silp wall condition(UDF)
 

Hi all
I'm doing simulation of NIL process using VOF and dynamic mesh.

As you know, slip wall condition is necessary at the nano scale because of Kn between 0.01 and 0.1.

So I made UDF for slip wall but it is not working. continuety eqn is divergencing.

Could u plz make a correct?

below my UDF I made.
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#include "udf.h"
#include "math.h"
#define temp 433
DEFINE_PROFILE(slipws, thread, nv)
{

face_t f;
cell_t c ;
Thread *t ;
real strain,mu_c,xx;
real x[ND_ND];
real n, delta, tau, d1, d2, d3, a1, a2, p1, p_operating, p, tg;
real ap, dummy1, eta0, Mus, b,y;
begin_f_loop (f,thread)
{
c = F_C0(f,thread);
t = THREAD_T0(thread);
Mus = C_MU_L(c,t);
strain = 0.5*(C_U_G(c,t)[1]+C_V_G(c,t)[0]);
b=delta*(eta0/Mus-1.);
F_PROFILE(f,thread,nv) = fabs(b)*fabs(strain);

Message ("strain = %.13f,Mu = %.13f", strain,Mus);
}
end_f_loop (f,thread)

}
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I used viscosity model proposed by Vinogradova that is simple eqn.
b(slip length)=(mub/mus-1)*delta
where mub is bulk viscosity, mus is near wall viscosity

Is this udf used for specified shear stress?