[letsroll]

Dear everybody,
I simulate the slip phenomenon at air-water interface by matching the tangential velocity and tangential shear stress. With flat interface, there is no problem. In curve interface, it is okay with the velocity but I cannot get the same tangential shear stress at both water phase and air phase.

Is there anybody familiar with this problem?

This is my UDF code for matching tangential shear stress (x-component):

#include "udf.h"//FILE * fout ;
#include "mem.h"
#include "math.h"

#define mu_air 1.7894e-05
#define mu_water 0.001003
#define cx 125.e-6 //coordinate of center of curvature
#define cy 0. //coordinate of center of curvature


real shear_x;

DEFINE_PROFILE(shear_x_water, thread, position)
{

real x[ND_ND];
real px, py, cos_teta, sin_teta;
real dudx, dudy, dvdx, dvdy;
real dvtdn;

face_t f;
cell_t c_air;
Thread *tc_air;

begin_f_loop(f, thread) // loop over all faces in thread 'thread'
{
F_CENTROID(x,f,thread);

px = x[0]; //coordinate of a point at the interface
py = x[1];

cos_teta = (px-cx)/sqrt( (px-cx)*(px-cx) + (py-cy)*(py-cy) );
sin_teta = (py-cy)/sqrt( (px-cx)*(px-cx) + (py-cy)*(py-cy) );

tc_air = THREAD_T1(thread); //return cell thread pointer for cell c1
c_air = F_C1(f,thread); //return cell c1, close to face f

dudx = C_DUDX(c_air,tc_air);
dudy = C_DUDY(c_air,tc_air);
dvdx = C_DVDX(c_air,tc_air);
dvdy = C_DVDY(c_air,tc_air);

dvtdn = mu_air* ( 2.*sin_teta*cos_teta*dudx + (cos_teta*cos_teta-sin_teta*sin_teta)*dudy + (cos_teta*cos_teta- sin_teta*sin_teta)*dvdx - 2.*sin_teta*cos_teta*dvdy );

shear_x = dvtdn*cos_teta;

F_PROFILE( f, thread, position) = shear_x;

}
end_f_loop(f,thread)

}