## Fluids

#### In order to include uds properly

• Austin_p
Subscriber

I 'm trying to use UDS which is written in the ansys fluent guide 2.7.3

```/**********************************************************************/
/*    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;

real NV_VEC(psi_vec), NV_VEC(A), flux = 0.0;

c0 = F_C0(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*/
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 */

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;
}
```

However, I cannot get the result of UDS as you can see in following residual graph.

• DrAmine
Ansys Employee
First of all you do not require UDF to be able to run with UDS. So please do not use the UDF and run again: moreover it seems that you are missing the UDS residula: so pretty sure it shows zero values in the Console residuals: so check its inflow/outflow/wall BC settings.