Wall law modification
 

Hi all,

I'm simulating a turbulent pipe flow and I need change the log law in Fluent...
I tried this in an UDF:

/*******************************************/
#include"udf.h"

DEFINE_WALL_FUNCTIONS(wall_law,f,t,c0,t0,wf_ret,yP lus,Emod)
{

real wf_value;

switch (wf_ret)
{
case UPLUS_LAM:
wf_value=yPlus;
break;
case UPLUS_TRB:
if(yPlus<=1500)
{
wf_value=log(yPlus)/KAPPA+log(Emod)/KAPPA;
}
if(yPlus>1500 && yPlus<=3000)
{
wf_value=11*log(yPlus)/KAPPA+log(Emod)/KAPPA-10*log(1500)/KAPPA;
}
if(yPlus>3000)
{
wf_value=0.85*log(yPlus)/KAPPA+log(Emod)/KAPPA+10.15*log(3000)-10*log(1500);
}
break;
case DUPLUS_LAM:
wf_value=1.0;
break;
case DUPLUS_TRB:
if(yPlus<=1500)
{
wf_value=1./(KAPPA*yPlus);
}
if(yPlus>1500 && yPlus<=3000)
{
wf_value=11/(KAPPA*yPlus);
}
if(yPlus>3000)
{
wf_value=0.85/(KAPPA*yPlus);
}
break;
case D2UPLUS_TRB:
if(yPlus<=1500)
{
wf_value=-1./(KAPPA*yPlus*yPlus);
}
if(yPlus>1500 && yPlus<=3000)
{
wf_value=-11/(KAPPA*yPlus*yPlus);
}
if(yPlus>3000)
{
wf_value=-0.85/(KAPPA*yPlus*yPlus);
}
break;
default:
printf("Wall function return value unavailable\n");
}
return wf_value;
}
/*****************************************/

I exported the data to excel and tried obtain u+(=u/utau) as a function of y+(=density*utau*yp/viscosity) in a graph, but what I obtain not corresponds to the profile introduced in the UDF.
Someone can help me... Can I write in the UDF the three different expressions for the log law in this way?

Please... Anyone know if the wall law expression for the fully turbulent flow can be divided into three regions in a UDF?
I was thinking that when I write an UDF similar to that I posted in the previous message, the modifications on the wall law interpreted by Fluent just consider the first part of the wall law modification (if(yPlus<=1500)).