When I performed the mesh motion in solve menu for MDM, I met the below message. What was wrong?? What should I do??

Error: Internal error at line 1595 in file 'grid.c'. replace_c_in_f: cell not found Error Object: ()

Can you show us your UDF? Maybe instead of looping on faces you should loop on cells.Luca

Oh, actually My UDF is really simple. It just is forced moving. So UDF is very simple.

#include "udf.h" DEFINE_CG_MOTION(stem, dt, vel, omega, time, dtime) { vel[1]=0.014; }

Above is all, My UDF. Futhermore, when I tested it using mesh motion at first, there was not any error.

Maybe you should initialize the omega vector...Actually I dont'know. Your UDF is simple...

Profile files are much easier for defining motion, once they are set up you don't have to reload them every time you restart Fluent.

As for your error, I'd suggest you contact Fluent support.

Shuto.