can meet the experimental requirements. First, representative CAD...
Air-Breathing Laminar Flow-Based Direct Methanol Fuel Cell with Alkaline Electrolyte
Kenis, Paul J. A.
methanol fuel cells DMFCs and polymer electrolyte membrane-based fuel cells PEMFCs, operated with hydrogen/oxygen .1-3 In most fuel cells, a polymer electrolyte membrane such as Nafion allows protons to dif- fuse to fuel cross- over, cathode flooding and anode dry-out water management due to osmotic drag of water
Kenis, Paul J. A.
2005-01-01
Available online 14 April 2005 Abstract The lack of a polymer electrolyte membrane (PEM, e.g. Nafion crossover, cathode flooding, and anode dry-out, as we reported previously. This paper explores the media: Membraneless micro fuel cells; Polymer electrolyte membrane (PEM); Open cell potential (OCP) 1. Introduction
Single Bubble in Laminar and Turbulent Shear Flows Using Interface Tracking
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservation ofAlbuquerque|Sensitive Species3 Outlook forSimulations Yield Clues
The dynamics of transition to turbulence in plane Couette flow
Viswanath, D
2007-01-01
In plane Couette flow, the incompressible fluid between two plane parallel walls is driven by the motion of those walls. The laminar solution, in which the streamwise velocity varies linearly in the wall-normal direction, is known to be linearly stable at all Reynolds numbers ($Re$). Yet, in both experiments and computations, turbulence is observed for $Re \\gtrsim 360$. In this article, we show that when the laminar flow is perturbed on to the transition {\\it threshold}, the flow approaches either steady or traveling wave solutions. These solutions exhibit some aspects of turbulence but are not fully turbulent even at $Re=4000$. However, these solutions are linearly unstable and flows that evolve along their unstable directions become fully turbulent. The solution approached by a threshold perturbation depends upon the nature of the perturbation. Surprisingly, the positive eigenvalue that corresponds to one family of solutions decreases in magnitude with increasing $Re$, with the rate of decrease given by $Re...
Van Hirtum, Annemie
Hot film/wire calibration for low to moderate flow velocities This article has been downloaded from fluid flow dynamic properties by deducing instantaneous velocities from local heat transfer information) or the characteristics of a laminar pipe flow (Yue and Malmstrom 1998). Despite the complexity of some techniques
Computations of Laminar Premixed Flames Ashraf N. Al-Khateeb , Joseph M. Powers , and Samuel Paolucci all detailed continuum physics in the re- action zone for one-dimensional steady laminar premixed/or unsteady laminar premixed flame simulations in the literature. I. Introduction It is well understood
Development of imaging methods to quantify the laminar microstructure in rat hearts
Hudson, Kristen Kay
2004-11-15
can be investigated and its laminar structure can be quantified. Many of the techniques that have been used to view the microstructure of the heart require the use of toxic or caustic chemicals for fixation or staining. An efficient imaging method...
Chen, Zheng [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China)
2011-02-15
Large discrepancies among the laminar flame speeds and Markstein lengths of methane/air mixtures measured by different researchers using the same constant-pressure spherical flame method are observed. As an effort to reduce these discrepancies, one linear model (LM, the stretched flame speed changes linearly with the stretch rate) and two non-linear models (NM I and NM II, the stretched flame speed changes non-linearly with the stretch rate) for extracting the laminar flame speed and Markstein length from propagating spherical flames are investigated. The accuracy and performance of the LM, NM I, and NM II are found to strongly depend on the Lewis number. It is demonstrated that NM I is the most accurate for mixtures with large Lewis number (positive Markstein length) while NM II is the most accurate for mixtures with small Lewis number (negative Markstein length). Therefore, in order to get accurate laminar flame speed and Markstein length from spherical flame experiments, different non-linear models should be used for different mixtures. The validity of the theoretical results is further demonstrated by numerical and experimental studies. The results of this study can be used directly in spherical flame experiments measuring the laminar flame speed and Markstein length. (author)
Measurement of laminar burning speeds and Markstein lengths using a novel methodology
Tahtouh, Toni; Halter, Fabien; Mounaim-Rousselle, Christine [Institut PRISME, Universite d'Orleans, 8 rue Leonard de Vinci-45072, Orleans Cedex 2 (France)
2009-09-15
Three different methodologies used for the extraction of laminar information are compared and discussed. Starting from an asymptotic analysis assuming a linear relation between the propagation speed and the stretch acting on the flame front, temporal radius evolutions of spherically expanding laminar flames are postprocessed to obtain laminar burning velocities and Markstein lengths. The first methodology fits the temporal radius evolution with a polynomial function, while the new methodology proposed uses the exact solution of the linear relation linking the flame speed and the stretch as a fit. The last methodology consists in an analytical resolution of the problem. To test the different methodologies, experiments were carried out in a stainless steel combustion chamber with methane/air mixtures at atmospheric pressure and ambient temperature. The equivalence ratio was varied from 0.55 to 1.3. The classical shadowgraph technique was used to detect the reaction zone. The new methodology has proven to be the most robust and provides the most accurate results, while the polynomial methodology induces some errors due to the differentiation process. As original radii are used in the analytical methodology, it is more affected by the experimental radius determination. Finally, laminar burning velocity and Markstein length values determined with the new methodology are compared with results reported in the literature. (author)
Nonlinear effects in the extraction of laminar flame speeds from expanding spherical flames
Kelley, A.P.; Law, C.K.
2009-09-15
Various factors affecting the determination of laminar flames speeds from outwardly propagating spherical flames in a constant-pressure combustion chamber were considered, with emphasis on the nonlinear variation of the stretched flame speed to the flame stretch rate, and the associated need to nonlinearly extrapolate the stretched flame speed to yield an accurate determination of the laminar flame speed and Markstein length. Experiments were conducted for lean and rich n-butane/air flames at 1atm initial pressure, demonstrating the complex and nonlinear nature of the dynamics of flame evolution, and the strong influences of the ignition transient and chamber confinement during the initial and final periods of the flame propagation, respectively. These experimental data were analyzed using the nonlinear relation between the stretched flame speed and stretch rate, yielding laminar flame speeds that agree well with data determined from alternate flame configurations. It is further suggested that the fidelity in the extraction of the laminar flame speed from expanding spherical flames can be facilitated by using small ignition energy and a large combustion chamber. (author)
Laminar Flame Speed Measurments of Synthetic Gas Blends with Hydrocarbon Impurities
Keesee, Charles Lewis
2015-04-09
New laminar flame speed measurements have been taken for a wide range of synthetic gas, or syngas, mixtures. These experiments began with two baseline mixtures. The first of these baseline mixtures was a bio-syngas surrogate with a 50/50 H2/CO split...
Bolster, Diogo
, demonstrated that at asymptotic times, for laminar flow conditions transport in a cylindrical tube canModeling preasymptotic transport in flows with significant inertial and trapping effects Borgne b , Jérémy Bouquain b , Phillipe Davy b a Environmental Fluid Dynamics Laboratories, Dept
Khandekar, Sameer
, Indian Institute of Technology Kanpur, Kanpur 208016, UP, India a r t i c l e i n f o Article history- scale mass transfer process, fuel cells, etc. The unique and complex flow characteristics require under.2e1.6 times more as compared with laminar single-phase liquid flow. In addition, for a given liquid
Bernhard Ketzer
2012-08-25
The SU(3)_flavor constituent quark model has been quite successful to explain the properties as well as the observed spectrum of mesons with pseudoscalar and vector quantum numbers. Many radial and orbital excitations of quark-antiquark systems predicted by the model, however, have not yet been observed experimentally or assigned unambiguously. In addition, a much richer spectrum of mesons is expected from QCD, in which quarks interact which each other through the exchange of colored self-interacting gluons. Owing to this particular structure of QCD, configurations are allowed in which an excited gluonic field contributes to the quantum numbers J^{PC} of the meson. States with a valence color-octet qqbar' pair neutralized in color by an excited gluon field are termed hybrids. The observation of such states, however, is difficult because they will mix with ordinary qqbar' states with the same quantum numbers, merely augmenting the observed spectrum for a given J^{PC}. Since the gluonic field may carry quantum numbers other than 0^{++}, however, this can give rise to states with "exotic" quantum numbers J^{PC}=0^{--}, 0^{+-}, 1^{-+}, 2^{+-},... The lowest-lying hybrid multiplet is expected to contain a state with exotic quantum numbers J^{PC}=1^{-+}. The identification of such a state is considered a "smoking gun" for the observation of non-qqbar mesons. The search for hybrid states has been a central goal of hadron spectroscopy in the last 20 years. Ongoing and upcoming high-statistics experiments are expected to shed new light on the existence of such states in nature. In this paper, theoretical predictions for masses and decay modes as well as recent experimental evidence for hybrid meson states and future experimental directions are discussed.
Absolute Measurement Of Laminar Shear Rate Using Photon Correlation Spectroscopy
Elliot Jenner; Brian D'Urso
2015-05-11
An absolute measurement of the components of the shear rate tensor $\\mathcal{S}$ in a fluid can be found by measuring the photon correlation function of light scattered from particles in the fluid. Previous methods of measuring $\\mathcal{S}$ involve reading the velocity at various points and extrapolating the shear, which can be time consuming and is limited in its ability to examine small spatial scale or short time events. Previous work in Photon Correlation Spectroscopy has involved only approximate solutions, requiring free parameters to be scaled by a known case, or different cases, such as 2-D flows, but here we present a treatment that provides quantitative results directly and without calibration for full 3-D flow. We demonstrate this treatment experimentally with a cone and plate rheometer.
Michikoshi, Shugo; Kokubo, Eiichiro [Center for Computational Astrophysics, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan); Inutsuka, Shu-ichiro, E-mail: michikoshi@cfca.j, E-mail: kokubo@th.nao.ac.j, E-mail: inutsuka@nagoya-u.j [Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)
2010-08-20
We investigate the formation process of planetesimals from the dust layer by the gravitational instability in the gas disk using local N-body simulations. The gas is modeled as a background laminar flow. We study the formation process of planetesimals and its dependence on the strength of the gas drag. Our simulation results show that the formation process is divided into three stages qualitatively: the formation of wake-like density structures, the creation of planetesimal seeds, and their collisional growth. The linear analysis of the dissipative gravitational instability shows that the dust layer is secularly unstable although Toomre's Q value is larger than unity. However, in the initial stage, the growth time of the gravitational instability is longer than that of the dust sedimentation and the decrease in the velocity dispersion. Thus, the velocity dispersion decreases and the disk shrinks vertically. As the velocity dispersion becomes sufficiently small, the gravitational instability finally becomes dominant. Then wake-like density structures are formed by the gravitational instability. These structures fragment into planetesimal seeds. The seeds grow rapidly owing to mutual collisions.
Choi, B.C.; Chung, S.H.
2010-12-15
The autoignition characteristics of laminar lifted flames of methane, ethylene, ethane, and n-butane fuels have been investigated experimentally in coflow air with elevated temperature over 800 K. The lifted flames were categorized into three regimes depending on the initial temperature and fuel mole fraction: (1) non-autoignited lifted flame, (2) autoignited lifted flame with tribrachial (or triple) edge, and (3) autoignited lifted flame with mild combustion. For the non-autoignited lifted flames at relatively low temperature, the existence of lifted flame depended on the Schmidt number of fuel, such that only the fuels with Sc > 1 exhibited stationary lifted flames. The balance mechanism between the propagation speed of tribrachial flame and local flow velocity stabilized the lifted flames. At relatively high initial temperatures, either autoignited lifted flames having tribrachial edge or autoignited lifted flames with mild combustion existed regardless of the Schmidt number of fuel. The adiabatic ignition delay time played a crucial role for the stabilization of autoignited flames. Especially, heat loss during the ignition process should be accounted for, such that the characteristic convection time, defined by the autoignition height divided by jet velocity was correlated well with the square of the adiabatic ignition delay time for the critical autoignition conditions. The liftoff height was also correlated well with the square of the adiabatic ignition delay time. (author)
Relation between plasma plume density and gas flow velocity in atmospheric pressure plasma
Yambe, Kiyoyuki; Taka, Shogo; Ogura, Kazuo [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan)] [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan)
2014-04-15
We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. To study the properties of the plasma plume, the plasma plume current is estimated from the difference in currents on the circuit, and the drift velocity is measured using a photodetector. The relation of the plasma plume density n{sub plu}, which is estimated from the current and the drift velocity, and the gas flow velocity v{sub gas} is examined. It is found that the dependence of the density on the gas flow velocity has relations of n{sub plu} ? log(v{sub gas}). However, the plasma plume density in the laminar flow is higher than that in the turbulent flow. Consequently, in the laminar flow, the density increases with increasing the gas flow velocity.
Scale invariance at the onset of turbulence in Couette flow
Shi, Liang; Hof, Bjoern
2013-01-01
Laminar-turbulent intermittency is intrinsic to the transitional regime of a wide range of fluid flows including pipe, channel, boundary layer and Couette flow. In the latter turbulent spots can grow and form continuous stripes, yet in the stripe-normal direction they remain interspersed by laminar fluid. We carry out direct numerical simulations in a long narrow domain and observe that individual turbulent stripes are transient. In agreement with recent observations in pipe flow we find that turbulence becomes sustained at a distinct critical point once the spatial proliferation outweighs the inherent decaying process. By resolving the asymptotic size distributions close to criticality we can for the first time demonstrate scale invariance at the onset of turbulence.
Hybrid ECAL: Optimization and Related Developments
T. Suehara; H. Hirai; H. Sumida; H. Ueno; Y. Sudo; T. Yoshioka; K. Kawagoe
2015-03-30
Hybrid ECAL is a cost-conscious option of electromagnetic calorimeter (ECAL) for particle flow calorimetry to be used in a detector of International Linear Collider (ILC). It is a combination of silicon-tungsten ECAL, which realizes high granularity and robust measurement of electromagnetic shower, and scintillator-tungsten ECAL, which gives affordable cost with similar performance to silicon. Optimization and a data acquisition trial in a test bench for the hybrid ECAL are described in this article.
Hybrid ECAL: Optimization and Related Developments
Suehara, T; Sumida, H; Ueno, H; Sudo, Y; Yoshioka, T; Kawagoe, K
2015-01-01
Hybrid ECAL is a cost-conscious option of electromagnetic calorimeter (ECAL) for particle flow calorimetry to be used in a detector of International Linear Collider (ILC). It is a combination of silicon-tungsten ECAL, which realizes high granularity and robust measurement of electromagnetic shower, and scintillator-tungsten ECAL, which gives affordable cost with similar performance to silicon. Optimization and a data acquisition trial in a test bench for the hybrid ECAL are described in this article.
Flanagan, C
2006-01-01
O’Callahan and J. -D. Choi. Hybrid dynamic data race detec-subtyping is sound, the hybrid compilation algorithmHybrid Type Checking Cormac Flanagan Department of Computer
Unsteady Reversed Stagnation-Point Flow over a Flat Plate
Sin, Vai Kuong
2013-01-01
This paper investigates the nature of the development of two-dimensional laminar flow of an incompressible fluid at the reversed stagnation-point. ". In this study, we revisit the problem of reversed stagnation-point flow over a flat plate. Proudman and Johnson (1962) first studied the flow and obtained an asymptotic solution by neglecting the viscous terms. This is no true in neglecting the viscous terms within the total flow field. In particular it is pointed out that for a plate impulsively accelerated from rest to a constant velocity V0 that a similarity solution to the self-similar ODE is obtained which is noteworthy completely analytical.
Stanley, H. Eugene
contribution to the laminar fluid flow through the void space. The calcu- lations we perform do not apply on Fluid Flow through Disordered Porous Media J. S. Andrade, Jr.,1,3 U. M. S. Costa,1 M. P. Almeida,1 H. A.11.+j A standard approach in the investigation of single- phase fluid flow in microscopically disordered
Dooley, S.; Burke, M. P.; Chaos, M.; Stein, Y.; Dryer, F. L.; Zhukov, V. P.; Finch, O.; Simmie, J. M.; Curran, H. J.
2010-07-16
The oxidation of methyl formate (CH{sub 3}OCHO) has been studied in three experimental environments over a range of applied combustion relevant conditions: 1. A variable-pressure flow reactor has been used to quantify reactant, major intermediate and product species as a function of residence time at 3 atm and 0.5% fuel concentration for oxygen/fuel stoichiometries of 0.5, 1.0, and 1.5 at 900 K, and for pyrolysis at 975 K. 2. Shock tube ignition delays have been determined for CH{sub 3}OCHO/O{sub 2}/Ar mixtures at pressures of ? 2.7, 5.4, and 9.2 atm and temperatures of 1275–1935 K for mixture compositions of 0.5% fuel (at equivalence ratios of 1.0, 2.0, and 0.5) and 2.5% fuel (at an equivalence ratio of 1.0). 3. Laminar burning velocities of outwardly propagating spherical CH{sub 3}OCHO/air flames have been determined for stoichiometries ranging from 0.8–1.6, at atmospheric pressure using a pressure-release-type high-pressure chamber. A detailed chemical kinetic model has been constructed, validated against, and used to interpret these experimental data. The kinetic model shows that methyl formate oxidation proceeds through concerted elimination reactions, principally forming methanol and carbon monoxide as well as through bimolecular hydrogen abstraction reactions. The relative importance of elimination versus abstraction was found to depend on the particular environment. In general, methyl formate is consumed exclusively through molecular decomposition in shock tube environments, while at flow reactor and freely propagating premixed flame conditions, there is significant competition between hydrogen abstraction and concerted elimination channels. It is suspected that in diffusion flame configurations the elimination channels contribute more significantly than in premixed environments.
General single phase wellbore flow model
Ouyang, Liang-Biao; Arbabi, S.; Aziz, K.
1997-02-05
A general wellbore flow model, which incorporates not only frictional, accelerational and gravitational pressure drops, but also the pressure drop caused by inflow, is presented in this report. The new wellbore model is readily applicable to any wellbore perforation patterns and well completions, and can be easily incorporated in reservoir simulators or analytical reservoir inflow models. Three dimensionless numbers, the accelerational to frictional pressure gradient ratio R{sub af}, the gravitational to frictional pressure gradient ratio R{sub gf}, and the inflow-directional to accelerational pressure gradient ratio R{sub da}, have been introduced to quantitatively describe the relative importance of different pressure gradient components. For fluid flow in a production well, it is expected that there may exist up to three different regions of the wellbore: the laminar flow region, the partially-developed turbulent flow region, and the fully-developed turbulent flow region. The laminar flow region is located near the well toe, the partially-turbulent flow region lies in the middle of the wellbore, while the fully-developed turbulent flow region is at the downstream end or the heel of the wellbore. Length of each region depends on fluid properties, wellbore geometry and flow rate. As the distance from the well toe increases, flow rate in the wellbore increases and the ratios R{sub af} and R{sub da} decrease. Consequently accelerational and inflow-directional pressure drops have the greatest impact in the toe region of the wellbore. Near the well heel the local wellbore flow rate becomes large and close to the total well production rate, here R{sub af} and R{sub da} are small, therefore, both the accelerational and inflow-directional pressure drops can be neglected.
Self-potential observations during hydraulic fracturing
Moore, Jeffrey R.; Glaser, Steven D.
2008-01-01
assumption that fluid flow is laminar; an assumption thatspecimens, fluid flow prior to fracturing remains laminar
Self-potential observations during hydraulic fracturing
Moore, J R; Glaser, Steven D
2007-01-01
assumption that fluid flow is laminar; an assumption thatspecimens, fluid flow prior to fracturing remains laminar
Hybrid Control of a Turret Wake Bojan Vukasinovic
Gordeyev, Stanislav
Effects of hybrid flow control and its active and passive components on the aerodynamic characteristics flow control is further assisted by global flow alterations induced by a passive forward partition housing for pointing and tracking laser beams from airborne platforms. An optical aperture is therefore
Electrical probe diagnostics for the laminar flame quenching distance
Karrer, Maxime; Makarov, Maxime; Bellenoue, Marc; Labuda, Sergei; Sotton, Julien
2010-02-15
A simplified theory, previously developed for the general case of weakly ionized gas flow, is used to predict electrical probe response when the flame is quenched on the probe surface. This theory is based on the planar model of space charge sheaths around the measuring electrode. For the flame quenching case, by assuming that the sheath thickness is comparable with the thermal boundary layer thickness, probe current can be related to flame quenching distance. The theoretical assumptions made to obtain the analytical formulation of probe current were experimentally proved by using direct visualization and high-frequency PIV. The direct visualization method was also used to validate the results of flame quenching distance values obtained with electrical probe. The electrical probe diagnostics have been verified for both head-on and sidewall flame quenching regimes and for stoichiometric methane/air and propane/air mixtures in a pressure range of 0.05-0.6 MPa. (author)
Investigation on the properties of a laminar grating as a soft x-ray beam splitter
Liu Ying; Fuchs, Hans-Joerg; Liu Zhengkun; Chen Huoyao; He Shengnan; Fu Shaojun; Kley, Ernst-Bernhard; Tuennermann, Andreas
2010-08-10
Laminar-type gratings as soft x-ray beam splitters for interferometry are presented. Gold-coated grating beam splitters with 1000 lines/mm are designed for grazing incidence operation at 13.9nm. They are routinely fabricated using electron beam lithography and ion etching techniques. The laminar grating is measured to have almost equal absolute efficiencies of about 20% in the zeroth and -1st orders, which enables a fringe visibility up to 0.99 in the interferometer. The discrepancy of the grating profiles between the optimized theoretical and the experimental results is analyzed according to the comparison of the optimized simulation results and the measurement realization of the grating efficiencies. By a precise control of the grating profile, the grating efficiency in the -1st order and the fringe visibility could be improved to 25% and 1, respectively.
Analysis of the flamelet concept in the numerical simulation of laminar partially premixed flames
Consul, R.; Oliva, A.; Perez-Segarra, C.D.; Carbonell, D.; de Goey, L.P.H.
2008-04-15
The aim of this work is to analyze the application of flamelet models based on the mixture fraction variable and its dissipation rate to the numerical simulation of partially premixed flames. Although the main application of these models is the computation of turbulent flames, this work focuses on the performance of flamelet concept in laminar flame simulations removing, in this way, turbulence closure interactions. A well-known coflow methane/air laminar flame is selected. Five levels of premixing are taken into account from an equivalence ratio {phi}={infinity} (nonpremixed) to {phi}=2.464. Results obtained using the flamelet approaches are compared to data obtained from the detailed solution of the complete transport equations using primitive variables. Numerical simulations of a counterflow flame are also presented to support the discussion of the results. Special emphasis is given to the analysis of the scalar dissipation rate modeling. (author)
The Laminar Flame Speedup by Neon-22 Enrichment in White Dwarf Supernovae
David A. Chamulak; Edward F. Brown; Francis X. Timmes
2006-12-18
Carbon-oxygen white dwarfs contain neon-22 formed from alpha-captures onto nitrogen during core He burning in the progenitor star. In a white dwarf (type Ia) supernova, the neon-22 abundance determines, in part, the neutron-to-proton ratio and hence the abundance of radioactive nickel-56 that powers the lightcurve. The neon-22 abundance also changes the burning rate and hence the laminar flame speed. We tabulate the flame speedup for different initial carbon and neon-22 abundances and for a range of densities. This increase in the laminar flame speed--about 30% for a neon-22 mass fraction of 6%--affects the deflagration just after ignition near the center of the white dwarf, where the laminar speed of the flame dominates over the buoyant rise, and in regions of lower density ~ 10^7 g/cm3 where a transition to distributed burning is conjectured to occur. The increase in flame speed will decrease the density of any transition to distributed burning.
An experimental investigation of the mean flow field of a wavy cylinder at critical Reynolds numbers
Damiana, Thomas Anthony
1994-01-01
at a Reynolds number which produces laminar separation (ReD= 100,000), one producing turbulent separation (ReD= 400,000), and one transitional Reynolds number (ReD= 200,000). These tests revealed that similar characteristics exist between flow fields...
Dynamic pressure response of water flow between closely spaced roughened flat plates
Hess, John Charles
1993-01-01
. The friction factors were found to differ significantly from the Moody diagram in that at small clearances, laminar flow appears to not always conform to the [] line predicted by theory. In addition, it is seen that increasing the gap between the plates from...
Application of the ``Ke'' model to open channel flows in a magnetic field
Abdou, Mohamed
of turbulence) by a strong magnetic field. Based on the experimental data, the laminarization in channel flows-133 Engineering IV, Los Angeles, CA 90095-1597, USA b Department of Nuclear Engineering, Kyoto University, Japan. The model coefficients have been tuned by a computer optimization using available experimental data
Flow of wet powder in a conical centrifugal filter--an analytical model A.F.M. Bizard, D.D. Symons n
Symons, Digby
Flow of wet powder in a conical centrifugal filter--an analytical model A.F.M. Bizard, D.D. Symons 14 August 2011 Available online 25 August 2011 Keywords: Centrifugation Filtration Laminar flow the wall of the cone along a generator under centrifugal force, which also forces the fluid out of the cone
Hybridization and Selective Release of DNA Microarrays
Beer, N R; Baker, B; Piggott, T; Maberry, S; Hara, C M; DeOtte, J; Benett, W; Mukerjee, E; Dzenitis, J; Wheeler, E K
2011-11-29
DNA microarrays contain sequence specific probes arrayed in distinct spots numbering from 10,000 to over 1,000,000, depending on the platform. This tremendous degree of multiplexing gives microarrays great potential for environmental background sampling, broad-spectrum clinical monitoring, and continuous biological threat detection. In practice, their use in these applications is not common due to limited information content, long processing times, and high cost. The work focused on characterizing the phenomena of microarray hybridization and selective release that will allow these limitations to be addressed. This will revolutionize the ways that microarrays can be used for LLNL's Global Security missions. The goals of this project were two-fold: automated faster hybridizations and selective release of hybridized features. The first study area involves hybridization kinetics and mass-transfer effects. the standard hybridization protocol uses an overnight incubation to achieve the best possible signal for any sample type, as well as for convenience in manual processing. There is potential to significantly shorten this time based on better understanding and control of the rate-limiting processes and knowledge of the progress of the hybridization. In the hybridization work, a custom microarray flow cell was used to manipulate the chemical and thermal environment of the array and autonomously image the changes over time during hybridization. The second study area is selective release. Microarrays easily generate hybridization patterns and signatures, but there is still an unmet need for methodologies enabling rapid and selective analysis of these patterns and signatures. Detailed analysis of individual spots by subsequent sequencing could potentially yield significant information for rapidly mutating and emerging (or deliberately engineered) pathogens. In the selective release work, optical energy deposition with coherent light quickly provides the thermal energy to single spots to release hybridized DNA. This work leverages LLNL expertise in optics, microfluids, and bioinformatics.
Pousse, E.; Tian, Z.Y.; Glaude, P.A.; Fournet, R.; Battin-Leclerc, F. [Laboratoire des Reactions et de Genie des Procedes, CNRS, Nancy Universite, 1 rue Grandville, BP 20451, 54001 NANCY Cedex (France)
2010-07-15
To better understand the chemistry of the combustion of components of diesel fuel, the structure of a laminar lean premixed methane flame doped with indane has been investigated. The inlet gases contained 7.1% (molar) of methane, 36.8% of oxygen and 0.9% of indane corresponding to an equivalence ratio of 0.67 and a ratio C{sub 10}H{sub 14}/CH{sub 4} of 12.8%. The flame has been stabilized on a burner at a pressure of 6.7 kPa (50 Torr) using argon as diluent, with a gas velocity at the burner of 49.1 cm s{sup -1} at 333 K. Quantified species included the usual methane C{sub 0}-C{sub 2} combustion products, but also 16 C{sub 3}-C{sub 5} non-aromatic hydrocarbons, 6 C{sub 1}-C{sub 3} non-aromatic oxygenated compounds, as well as 22 aromatic products, namely benzene, toluene, xylenes, phenylacetylene, ethylbenzene, styrene, propenylbenzene, allylbenzene, n-propylbenzene, methylstyrenes, ethyltoluenes, trimethylbenzenes, n-butylbenzene, dimethylethylbenzene, indene, methylindenes, methylindane, benzocyclobutene, naphthalene, phenol, benzaldehyde, and benzofuran. A new mechanism for the oxidation of indane was proposed whose predictions were in satisfactory agreement with measured species profiles in both flames and jet-stirred reactor experiments. The main reaction pathways of consumption of indane have been derived from flow rate analyses in the two types of reactors. A comparison of the effect of the addition of three components of diesel fuel, namely indane, n-butylbenzene and n-propylcyclohexane (parts I and II of this series of paper), on the structure of a laminar lean premixed methane flame is also presented. (author)
The Flow of Newtonian Fluids in Axisymmetric Corrugated Tubes
Taha Sochi
2010-06-08
This article deals with the flow of Newtonian fluids through axially-symmetric corrugated tubes. An analytical method to derive the relation between volumetric flow rate and pressure drop in laminar flow regimes is presented and applied to a number of simple tube geometries of converging-diverging nature. The method is general in terms of fluid and tube shape within the previous restrictions. Moreover, it can be used as a basis for numerical integration where analytical relations cannot be obtained due to mathematical difficulties.
The Flow of Newtonian Fluids in Axisymmetric Corrugated Tubes
Sochi, Taha
2010-01-01
This article deals with the flow of Newtonian fluids through axially-symmetric corrugated tubes. An analytical method to derive the relation between volumetric flow rate and pressure drop in laminar flow regimes is presented and applied to a number of simple tube geometries of converging-diverging nature. The method is general in terms of fluid and tube shape within the previous restrictions. Moreover, it can be used as a basis for numerical integration where analytical relations cannot be obtained due to mathematical difficulties.
Gore, R.A. (Los Alamos National Lab., NM (USA)); Crowe, C.T. (Washington State Univ., Pullman, WA (USA). Dept. of Mechanical and Materials Engineering); Bejan, A. (Duke Univ., Durham, NC (USA). Dept. of Mechanical Engineering and Materials Science)
1990-01-01
Experiments performed demonstrate the transition to turbulent flow of water jets discharging coaxially into a stream confined in a round duct. The critical Reynolds number is shown to be a strong function of velocity ratio. From the flow visualization it is shown that a proportionality between the laminar length of the jet (L) and the wavelength ({lambda}) can be seen in the region of transition to turbulence. The proportionality coincides with similar observations concerning the transition to turbulence in various other flows. A brief argument based on scale analysis is presented for the confined coaxial jet and round plume. The apparent universality of the L/{lambda} {approximately} O(10) scaling law supports the conclusion that the laminar sections of all naturally progressing boundary layer-type flows are geometrically similar. 21 refs., 8 figs.
Tang Jie; Li Shibo; Zhao Wei; Wang Yishan [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an (China); Duan Yixiang [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an (China); Research Center of Analytical Instrumentation, Sichuan University, Chengdu (China)
2012-06-18
A stable nonthermal laminar atmospheric-pressure plasma source equipped with dielectric-barrier discharge was developed to realize more efficient plasma generation, with the total energy consumption reduced to nearly 25% of the original. Temperature and emission spectra monitoring indicates that this plasma is uniform in the lateral direction of the jet core region. It is also found that this plasma contains not only abundant excited argon atoms but also sufficient excited N{sub 2} and OH. This is mainly resulted from the escape of abundant electrons from the exit, due to the sharp decrease of sustaining voltage and the coupling between ions and electrons.
Towards a model of large scale dynamics in transitional wall-bounded flows
Manneville, Paul
2015-01-01
A system of simplified equations is proposed to govern the feedback interactions of large-scale flows present in laminar-turbulent patterns of transitional wall-bounded flows, with small-scale Reynolds stresses generated by the self-sustainment process of turbulence itself modeled using an extension of Waleffe's approach (Phys. Fluids 9 (1997) 883-900), the detailed expression of which is displayed as an annex to the main text.
Michael R. Gross; Kajari Ghosh; Alex K. Manda; Sumanjit Aich
2006-05-08
The theory behind how chemically reactive tracers are used to characterize the velocity and temperature distribution in steady flowing systems is reviewed. Kinetic parameters are established as a function of reservoir temperatures and fluid residence times for selecting appropriate reacting systems. Reactive tracer techniques are applied to characterize the temperature distribution in a laminar-flow heat exchanger. Models are developed to predict reactive tracer behavior in fractured geothermal reservoirs of fixed and increasing size.
Temperature distribution in a flowing fluid heated in a microwave resonant cavity
Thomas, J.R. Jr. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States); Nelson, E.M.; Kares, R.J.; Stringfield, R.M. [Los Alamos National Lab., NM (United States)
1996-04-01
This paper presents results of an analytical study of microwave heating of a fluid flowing through a tube situated along the axis of a cylindrical microwave applicator. The interaction of the microwave field pattern and the fluid velocity profiles is illustrated for both laminar and turbulent flow. Resulting temperature profiles are compared with those generated by conventional heating through a surface heat flux. It is found that microwave heating offers several advantages over conventional heating.
Hybrid and multifield inflation
Sfakianakis, Evangelos I
2014-01-01
In this thesis I study the generation of density perturbations in two classes of inflationary models: hybrid inflation and multifield inflation with non-minimal coupling to gravity. In the case of hybrid inflation, we ...
Garcia, L.; Carreras, B. A.; Llerena, I.; Calvo, I. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes, Madrid (Spain); Departament d'Algebra i Geometria, Facultat de Matematiques, Universitat de Barcelona, Barcelona (Spain); Laboratorio Nacional de Fusion, Asociacion EURATOM-CIEMAT, 28040 Madrid (Spain)
2009-10-15
For the resistive pressure-gradient-driven turbulence model, the transition from laminar regime to fully developed turbulence is not simple and goes through several phases. For low values of the plasma parameter {beta}, a single quasicoherent structure forms. As {beta} increases, several of these structures may emerge and in turn take the dominant role. Finally, at high {beta}, fully developed turbulence with a broad spectrum is established. A suitable characterization of this transition can be given in terms of topological properties of the flow. Here, we analyze these properties that provide an understanding of the turbulence-induced transport and give a measure of the breaking of the homogeneity of the turbulence. To this end, an approach is developed that allows discriminating between topological properties of plasma turbulence flows that are relevant to the transport dynamics and the ones that are not. This is done using computational homology tools and leads to a faster convergence of numerical results for a fixed level of resolution than previously presented in Phys. Rev. E 78, 066402 (2008)
Valenzuela, Javier (Hanover, NH)
2001-01-01
A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.
NONE
1996-06-01
This document describes efforts by the National Renewable Energy Laboratory to simulate hybrid power systems. Hybrid power systems combine multiple power sources such as wind turbines, photovoltaic (PV) arrays, diesel generators, and battery storage systems. They typically are used in remote areas, away from major electric grids. The Hybrid Power Test Bed is designed to assist the U.S. wind industry in developing and testing hybrid power generation systems. Test bed capabilities, features, and equipment are described.
Mesoscale hybrid calibration artifact
Tran, Hy D. (Albuquerque, NM); Claudet, Andre A. (Albuquerque, NM); Oliver, Andrew D. (Waltham, MA)
2010-09-07
A mesoscale calibration artifact, also called a hybrid artifact, suitable for hybrid dimensional measurement and the method for make the artifact. The hybrid artifact has structural characteristics that make it suitable for dimensional measurement in both vision-based systems and touch-probe-based systems. The hybrid artifact employs the intersection of bulk-micromachined planes to fabricate edges that are sharp to the nanometer level and intersecting planes with crystal-lattice-defined angles.
Hybrid Systems Frits Vaandrager
Vaandrager, Frits
on these data, the computer may decide to turn on a heating system, switch off a pump, etc. When a dangerous1 Hybrid Systems Frits Vaandrager 1 Introduction Hybrid systems are systems that intermix discrete. The specification, design and analysis of hybrid systems require a synthesis of ideas, concepts, mathe matical
Hawke, Ronald S. (Livermore, CA); Asay, James R. (Los Lunas, NM); Hall, Clint A. (Albuquerque, NM); Konrad, Carl H. (Albuquerque, NM); Sauve, Gerald L. (Berthoud, CO); Shahinpoor, Mohsen (Albuquerque, NM); Susoeff, Allan R. (Pleasanton, CA)
1993-01-01
A projectile for a railgun that uses a hybrid armature and provides a seed block around part of the outer surface of the projectile to seed the hybrid plasma brush. In addition, the hybrid armature is continuously vaporized to replenish plasma in a plasma armature to provide a tandem armature and provides a unique ridge and groove to reduce plasama blowby.
Liskiewicz, Maciej
Virginia Corn Hybrid and Management Trials 2007 Virginia Corn & Small Grain Management #12;VIRGINIA CORN HYBRID AND MANAGEMENT TRIALS IN 2007 Coordinators of Virginia Corn Hybrid Trials in 2007 Wade Thomason, Extension Specialist, Department of Crop and Soil Environmental Sciences, Virginia Tech Harry
Liskiewicz, Maciej
Virginia Corn Hybrid Management and Trials 2006 Virginia Corn & Small Grain Management #12;#12;Virginia Corn Hybrid and Management Trials 2006 Coordinators of Virginia Corn Hybrid Trials in 2006 Wade Thomason, Extension Specialist, Department of Crop and Soil Environmental Sciences, Virginia Tech Harry
Particle Migration of Quasi-Steady Flow in Concentrated Suspension for Powder Injection Molding
Chen, X.
A hybrid FEM/FDM algorithm for particle migration of quasi-steady flow in concentrated suspension materials is proposed in this study. This hybrid FEM/FDM algorithm in which the planar variables, such as pressure field, ...
Solids flow rate measurement in dense slurries
Porges, K.G.; Doss, E.D.
1993-09-01
Accurate and rapid flow rate measurement of solids in dense slurries remains an unsolved technical problem, with important industrial applications in chemical processing plants and long-distance solids conveyance. In a hostile two-phase medium, such a measurement calls for two independent parameter determinations, both by non-intrusive means. Typically, dense slurries tend to flow in laminar, non-Newtonian mode, eliminating most conventional means that usually rely on calibration (which becomes more difficult and costly for high pressure and temperature media). These issues are reviewed, and specific solutions are recommended in this report. Detailed calculations that lead to improved measuring device designs are presented for both bulk density and average velocity measurements. Cross-correlation, chosen here for the latter task, has long been too inaccurate for practical applications. The cause and the cure of this deficiency are discussed using theory-supported modeling. Fluid Mechanics are used to develop the velocity profiles of laminar non-Newtonian flow in a rectangular duct. This geometry uniquely allows the design of highly accurate `capacitive` devices and also lends itself to gamma transmission densitometry on an absolute basis. An absolute readout, though of less accuracy, is also available from a capacitive densitometer and a pair of capacitive sensors yields signals suitable for cross-correlation velocity measurement.
Jerzembeck, S.; Peters, N. [RWTH, Aachen (Germany); Pepiot-Desjardins, P.; Pitsch, H. [Department of Mechanical Engineering, Stanford University, CA (United States)
2009-02-15
Spherical flames of n-heptane, iso-octane, PRF 87 and gasoline/air mixtures are experimentally investigated to determine laminar burning velocities and Markstein lengths under engine-relevant conditions by using the constant volume bomb method. Data are obtained for an initial temperature of 373 K, equivalence ratios varying from {phi}=0.7 to {phi}=1.2, and initial pressures from 10 to 25 bar. To track the flame front in the vessel a dark field He-Ne laser Schlieren measurement technique and digital image processing were used. The propagating speed with respect to the burned gases and the stretch rate are determined from the rate of change of the flame radius. The laminar burning velocities are obtained through a linear extrapolation to zero stretch. The experimentally determined Markstein numbers are compared to theoretical predictions. A reduced chemical kinetic mechanism for n-heptane and iso-octane was derived from the Lawrence Livermore comprehensive mechanisms. This mechanism was validated for ignition delay times and flame propagation at low and high pressures. In summary an overall good agreement with the various experimental data sets used in the validation was obtained. (author)
Laminar burn rates of gun propellants measured in the high-pressure strand burner
Reaugh, J. E., LLNL
1997-10-01
The pressure dependence of the laminar burn rate of gun propellants plays a role in the design and behavior of high-performance guns. We have begun a program to investigate the effects of processing variables on the laminar burn rates, using our high-pressure strand burner to measure these rates at pressures exceeding 700 MPa. We have burned JA2 and M43 propellant samples, provided by Dr. Arpad Juhasz, ARL, from propellant lots previously used in round-robin tests. Our results at room temperature are in accord with other measurements. In addition, we present results measured for propellant that has been preheated to 50 C before burning. We used our thermochemical equilibrium code, CHEETAH, to help interpret the simultaneous pressure and temperature measurements taken during the testing, and show examples of its use. It has been modified to provide performance measures and equations of state for the products that are familiar to the gun-propellant community users of BLAKE.
Smith, J.R.
1993-10-15
The energy efficiency of various piston engine options for series hybrid automobiles are compared with conventional, battery powered electric, and proton exchange membrane (PEM) fuel cell hybrid automobiles. Gasoline, compressed natural gas (CNG), and hydrogen are considered for these hybrids. The engine and fuel comparisons are done on a basis of equal vehicle weight, drag, and rolling resistance. The relative emissions of these various fueled vehicle options are also presented. It is concluded that a highly optimized, hydrogen fueled, piston engine, series electric hybrid automobile will have efficiency comparable to a similar fuel cell hybrid automobile and will have fewer total emissions than the battery powered vehicle, even without a catalyst.
Subcritical transition to turbulence of a precessing flow in a cylindrical vessel
Herault, Johann; Giesecke, Andre; Stefani, Frank
2015-01-01
The transition to turbulence in a precessing cylindrical vessel is experimentally investigated. Our measurements are performed for a { nearly-resonant} configuration with an initially laminar flow dominated by an inertial mode with azimuthal wave number $m=1$ superimposed on a solid body rotation. By increasing the precession ratio, we observe a transition from the laminar to a non-linear regime, which then breakdowns to turbulence for larger precession ratio. Our measurements show that the transition to turbulence is subcritical, with a discontinuity of the wall-pressure and the power consumption at the threshold $\\epsilon_{LT}$. The turbulence is self-sustained below this threshold, describing a bifurcation diagram with a hysteresis. In this range of the control parameters, the turbulent flows can suddenly collapse after a finite duration, leading to a definitive relaminarization of the flow. The average lifetime $\\langle \\tau \\rangle$ of the turbulence increases rapidly when $\\epsilon$ tends to $\\epsilon_{...
Oblique inlet pressure loss for swirling flow entering a catalyst substrate
Persoons, T.; Vanierschot, M.; Van den Bulck, E. [Katholieke Universiteit Leuven, Department of Mechanical Engineering, Celestijnenlaan 300A, B-3001 Leuven (Belgium)
2008-05-15
This experimental study investigates the oblique inlet pressure loss for the entry of an annular swirling flow into an automotive catalyst substrate. The results are applicable to a wide range of compact heat exchangers. For zero swirl, the total pressure loss agrees with established expressions for pressure loss in developing laminar flow in parallel channels with finite wall thickness. For positive swirl, the additional pressure loss due to oblique flow entry is correlated to the tangential velocity upstream of the catalyst, measured using laser-Doppler anemometry. The obtained oblique inlet pressure loss correlation can improve the accuracy of numerical calculations of the flow distribution in catalysts. (author)
Influence of the gas-flow Reynolds number on a plasma column in a glass tube
Jin, Dong Jun; Uhm, Han S.; Cho, Guangsup [Department of Electronic and Biological Physics, Kwangwoon University, 20 Kwangwon-Ro, Nowon-Gu, Seoul 139-701 (Korea, Republic of)] [Department of Electronic and Biological Physics, Kwangwoon University, 20 Kwangwon-Ro, Nowon-Gu, Seoul 139-701 (Korea, Republic of)
2013-08-15
Atmospheric-plasma generation inside a glass tube is influenced by gas stream behavior as described by the Reynolds number (Rn). In experiments with He, Ne, and Ar, the plasma column length increases with an increase in the gas flow rate under laminar flow characterized by Rn < 2000. The length of the plasma column decreases as the flow rate increases in the transition region of 2000 < Rn < 4000. For a turbulent flow beyond Rn > 4000, the length of the plasma column is short in front of the electrode, eventually leading to a shutdown.
Suo, Zhigang
Laminar tendon composites with enhanced mechanical properties Kyle A. Alberti · Jeong-Yun Sun University, 4 Colby Street, Medford, MA 02155, USA e-mail: qiaobing.xu@tufts.edu J.-Y. Sun Á W. R. Illeperuma.-Y. Sun Á W. R. Illeperuma Á Z. Suo Kavli Institute for Bionano Science and Technology, Harvard University
Chen, Jacqueline H.; Hawkes, Evatt R.
2004-08-01
Direct numerical simulation (DNS) with complex chemistry was used to study statistics of displacement and consumption speeds in turbulent lean premixed methane-air flames. The main focus of the study is an evaluation of the extent to which a turbulent flame in the thin reaction zones regime can be described by an ensemble of strained laminar flames. Conditional averages with respect to strain for displacement and consumption speeds are presented over a wide range of strain typically encountered in a turbulent flame, compared with previous studies that either made local pointwise comparisons or conditioned the data on small strain and curvature. The conditional averages for positive strains are compared with calculated data from two different canonical strained laminar configurations to determine which is the optimal representation of a laminar flame structure embedded in a turbulent flame: the reactant-to-product (R-to-P) configuration or the symmetric twin flame configuration. Displacement speed statistics are compared for the progress-variable isosurface of maximum reaction rate and an isosurface toward the fresh gases, which are relevant for both modeling and interpretation of experiment results. Displacement speeds in the inner reaction layer are found to agree very well with the laminar R-to-P calculations over a wide range of strain for higher Damkhler number conditions, well beyond the regime in which agreement was expected. For lower Damkhler numbers, a reduced response to strain is observed, consistent with previous studies and theoretical expectations. Compared with the inner layer, broader and shifted probability density functions (PDFs) of displacement speed were observed in the fresh gases, and the agreement with the R-to-P calculations deteriorated. Consumption speeds show a poorer agreement with strained laminar calculations, which is attributed to multidimensional effects and a more attenuated unsteady response to strain fluctuations; however, they also show less departure from the unstrained laminar value, suggesting that detailed modeling of this quantity may not be critical for the conditions considered. For all quantities investigated, including CO production, the R-to-P laminar configuration provides an improved description relative to the twin flame configuration, which predicts qualitatively incorrect trends and overestimates extinction.
Linear and non-linear forced response of a conical, ducted, laminar premixed flame
Karimi, Nader; Brear, Michael J.; Jin, Seong-Ho; Monty, Jason P. [Department of Mechanical Engineering, University of Melbourne, Parkville, 3010 Vic. (Australia)
2009-11-15
This paper presents an experimental study on the dynamics of a ducted, conical, laminar premixed flame subjected to acoustic excitation of varying amplitudes. The flame transfer function is measured over a range of forcing frequencies and equivalence ratios. In keeping with previous works, the measured flame transfer function is in good agreement with that predicted by linear kinematic theory at low amplitudes of acoustic velocity excitation. However, a systematic departure from linear behaviour is observed as the amplitude of the velocity forcing upstream of the flame increases. This non-linearity is mostly in the phase of the transfer function and manifests itself as a roughly constant phase at high forcing amplitude. Nonetheless, as predicted by non-linear kinematic arguments, the response always remains close to linear at low forcing frequencies, regardless of the forcing amplitude. The origin of this phase behaviour is then sought through optical data post-processing. (author)
Experimental investigation of sound generation by a protuberance in a laminar boundary layer
Kobayashi, M.; Asai, M.; Inasawa, A. [Department of Aerospace Engineering, Tokyo Metropolitan University, 6-6 Asahigaoka, Hino, Tokyo 191-0065 (Japan)
2014-08-15
Sound radiation from a two-dimensional protuberance glued on the wall in a laminar boundary layer was investigated experimentally at low Mach numbers. When the protuberance was as high as the boundary-layer thickness, a feedback-loop mechanism set in between protuberance-generated sound and Tollmien-Schlichting (T-S) waves generated by the leading-edge receptivity to the upstream-propagating sound. Although occurrence of a separation bubble immediately upstream of the protuberance played important roles in the evolution of instability waves into vortices interacting with the protuberance, the frequency of tonal vortex sound was determined by the selective amplification of T-S waves in the linear instability stage upstream of the separation bubble and was not affected by the instability of the separation bubble.
DNS of laminar-turbulent boundary layer transition induced by solid obstacles
Orlandi, Paolo; Bernardini, Matteo
2015-01-01
Results of numerical simulations obtained by a staggered finite difference scheme together with an efficient immersed boundary method are presented to understand the effects of the shape of three-dimensional obstacles on the transition of a boundary layer from a laminar to a turbulent regime. Fully resolved Direct Numerical Simulations (DNS), highlight that the closer to the obstacle the symmetry is disrupted the smaller is the transitional Reynolds number. It has been also found that the transition can not be related to the critical roughness Reynolds number used in the past. The simulations highlight the differences between wake and inflectional instabilities, proving that two-dimensional tripping devices are more efficient in promoting the transition. Simulations at high Reynolds number demonstrate that the reproduction of a real experiment with a solid obstacle at the inlet is an efficient tool to generate numerical data bases for understanding the physics of boundary layers. The quality of the numerical ...
are used to estimate the external forces created by animal propulsion, the energetic costs of feeding laminar jet. Quarterly Journal of Mechanics and Applied Math 4: 321-329. In our study, the flow fields was in the fluid upstream of the tethered copepod, whereas the location of maximum velocity was in the fluid
ENERGY & ENVIRONMENT DIVISION ANNUAL REPORT 1979
Cairns, E.J.
2010-01-01
pores in laminar flow. The Newtonian fluid flows with afor laminar flow cylinder of (a) Newtonian fluid and (b)
Pulsed laser microbeams for cellular manipulation : applications in cell biology and microfluidics
Hellman, Amy Noel Stacy
2008-01-01
the parallel laminar flow of two fluids. The bubblerapidly mixing two fluids within a laminar flow has receiveddisrupts the laminar flow of the parallel fluid streams and
Fluidic Microvalve Digital Processors for Automated Biochemical Analysis
Jensen, Erik Christian
2011-01-01
for mixing. Non-laminar fluid flow during valve actuationFluid Dynamics Fluids typically have laminar flow profilesto the laminar flow profile of fluids within microchannels.
S. A. Voloshin
2002-11-20
Recent experimental results on directed and elliptic flow, theoretical developments, and new techniques for anisotropic flow analysis are reviewed.
Kondle, Satyanarayana
2011-10-21
the geometry shape, solid and fluid materials used, and surface roughness, among others. Many configurations of microchannels have been studied with various materials and compared for their effectiveness in heat removal. However, there is little research done...
Rothstein, Jonathan
schemes for passive mixing have been developed and studied, including T-type mixers 10 , serpentine, mixing rates are governed by molecular diffusion, and in the absence of enhanced mixing techniques on chips 1,2 . Molecular diffusion may be sufficient to mix ultrasmall volumes of fluid in the subpicoliter
Graviss, Matthew Sheridan
2005-08-29
This thesis provides experimental static and dynamic results for four pairs of seals, including a pair of smooth seals and three pairs of centrally grooved seals. The grooved seals have groove depth to clearance ratios ...
Formula Hybrid International Competition
Carver, Jeffrey C.
, and computerized control systems. But the greatest obstacle of all was that hybrid cars could not meet newlyFormula Hybrid International Competition May 4, 5, 6, 2009 #12;09 annual third We are thrilled to have 30 cars competing this year. The competition is the result of the hard work of many people
Hybrid Quantum Cloning Machine
Satyabrata Adhikari; A. K. Pati; Indranil Chakrabarty; B. S. Choudhury
2007-06-14
In this work, we introduce a special kind of quantum cloning machine called Hybrid quantum cloning machine. The introduced Hybrid quantum cloning machine or transformation is nothing but a combination of pre-existing quantum cloning transformations. In this sense it creates its own identity in the field of quantum cloners. Hybrid quantum cloning machine can be of two types: (i) State dependent and (ii) State independent or Universal. We study here the above two types of Hybrid quantum cloning machines. Later we will show that the state dependent hybrid quantum-cloning machine can be applied on only four input states. We will also find in this paper another asymmetric universal quantum cloning machine constructed from the combination of optimal universal B-H quantum cloning machine and universal anti-cloning machine. The fidelities of the two outputs are different and their values lie in the neighborhood of ${5/6} $
Hybrid Automata-based CEGAR for Rectangular Hybrid Systems
Liberzon, Daniel
Hybrid Automata-based CEGAR for Rectangular Hybrid Systems Pavithra Prabhakar, Sridhar Duggirala- example guided abstraction-refinement (CEGAR) for systems modelled as rectangular hybrid automata. The main difference, between our ap- proach and previous proposals for CEGAR for hybrid automata
Hybrid 2012 Innovative Hybrid Approaches to the Processing of
EACL 2012 Hybrid 2012 Innovative Hybrid Approaches to the Processing of Textual Data Proceedings@aclweb.org ii #12;Introduction The hybrid approach term covers a large set of situations in which different of the dedicated task. Hybrid approaches are commonly used in various NLP applications (i.e., automatic creation
Hybrid Systems State estimation for hybrid systems: applications
Tomlin, Claire
Hybrid Systems State estimation for hybrid systems: applications to aircraft tracking I. Hwang, H of a stochastic linear hybrid system, given only the continuous system output data, is studied. Well established techniques for hybrid estimation, known as the multiple model adaptive estimation algorithm
van de Meent, Jan-Willem; Somfai, Ellak; Sultan, Eric; van Saarloos, Wim
2008-01-01
We present simulations of coherent structures in compressible flows near the transition to turbulence using the Dissipative Particle Dynamics (DPD) method. The structures we find are remarkably consistent with experimental observations and DNS simulations of incompressible flows, despite a difference in Mach number of several orders of magnitude. The bifurcation from the laminar flow is bistable and shifts to higher Reynolds numbers when the fluid becomes more compressible. This work underlines the robustness of coherent structures in the transition to turbulence and illustrates the ability of particle-based methods to reproduce complex non-linear instabilities.
The Flow of Power-Law Fluids in Axisymmetric Corrugated Tubes
Sochi, Taha
2010-01-01
In this article we present an analytical method for deriving the relationship between the pressure drop and flow rate in laminar flow regimes, and apply it to the flow of power-law fluids through axially-symmetric corrugated tubes. The method, which is general with regards to fluid and tube shape within certain restrictions, can also be used as a foundation for numerical integration where analytical expressions are hard to obtain due to mathematical or practical complexities. Five converging-diverging geometries are used as examples to illustrate the application of this method.
The Flow of Power-Law Fluids in Axisymmetric Corrugated Tubes
Taha Sochi
2010-06-13
In this article we present an analytical method for deriving the relationship between the pressure drop and flow rate in laminar flow regimes, and apply it to the flow of power-law fluids through axially-symmetric corrugated tubes. The method, which is general with regards to fluid and tube shape within certain restrictions, can also be used as a foundation for numerical integration where analytical expressions are hard to obtain due to mathematical or practical complexities. Five converging-diverging geometries are used as examples to illustrate the application of this method.
Effects of CO addition on the characteristics of laminar premixed CH{sub 4}/air opposed-jet flames
Wu, C.-Y. [Advanced Engine Research Center, Kao Yuan University, Kaohsiung County, 821 (China); Chao, Y.-C.; Chen, C.-P.; Ho, C.-T. [Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 701 (China); Cheng, T.S. [Department of Mechanical Engineering, Chung Hua University, Hsinchu, 300 (China)
2009-02-15
The effects of CO addition on the characteristics of premixed CH{sub 4}/air opposed-jet flames are investigated experimentally and numerically. Experimental measurements and numerical simulations of the flame front position, temperature, and velocity are performed in stoichiometric CH{sub 4}/CO/air opposed-jet flames with various CO contents in the fuel. Thermocouple is used for the determination of flame temperature, velocity measurement is made using particle image velocimetry (PIV), and the flame front position is measured by direct photograph as well as with laser-induced predissociative fluorescence (LIPF) of OH imaging techniques. The laminar burning velocity is calculated using the PREMIX code of Chemkin collection 3.5. The flame structures of the premixed stoichiometric CH{sub 4}/CO/air opposed-jet flames are simulated using the OPPDIF package with GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. The measured flame front position, temperature, and velocity of the stoichiometric CH{sub 4}/CO/air flames are closely predicted by the numerical calculations. Detailed analysis of the calculated chemical kinetic structures reveals that as the CO content in the fuel is increased from 0% to 80%, CO oxidation (R99) increases significantly and contributes to a significant level of heat-release rate. It is also shown that the laminar burning velocity reaches a maximum value (57.5 cm/s) at the condition of 80% of CO in the fuel. Based on the results of sensitivity analysis, the chemistry of CO consumption shifts to the dry oxidation kinetics when CO content is further increased over 80%. Comparison between the results of computed laminar burning velocity, flame temperature, CO consumption rate, and sensitivity analysis reveals that the effect of CO addition on the laminar burning velocity of the stoichiometric CH{sub 4}/CO/air flames is due mostly to the transition of the dominant chemical kinetic steps. (author)
A Measure of Flow Vorticity with Helical Beams of Light
Rosales-Guzmán, Aniceto Belmonte Carmelo
2015-01-01
Vorticity describes the spinning motion of a fluid, i.e., the tendency to rotate, at every point in a flow. The interest in performing accurate and localized measurements of vorticity reflects the fact that many of the quantities that characterize the dynamics of fluids are intimately bound together in the vorticity field, being an efficient descriptor of the velocity statistics in many flow regimes. It describes the coherent structures and vortex interactions that are at the leading edge of laminar, transitional, and turbulent flows in nature. The measurement of vorticity is of paramount importance in many research fields as diverse as biology microfluidics, complex motions in the oceanic and atmospheric boundary layers, and wake turbulence on fluid aerodynamics. However, the precise measurement of flow vorticity is difficult. Here we put forward an optical sensing technique to obtain a direct measurement of vorticity in fluids using Laguerre-Gauss (LG) beams, optical beams which show an azimuthal phase vari...
Karney, Charles
. INTRODUCTIO In typical lower hybrid heating schemes, lower hybrid waves are launched at the wall sf tokamak. In this paper we study the C numerically, and determine the consequences of our results for lower hybrid heating hybrid heating of a tokamak. 11. THE CMKDV EQUAT The two-dimensional steady-state propagation of a single
Hybrid matrix fiber composites
Deteresa, Steven J.; Lyon, Richard E.; Groves, Scott E.
2003-07-15
Hybrid matrix fiber composites having enhanced compressive performance as well as enhanced stiffness, toughness and durability suitable for compression-critical applications. The methods for producing the fiber composites using matrix hybridization. The hybrid matrix fiber composites include two chemically or physically bonded matrix materials, whereas the first matrix materials are used to impregnate multi-filament fibers formed into ribbons and the second matrix material is placed around and between the fiber ribbons that are impregnated with the first matrix material and both matrix materials are cured and solidified.
Effect of a uniform electric field on soot in laminar premixed ethylene/air flames
Wang, Y.; Yao, Q. [Key Laboratory of Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, 100084 Beijing (China); Nathan, G.J. [School of Mechanical Engineering, Centre for Energy Technology, The University of Adelaide, S.A. 5005 (Australia); Alwahabi, Z.T.; King, K.D.; Ho, K. [School of Chemical Engineering, Centre for Energy Technology, The University of Adelaide, S.A. 5005 (Australia)
2010-07-15
The effect of a nominally uniform electric field on the initially uniform distribution of soot has been assessed for laminar premixed ethylene/air flames from a McKenna burner. An electrophoretic influence on charged soot particles was measured through changes to the deposition rate of soot on the McKenna plug, using laser extinction (LE). Soot volume fraction was measured in situ using laser-induced incandescence (LII). Particle size and morphologies were assessed through ex situ transmission electron microscopy (TEM) using thermophoretic sampling particle diagnostics (TSPD). The results show that the majority of these soot particles are positively charged. The presence of a negatively charged plug was found to decrease the particle residence times in the flame and to influence the formation and oxidation progress. A positively charged plug has the opposite effect. The effect on soot volume fraction, particles size and morphology with electric field strength is also reported. Flame stability was also found to be affected by the presence of the electric field, with the balance of the electrophoretic force and drag force controlling the transition to unstable flame flicker. The presence of charged species generated by the flame was found to reduce the dielectric field strength to one seventh that of air. (author)
Electric fields effect on liftoff and blowoff of nonpremixed laminar jet flames in a coflow
Kim, M.K.; Ryu, S.K.; Won, S.H. [School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742 (Korea); Chung, S.H. [Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia)
2010-01-15
The stabilization characteristics of liftoff and blowoff in nonpremixed laminar jet flames in a coflow have been investigated experimentally for propane fuel by applying AC and DC electric fields to the fuel nozzle with a single-electrode configuration. The liftoff and blowoff velocities have been measured by varying the applied voltage and frequency of AC and the voltage and the polarity of DC. The result showed that the AC electric fields extended the stabilization regime of nozzle-attached flame in terms of jet velocity. As the applied AC voltage increased, the nozzle-attached flame was maintained even over the blowout velocity without having electric fields. In such a case, a blowoff occurred directly without experiencing a lifted flame. While for the DC cases, the influence on liftoff was minimal. There existed three different regimes depending on the applied AC voltage. In the low voltage regime, the nozzle-detachment velocity of either liftoff or blowoff increased linearly with the applied voltage, while nonlinearly with the AC frequency. In the intermediate voltage regime, the detachment velocity decreased with the applied voltage and reasonably independent of the AC frequency. At the high voltage regime, the detachment was significantly influenced by the generation of discharges. (author)
Lean methane premixed laminar flames doped by components of diesel fuel II: n-propylcyclohexane
Pousse, E.; Porter, R.; Warth, V.; Glaude, P.A.; Fournet, R.; Battin-Leclerc, F. [Departement de Chimie-Physique des Reactions, Nancy Universite, CNRS, ENSIC, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)
2010-01-15
For a better understanding of the chemistry involved during the combustion of components of diesel fuel, the structure of a laminar lean premixed methane flame doped with n-propylcyclohexane has been investigated. The inlet gases contained 7.1% (molar) methane, 36.8% oxygen, and 0.81% n-propylcyclohexane (C{sub 9}H{sub 18}), corresponding to an equivalence ratio of 0.68 and a C{sub 9}H{sub 18}/CH{sub 4} ratio of 11.4%. The flame has been stabilized on a burner at a pressure of 6.7 kPa (50 Torr) using argon as diluent, with a gas velocity at the burner of 49.2 cm/s at 333 K. Quantified species included the usual methane C{sub 0}-C{sub 2} combustion products, but also 17 C{sub 3}-C{sub 5} hydrocarbons, seven C{sub 1}-C{sub 3} oxygenated compounds, and only four cyclic C{sub 6+} compounds, namely benzene, 1,3-cyclohexadiene, cyclohexene, and methylenecyclohexane. A new mechanism for the oxidation of n-propylcyclohexane has been proposed. It allows the proper simulation of profiles of most of the products measured in flames, as well as the satisfactory reproduction of experimental results obtained in a jet-stirred reactor. The main reaction pathways of consumption of n-propylcyclohexane have been derived from rate-of-production analysis. (author)
A numerical study of soot aggregate formation in a laminar coflow diffusion flame
Zhang, Q.; Thomson, M.J. [Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8 (Canada); Guo, H.; Liu, F.; Smallwood, G.J. [Institute for Chemical Process and Environmental Technology, National Research Council of Canada, Building M-9, 1200 Montreal Road, Ottawa, Ontario, K1A 0R6 (Canada)
2009-03-15
Soot aggregate formation in a two-dimensional laminar coflow ethylene/air diffusion flame is studied with a pyrene-based soot model, a detailed sectional aerosol dynamics model, and a detailed radiation model. The chemical kinetic mechanism describes polycyclic aromatic hydrocarbon formation up to pyrene, the dimerization of which is assumed to lead to soot nucleation. The growth and oxidation of soot particles are characterized by the HACA surface mechanism and pyrene-soot surface condensation. The mass range of the solid soot phase is divided into thirty-five discrete sections and two equations are solved in each section to model the formation of the fractal-like soot aggregates. The coagulation model is improved by implementing the aggregate coagulation efficiency. Several physical processes that may cause sub-unitary aggregate coagulation efficiency are discussed. Their effects on aggregate structure are numerically investigated. The average number of primary soot particles per soot aggregate n{sub p} is found to be a strong function of the aggregate coagulation efficiency. Compared to the available experimental data, n{sub p} is well reproduced with a constant 20% aggregate coagulation efficiency. The predicted axial velocity, OH mole fraction, and C{sub 2}H{sub 2} mole fraction are validated against experimental data in the literature. Reasonable agreements are obtained. Finally, a sensitivity study of the effects of particle coalescence on soot volume fraction and soot aggregate nanostructure is conducted using a coalescence cutoff diameter method. (author)
Aromatic and polycyclic aromatic hydrocarbon formation in a laminar premixed n-butane flame
Marinov, N.M.; Pitz, W.J.; Westbrook, C.K.; Vincitore, A.M.; Castaldi, M.J.; Senkan, S.M.; Melius, C.F.
1998-07-01
Experimental and detailed chemical kinetic modeling work has been performed to investigate aromatic and polycyclic aromatic hydrocarbon (PAH) formation pathways in a premixed, rich, sooting, n-butane-oxygen-argon burner stabilized flame. An atmospheric pressure, laminar flat flame operated at an equivalence ratio of 2.6 was used to acquire experimental data for model validation. Gas composition analysis was conducted by an on-line gas chromatograph/mass spectrometer technique. Measurements were made in the main reaction and post-reaction zones for a number of low molecular weight species, aliphatics, aromatics, and polycyclic aromatic hydrocarbons (PAHs) ranging from two to five-fused aromatic rings. Reaction flux and sensitivity analysis were used to help identify the important reaction sequences leading to aromatic and PAH growth and destruction in the n-butane flame. Reaction flux analysis showed the propargyl recombination reaction was the dominant pathway to benzene formation. The consumption of propargyl by H atoms was shown to limit propargyl, benzene, and naphthalene formation in flames as exhibited by the large negative sensitivity coefficients. Naphthalene and phenanthrene production was shown to be plausibly formed through reactions involving resonantly stabilized cyclopentadienyl and indenyl radicals. Many of the low molecular weight aliphatics, combustion by-products, aromatics, branched aromatics, and PAHs were fairly well simulated by the model. Additional work is required to understand the formation mechanisms of phenyl acetylene, pyrene, and fluoranthene in the n-butane flame. 73 refs.
Rich methane laminar flames doped with light unsaturated hydrocarbons. Part II: 1,3butadiene
Gueniche, Hadj-Ali; Fournet, René; Battin-Leclerc, Frédérique
2007-01-01
In line with the study presented in the part I of this paper, the structure of a laminar rich premixed methane flame doped with 1,3-butadiene has been investigated. The flame contains 20.7% (molar) of methane, 31.4% of oxygen and 3.3% of 1,3-butadiene, corresponding to an equivalence ratio of 1.8, and a ratio C4H6 / CH4 of 16 %. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The temperature ranged from 600 K close to the burner up to 2150 K. Quantified species included usual methane C0-C2 combustion products and 1,3-butadiene, but also propyne, allene, propene, propane, 1,2-butadiene, butynes, vinylacetylene, diacetylene, 1,3-pentadiene, 2-methyl-1,3-butadiene (isoprene), 1-pentene, 3-methyl-1-butene, benzene and toluene. In order to model these new results, some improvements have been made to a mechanism previously developed in our laboratory for the reactions of C3-C4 unsaturated hydrocarbons. The main reacti...
The response of buoyant laminar diffusion flames to low-frequency forcing
Williams, Timothy C.; Shaddix, Christopher R.; Schefer, Robert W. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550 (United States); Desgroux, Pascale [Physicochimie des Processus de Combustion et de l'Atmosphere, Universite des Sciences et Technologies de Lille, Villeneuve d'Ascq Cedex (France)
2007-12-15
Buoyant jet diffusion flames are frequently used to investigate phenomena associated with flares or fires, such as the formation and emission of soot, polycyclic aromatic hydrocarbons (PAH), and carbon monoxide (CO). To systematically investigate the influence of transient vortex-flame interactions on these processes, laminar jet flames may be periodically forced. Previous work has demonstrated that forcing the fuel stream at a (low) frequency close to the natural buoyant instability frequency will trigger the production of vortices on the air side of the high-temperature reaction zone, coupling the overall flame response to the forcing frequency. In the work reported here, measurements in methane/air and ethylene/air slot flames show that over a substantial range of forcing frequencies and amplitudes, the dominant, air-side vortex production is locked at precisely one-half the excitation frequency of the fuel stream. This phenomenon is examined in detail through the utilization of several laser diagnostic techniques, yielding measurements of both the frequency response of the flames and phase-locked images of the internal flame structure. Under some conditions the subharmonic response of the flame leads to transient separation of the PAH and soot layers from the surrounding high-temperature flame zone, potentially affecting the soot formation and radiation processes. This data should provide useful information for comparison with detailed modeling aimed to improve the understanding of the complex nature of the buoyant instability in jet flames. (author)
Schenato, Luca
analysis Experimental results Conclusion Real-Time Networks and Protocols for Industrial Automation Lucia-Time Networks & Protocols for Industrial Automation Hybrid ICNs Modeling of real wireless components IEEE 802 Simulative analysis Experimental results Conclusion Industrial Communication Networks Nowadays Industrial
Assimilating hybridized architecture
Wu, Jane C., 1977-
2005-01-01
The thesis searches for means of operation to deal with hybridized architecture. As a conceptual framework, sociology theory appears to be an insightful precedent, for it analyzes and classifies how multiple constituents ...
F. Iddir; L. Semlala
2006-11-25
We estimate the ground state masses of the heavy hybrid mesons using a phenomenological QCD-type potential. 0^{- -},1^{- -},0^{- +},1^{- +} and 0^{+ -} J^{PC} states are considered.
Hybrid adsorptive membrane reactor
Tsotsis, Theodore T. (Huntington Beach, CA); Sahimi, Muhammad (Altadena, CA); Fayyaz-Najafi, Babak (Richmond, CA); Harale, Aadesh (Los Angeles, CA); Park, Byoung-Gi (Yeosu, KR); Liu, Paul K. T. (Lafayette Hill, PA)
2011-03-01
A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.
Diesel hybridization and emissions.
Pasquier, M.; Monnet, G.
2004-04-21
The CTR Vehicle Systems and Fuels team a diesel hybrid powertrain. The goal of this experiment was to investigate and demonstrate the potential of diesel engines for hybrid electric vehicles (HEVs) in a fuel economy and emissions. The test set-up consisted of a diesel engine coupled to an electric motor driving a Continuously Variable Transmission (CVT). This hybrid drive is connected to a dynamometer and a DC electrical power source creating a vehicle context by combining advanced computer models and emulation techniques. The experiment focuses on the impact of the hybrid control strategy on fuel economy and emissions-in particular, nitrogen oxides (NO{sub x}) and particulate matter (PM). The same hardware and test procedure were used throughout the entire experiment to assess the impact of different control approaches.
Hybrid silicon evanescent approach to optical interconnects
2009-01-01
Big Island, HI, USA, 2006 Hybrid silicon evanescent approach10.1007/s00339-009-5118-1 Hybrid silicon evanescent approachthe recently developed hybrid silicon evanescent platform (
Quantifying the benefits of hybrid vehicles
Turrentine, Tom; Delucchi, Mark; Heffner, Reid R.; Kurani, Kenneth S; Sun, Yongling
2006-01-01
Citroën Unveils 69mpg Diesel Hybrid Prototypes. 31 January.Citröen, have developed diesel-hybrid prototypes thatalso apply hybrid technologies to diesel vehicles, further
Coherent structures in compressible free-shear-layer flows
Aeschliman, D.P.; Baty, R.S.; Kennedy, C.A.; Chen, J.H.
1997-08-01
Large scale coherent structures are intrinsic fluid mechanical characteristics of all free-shear flows, from incompressible to compressible, and laminar to fully turbulent. These quasi-periodic fluid structures, eddies of size comparable to the thickness of the shear layer, dominate the mixing process at the free-shear interface. As a result, large scale coherent structures greatly influence the operation and efficiency of many important commercial and defense technologies. Large scale coherent structures have been studied here in a research program that combines a synergistic blend of experiment, direct numerical simulation, and analysis. This report summarizes the work completed for this Sandia Laboratory-Directed Research and Development (LDRD) project.
Second law analysis of water flow through smooth microtubes under adiabatic conditions
Parlak, Nezaket; Guer, Mesut; Ari, Vedat; Kuecuek, Hasan; Engin, Tahsin [The University of Sakarya, Faculty of Engineering, Department of Mechanical Engineering, Esentepe Campus, 54187 Sakarya (Turkey)
2011-01-15
In the study, a second law analysis for a steady-laminar flow of water in adiabatic microtubes has been conducted. Smooth microtubes with the diameters between 50 and 150 {mu}m made of fused silica were used in the experiments. Considerable temperature rises due to viscous dissipation and relatively high pressure losses of flow were observed in experiments. To identify irreversibility of flow, rate of entropy generation from the experiments have been determined in the laminar flow range of Re = 20-2200. The second law of thermodynamics was applied to predict the entropy generation. The results of model taken from the literature, proposed to predict the temperature rise caused by viscous heating, correspond well with the experimental data. The second law analysis results showed that the flow characteristics in the smooth microtubes distinguish substantially from the conventional theory for flow in the larger tubes with respect to viscous heating/dissipation (temperature rise of flow) total entropy generation rate and lost work. (author)
Hybrid models for complex fluids with multipolar interactions
Cesare Tronci
2011-11-06
Multipolar order in complex fluids is described by statistical correlations. This paper presents a novel dynamical approach, which accounts for microscopic effects on the order parameter space. Indeed, the order parameter field is replaced by a statistical distribution function that is carried by the fluid flow. Inspired by Doi's model of colloidal suspensions, the present theory is derived from a hybrid moment closure for Yang-Mills Vlasov plasmas. This hybrid formulation is constructed under the assumption that inertial effects dominate over dissipative phenomena, so that the total energy is conserved. After presenting the basic geometric properties of the theory, the effect of Yang-Mills fields is considered and a direct application is presented to magnetized fluids with quadrupolar order (spin nematic phases). Hybrid models are also formulated for complex fluids with symmetry breaking. For the special case of liquid crystals, the moment method can be applied to the hybrid formulation to study to the dynamics of cubatic phases.
Wave theories of non-laminar charged particle beams: from quantum to thermal regime
Renato Fedele; Fatema Tanjia; Dusan Jovanovic; Sergio De Nicola; Concetta Ronsivalle
2013-04-01
The standard classical description of non-laminar charge particle beams in paraxial approximation is extended to the context of two wave theories. The first theory is the so-called Thermal Wave Model (TWM) that interprets the paraxial thermal spreading of the beam particles as the analog of the quantum diffraction. The other theory, hereafter called Quantum Wave Model (QWM), that takes into account the individual quantum nature of the single beam particle (uncertainty principle and spin) and provides the collective description of the beam transport in the presence of the quantum paraxial diffraction. QWM can be applied to beams that are sufficiently cold to allow the particles to manifest their individual quantum nature but sufficiently warm to make overlapping-less the single-particle wave functions. In both theories, the propagation of the beam transport in plasmas or in vacuo is provided by fully similar set of nonlinear and nonlocal governing equations, where in the case of TWM the Compton wavelength (fundamental emittance) is replaced by the beam thermal emittance. In both models, the beam transport in the presence of the self-fields (space charge and inductive effects) is governed by a suitable nonlinear nonlocal 2D Schroedinger equation that is used to obtain the envelope beam equation in quantum and quantum-like regimes, respectively. An envelope equation is derived for both TWM and QWM regimes. In TWM we recover the well known Sacherer equation whilst, in QWM we obtain the evolution equation of the single-particle spot size, i.e., single quantum ray spot in the transverse plane (Compton regime). We show that such a quantum evolution equation contains the same information carried out by an evolution equation for the beam spot size (description of the beam as a whole). This is done by defining the lowest QWM state reachable by a system of overlapping-less Fermions.
Cheng, T.S. [Department of Mechanical Engineering, Chung Hua University, Hsinchu 300 (China); Wehrmeyer, J.A. [Aerospace Testing Alliance, Arnold Air Force Base, TN 37389 (United States); Pitz, R.W. [Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235 (United States)
2007-09-15
Simultaneous point measurements of temperature, mixture fraction, major species, and OH concentrations in a lifted turbulent hydrogen jet flame are reprocessed to obtain the Favre average and conditional mean profiles. Large discrepancies between the Favre average and the ensemble average temperature, H{sub 2}O, and OH mole fractions are found at the lifted flame base, due to density weighting of fairly large samples of unreacted mixtures. Conditional statistics are used to reveal the reaction zone structure in mixture fraction coordinates. The cross-stream dependence of conditional reactive scalars, which is most notable at the lifted flame base and decreases to negligible levels with increasing streamwise positions, could be attributed to radial differences in both the Damkoehler number and the level of partial premixing. Conditional results indicate that the lifted flame is stabilized at the outer region of the jet characterized by low strain rates and lean mixtures. Comparison of the measured conditional mean OH vs H{sub 2}O with a series of stretched laminar partially premixed flame and diffusion flame calculations reveals that strong partial premixing takes place at the lifted flame base and the strain rates vary from a=14,000 to 100 s{sup -1}. The level of partial premixing and the strain rate decrease with increasing downstream locations. The range of estimated scalar dissipation rates ({chi}{approx}1-0.13 s{sup -1}) at a further downstream location (x/D=33.3) is in agreement with reported values and the flame composition reaches an equilibrium condition at x/D=194.4. These results combined with previously reported data provide a benchmark data set for evaluation and refinement of turbulent combustion models for lifted hydrogen jet flame predictions. (author)
Pan, Dongqing; Chien Jen, Tien [Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201 (United States); Li, Tao [School of Mechanical Engineering, Dalian University of Technology, Dalian 116024 (China); Yuan, Chris, E-mail: cyuan@uwm.edu [Department of Mechanical Engineering, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, Wisconsin 53211 (United States)
2014-01-15
This paper characterizes the carrier gas flow in the atomic layer deposition (ALD) vacuum reactor by introducing Lattice Boltzmann Method (LBM) to the ALD simulation through a comparative study of two LBM models. Numerical models of gas flow are constructed and implemented in two-dimensional geometry based on lattice Bhatnagar–Gross–Krook (LBGK)-D2Q9 model and two-relaxation-time (TRT) model. Both incompressible and compressible scenarios are simulated and the two models are compared in the aspects of flow features, stability, and efficiency. Our simulation outcome reveals that, for our specific ALD vacuum reactor, TRT model generates better steady laminar flow features all over the domain with better stability and reliability than LBGK-D2Q9 model especially when considering the compressible effects of the gas flow. The LBM-TRT is verified indirectly by comparing the numerical result with conventional continuum-based computational fluid dynamics solvers, and it shows very good agreement with these conventional methods. The velocity field of carrier gas flow through ALD vacuum reactor was characterized by LBM-TRT model finally. The flow in ALD is in a laminar steady state with velocity concentrated at the corners and around the wafer. The effects of flow fields on precursor distributions, surface absorptions, and surface reactions are discussed in detail. Steady and evenly distributed velocity field contribute to higher precursor concentration near the wafer and relatively lower particle velocities help to achieve better surface adsorption and deposition. The ALD reactor geometry needs to be considered carefully if a steady and laminar flow field around the wafer and better surface deposition are desired.
Single-cell dynamics of mammalian gene regulation
Kolnik, Martin
2012-01-01
Given the laminar nature of fluid flow on the microscale,laminar flow regime that is characteristic of fluid dynamics
Fluid-Particle and Fluid-Structure Interactions in Inertial Microfluidics
Amini, Hamed
2012-01-01
large-inertia laminar pipe flow. Journal of Fluid Mechanicsfluid are finite, still lies within the realm of laminar flow (
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Dudek, Jozef J.; Edwards, Robert G.
2012-03-21
In this study, we present the first comprehensive study of hybrid baryons using lattice QCD methods. Using a large basis of composite QCD interpolating fields we extract an extensive spectrum of baryon states and isolate those of hybrid character using their relatively large overlap onto operators which sample gluonic excitations. We consider the spectrum of Nucleon and Delta states at several quark masses finding a set of positive parity hybrid baryons with quantum numbers $N_{1/2^+},\\,N_{1/2^+},\\,N_{3/2^+},\\, N_{3/2^+},\\,N_{5/2^+},\\,$ and $\\Delta_{1/2^+},\\, \\Delta_{3/2^+}$ at an energy scale above the first band of `conventional' excited positive parity baryons. This pattern of states is compatible withmore »a color octet gluonic excitation having $J^{P}=1^{+}$ as previously reported in the hybrid meson sector and with a comparable energy scale for the excitation, suggesting a common bound-state construction for hybrid mesons and baryons.« less
Rivulet Flow In Vertical Parallel-Wall Channel
D. M. McEligot; G. E. Mc Creery; P. Meakin
2006-04-01
In comparison with studies of rivulet flow over external surfaces, rivulet flow confined by two surfaces has received almost no attention. Fully-developed rivulet flow in vertical parallel-wall channels was characterized, both experimentally and analytically for flows intermediate between a lower flow limit of drop flow and an upper limit where the rivulets meander. Although this regime is the most simple rivulet flow regime, it does not appear to have been previously investigated in detail. Experiments were performed that measured rivulet widths for aperture spacing ranging from 0.152 mm to 0.914 mm. The results were compared with a simple steadystate analytical model for laminar flow. The model divides the rivulet cross-section into an inner region, which is dominated by viscous and gravitational forces and where essentially all flow is assumed to occur, and an outer region, dominated by capillary forces, where the geometry is determined by the contact angle between the fluid and the wall. Calculations using the model provided excellent agreement with data for inner rivulet widths and good agreement with measurements of outer rivulet widths.
Valeri P. Frolov; Andrei V. Frolov
2014-12-30
We discuss a solution of the Einstein equations, obtained by gluing the external Kerr metric and the internal Weyl metric, describing an axisymmetric static vacuum distorted black hole. These metrics are glued at the null surfaces representing their horizons. For this purpose we use the formalism of massive thin null shells. The corresponding solution is called a "hybrid" black hole. The massive null shell has an angular momentum which is the origin of the rotation of the external Kerr spacetime. At the same time, the shell distorts the geometry inside the horizon. The inner geometry of the "hybrid" black hole coincides with the geometry of the interior of a non-rotating Weyl-distorted black hole. Properties of the "hybrid" black holes are briefly discussed.
Schaefer, D.W.; Beaucage, G.; Loy, D. [Sandia National Labs., Albuquerque, NM (United States)
1995-12-31
Multicomponent, or hybrid composites are emerging as precursors to porous materials. Sacrifice of an ephemeral phase can be used to generate porosity, the nature of which depends on precursor structure. Retention of an organic constituent, on the other hand, can add desirable toughness to an otherwise brittle ceramic. We use small-angle x-ray and neutron scattering to examine porosity in both simple and hybrid materials. We find that microphase separation controls porosity in almost all systems studied. Pore distributions are controlled by the detailed bonding within and between phases as well as the flexibility of polymeric constituents. Thus hybridization opens new regions of pore distributions not available in simple systems. We look at several sacrificial concepts and show that it is possible to generate multimodal pore size distributions due to the complicated phase structure in the precursor.
Prathap, C.; Ray, Anjan; Ravi, M.R. [Department of Mechanical Engineering, Indian Institute of Technology, Delhi, New Delhi 110016 (India)
2008-10-15
The objective of this investigation was to study the effect of dilution with nitrogen on the laminar burning velocity and flame stability of syngas fuel (50% H{sub 2}-50% CO by volume)-air (21% O{sub 2}-79% N{sub 2} by volume) mixtures. The syngas fuel composition considered in this work comprised x% N{sub 2} by volume and (100-x)% an equimolar mixture of CO and H{sub 2}. The proportion x (i.e., %N{sub 2}) was varied from 0 to 60% while the H{sub 2}/CO ratio was always kept as unity. Spherically expanding flames were generated by centrally igniting homogeneous fuel-air gas mixtures in a 40-L cylindrical combustion chamber fitted with optical windows. Shadowgraphy technique with a high-speed imaging camera was used to record the propagating spherical flames. Unstretched burning velocity was calculated following the Karlovitz theory for weakly stretched flames. Also, Markstein length was calculated to investigate the flame stability conditions for the fuel-air mixtures under consideration. Experiments were conducted for syngas fuel with different nitrogen proportions (0-60%) at 0.1 MPa (absolute), 302{+-}3K, and equivalence ratios ranging from 0.6 to 3.5. All the measurements were compared with the numerical predictions obtained using RUN-1DL and PREMIX with a contemporary chemical kinetic scheme. Dilution with nitrogen in different proportions in syngas resulted in (a) decrease in laminar burning velocity due to reduction in heat release and increase in heat capacity of unburned gas mixture and hence the flame temperature, (b) shift in occurrence of peak laminar burning velocity from {phi}=2.0 for 0% N{sub 2} dilution to {phi}=1.4 for 60% N{sub 2} dilution, (c) augmentation of the coupled effect of flame stretch and preferential diffusion on laminar burning velocity, and (d) shift in the equivalence ratio for transition from stable to unstable flames from {phi}=0.6 for 0% N{sub 2} dilution to {phi}=1.0 for 60% N{sub 2} dilution. The present work also indicated that if the fuel mole fraction in the wide range of fuel-air mixtures investigated is less than 22%, then those fuel mixtures are in the unstable regime with regard to preferential diffusion. (author)
Lowry, William Baugh
2012-02-14
for teaching me what hard work means and how to do it. vi NOMENCLATURE Abbreviations g1855g3043 Specific heat (KJ/kg-K) Di,j Diffusivity of species i into j (m 2/s) g1860 Specific enthalpy (KJ/kg) Le Lewis Number g1865g4662 " Mass... burning rate per unit area (kg/m2-s) g1839g3050 Molecular weight (kg/kmol) X Mole fraction (kmol/kmol) g1851 Mass fraction (kg/kg) Subscripts b Burned condition i For species i L Laminar flame u Unburned condition Superscripts o Un...
Rogers, J. S.; McAfee, T. E.
1954-01-01
Corn Hybrids for Terns ST LOCATIONS AREA I AREA II ARE4 Ill AREA IV 2Prdrie View 7.Tylw lZ.Lockhart 17.Waxahachie 22San Antonio 3.Cleveland 8.Mt. Pbctont I3Brsnha B.Garland 23Lamposas 4.Colbqe Sta. 9Sulphw Spp. 14Holland l9.0reenvilb 24...Stephenville ,J* 5.K'rbyvilb I0.Cbrkdb 15.Tanpk 2ODetiion 25.Wllothe TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS. DIRECTOR, COLLEGE STATION, TEXAS DIGEST The Texas corn acreage planted to hybrids increased from less than 1 percent of the total acrea...
Hybrid Cryptography Alexander W. Dent
International Association for Cryptologic Research (IACR)
Hybrid Cryptography Alexander W. Dent January 3, 2009 Version 1.1 This version is an update asymmetÂ ric encryption schemes can benefit from a formalisation of the prinÂ ciples of hybrid cryptography. The main focus of research in hybrid cryptography has been in producing e#cient asymmetric
Hybrid Cryptography Alexander W. Dent
International Association for Cryptologic Research (IACR)
Hybrid Cryptography Alexander W. Dent January 3, 2009 Version 1.1 This version is an update asymmet- ric encryption schemes can benefit from a formalisation of the prin- ciples of hybrid cryptography. The main focus of research in hybrid cryptography has been in producing efficient asymmetric
Hybrid & Hydrogen Vehicle Research Laboratory
Lee, Dongwon
Hybrid & Hydrogen Vehicle Research Laboratory www.vss.psu.edu/hhvrl Joel R. Anstrom, Director 201 The Pennsylvania Transportation Institute Hybrid and Hydrogen Vehicle Research Laboratory will contribute to the advancement of hybrid and hydrogen vehicle technology to promote the emerging hydrogen economy by providing
Microgravity Laminar Diffusion Flame In A Perpendicular Fuel And Oxidizer Streams Configuration
Brahmi, Lynda; Vietoris, Thomas; Rouvreau, Sebastien; Joulain, Pierre; David, L; Torero, Jose L
2005-01-01
Fuel is injected through a porous flat plate perpendicular to a stream of oxidizer flowing parallel to the surface of the burner for regimes corresponding to fire scenario in spacecrafts. Particle Image Velocimetry is ...
Coupling of Kelvin-Helmholtz instability and buoyancy instability in a thermally laminar plasma
Ren Haijun; Wu Zhengwei [CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei 230026 (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Cao Jintao; Dong Chao [CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei 230026 (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)
2011-02-15
Thermal convective instability is investigated in a thermally stratified plasma in the presence of shear flow, which is known to give rise to the Kelvin-Helmholtz (KH) instability. We examine how the KH instability and magnetothermal instability (MTI) affect each other. Based on the sharp boundary model, the KH instability coupled with the MTI is studied. We present the growth rate and instability criteria. The shear flow is shown to significantly alter the critical condition for the occurrence of thermal convective instability.
Dowling, Charlie
2012-02-14
but towards marginal and abandoned grasslands. In order to reach the goal of producing 36 billion gallons of bioethanol production by 2022 and address the mandatory cap on corn ethanol production that was mandated by the U.S. federal government... Flow Cytometry Hybrid Verification Histograms ..................................... 35 3 PCR Products of PMN Hybrid PEGL09TX04 x PEPU09FL01 showing 10/10 Hybrids in These Progeny...
Microfluidic gas flow profiling using remote detection NMR
Hilty, Christian; McDonnell, Erin; Granwehr, Josef; Pierce,Kimberly; Han, Song-I Han; Pines, Alexander
2005-05-06
Miniaturized fluid handling devices have recently attracted considerable interest in many areas of science1. Such microfluidic chips perform a variety of functions, ranging from analysis of biological macromolecules2,3 to catalysis of reactions and sensing in the gas phase4,5. To enable precise fluid handling, accurate knowledge of the flow properties within these devices is important. Due to low Reynolds numbers, laminar flow is usually assumed. However, either by design or unintentionally, the flow characteristic in small channels is often altered, for example by surface interactions, viscous and diffusional effects, or electrical potentials. Therefore, its prediction is not always straight-forward6-8. Currently, most microfluidic flow measurements rely on optical detection of markers9,10, requiring the injection of tracers and transparent devices. Here, we show profiles of microfluidic gas flow in capillaries and chip devices obtained by NMR in the remote detection modality11,12. Through the transient measurement of dispersion13, NMR is well adaptable for non-invasive, yet sensitive determination of the flow field and provides a novel and potentially more powerful tool to profile flow in capillaries and miniaturized flow devices.
Tang, C. L.; Huang, Z. H.; Law, C. K.
2010-08-30
The stretch-affected propagation speeds of expanding spherical flames of n-butane–air mixtures with hydrogen addition were measured at atmospheric pressure and subsequently processed through a nonlinear regression analysis to yield the stretch-free laminar flame speeds. Based on a hydrogen addition parameter (R_{H}) and an effective fuel equivalence ratio (?_{F}), these laminar flame speeds were found to increase almost linearly with R_{H}, for ?_{F} between 0.6 and 1.4 and RHRH from 0 to 0.5, with the slope of the variation assuming a minimum around stoichiometry. These experimental results also agree well with computed values using a detailed reaction mechanism. Furthermore, a mechanistic investigation aided by sensitivity analysis identified that kinetic effects through the global activation energy, followed by thermal effects through the adiabatic flame temperature, have the most influence on the increase in the flame speeds and the associated linear variation with R_{H} due to hydrogen addition. Nonequidiffusion effects due to the high mobility of hydrogen, through the global Lewis number, have the least influence. Further calculations for methane, ethene, and propane as the fuel showed similar behavior, leading to possible generalization of the phenomena and correlation.
A MEMS Based Hybrid Preconcentrator/Chemiresistor Chemical Sensor
HUGHES,ROBERT C.; PATEL,SANJAY V.; MANGINELL,RONALD P.
2000-06-12
A hybrid of a microfabricated planar preconcentrator and a four element chemiresistor array chip has been fabricated and the performance as a chemical sensor system has been demonstrated. The close proximity of the chemiresistor sensor to the preconcentrator absorbent layer allows for fast transfer of the preconcentrated molecules during the heating and resorption step. The hybrid can be used in a conventional flow sampling system for detection of low concentrations of analyte molecules or in a pumpless/valveless mode with a grooved lid to confine the desorption plume from the preconcentrator during heating.
Homoclinic snaking in plane Couette flow: bending, skewing, and finite-size effects
Gibson, John F
2015-01-01
Invariant solutions of shear flows have recently been extended from spatially periodic solutions in minimal flow units to spatially localized solutions on extended domains. One set of spanwise-localized solutions of plane Couette flow exhibits homoclinic snaking, a process by which steady-state solutions grow additional structure smoothly at their fronts when continued parametrically. Homoclinic snaking is well understood mathematically in the context of the one-dimensional Swift-Hohenberg equation. Consequently, the snaking solutions of plane Couette flow form a promising connection between the largely phenomenological study of laminar-turbulent patterns in viscous shear flows and the mathematically well-developed field of pattern-formation theory. In this paper we present a numerical study of the snaking solutions, generalizing beyond the fixed streamwise wavelength of previous studies. We find a number of new solution features, including bending, skewing, and finite-size effects. We show that the finite-si...
Flow-Induced Deformation of a Flexible Thin Structure as Manifestation of Heat Transfer Enhancement
Soti, Atul Kumar; Sheridan, John
2015-01-01
Flow-induced deformation of thin structures coupled with convective heat transfer has potential applications in energy harvesting and is important for understanding functioning of several biological systems. We numerically demonstrate large-scale flow-induced deformation as an effective passive heat transfer enhancement technique. An in-house, strongly-coupled fluid-structure interaction (FSI) solver is employed in which flow and structure solvers are based on sharp-interface immersed boundary and finite element method, respectively. In the present work, we validate convective heat transfer module of the in-house FSI solver against several benchmark examples of conduction and convective heat transfer including moving structure boundaries. The thermal augmentation is investigated as well as quantified for the flow-induced deformation of an elastic thin plate attached to lee side of a rigid cylinder in a heated channel laminar flow. We show that the wake vortices past the plate sweep higher sources of vorticity...
Rogers, J. S.; Bockholt, A. J.; Collier, J. W.
1957-01-01
practices which would bring their corn into tassel around June 1. This can be done by planting adapted hybrids at the dates recom- mended in Table 1. When planting is delayed, or if it is necessary to replant, hybrids with earlier maturity should... 90 ' 65.2 Coker 911 67.3 Texas 28 64.9 Texas 26 62.7 Texas 17W 73.0 Tennessee 29 67.5 Texas 9W 74.0 North Carolina 29 65.9 Georgia lOlW 70.7 Dixie 18 63.0 Asgrow lOlW 59.0 TRF 3 62.2 Coker 811 40.0 Surcropper 47.6 - - Averase yield 67...
Sampayan, S.E.
1998-03-03
A hybrid emitter exploits the electric field created by a rapidly depoled ferroelectric material. Combining the emission properties of a planar thin film diamond emitter with a ferroelectric alleviates the present technological problems associated with both types of emitters and provides a robust, extremely long life, high current density cathode of the type required by emerging microwave power generation, accelerator technology and display applications. This new hybrid emitter is easy to fabricate and not susceptible to the same failures which plague microstructure field emitter technology. Local electrode geometries and electric field are determined independently from those for optimum transport and brightness preservation. Due to the large amount of surface charge created on the ferroelectric, the emitted electrons have significant energy, thus eliminating the requirement for specialized phosphors in emissive flat-panel displays. 11 figs.
Sampayan, Stephen E. (Manteca, CA)
1998-01-01
A hybrid emitter exploits the electric field created by a rapidly depoled ferroelectric material. Combining the emission properties of a planar thin film diamond emitter with a ferroelectric alleviates the present technological problems associated with both types of emitters and provides a robust, extremely long life, high current density cathode of the type required by emerging microwave power generation, accelerator technology and display applications. This new hybrid emitter is easy to fabricate and not susceptible to the same failures which plague microstructure field emitter technology. Local electrode geometries and electric field are determined independently from those for optimum transport and brightness preservation. Due to the large amount of surface charge created on the ferroelectric, the emitted electrons have significant energy, thus eliminating the requirement for specialized phosphors in emissive flat-panel displays.
Hybrid electroluminescent devices
Shiang, Joseph John (Niskayuna, NY); Duggal, Anil Raj (Niskayuna, NY); Michael, Joseph Darryl (Schenectady, NY)
2010-08-03
A hybrid electroluminescent (EL) device comprises at least one inorganic diode element and at least one organic EL element that are electrically connected in series. The absolute value of the breakdown voltage of the inorganic diode element is greater than the absolute value of the maximum reverse bias voltage across the series. The inorganic diode element can be a power diode, a Schottky barrier diode, or a light-emitting diode.
Drag force in the open-loop control of the cylinder wake in the laminar regime
Protas, Bartosz
flow subject to rotary control. We consider simple control laws where the obstacle rotates harmonically Bluff body wakes play a very important role in various engineering applications. This is mainly due in fluid dynamics. From the implementation point of view, one of the simplest control methods is the rotary
Barley, C.D.; Winn, C.B. [Colorado State Univ., Fort Collins, CO (United States)
1997-12-31
This paper provides an overview of the emerging technology of remote, stand-alone electrical power systems featuring a renewable source (wind or photovoltaics [PV]) as well as a diesel generator, with or without an energy storage device. Other stand-alone power systems are discussed briefly, mainly to emphasize the domain of hybrid systems. The history of hybrid systems is reviewed, beginning with the first wind/diesel system in the late 1970s. Other topics include issues arising from the characteristics of diesel engine/generator sets; simple vs. complex systems; the various energy storage technologies that have been used or proposed; control strategies; modeling; optimization; and some {open_quotes}nuts & bolts{close_quotes} details. The bibliography includes over 130 references which are cited throughout the topical discussions. It is concluded that the technical feasibility of hybrid systems has been demonstrated through many prototype installations, and that areas for further improvements include higher reliability and more economical energy storage devices. 139 refs., 7 figs., 1 tab.
Model Reduction of Turbulent Fluid Flows Using the Supply Rate
Sharma, A S
2013-01-01
A method for finding reduced-order approximations of turbulent flow models is presented. The method preserves bounds on the production of turbulent energy in the sense of the $\\curly{L}_2$ norm of perturbations from a notional laminar profile. This is achieved by decomposing the Navier-Stokes system into a feedback arrangement between the linearised system and the remaining, normally neglected, nonlinear part. The linear system is reduced using a method similar to balanced truncation, but preserving bounds on the supply rate. The method involves balancing two algebraic Riccati equations. The bounds are then used to derive bounds on the turbulent energy production. An example of the application of the procedure to flow through a long straight pipe is presented. Comparison shows that the new method approximates the supply rate at least as well as, or better than, canonical balanced truncation.
Pre-test CFD Calculations for a Bypass Flow Standard Problem
Rich Johnson
2011-11-01
The bypass flow in a prismatic high temperature gas-cooled reactor (HTGR) is the flow that occurs between adjacent graphite blocks. Gaps exist between blocks due to variances in their manufacture and installation and because of the expansion and shrinkage of the blocks from heating and irradiation. Although the temperature of fuel compacts and graphite is sensitive to the presence of bypass flow, there is great uncertainty in the level and effects of the bypass flow. The Next Generation Nuclear Plant (NGNP) program at the Idaho National Laboratory has undertaken to produce experimental data of isothermal bypass flow between three adjacent graphite blocks. These data are intended to provide validation for computational fluid dynamic (CFD) analyses of the bypass flow. Such validation data sets are called Standard Problems in the nuclear safety analysis field. Details of the experimental apparatus as well as several pre-test calculations of the bypass flow are provided. Pre-test calculations are useful in examining the nature of the flow and to see if there are any problems associated with the flow and its measurement. The apparatus is designed to be able to provide three different gap widths in the vertical direction (the direction of the normal coolant flow) and two gap widths in the horizontal direction. It is expected that the vertical bypass flow will range from laminar to transitional to turbulent flow for the different gap widths that will be available.
Hybrid Computer Architectures Motivations for Research
Kavi, Krishna
Hybrid Computer Architectures Motivations for Research What Is a Hybrid Processor? Hybrid commercial hybrid chips provide fixed processing cores and Field Programmable Gate Array (FPGA) elements an Application Specific Integrated Service (ASIC) can provide. How Do We Use Them? Hybrid chips seem uniquely
Hybrid solar lighting distribution systems and components
Muhs, Jeffrey D. (Lenoir City, TN); Earl, Dennis D. (Knoxville, TN); Beshears, David L. (Knoxville, TN); Maxey, Lonnie C. (Powell, TN); Jordan, John K. (Oak Ridge, TN); Lind, Randall F. (Lenoir City, TN)
2011-07-05
A hybrid solar lighting distribution system and components having at least one hybrid solar concentrator, at least one fiber receiver, at least one hybrid luminaire, and a light distribution system operably connected to each hybrid solar concentrator and each hybrid luminaire. A controller operates all components.
Hybrid solar lighting systems and components
Muhs, Jeffrey D. (Lenoir City, TN); Earl, Dennis D. (Knoxville, TN); Beshears, David L. (Knoxville, TN); Maxey, Lonnie C. (Powell, TN); Jordan, John K. (Oak Ridge, TN); Lind, Randall F. (Lenoir City, TN)
2007-06-12
A hybrid solar lighting system and components having at least one hybrid solar concentrator, at least one fiber receiver, at least one hybrid luminaire, and a light distribution system operably connected to each hybrid solar concentrator and each hybrid luminaire. A controller operates each component.
Greif, Ralph (University of California, Berkeley, CA); Evans, Gregory Herbert; Kearney, Sean Patrick (Sandia National Laboratories, Albuquerque, NM); Laskowski, Gregory Michael
2006-02-01
Heat transfer to and from a circular cylinder in a cross-flow of water at low Reynolds number was studied both experimentally and numerically. The experiments were carried out in a high aspect ratio water channel. The test section inflow temperature and velocity, channel lower surface temperature and cylinder surface temperature were controlled to yield either laminar or turbulent flow for a desired Richardson number. When the lower surface was unheated, the temperatures of the lower surface and water upstream of the cylinder were maintained approximately equal and the flow was laminar. When the lower surface was heated, turbulence intensities as high as 20% were measured several cylinder diameters upstream of the cylinder due to turbulent thermal plumes produced by heating the lower surface. Variable property, two-dimensional simulations were undertaken using a variant of the u{sup 2}-f turbulence model with buoyancy production of turbulence accounted for by a simple gradient diffusion model. Predicted and measured heat flux distributions around the cylinder are compared for values of the Richardson number, Gr{sub d}/Re{sub d}{sup 2} from 0.3 to 9.3. For laminar flow, the predicted and measured heat flux results agreed to within the experimental uncertainty. When the lower surface was heated, and the flow was turbulent, there was qualitative agreement between predicted and measured heat flux distributions around the cylinder. However the predicted spatially averaged Nusselt number was from 37% to 53% larger than the measured spatially averaged Nusselt number. Additionally, spatially averaged Nusselt numbers are compared to correlations in the literature for mixed convection heat transfer to/from cylinders in cross-flow. The results presented here are larger than the correlation values. This is believed to be due to the effects of buoyancy-induced turbulence resulting from heating the lower surface and the proximity of the cylinder to that surface.
Ionization based multi-directional flow sensor
Chorpening, Benjamin T. (Morgantown, WV); Casleton, Kent H. (Morgantown, WV)
2009-04-28
A method, system, and apparatus for conducting real-time monitoring of flow (airflow for example) in a system (a hybrid power generation system for example) is disclosed. The method, system and apparatus measure at least flow direction and velocity with minimal pressure drop and fast response. The apparatus comprises an ion source and a multi-directional collection device proximate the ion source. The ion source is configured to generate charged species (electrons and ions for example). The multi-directional collection source is configured to determine the direction and velocity of the flow in real-time.
Morozov, Victor (Manassas, VA)
2011-01-18
A flow chamber having a vacuum chamber and a specimen chamber. The specimen chamber may have an opening through which a fluid may be introduced and an opening through which the fluid may exit. The vacuum chamber may have an opening through which contents of the vacuum chamber may be evacuated. A portion of the flow chamber may be flexible, and a vacuum may be used to hold the components of the flow chamber together.
Fluid mechanics experiments in oscillatory flow. Volume 1
Seume, J.; Friedman, G.; Simon, T.W.
1992-03-01
Results of a fluid mechanics measurement program is oscillating flow within a circular duct are present. The program began with a survey of transition behavior over a range of oscillation frequency and magnitude and continued with a detailed study at a single operating point. Such measurements were made in support of Stirling engine development. Values of three dimensionless parameters, Re{sub max}, Re{sub W}, and A{sub R}, embody the velocity amplitude, frequency of oscillation and mean fluid displacement of the cycle, respectively. Measurements were first made over a range of these parameters which included operating points of all Stirling engines. Next, a case was studied with values of these parameters that are representative of the heat exchanger tubes in the heater section of NASA`s Stirling cycle Space Power Research Engine (SPRE). Measurements were taken of the axial and radical components of ensemble-averaged velocity and rms-velocity fluctuation and the dominant Reynolds shear stress, at various radial positions for each of four axial stations. In each run, transition from laminar to turbulent flow, and in reverse, were identified and sufficient data was gathered to propose the transition mechanism. Models of laminar and turbulent boundary layers were used to process the data into wall coordinates and to evaluate skin friction coefficients. Such data aids in validating computational models and is useful in comparing oscillatory flow characteristics to those of fully-developed steady flow. Data were taken with a contoured entry to each end of the test section and with flush square inlets so that the effects of test section inlet geometry on transition and turbulence are documented. The following is presented in two-volumes. Volume I contains the text of the report including figures and supporting appendices. Volume II contains data reduction program listings and tabulated data (including its graphical presentation).
Yu Xin; Peng Jiangbo; Yi Yachao; Zhao Yongpeng; Chen Deying; Yu Junhua [National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin 150080 (China); Institute of Opto-electronics, Harbin Institute of Technology, Harbin 150080 (China); Yang Peng; Sun Rui [Institute of Combustion Engineering, Harbin Institute of Technology, Harbin 150001 (China)
2010-07-05
We first investigate the effects of femtosecond-laser-induced plasma on the flame speed of a laminar premixed methane/oxygen/nitrogen flame with a wide range of the equivalence ratios (0.8-1.05) at atmospheric pressure. It is experimentally found that the flame speed increases 20.5% at equivalence ratios 1.05. The self-emission spectra from the flame and the plasma are studied and an efficient production of active radicals under the action of femtosecond (fs)-laser pulses has been observed. Based on the experimental data obtained, the presence of oxygen atom and hydrocarbon radicals is suggested to be a key factor enhancing flame speed.
A New Type of Steady and Stable, Laminar, Premixed Flame in Ultra-Lean, Hydrogen-Air Combustion
Grcar, Joseph F; Grcar, Joseph F
2008-06-30
Ultra-lean, hydrogen-air mixtures are found to support another kind of laminar flame that is steady and stable beside flat flames and flame balls. Direct numerical simulations are performed of flames that develop into steadily and stably propagating cells. These cells were the original meaning of the word"flamelet'' when they were observed in lean flammability studies conducted early in the development of combustion science. Several aspects of these two-dimensional flame cells are identified and are contrasted with the properties of one-dimensional flame balls and flat flames. Although lean hydrogen-air flames are subject to thermo-diffusive effects, in this case the result is to stabilize the flame rather than to render it unstable. The flame cells may be useful as basic components of engineering models for premixed combustion when the other types of idealized flames are inapplicable.
Yu. N. Bratkov
2008-11-19
In this paper geology and planetology are considered using new conceptual basis of high-speed flow dynamics. Recent photo technics allow to see all details of a flow, 'cause the flow is static during very short time interval. On the other hand, maps and images of many planets are accessible. Identity of geological flows and high-speed gas dynamics is demonstrated. There is another time scale, and no more. All results, as far as the concept, are new and belong to the author. No formulae, pictures only.
Liles, D.R.
1982-01-01
Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced.
Bradley, D.; Lawes, M.; Mansour, M.S. [School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)
2009-07-15
The principal burning characteristics of a laminar flame comprise the fuel vapour pressure, the laminar burning velocity, ignition delay times, Markstein numbers for strain rate and curvature, the stretch rates for the onset of flame instabilities and of flame extinction for different mixtures. With the exception of ignition delay times, measurements of these are reported and discussed for ethanol-air mixtures. The measurements were in a spherical explosion bomb, with central ignition, in the regime of a developed stable, flame between that of an under or over-driven ignition and that of an unstable flame. Pressures ranged from 0.1 to 1.4 MPa, temperatures from 300 to 393 K, and equivalence ratios were between 0.7 and 1.5. It was important to ensure the relatively large volume of ethanol in rich mixtures at high pressures was fully evaporated. The maximum pressure for the measurements was the highest compatible with the maximum safe working pressure of the bomb. Many of the flames soon became unstable, due to Darrieus-Landau and thermo-diffusive instabilities. This effect increased with pressure and the flame wrinkling arising from the instabilities enhanced the flame speed. Both the critical Peclet number and the, more rational, associated critical Karlovitz stretch factor were evaluated at the onset of the instability. With increasing pressure, the onset of flame instability occurred earlier. The measured values of burning velocity are expressed in terms of their variations with temperature and pressure, and these are compared with those obtained by other researchers. Some comparisons are made with the corresponding properties for iso-octane-air mixtures. (author)
Quantifying the benefits of hybrid vehicles
Turrentine, Tom; Delucchi, Mark; Heffner, Reid R.; Kurani, Kenneth S; Sun, Yongling
2006-01-01
secrets, but the price of hybrid cars and trucks are betweenCosts of hybrid vehicles Depending on whether a car companydiesel-hybrid prototypes that attained 70 MPG (Green Car
Issue 5: High Interest in Hybrid Cars
Ong, Paul M.; Haselhoff, Kim
2005-01-01
2005). “High Interest in Hybrid Cars. ” SCS Fact Sheet, Vol.May 2005 High Interest in Hybrid Cars I NTRODUCTION PublicThe unique features of a hybrid car mean that it is more
Hybrid Silicon Photonic Integrated Circuit Technology
2013-01-01
and J. E. Bowers, “Hybrid silicon evanescent devices,”and J. E. Bowers, “A hybrid AlGaInAs-silicon evanescentColdren, and J. E. Bowers, “Hybrid III/V sili- con photonic
A hybrid tissue-engineered heart valve
Alavi, SH; Kheradvar, A
2015-01-01
load-bearing component of the hybrid lea?et, and it shouldin the left ventricle. Hybrid tissue was also previouslyA Hybrid Tissue-Engineered Heart Valve S. Hamed Alavi, PhD,
Hybrid Publicly Verifiable Computation James Alderman
International Association for Cryptologic Research (IACR)
Hybrid Publicly Verifiable Computation James Alderman , Christian Janson, Carlos Cid , and Jason introduce Hybrid PVC (HPVC) which, with a single setup stage, provides a flexible solution to outsourced for such systems. Keywords-- Hybrid Publicly Verifiable Computation, Verifiable Delegable Computation, Dual
Hybrid Silicon Photonics for Optical Interconnects
2011-01-01
Promising Technology for the hybrid silicon laser in 2007.Electrically pumped hybrid AlGaInAs-silicon evanescentA. Yariv, “Electrically pumped hybrid evanescent Si/InGaAsP
Experimental study of libration-driven zonal flows in non-axisymmetric containers
Noir, Jerome; Bars, Michael Le; Sauret, Alban; Aurnou, J M; 10.1016/j.pepi.2012.05.005
2013-01-01
Orbital dynamics that lead to longitudinal libration of celestial bodies also result in an elliptically deformed equatorial core-mantle boundary. The non-axisymmetry of the boundary leads to a topographic coupling between the assumed rigidmantle and the underlying low viscosity fluid.The present experimental study investigates theeffect of non axisymmetric boundaries on the zonal flow driven by longitudinal libration. For large enough equatorial ellipticity, we report intermittent space-filling turbulence in particular bands of resonant frequency correlated with larger amplitude zonal flow. The mechanism underlying the intermittent turbulence has yet to be unambiguously determined. Nevertheless, recent numerical simulations in triaxial and biaxial ellipsoids suggest that it may be associated with the growth and collapse of an elliptical instability (Cebron et al., 2012). Outside of the band of resonance, we find that the background flow is laminar and the zonal flow becomes independent of the geometry at firs...
Optimized boundary driven flows for dynamos in a sphere
Khalzov, I. V.; Brown, B. P.; Cooper, C. M.; Weisberg, D. B.; Forest, C. B. [Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States)
2012-11-15
We perform numerical optimization of the axisymmetric flows in a sphere to minimize the critical magnetic Reynolds number Rm{sub cr} required for dynamo onset. The optimization is done for the class of laminar incompressible flows of von Karman type satisfying the steady-state Navier-Stokes equation. Such flows are determined by equatorially antisymmetric profiles of driving azimuthal (toroidal) velocity specified at the spherical boundary. The model is relevant to the Madison plasma dynamo experiment, whose spherical boundary is capable of differential driving of plasma in the azimuthal direction. We show that the dynamo onset in this system depends strongly on details of the driving velocity profile and the fluid Reynolds number Re. It is found that the overall lowest Rm{sub cr} Almost-Equal-To 200 is achieved at Re Almost-Equal-To 240 for the flow, which is hydrodynamically marginally stable. We also show that the optimized flows can sustain dynamos only in the range Rm{sub cr}
Hybrid classical-quantum formulations ask for hybrid notions
Carlos Barceló; Raúl Carballo-Rubio; Luis J. Garay; Ricardo Gómez-Escalante
2013-01-28
We reappraise some of the hybrid classical-quantum models proposed in the literature with the goal of retrieving some of their common characteristics. In particular, first, we analyze in detail the Peres-Terno argument regarding the inconsistency of hybrid quantizations of the Sudarshan type. We show that to accept such hybrid formalism entails the necessity of dealing with additional degrees of freedom beyond those in the straight complete quantization of the system. Second, we recover a similar enlargement of degrees of freedom in the so-called statistical hybrid models. Finally, we use Wigner's quantization of a simple model to illustrate how in hybrid systems the subsystems are never purely classical or quantum. A certain degree of quantumness (classicality) is being exchanged between the different sectors of the theory, which in this particular unphysical toy model makes them undistinguishable.
Hybrid conformal field theories
Marco Bertolini; Ilarion V. Melnikov; M. Ronen Plesser
2013-07-26
We describe a class of (2,2) superconformal field theories obtained by fibering a Landau-Ginzburg orbifold CFT over a compact Kaehler base manifold. While such models are naturally obtained as phases in a gauged linear sigma model, our construction is independent of such an embedding. We discuss the general properties of such theories and present a technique to study the massless spectrum of the associated heterotic compactification. We test the validity of our method by applying it to hybrid phases of linear models and comparing spectra among the phases.
Advanced Coal Wind Hybrid: Economic Analysis
Phadke, Amol
2008-01-01
Source: Velocity Suite, Global Energy Data Advanced Coal Wind Hybrid: Economic Analysis 6.3.2 Comparison with Non-hybrid Competing
Advanced Hybrid Water Heater using Electrochemical Compressor...
Advanced Hybrid Water Heater using Electrochemical Compressor Advanced Hybrid Water Heater using Electrochemical Compressor Xergy is using its Electro Chemical Compression (ECC)...
Advanced Coal Wind Hybrid: Economic Analysis
Phadke, Amol
2008-01-01
of Figures Figure ES-1. Advanced Coal Wind Hybrid: Basicviii Figure 1. Advanced-Coal Wind Hybrid: Basic29 Figure 9. Sensitivity to Coal
Hybrid Rotaxanes: Interlocked Structures for Quantum Computing...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Hybrid Rotaxanes: Interlocked Structures for Quantum Computing? Hybrid Rotaxanes: Interlocked Structures for Quantum Computing? Print Wednesday, 26 August 2009 00:00 Rotaxanes are...
Advanced Coal Wind Hybrid: Economic Analysis
Phadke, Amol
2008-01-01
of Figures Figure ES-1. Advanced Coal Wind Hybrid: Basicviii Figure 1. Advanced-Coal Wind Hybrid: Basic21 Figure 6. Comparison of ACWH and CCGT-Wind
Quantifying the benefits of hybrid vehicles
Turrentine, Tom; Delucchi, Mark; Heffner, Reid R.; Kurani, Kenneth S; Sun, Yongling
2006-01-01
century. Hybrid electric vehicles (HEVs) reduce emissionsas plug-in HEVs and full electric vehicles to market. In theon their design, hybrid electric vehicles employ electric
Hybrid spread spectrum radio system
Smith, Stephen F. (London, TN) [London, TN; Dress, William B. (Camas, WA) [Camas, WA
2010-02-09
Systems and methods are described for hybrid spread spectrum radio systems. A method, includes receiving a hybrid spread spectrum signal including: fast frequency hopping demodulating and direct sequence demodulating a direct sequence spread spectrum signal, wherein multiple frequency hops occur within a single data-bit time and each bit is represented by chip transmissions at multiple frequencies.
Design Criteria Document Hybrid Spectrometer
Johnson, Peter D.
Design Criteria Document for the Hybrid Spectrometer (HYSPEC) SNS SING14B-00-DC0001-R00 Date: 15 contract DE-AC05-00OR22725 #12;DESIGN CRITERIA DOCUMENT FOR THE HYBRID SPECTROMETER (HYSPEC) August 2005 or reflect those of the United States government or any agency thereof. #12;SING14B-00-DC0001-R00 DESIGN
Design Criteria Document Hybrid Spectrometer
Johnson, Peter D.
Design Criteria Document for the Hybrid Spectrometer (HYSPEC) SNS SING14B-00-DC0001-R01 Date: 1 contract DE-AC05-00OR22725 #12;DESIGN CRITERIA DOCUMENT FOR THE HYBRID SPECTROMETER (HYSPEC) Mark Hagen or reflect those of the United States government or any agency thereof. #12;SING14B-00-DC0001-R01 DESIGN
Massive Hybrid Stars with Strangeness
Tatsuyuki Takatsuka; Tetsuo Hatsuda; Kota Masuda
2014-02-19
How massive the hybrid stars could be is discussed by a "3-window model" proposed from a new strategy to construct the equation of state with hadron-quark transition. It is found that hybrid stars have a strong potentiality to generate a large mass compatible with two-solar-mass neutron star observations.
Essays On Hybrid Bundle Pricing
Meyer, Jeffrey Dean
2011-10-21
model of optimal pricing for hybrid bundles by a monopolist. My results show that an increase in quality variability of the service is generally associated with a higher optimal hybrid bundle price and a lower optimal price of the good, but lower overall...
Mare, Thierry; Voicu, Ionut; Miriel, Jacques [Laboratoire de Genie Civil et de Genie Mecanique (LGCGM), INSA de Rennes, IUT Saint Malo, 35043 Rennes (France); Galanis, Nicolas [Faculte de genie, Universite de Sherbrooke, Sherbrooke, QC (Canada); Sow, Ousmane [Laboratoire d'Energie Appliquee, Ecole superieure Polytechnique, Dakar (Senegal)
2008-04-15
Velocity vectors in a vertical coaxial double-duct heat exchanger for parallel ascending flow of water under conditions of laminar mixed convection have been determined experimentally using the particle image velocimetry technique. The measured velocity distributions for large annular flow rates, resulting in an essentially isothermal environment for the stream in the inner tube, are in very good agreement with corresponding numerical predictions. For flow rates of the same order of magnitude in the inner tube and the annulus, and corresponding temperature differences of about 20 C, experimental observations show that flow reversal occurs simultaneously in both streams over large axial distances for both heating and cooling of the flow in the inner tube. (author)
Rieseberg, Loren
Copyright © 1999 by the Genetics Society of America Hybrid Zones and the Genetic Architecture to interspecific gene flow orin the architecture of barriers to interspecific gene flow. Genetic architecture be used to describequence of genetic changes that accompany or facilitate genetic architecture in natural
Uribe, A. L. [University of Chicago, Chicago, IL 60637 (United States); Klahr, H.; Henning, Th., E-mail: uribe@oddjob.uchicago.edu [Max-Planck-Institut fuer Astronomie, Heidelberg (Germany)
2013-06-01
We have performed three-dimensional magnetohydrodynamical simulations of stellar accretion disks, using the PLUTO code, and studied the accretion of gas onto a Jupiter-mass planet and the structure of the circumplanetary gas flow after opening a gap in the disk. We compare our results with simulations of laminar, yet viscous disks with different levels of an {alpha}-type viscosity. In all cases, we find that the accretion flow across the surface of the Hill sphere of the planet is not spherically or azimuthally symmetric, and is predominantly restricted to the mid-plane region of the disk. Even in the turbulent case, we find no significant vertical flow of mass into the Hill sphere. The outer parts of the circumplanetary disk are shown to rotate significantly below Keplerian speed, independent of viscosity, while the circumplanetary disk density (therefore the angular momentum) increases with viscosity. For a simulation of a magnetized turbulent disk, where the global averaged alpha stress is {alpha}{sub MHD} = 10{sup -3}, we find the accretion rate onto the planet to be M-dot {approx}2 Multiplication-Sign 10{sup -6}M{sub J} yr{sup -1} for a gap surface density of 12 g cm{sup -2}. This is about a third of the accretion rate obtained in a laminar viscous simulation with equivalent {alpha} parameter.
Electron flow stability in magnetically insulated vacuum transmission lines
Rose, D. V.; Genoni, T. C.; Clark, R. E.; Welch, D. R. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Stygar, W. A. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
2011-03-15
We evaluate the stability of electron current flow in high-power magnetically insulated transmission lines (MITLs). A detailed model of electron flow in cross-field gaps yields a dispersion relation for electromagnetic (EM) transverse magnetic waves [R. C. Davidson et al., Phys. Fluids 27, 2332 (1984)] which is solved numerically to obtain growth rates for unstable modes in various sheath profiles. These results are compared with two-dimensional (2D) EM particle-in-cell (PIC) simulations of electron flow in high-power MITLs. We find that the macroscopic properties (charge and current densities and self-fields) of the equilibrium profiles observed in the simulations are well represented by the laminar-flow model of Davidson et al. Idealized simulations of sheared flow in electron sheaths yield growth rates for both long (diocotron) and short (magnetron) wavelength instabilities that are in good agreement with the dispersion analysis. We conclude that electron sheaths that evolve self-consistently from space-charged-limited emission of electrons from the cathode in well-resolved 2D EM PIC simulations form stable profiles.
Electron flow stability in magnetically insulated vacuum transmission lines.
Genoni, Thomas C. (Voss Scientific, LLC, Albuquerque, NM); Stygar, William A.; Welch, Dale Robert (Voss Scientific, LLC, Albuquerque, NM); Clark, R. E. (Voss Scientific, LLC, Albuquerque, NM); Rose, David V. (Voss Scientific, LLC, Albuquerque, NM)
2010-11-01
We evaluate the stability of electron current flow in high-power magnetically insulated transmission lines (MITLs). A detailed model of electron flow in cross-field gaps yields a dispersion relation for electromagnetic (EM) transverse magnetic waves [R. C. Davidson et al., Phys. Fluids 27, 2332 (1984)] which is solved numerically to obtain growth rates for unstable modes in various sheath profiles. These results are compared with two-dimensional (2D) EM particle-in-cell (PIC) simulations of electron flow in high-power MITLs. We find that the macroscopic properties (charge and current densities and self-fields) of the equilibrium profiles observed in the simulations are well represented by the laminar-flow model of Davidson et al. Idealized simulations of sheared flow in electron sheaths yield growth rates for both long (diocotron) and short (magnetron) wavelength instabilities that are in good agreement with the dispersion analysis. We conclude that electron sheaths that evolve self-consistently from space-charged-limited emission of electrons from the cathode in well-resolved 2D EM PIC simulations form stable profiles.
Microfluidics: Kinetics of Hybridized DNA With Fluid Flow Variations.
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Wankel engine for hybrid powertrain
Butti, A.; Site, V.D.
1995-12-31
The Wankel engine is suited to be used to drive hybrid propulsion systems. The main disadvantage of hybrid propulsion systems is the complexity that causes a high weight and large dimensions. For these reason hybrid systems are more suitable for large size vehicle (buses, vans) rather than for small passenger cars. A considerable reduction of hybrid systems weight and dimensions can be obtained using a Wankel rotary engine instead of a conventional engine. The Wankel engine is light, compact, simple, and produces low noise and low vibrations. Therefore a Wankel engine powered hybrid system is suited to be used on small cars. In this paper a 1,000 kg parallel hybrid car with continuously variable transmission and a 6,000 kg series hybrid minibus both equipped with Wankel engines are considered. The Wankel engine works at steady state to minimize fuel consumption and exhaust emissions. The simulation of the behavior of these two vehicles during a ECE + EUDC test cycle is presented in order to evaluate the performances of the systems.
Jankovic, Miroslava (Birmingham, MI); Powell, Barry Kay (Belleville, MI)
2000-12-26
A hybrid powertrain for a vehicle comprising a diesel engine and an electric motor in a parallel arrangement with a multiple ratio transmission located on the torque output side of the diesel engine, final drive gearing connecting drivably the output shaft of transmission to traction wheels of the vehicle, and an electric motor drivably coupled to the final drive gearing. A powertrain controller schedules fuel delivered to the diesel engine and effects a split of the total power available, a portion of the power being delivered by the diesel and the balance of the power being delivered by the motor. A shifting schedule for the multiple ratio transmission makes it possible for establishing a proportional relationship between accelerator pedal movement and torque desired at the wheels. The control strategy for the powertrain maintains drivability of the vehicle that resembles drivability of a conventional spark ignition vehicle engine powertrain while achieving improved fuel efficiency and low exhaust gas emissions.
Grillo, Ricardo C.; O'Neil, Walter K.; Preston, David M.
2005-09-20
A hybrid powertrain system is provided that includes a first prime mover having a rotational output, a second prime mover having a rotational output, and a transmission having a main shaft supporting at least two main shaft gears thereon. The transmission includes a first independent countershaft drivingly connected to the first prime mover and including at least one ratio gear supported thereon that meshes with a respective main shaft gear. A second independent countershaft is drivingly connected to the second prime mover and includes at least one ratio gear supported thereon that meshes with a respective main shaft gear. The ratio gears on the first and second countershafts cooperate with the main shaft gears to provide at least one gear ratio between the first and second countershafts and the main shaft. A shift control mechanism selectively engages and disengages the first and second countershafts for rotation with the main shaft.
Shallvari, Iva; Velnati, Sashidhar; DeGroot, Kenneth P.
2015-07-28
A method and apparatus for heating a catalytic converter's catalyst to an efficient operating temperature in a hybrid electric vehicle when the vehicle is in a charge limited mode such as e.g., the charge depleting mode or when the vehicle's high voltage battery is otherwise charge limited. The method and apparatus determine whether a high voltage battery of the vehicle is incapable of accepting a first amount of charge associated with a first procedure to warm-up the catalyst. If it is determined that the high voltage battery is incapable of accepting the first amount of charge, a second procedure with an acceptable amount of charge is performed to warm-up the catalyst.
J. S. Alcaniz; R. Silva; F. C. Carvalho; Zong-Hong Zhu
2008-07-16
Extending previous results [Phys. Rev. Lett. 97, 081301 (2006)], we explore the cosmological implications of a new quintessence scenario driven by a slow rolling homogeneous scalar field whose equation of state behaved as freezing over the entire cosmic evolution, is approaching -1 today, but will become thawing in the near future, thereby driving the Universe to an eternal deceleration. We argue that such a mixed behavior, named \\emph{hybrid}, may reconcile the slight preference of current observational data for freezing potentials with the impossibility of defining observables in the String/M-theory context due to the existence of a cosmological event horizon in asymptotically de Sitter universes as, e.g., pure freezing scenarios.
Nonminimally coupled hybrid inflation
Koh, Seoktae [Center for Quantum Spacetime, Sogang University, Shinsu-dong 1, Mapo-gu, 121-742, Seoul (Korea, Republic of); Minamitsuji, Masato [Department of Physics, Graduate School of Science and Technology, Kwansei Gakuin University, Sanda 669-1337 (Japan)
2011-02-15
We discuss the hybrid inflation model where the inflaton field is nonminimally coupled to gravity. In the Jordan frame, the potential contains {phi}{sup 4} term as well as terms in the original hybrid inflation model. In our model, inflation can be classified into the type (I) and the type (II). In the type (I), inflation is terminated by the tachyonic instability of the waterfall field, while in the type (II) by the violation of slow-roll conditions. In our model, the reheating takes place only at the true minimum and even in the case (II) finally the tachyonic instability occurs after the termination of inflation. For a negative nonminimal coupling, inflation takes place in the vacuum-dominated region, in the large field region, or near the local minimum/maximum. Inflation in the vacuum-dominated region becomes either the type (I) or (II), resulting in a blue or red spectrum of the curvature perturbations, respectively. Inflation around the local maximum can be either the type (I) or the type (II), which results in the red spectrum of the curvature perturbations, while around the local minimum it must be the type (I), which results in the blue spectrum. In the large field region, to terminate inflation, potential in the Einstein frame must be positively tilted, always resulting in the red spectrum. We then numerically solve the equations of motion to investigate the whole dynamics of inflaton and confirm that the spectrum of curvature perturbations changes from red to blue ones as scales become smaller.
Hybrid Systems: From Verification to Falsification
Kavraki, Lydia E.
Hybrid Systems: From Verification to Falsification Erion Plaku, Lydia E. Kavraki, and Moshe Y}@cs.rice.edu Abstract. We propose HyDICE, Hybrid DIscrete Continuous Exploration, a multi-layered approach for hybrid. The discrete search uses the discrete transitions of the hybrid system and coarse-grained decompositions
Hybrid Abstractions that Preserve Timed Languages
Pappas, George J.
Hybrid Abstractions that Preserve Timed Languages Paulo Tabuada1 and George J. Pappas2 1 Instituto@ee.upenn.edu Abstract. In this paper we consider the problem of extracting an ab- straction from a hybrid control system that determine when trajectories of the original hybrid system can be generated by the abstracted hybrid system
Hybrid Geometric Reduction of Hybrid Systems Aaron D. Ames and Shankar Sastry
Sastry, S. Shankar
Hybrid Geometric Reduction of Hybrid Systems Aaron D. Ames and Shankar Sastry Abstract-- This paper presents a unifying framework in which to carry out the hybrid geometric reduction of hybrid systems, generalizing classical reduction to a hybrid setting. I. INTRODUCTION The reduction of mechanical systems
Hybrid Charmonium and the $?-?$ Puzzle
Leonard S. Kisslinger; Diana Parno; Seamus Riordan
2008-11-21
Using the method of QCD Sum Rules, we estimate the energy of the lowest hybrid Charmonium state, and find it to be at the energy of the $\\Psi'(2S)$ state, about 600 Mev above the $J/\\Psi(1S)$ state. Since our solution is not consistent with a pure hybrid at this energy, we conclude that the $\\Psi'(2S)$ state is probably an admixed $c \\bar{c}$ and hybrid $c \\bar{c}g$ state. From this conjecture we find a possible explanation of the famous $\\rho-\\pi$ puzzle.