How to define unsteady term in scaler function?

olivia

Hi: I want to define unsteady term in scaler function . But it have some error message in line 6 message is UDS:undeclared variable.

Can anyone know how to solve this problem? Thanks!!

#include "udf.h"

DEFINE_SOURCE(usr_ensource, cell, thread, ds, eqn) {

real lg,l,unst;UDS

unst = DEFINE_UDS_UNSTEADY(c, t, i);

l = 2440.0;

lg = l * ( 1.0 + 8.31 * exp(-1.0 * 0.436 * C_UDSI(c,t,i) ) );

source = 1.0 / 0.5 * unst * lg;

return source; }