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-   -   can't get pretty data from dynamic SGS model (https://www.cfd-online.com/Forums/main/80635-cant-get-pretty-data-dynamic-sgs-model.html)

 fluidzhang October 1, 2010 08:28

can't get pretty data from dynamic SGS model

hello,everyone.
i'm learning LES channel flow,and using dynamic sgs model to compute the compressible channel flow at 0.6 Mach.But I haven't got the right data and the corresponding curves,such as RMS velocity fluctuations,Renolds stress.So,I have to ask you for help.The first problem is that how to perform the grid_filter in the finite volume method? I think the grid discretization is equal to the grid filter.It's an implicit filtering method when then FVM is adopted.Am I ringt?

And I can't get the right and nice curves which are in bad agreement with the correspongding curves from the DNS data.My value of C has a large variation including negative and positive values,and is not get a steady state after long computation.
How can I amend it? I guess the problem is the initial condition.
I try this Ic from our CFD-online forums,
u(x,y,z) = C(1-y^8) + E*2*pi*sin(pi*y)*cos(x)*sin(z) v(x,y,z) = -E*(1+cos(pi*y))*sin(x)*sin(z) w(x,y,z) = -E*pi*sin(x)*sin(pi*y)*cos(z)

C is the centerline velocity and E=0.1*C

But I think it's not fit for me,anyone who have pretty Ic please let me know.
Thanks.

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