{"id":318344,"date":"2023-11-19T16:46:32","date_gmt":"2023-11-19T16:46:32","guid":{"rendered":"\/forum\/forums\/reply\/318344\/"},"modified":"2023-11-19T16:46:32","modified_gmt":"2023-11-19T16:46:32","slug":"318344","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/318344\/","title":{"rendered":"Reply To: use of temperature and mass fraction gradients in UDF"},"content":{"rendered":"

<p>Hi<\/p><p>i am solving an equation which requires concentration gradient as a term. So i write concentration as mass fraction*density to a C_UDSI and then use C_UDSI_G to solve the equation. But I am getting zero everytime. Please note that i don’t disable solving the equation for UDS. Is it because of that or there is something to be done in my case file?<\/p><p>A snippet of code is as follows:<\/p><div>thread_loop_f(t, d)<\/div><div>{<\/div><div>    begin_f_loop(f,t)<\/div><div>    {<\/div><div>        F_CENTROID(x, f, t);<\/div><div>if (x[0] >= 108  && x[0] <=  126 &&  x[1] == 18 && x[2] >= 90  && x[2] <= 126 )<\/div><div>{<\/div><div>                    F_AREA(A,f,t);<\/div><div>co = F_C0(f, t);              <\/div><div>to = THREAD_T0(t);      \/\/obtaining corresponding thread of adjacent cell<\/div><div>real integrand;<\/div><div>real conc_grad_roof;<\/div><div>real mu_t_roof = C_MU_T(co,to);        \/\/turbulent viscosity <\/div><div>C_UDSI(co,to,0)= C_YI(co,to,0) * RHO_1;   \/\/storing concentration of CO as user defined scalar(UDS)<\/div><div>conc_grad_roof=(C_UDSI_G(co,to,0)[1]);       \/\/concentration gradient of CO<\/div><div> <\/div><div>integrand = (mu_t_roof \/0.7)*conc_grad_roof;     \/\/TURBULENT POLLUTANT FLUX<\/div><div>PCH_turb_roof -= integrand*NV_MAG(A);            \/\/Overall value of PCH integral<\/div><div>                }<\/div><div>            }<\/div><div>                          <\/div><div>        end_f_loop(f,t)<\/div><div>}<\/div><\/p>\n","protected":false},"template":"","class_list":["post-318344","reply","type-reply","status-publish","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