hi, Iam giving outflow boundary condition for all flow variables at the exit. For User defined scalars at the exit, I want to give normal gradient is zero( which is different from the two options given in for UDS). For that i want to write a UDF. Can u tell me which Define macro can be used for this, if we can write UDF for defining BC for UDS. Please help me in this.

Thanks a lot

Hi ramesh vedula. I have a same problem.I want to set the derivative of velocity to zero at boundary.If you find this please help me. thanks.

[Maryam-A]

I would appreciate if anyone can help me.
I wanted to return derivative of UDS as wall boundary value, but I face with "fatal signal" that I found this because of boundary condition UDS.
this is part of my udf for B.C of UDS( volume fraction of nanoparticle in my case)

DEFINE_PROFILE(alpha_bc1,thread,position)
{
Thread *t;
cell_t c;
.
.
.

begin_f_loop(f,thread)
{

C_UDSI_G(c,t,0)[0]=-(D_T/D_B)*C_T_G(c,t)[0];
F_PROFILE(f,thread,position)=C_UDSI_G(c,t,0)[0];
}
end_f_loop(f,t)
}

[MayTheFlowBeWithYou]

Hi,

Did you ever manage to figure this out? I have a similar issue...