problem in UDF for Accesing previous Time
 

Hi Dear All I want to define the source term in Energy Equation. After compiling it in Fluent and starting to iteration, this error appears and solver goes out from running mode.This error is for """"C_T_M1(c,t)"""" for taking the temperature value in previous time step.I write this Text Command """""">Solve/set/expert""""" and then answering ""Yes"" to this question""keep temporary solver memory from being freed?"" but my problem has not been solved yet. Please Help me. Best Regards.

#include "udf.h"

#define C2 100.0

DEFINE_SOURCE(amir_source4,c,t,dtime,dS,eqn) { real x[ND_ND]; real con, source,delti,al,rol;

C_CENTROID(x,c,t); con = C2*0.5*C_R(c,t)*x[1]; al = RP_Get_Real("physical-time-step"); rol=C_T_M1(c,t);

source = -.000000001*C_T_G(c,t)[0]*C_T(c,t)*rol;

return source; }