[AS_Aero]

Hi All

I have an LES simulation running and I intialized using my RANS result of same mesh. Now my instanteneous results from LES is similar to that of the RANs eventhough not perfectly similar, but I could imagine that. My question is how can I validate that my LES is correct or the results are correct, and the mesh is fare enough for the case ? I am asking in terms of cross checking in the post process.

For Example.
When I see the Eddy Viscosity contour plot my RANS results shows high value at the sharp corners etc compared to my LES which has less value for a same scale Or in another way my eddy viscosity gradient is high on RANS and low on LES !! Does it mean that the LES have to run more or I have to check for some mesh refinement or something else !!
Thanks

[ghorrocks]

You should validate your LES against a benchmark result, either high quality experimental results or a benchmark LES simulation. You might need to do a literature search to find a suitable one.

If you are interested in the pseudo steady state condition then you need to run long enough to establish the pseudo steady state. Put in some monitor points at key points and wait until they settle to a pseudo steady state. I say pseudo steady state as LES is not steady state by definition, I am defining pseudo steady state as when the time averaged results are not changing.

[AS_Aero]

Hi Glenn

So To benchmark I have tried to find some papers but I dont have any. Also experimental results as well I dont have. Only thing I can do is an approximation with the external flow related to my case. Well I would like to know how do you do a statistical averaging in CFX ?

[ghorrocks]

If you cannot find papers directly relevant to your flow then just do a general LES benchmark. There are lots of these, lid driven cavity, flow over a back facing step etc.