CFD Online Discussion Forums

CFD Online Discussion Forums (
-   Fluent UDF and Scheme Programming (
-   -   uds flux - drift velocity - udf (

johnwinter August 11, 2011 04:51

uds flux - drift velocity - udf
Hi All,

I am calculation ion density using UDS udf, i have a flux term in transport equation as (u+mu.E). My udf is given below. I could see nothing wrong with my udf but ion density is rising gradually beyond input value with every iteration due to this term

#if !RP_HOST
double NV_VEC(A), NV_VEC(E_vec), F_Evec[ND_ND] = {0.}, E_flux = 0.;
cell_t c0, c1 = -1;
Thread *t0, *t1 = NULL;
c0 = F_C0(f,t);
t0 = F_C0_THREAD(f,t);
E_flux = 0.0;
c1 = F_C1(f,t);
t1 = F_C1_THREAD(f,t);
NV_DS(E_vec, =, E_X(c0,t0), E_Y(c0,t0), E_Z(c0,t0), *, ionmob);
NV_DS(E_vec, +=, E_X(c1,t1), E_Y(c1,t1), E_Z(c1,t1), *, ionmob);
E_flux = NV_DOT(E_vec,A)/2.0;

if (i==0)
return (F_FLUX(f,t)/rho+E_flux);


else return (0.);

return 0.0;

After 3 iterations i could see that the iondensity value at the node near electorde is rising beyond my input value.

Any suggestion are welcome.

PS: I am stroing E_X, E_Y and E_Z values using memory option.


johnwinter August 12, 2011 05:29

i need results badly. please somebody help!

beastieboys6 February 9, 2017 11:26

Hi, John,

I'm facing exactly the same problem when using similar UDF.
I was wondering if you had solved problem. If you had, could you share the solution? Thanks.

Or if there is anyone knowing the soluation? Any suggestion would be highly appreciated.

All times are GMT -4. The time now is 17:34.