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Title: Challenges in engineering simulations of complex, turbulent flows.


No abstract prepared.

Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
OSTI Identifier:
Report Number(s):
TRN: US201214%%862
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: Proposed for presentation at the Seventh Biennial Tri-Laboratory Engineering Conference held May 7-10, 2007 in Albuquerque, NM.
Country of Publication:
United States

Citation Formats

Barone, Matthew Franklin. Challenges in engineering simulations of complex, turbulent flows.. United States: N. p., 2007. Web.
Barone, Matthew Franklin. Challenges in engineering simulations of complex, turbulent flows.. United States.
Barone, Matthew Franklin. Tue . "Challenges in engineering simulations of complex, turbulent flows.". United States. doi:.
title = {Challenges in engineering simulations of complex, turbulent flows.},
author = {Barone, Matthew Franklin},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}

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  • Abstract not provided.
  • This short note discusses some of the challenges for design of suitable spatial numerical schemes for hypersonic turbulent flows, including combustion, and thermal and chemical nonequilibrium flows. Often, hypersonic turbulent flows in re-entry space vehicles and space physics involve mixed steady strong shocks and turbulence with unsteady shocklets. Material mixing in combustion poses additional computational challenges. Proper control of numerical dissipation in numerical methods beyond the standard shock-capturing dissipation at discontinuities is an essential element for accurate and stable simulations of the subject physics. On one hand, the physics of strong steady shocks and unsteady turbulence/shocklet interactions under the nonequilibriummore » environment is not well understood. On the other hand, standard and newly developed high order accurate (fourth-order or higher) schemes were developed for homogeneous hyperbolic conservation laws and mixed hyperbolic and parabolic partial differential equations (PDEs) (without source terms). The majority of finite rate chemistry and thermal nonequilibrium simulations employ methods for homogeneous time-dependent PDEs with a pointwise evaluation of the source terms. The pointwise evaluation of the source term might not be the best choice for stability, accuracy and minimization of spurious numerics for the overall scheme.« less
  • Large-eddy simulations were performed to study the turbulent reacting flows in a simulated solid-fuel combustion chamber. The time-dependent axisymmetric compressible conservation equations were solved directly without using subgrid-scale turbulence models. The combustion process considered was a one-step, irreversible, and infinitely fast chemical reaction and the pyrolizing solid fuel was simulated by gaseous ethylene injected through a porous wall for a practical range of fuel blowing velocity encountered in solid-fuel combustion chambers for the first time. The numerical code used the finite-volume technique which involved alternating in time the second-order, explicit MacCormack's and Godunov's methods. Characteristic-based boundary conditions were applied onmore » inflow and outflow boundaries, which allow outlet boundary conditions to be nonzero gradients, and in turn, a practical length of computational domain to be realized. The effects of combustion on the large-scale unsteady flow structure and the mean flameholder recirculation zone were documented in terms of the density contours, vorticity dynamics, streamlines, mean-velocity vector fields, temperature profiles, flame position, and fuel blowing velocity. A comparison of the distributions of instantaneous and mean mass fractions of reactants shows that the present method appropriately reveals the effects of large-scale turbulent motions on combustion. Furthermore, the present large-eddy simulations have achieved a significant improvement in predicting the mean effective reattachment length over the previous calculations incorporating with turbulence models. The physical insight regarding the decrease of the mean effective reattachment length with combustion was also addressed.« less
  • A parallel pseudospectral code for direct numerical simulations of transitional and turbulent flows on distributed-memory, medium-grained, parallel architectures has been developed. The code uses Fourier series in two dimensions, and Chebyshev collocation in the third. All operations are performed with no communications except for the evaluation of the multi-dimensional FFTs. These are computed using a transpose algorithm. In actual double precision computations performed on a 64-node iPSC/860 the code ran with efficiencies in excess of 80%. Timings compared favorably (faster by a factor of about 2) with timings on a CRAY-YMP. The code has been applied towards the study ofmore » small scale dynamics and mixing in turbulent jets.« less
  • An explicit Galerkin finite-element formulation of the Spalart-Allmaras (SA) 1 - equation turbulent transport model was implemented into the incompressible flow module of a parallel, multi-domain, Galerkin finite-element, multi-physics code, using both a RANS formulation and a DES formulation. DES is a new technique for simulating/modeling turbulence using a hybrid RANSkES formulation. The turbulent viscosity is constructed from an intermediate viscosity obtained from the transport equation which is spatially discretized using Q1 elements and integrated in time via forward Euler time integration. Three simulations of plane channel flow on a RANS-type grid, using different turbulence models, were conducted in ordermore » to validate the implementation of the SA model: SA-RANS, SA-DES and Smagorinksy (without wall correction). Very good agreement was observed between the SA-RANS results and theory, namely the Log Law of the Wall (LLW), especially in the viscous sublayer region and, to a lesser extent, in the log-layer region. The results obtained using the SA-DES model did not agree as well with the LLW, and it is believed that this poor agreement can be attributed to using a DES model on a RANS grid, namely using an incorrect length-scale. It was observed that near the wall, the SA-DES model acted as an RANS model, and away from the wall it acted as an LES model.« less