{"id":250719,"date":"2023-02-21T09:35:48","date_gmt":"2023-02-21T09:35:48","guid":{"rendered":"\/forum\/forums\/topic\/species-transport-equation-as-uds\/"},"modified":"2023-02-21T10:01:34","modified_gmt":"2023-02-21T10:01:34","slug":"species-transport-equation-as-uds","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/species-transport-equation-as-uds\/","title":{"rendered":"Species transport equation as UDS"},"content":{"rendered":"

Hey all, <\/p>\n

I am defining my species transport equations through UDS. This is because my scalar is the molar concentration. 
 
So I thought I could divide it by rho.<\/p>\n

\n
return F_FLUX(f,t)\/rho;<\/p>\n

What is the meaning of this? What am I returning and which units?<\/p>\n

This is the example from the manual. I dont understand if I need to have this part 
 NV_DS(psi_vec, =, C_U(c0,t0),C_V(c0,t0),C_W(c0,t0),*,C_R(c0,t0));
 NV_DS(psi_vec, +=, C_U(c1,t1),C_V(c1,t1),C_W(c1,t1),*,C_R(c1,t1));
 flux = NV_DOT(psi_vec, A)\/2.0; \/* Average flux through face *\/<\/p>\n

If I use the F_FLUX(f,t).<\/p>\n

<\/div>\n<\/div>\n

**********************************************************************\/
 \/* UDF that implements a simplified advective term in the *\/
 \/* scalar transport equation *\/
 \/**********************************************************************\/
 #include “udf.h”
 DEFINE_UDS_FLUX(my_uds_flux,f,t,i)
 {
 cell_t c0, c1 = -1;
 Thread *t0, *t1 = NULL;
 real NV_VEC(psi_vec), NV_VEC(A), flux = 0.0;
 c0 = F_C0(f,t);
 t0 = F_C0_THREAD(f,t);
 F_AREA(A, f, t);
 \/* If face lies at domain boundary, use face values; *\/
 \/* If face lies IN the domain, use average of adjacent cells. *\/
 if (BOUNDARY_FACE_THREAD_P(t)) \/*Most face values will be available*\/
 {
 real dens;
 \/* Depending on its BC, density may not be set on face thread*\/
 if (NNULLP(THREAD_STORAGE(t,SV_DENSITY)))
 dens = F_R(f,t); \/* Set dens to face value if available *\/
 else
 dens = C_R(c0,t0); \/* else, set dens to cell value *\/
 NV_DS(psi_vec, =, F_U(f,t), F_V(f,t), F_W(f,t), *, dens);
 flux = NV_DOT(psi_vec, A); \/* flux through Face *\/ }
 else
 {
 c1 = F_C1(f,t); \/* Get cell on other side of face *\/
 t1 = F_C1_THREAD(f,t);
 NV_DS(psi_vec, =, C_U(c0,t0),C_V(c0,t0),C_W(c0,t0),*,C_R(c0,t0));
 NV_DS(psi_vec, +=, C_U(c1,t1),C_V(c1,t1),C_W(c1,t1),*,C_R(c1,t1));
 flux = NV_DOT(psi_vec, A)\/2.0; \/* Average flux through face *\/
 }
 \/* Ansys Fluent will multiply the returned value by phi_f (the scalar’s
 value at the face) to get the ‘‘complete’’ advective term. *\/
 return flux;
 } <\/p>\n","protected":false},"template":"","class_list":["post-250719","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t