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TECHNICAL PAPERS

Numerical Simulation of Two-Dimensional Laminar Incompressible Wall Jet Flow Under Backward-Facing Step

[+] Author and Article Information
P. Rajesh Kanna

Department of Mechanical Engineering, Indian Institute of Technology Guwahati, North Guwahati, Guwahati-781039, Assam, India

Manab Kumar Das1

Department of Mechanical Engineering, Indian Institute of Technology Guwahati, North Guwahati, Guwahati-781039, Assam, Indiamanab@iitg.ernet.in

1

Author to whom all correspondence should be addressed.

J. Fluids Eng 128(5), 1023-1035 (Jan 25, 2006) (13 pages) doi:10.1115/1.2243298 History: Received January 27, 2005; Revised January 25, 2006

Two-dimensional laminar incompressible wall jet flow over a backward-facing step is solved numerically to gain insight into the expansion and recirculation of flow processes. Transient streamfunction vorticity formulation of the Navier-Stokes equation is solved with clustered grids on the physical domain. The behavior of the jet has been studied for different step geometry (step length, l, step height, s) and Reynolds number (Re). It is found that the presence of a step in the wall jet flow creates recirculation and the reattachment length follows an almost linear trend within the range considered for both parameters Re and step geometry. Simulations are made to show the effect of entrainment on recirculation eddy. Detailed study of u velocity decay is reported. The velocity profile in the wall jet region shows good agreement with experimental as well as similarity results. The distance where the similarity profile forms is reduced by increasing the step geometry whereas an increment in Re increases this distance. The effects of Re, step length, and step height on wall vorticity are presented. The parametric study is helpful to predict the reattachment location for wall jet flows over step.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 11

Similarity profile Re=400, l=2h, s=1h

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Figure 12

Effect of step height on upstream velocity at x=1h: Re=400, l=2h

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Figure 13

Local maximum u velocity: l=2h, s=1h

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Figure 14

Reattachment length for different geometry and Reynolds number: l=0h, s=1h(29)

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Figure 4

Backward-facing step flow with upstream channel problem. (Domain shown near the step.)

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Figure 5

Reattachment length for different Reynolds number: parabolic inlet profile

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Figure 6

Streamline contour

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Figure 7

Vorticity contour

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Figure 8

Effect of Re on wall vorticity: l=2h, s=1h

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Figure 9

Effect of step length on wall vorticity: Re=400, s=1h

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Figure 10

Effect of step height on wall vorticity: Re=400, l=2h

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Figure 1

Schematic diagram and boundary conditions in a wall jet under backward-facing step problem

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Figure 2

Schematic diagram and boundary conditions of L-shaped lid driven cavity flow problem (30)

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Figure 3

Velocity profiles along CL1 and CL2

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