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-   -   LES initialization (https://www.cfd-online.com/Forums/fluent/49252-les-initialization.html)

 Abdel Dehbi September 13, 2008 12:59

LES initialization

Hello all,

I want to use LES for turbulent pipe flow. After initialization of the RANS field following Fluent guidelines, I switch to LES, but I always end up with laminar flow. Any clue how I could initialize the flow to reach turbulent conditions with LES? Thanks.

Abdel

 Paolo Lampitella September 19, 2008 07:54

Re: LES initialization

I'm simulating the turbulent channel flow and i used the logistic map:

/************************************************** ******************** UDF for initialize the field with the logistic map ************************************************** ********************/

#include "udf.h"

DEFINE_INIT(init_func,d)

{

cell_t c;

real x[ND_ND];

real x0, y0, z0;

real pi, ck, cn;

real ax, ay, a0, ak;

pi = M_PI;

ck = 0.5;

cn = 3.891;

ax = 20.0*pi;

ay = 20.0*pi;

ak = ck;

{

begin_c_loop_all(c,t)

{

C_CENTROID(x,c,t);

x0 = x[0];

y0 = x[1];

z0 = x[2];

a0 = ak;

ak = cn*a0*(1-a0);

C_U(c,t) = -20.0*y0*(y0-2) + 4.0*(0.5-ak);

a0 = ak;

ak = cn*a0*(1-a0);

C_V(c,t) = 4.0*(0.5-ak);

a0 = ak;

ak = cn*a0*(1-a0);

C_W(c,t) = 4.0*(0.5-ak);

}

end_c_loop_all(c,t)

}

}

and it seems to work properly. Some stuff in the UDF is not used but it should work

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