backward facing step problem
 

Hi, there,

I am trying to test a CFD code. One of the example I plan to test is the problem of "2D backward facing step" problem, i.e., a flow pass through a duct, at downstream the duct has a step down. Could any of you direct me to dig out some literature about the nature of this example? e.g., any analytical or approximation solution for this example, numerical difficulties perople are facing ... etc.. The following is a schematic picture of the duct. The flow is flowing from the left to the right. Any help is appreciate it.

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Yung

Re: backward facing step problem
 

I know there are lots of work has been don on backward step. So you should not find a problem to find it in the literature

Re: backward facing step problem
 

It is one of the standard test case in CFD to test the numerical algorithm and turbulence modeling. It cas be either laminar or turbulent. You need to know the flow separation bubble size in order to make the computational domain large enough to cover the downstream duct and part of the upstream duct. The separation bubble size for turbulent flow is about six step heights. It is a function of Reynolds number for laminar flow.

Re: backward facing step problem
 

Yung,

You may start with this

Speziale, C.G.; Thangam, S. Analysis of an RNG based turbulence modeling for separated flows. Int. Journal of Eng. Sci. 1992

OR

Turbulence Modeling for CFD by Wilcox

Hope this help

Budi