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Title: Influence of outlet geometry on strongly swirling turbulent flow through a circular tube

Abstract

The results are reported for an extensive series of measurements (using laser Doppler anemometry) of the mean and fluctuating flow fields for swirling turbulent flow downstream of an orifice in a tube. The influence of a concentric outlet contraction is found to be negligible for low 'supercritical' swirl. For high 'subcritical' swirl, the outlet geometry is found to have a significant influence throughout the flow field and, in the case of an eccentric (i.e., offset) outlet, to lead to an asymmetric flow with a distorted core. In no case was the core found to precess or the flow to be periodic.

Authors:
; ;  [1]
  1. Department of Engineering (Mechanical Engineering), University of Liverpool, Brownlow Street, Liverpool, Merseyside L69 3GH (United Kingdom)
Publication Date:
OSTI Identifier:
20849477
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Fluids (1994); Journal Volume: 18; Journal Issue: 12; Other Information: DOI: 10.1063/1.2400075; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ASYMMETRY; GEOMETRY; LASERS; ORIFICES; PERIODICITY; TUBES; TURBULENT FLOW

Citation Formats

Escudier, M.P., Nickson, A.K., and Poole, R.J. Influence of outlet geometry on strongly swirling turbulent flow through a circular tube. United States: N. p., 2006. Web. doi:10.1063/1.2400075.
Escudier, M.P., Nickson, A.K., & Poole, R.J. Influence of outlet geometry on strongly swirling turbulent flow through a circular tube. United States. doi:10.1063/1.2400075.
Escudier, M.P., Nickson, A.K., and Poole, R.J. Fri . "Influence of outlet geometry on strongly swirling turbulent flow through a circular tube". United States. doi:10.1063/1.2400075.
@article{osti_20849477,
title = {Influence of outlet geometry on strongly swirling turbulent flow through a circular tube},
author = {Escudier, M.P. and Nickson, A.K. and Poole, R.J.},
abstractNote = {The results are reported for an extensive series of measurements (using laser Doppler anemometry) of the mean and fluctuating flow fields for swirling turbulent flow downstream of an orifice in a tube. The influence of a concentric outlet contraction is found to be negligible for low 'supercritical' swirl. For high 'subcritical' swirl, the outlet geometry is found to have a significant influence throughout the flow field and, in the case of an eccentric (i.e., offset) outlet, to lead to an asymmetric flow with a distorted core. In no case was the core found to precess or the flow to be periodic.},
doi = {10.1063/1.2400075},
journal = {Physics of Fluids (1994)},
number = 12,
volume = 18,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • By applying the mass, momentum, and angular momentum conservation laws and the maximum flow rate principle to swirling, effectively inviscid, incompressible flows in a circular tube with a sudden expansion and the direct-flow and reversed-flow Borda mouthpieces the dependence of the flow rate coefficient and mechanical energy losses on the radius ratio and nondimensional circulation is obtained. Several calculating approaches with potential and helical motion are introduced and investigated. In the case of helical motion, as the swirl decreases the axial core of the flow is found to close with a sudden change of the flow parameters.
  • In the present study, the influences of twin-counter/co-twisted tapes (counter/co-swirl tape) on heat transfer rate (Nu), friction factor (f) and thermal enhancement index ({eta}) are experimentally determined. The twin counter twisted tapes (CTs) are used as counter-swirl flow generators while twin co-twisted tapes (CoTs) are used as co-swirl flow generators in a test section. The tests are conducted using the CTs and CoTs with four different twist ratios (y/w = 2.5, 3.0, 3.5 and 4.0) for Reynolds numbers range between 3700 and 21,000 under uniform heat flux conditions. The experiments using the single twisted tape (ST) are also performed undermore » similar operation test conditions, for comparison. The experimental results demonstrate that Nusselt number (Nu), friction factor (f) and thermal enhancement index ({eta}) increase with decreasing twist ratio (y/w). The results also show that the CTs are more efficient than the CoTs for heat transfer enhancement. In the range of the present work, heat transfer rates in the tube fitted with the CTs are around 12.5-44.5% and 17.8-50% higher than those with the CoTs and ST, respectively. The maximum thermal enhancement indices ({eta}) obtained at the constant pumping power by the CTs with y/w = 2.5, 3.0, 3.5 and 4.0, are 1.39, 1.24, 1.12 and 1.03, respectively, while those obtained by using the CoTs with the same range of y/w are 1.1, 1.03, 0.97 and 0.92, respectively. In addition, the empirical correlations of the heat transfer (Nu), friction factor (f) and thermal enhancement index ({eta}) are also reported. (author)« less
  • Experimental data are presented for local heat transfer rates in the tube downstream of an abrupt 2:1 expansion. Water, with a nominal inlet Prandtl number of 6, was used as the working fluid. In the upstream tube, the Reynolds number was varied from 30,000 to 100,000 and the swirl number was varied from zero to 1.2. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk fluid temperatures ranging from 14C to 50C. Plots of local Nusselt numbers show a sharply peaked behavior at the point of maximum heat transfer, with increasing swirl greatly exaggerating the peaking.more » As swirl increased from zero to its maximum value, the location of peak Nusselt numbers was observed to shift from 8.0 to 1.5 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 3 to 9.5 times larger than fully developed tube flow values. For all cases, the location of maximum heat transfer occurred upstream of the flow reattachment point.« less
  • A spillway with a regulating device called an eddy gate, which swirls the flow in the outlet section of the spillway, was proposed as an alternative to the ordinary tunnel spillway of a high-head river hydropower project to reduce the construction time, cost, and work involved. Energy dissipation is accomplished inside the proposed spillway and thus, energy dissipators at the spillway exit are not required. Ordinary, simple vertical-lift and radial gates can be used in the proposed spillway to regulate and discharge the flow. The hydraulic model investigation performed indicates that at all openings of the main gate of themore » spillway, the gate operated in the same manner as in ordinary tunnel spillways. Swirling of the flow in the outlet section behind the gate did not affect the operation of the gate. The proposed spillway does not require a long shutdown for converting from a diversion regime to a service regime because the gates can be installed during the construction. 4 figures.« less