Howe to get swirl velocity component in 2D axisymtric swirl modeling
I am reconstucting a old UDF that is used for a partial slip boundary condition from 3D to a 2D axisymetric swirl model. The UDF works fine with no modifications when hooking only the X and Y components but when adding the swirl component the solution diverges directly.
My thoughts are that when using ND_ SET for the nol vector I dont get the third component, same for the ND_DOT and NV_V_VS oprations. So when I call for vel_normal; it should not exists I guess?
Am I corect in this? And also I wounder if the F_W(f,t) comand works in 2D axisymetric swirl flow to get the swirl component of the flow or if there is another way?
part of the UDF:
begin_f_loop(f, t) /* loops over faces in a face thread */
distance_cell = 2.0*NV_MAG(distance);
F_AREA(normal,f,t); /* obtaining normal direction of the wall */
U_vel=F_U(f,t); /* obtaining u direction of velocity on the wall */
V_vel=F_V(f,t); /* obtaining v direction of velocity on the wall */
W_vel=F_W(f,t); /* obtaining w direction of velocity on the wall */
mag_normal=ND_DOT(U_vel, V_vel, W_vel, normal, normal, normal);
NV_V_VS(vel_normal, =, nol, +, normal, *, mag_normal);
velz_tangen=W_vel - velz_normal;
tao_z=vfrac*mu*(aN*velz_normal/bN + aT*velz_tangen/bT);
F_PROFILE(f, t, i) = tao_z;
Greatful for coments
One necessary modification is for the area: in an axisymmetric computation, you should multiply the result with 2*PI. See chapter 3.2.1 in Fluent UDF Manual.
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