Cannot set correct inlet velocity by UDF?!?

Bob

Hi,

While performing simulations of tracer transport in a reactor, I encountered the following problem. By a UDF DEFINE_PROFILE, I set a fixed normal velocity at the inlet (see UDF below). The velocities returned by Fluent are smaller than the imposed ones however. When imposing a velocity of e.g. 0.213 m/s, Fluent returns 0.194 m/s. Setting boundary mass fractions for scalars with DEFINE_PROFILE returns correct values. Is this a bug in Fluent 6.1? And how should I deal with the problem?

Thanks a lot in advance.

best regards, Bob De Clercq

DEFINE_PROFILE(inlet_vel_tracertest, t, i) {

real time;

face_t f;

int k, j = 0;

real surface = 0.745;

float dat_time[902] = {...data...};

float dat_flow[902] = {...data...};

time = RP_Get_Real("flow-time");

for (j=0; j<= 901; ++j)

{

if (time > dat_time[j])

k=j;

}

begin_f_loop(f, t)

{

if (time >= dat_time[901])

F_PROFILE(f,t,i) = dat_flow[901]/surface;

else

F_PROFILE(f, t, i) = dat_flow[k]/surface;

}

end_f_loop(f, t) }