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Old   September 13, 2008, 12:59
Default LES initialization
Abdel Dehbi
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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.

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Old   September 19, 2008, 07:54
Default Re: LES initialization
Paolo Lampitella
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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"



cell_t c;

Thread *t;

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;






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);





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