Backward-Facing Step
DNS by Le and Moin
Description
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Simulation of flow over a backward-facing step.
The mean velocity profile obtained from a boundary layer simulation by Spalart (1986) is
imposed at the inlet at 
= 667.
Random velocity fluctuations u', v', and w' are superimposed on
this profile according to a variant of the method of Lee et al. (1992). The fluctuations
are prescribed such that, at the inlet, the turbulence intensities and Reynolds shear
stress of Spalart's data are also duplicated. A convective boundary condition (Pauley et
al., 1988) is imposed at the exit. The streamwise domain consists of an entry section of
length l0h prior to the step and a 20h post-expansion section, where h is the step height.
The vertical dimensions before and after the expansion are W1 = 5h and
W2 = 6h which give an expansion ratio ER of 1.20.
The Reynolds number, based on h and the mean inlet free stream
velocity U0, is Reh = 5100.
The above figure shows contour plots of the instantaneous spanwise vorticity
on a typical vertical plane. The vorticity is
normalised by U0/h. A free-shear layer spreading from the step and
interacting with the lower wall near the mean reattachment
location, xR = 6h, is discernible.
The basic statistical quantities are compared to results from concurrent experiments by
Jovic and Driver. In 1991, they conducted a backward facing step experiment at
Reh = 6800 and ER = 1.09, herein referred as "JD1". However,
the results indicated
that these parameters are not sufficiently close to those used in simulations. Thus, Jovic
and Driver in 1992 conducted a second experiment with Reh = 4950
and ER = 1.20 ("JD2").
Simulation Details
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Previous and Reference Numerical Solutions
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References
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