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-   -   Inlet turbulence generation for LES (http://www.cfd-online.com/Forums/cfx/26602-inlet-turbulence-generation-les.html)

Sungho Yoon October 31, 2008 06:49

Inlet turbulence generation for LES
 
I'm doing LES calculations for a backward-facing step. Currently I try to generate turbulent flows for my inlet boundary condition.

A way to do it is to conduct a precursor LES calculation (an auxilary calculation) for a channel flow with peridioc boundary condition in the streamwise direction and store data at a plane at each time step. Then I can produce, say, ten thousands inlet boundary condition files at each time step.

My question is, then, how can I read those inlet boundary condition at each time step?

Thank you in advance.

Sungho


underGroundMan November 4, 2008 08:02

Re: Inlet turbulence generation for LES
 
Its not clear to me how you are trying to impose turbulence at the inlet. How long is your duct? I would say you should create a very long duct with normal inlet and outlet BCs and run the simulation. Then you export the outlet values for velocity and impose that file at the inlet. It will be a single file not multiple file.

Another method would be to compile subroutines. Google for vortex method. I have some papers on the subject, if you need them let me know.

Regards


Sungho Yoon November 4, 2008 10:09

Re: Inlet turbulence generation for LES
 
Thank you for your advice.

Firstly, if you send a couple of papers regarindg vortex method, it will be very helpful.

Currently, I try to implement Lars Davidson's method to generate synthetic fluctuations as inlet boundary conditions using user fortran. (Advances and applications in fluid mechanics, vol. 1., issue 1, 2007, page 1-35 )

What I meant regarding a channel is to impose a periodic boundary condition (streamwise) and run for a long time. Then it would be like a infinite channel. When the flow is fully developed, I imagine I can store data (fluctuation) at each time step and use them as an inlet boundary condition for my main application.

Anyway, I will keep trying in various ways.

Regards, Sungho


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