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Research Papers: Fundamental Issues and Canonical Flows

Secondary Flow in Semi-Circular Ducts

[+] Author and Article Information
I. A. S. Larsson

Division of Fluid Mechanics,  Luleå University of Technology, SE-97187 Luleå, Swedensofia.larsson@ltu.se

E. M. Lindmark, T. S. Lundström

Division of Fluid Mechanics,  Luleå University of Technology, SE-97187 Luleå, Sweden

G. J. Nathan

School of Mechanical Engineering,  University of Adelaide, Adelaide, Australia

J. Fluids Eng 133(10), 101206 (Oct 04, 2011) (8 pages) doi:10.1115/1.4004991 History: Received May 02, 2011; Accepted August 26, 2011; Published October 04, 2011; Online October 04, 2011

Turbulent secondary flows are motions in the transverse plane, perpendicular to a main, axial flow. They are encountered in non-circular ducts and can, although the velocity is only of the order of 1–3% of the streamwise bulk velocity, affect the characteristics of the mean flow and the turbulent structure. In this work, the focus is on secondary flow in semi-circular ducts which has previously not been reported. Both numerical and experimental analyses are carried out with high accuracy. It is found that the secondary flow in semi-circular ducts consists of two pairs of counter rotating corner vortices, with a velocity in the range reported previously for related configurations. Agreement between simulation and experimental results are excellent when using a second moment closure turbulence model, and when taking the experimental and numerical uncertainty into account. New and unique results of the secondary flow in semi-circular ducts have been derived from verified simulations and validating laser-based experiments.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Geometry with grid structure

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Figure 2

Experimental arrangement

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Figure 3

The sensitivity of the calculated flows to grid refinement, showing velocity profiles at x = −20 mm, Re = 8 × 104 , using the BSL-model

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Figure 4

Calculated axial flow contours with streamlines of the main, axial flow from inlet to outlet of the duct. Simulations were performed with Reynolds stress model BSL (left) and SST turbulence model (right). Re=8 × 104.

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Figure 5

Measured axial flow contours, Re=8 × 104, obtained at z/Dh=92

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Figure 6

Secondary flow in the semi-circular duct, calculated with a Reynolds stress model (BSL) to the left, a standard two-equation model (SST) to the right. Re=8 × 104.

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Figure 7

Vorticity contour plot, simulation result with Re=8 × 104.

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Figure 8

Vector and contour plots of the x-component of the secondary flow

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Figure 9

Reynolds normal stress τxx. Simulation results to the left, experimental results to the right. Re=8 × 104.

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Figure 10

Reynolds normal stress τzz. Simulation results to the left, experimental results to the right. Re=8 × 104.

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Figure 11

Reynolds normal stress τyy, simulation results with Re=8 × 104

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Figure 12

Contour plot of turbulent kinetic energy. Simulation results to the left, experimental results to the right. Re=8 × 104.

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Figure 13

Contour plot of turbulence intensity. Simulation results to the left, experimental results to the right. Re=8 × 104.

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Figure 14

Anisotropy of the normal stresses (τxx-τyy) to the left, Reynolds shear stress (τxy) to the right. Simulation results with Re=8 × 104.

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Figure 15

Velocity profiles, a comparison of the simulated and experimental data (obtained at z/Dh=92), at Re=8 × 104

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