Computation of backward-facing step flows by a second-order Reynolds stress closure model

1995 ◽  
Vol 21 (3) ◽  
pp. 223-235 ◽  
Author(s):  
Robert R. Hwang ◽  
Y. F. Peng
Keyword(s):  
Reynolds Stress ◽  
Second Order ◽  
Closure Model ◽  
Backward Facing Step ◽  
Reynolds Stress Closure Model

A.R.A.P.'s Second-Order Closure Model: Comparison with a Number of Complex Turbulent Flows.

1982 ◽  
Author(s):  
W. Stephen Kewellen ◽  
Brian Quinn ◽  
Roger D. Sullivan ◽  
R. Ian Sykes
Keyword(s):  
Turbulent Flows ◽  
Model Comparison ◽  
Second Order ◽  
Closure Model

PIV Measurements in Square Backward-Facing Step

2007 ◽  
Vol 129 (8) ◽  
pp. 984-990 ◽  
Author(s):  
Mika Piirto ◽  
Aku Karvinen ◽  
Hannu Ahlstedt ◽  
Pentti Saarenrinne ◽  
Reijo Karvinen
Keyword(s):  
Shear Stress ◽  
Reynolds Stress ◽  
Reynolds Shear Stress ◽  
Experimental Tests ◽  
Expansion Ratio ◽  
Spanwise Direction ◽  
Duct Flow ◽  
Backward Facing Step ◽  
Mean Velocity ◽  
Stress Profiles

Measurements with both two-dimensional (2D) two-component and three-component stereo particle image velocimetry (PIV) and computation in 2D and three-dimensional (3D) using Reynolds stress turbulence model with commercial code are carried out in a square duct backward-facing step (BFS) in a turbulent water flow at three Reynolds numbers of about 12,000, 21,000, and 55,000 based on the step height h and the inlet streamwise maximum mean velocity U0. The reattachment locations measured at a distance of Δy=0.0322h from the wall are 5.3h, 5.6h, and 5.7h, respectively. The inlet flow condition is fully developed duct flow before the step change with the expansion ratio of 1.2. PIV results show that the mean velocity, root mean square (rms) velocity profiles, and Reynolds shear stress profiles in all the experimental flow cases are almost identical in the separated shear-layer region when they are nondimensionalized by U0. The sidewall effect of the square BFS flow is analyzed by comparing the experimental statistics with direct numerical simulation (DNS) and Reynolds stress model (RSM) data. For this purpose, the simulation is carried out for both 2D BFS and for square BFS having the same geometry in the 3D case as the experimental case at the lowest Reynolds number. A clear difference is observed in rms and Reynolds shear stress profiles between square BFS experimental results and DNS results in 2D channel in the spanwise direction. The spanwise rms velocity difference is about 30%, with experimental tests showing higher values than DNS, while in contrast, turbulence intensities in streamwise and vertical directions show slightly lower values than DNS. However, with the modeling, the turbulence statistical differences between 2D and 3D RSM cases are very modest. The square BFS indicates 0.5h–1.5h smaller reattachment distances than the reattachment lengths of 2D flow cases.

Computational Study of the Synthetic Jet on Separated Flow Over a Backward-Facing Step

2010 ◽  
Author(s):  
Koichi Okada ◽  
Kozo Fujii ◽  
Koji Miyaji ◽  
Akira Oyama ◽  
Taku Nonomura ◽  
...  
Keyword(s):  
Shear Layer ◽  
Reynolds Stress ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Frequency Characteristics ◽  
Synthetic Jet ◽  
Recirculation Region ◽  
Backward Facing Step ◽  
Freestream Velocity ◽  
Jet Control

Frequency effects of the synthetic jet on the flow field over a backward facing step are investigated using numerical analysis. Three-dimensional Navier-Stokes equations are solved. Implicit large-eddy simulation using high-order compact difference scheme is conducted. The present analysis is addressed on the frequency characteristics of the synthetic jet for understanding frequency characteristics and flow filed. Three cases are analyzed; the case computing flow over backward facing step without control, the case computing flow with synthetic jet control at F+h = 0.2, and the case computing flow with synthetic jet control at F+h = 2.0, where non-dimensional frequency F+h is normalized with the height of backward-facing step and the freestream velocity. The present computation shows that separation length in the case of the flow controlled at F+h = 0.2 is 20 percent shorter than the case without control. Strong two-dimensional vortices generated from the synthetic jet interact with the shear layer, which results in the increase of the Reynolds stress in the shear layer region. These vortices are deformed into three-dimensional structures, which make Reynolds stress stronger in the recirculation region. Size of the separation length in the case of the flow controlled at F+h = 2.0 is almost the same as the case without control because the mixing between the synthetic jet and the shear layer is not enhanced. Weak and short periodic vortices induced from the synthetic jet do not interacts with the shear layer very much and diffuse in the recirculation region.

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