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-   -   modelling wall shear stress through fluent (https://www.cfd-online.com/Forums/fluent-udf/89021-modelling-wall-shear-stress-through-fluent.html)

rakadit June 1, 2011 12:52
modelling wall shear stress through fluent
 
Dear all!

Please help me to write UDF for wall shear stress equation: tau=constant*viscosity*velocitygradient.

I have tried with define profile UDF using cell loop but it is resulting in acess violation error?

thanks

Amir June 2, 2011 02:14
Hi,
when you want to use gradients, you have to prevent the solver from freeing up memory by issuing the text command solve/set/expert and then answering yes to the question Keep temporary solver memory from being freed?
if it doesn't work, post your UDF and I'll correct it for you.

rakadit June 6, 2011 02:06
UDF wall shear
 
Thanks for your suggestion! The UDF which I had written for calculating wall shear is like this:please correct the UDF and send the corrected one to me.

#include "udf.h"
DEFINE_PROFILE(stressx,t,i)
{
cell_t c;
real dvdy_r;
real alpha=0.7;
real dvdy=C_DVDY(c,t);
real mu_a=C_MU_L(c,t);
dvdy_r=alpha*dvdy;
begin_c_loop(c,t)
{
F_PROFILE(c,t,i)=mu_a*dvdy_r ;
}
end_c_loop(c,t)
}

Amir June 6, 2011 03:31
It seems that you need to focus on UDF concepts more carefully.:)
Code:
#include "udf.h"
DEFINE_PROFILE(stressx,t,i)
{
face_t f;
cell_t c;
Thread *tc;
real dvdy_r;
real alpha=0.7;
real dvdy;
real mu_a;
begin_f_loop(f,t)
{
    c=F_C0(f,t);
    tc=THREAD_T0(t);
    mu_a=C_MU_L(c,tc);
    dvdy=C_DVDY(c,tc);
    dvdy_r=alpha*dvdy;
    F_PROFILE(f,t,i)=mu_a*dvdy_r;
}
end_f_loop(f,t)
}
Regards,

Amir

rakadit June 9, 2011 01:50
Dear Mr. Amir,

Thanks for correcting UDF.Yes,you are right I am new to UDF writing .I will soon give u feedback on corrected UDF.

with regards,


Rakesh

rakadit June 27, 2011 12:33
Dear Mr. Amir,

Sorry for late response.I had gone to some remote place.I am working with the UDF.it is working fine.Results are coming but correctness of results is to be confirmed.
Thanks again!


Rakesh


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