fluent error
 

I tried to simulate hydrodynamics of porous media in a pipe. after several run I received "solution is converged " ,for getting a correct answer (and removing reverse flow) I set residual criteria of x,y-velocity in small number. but after I began iteration the fluent was became "not response" or exited. and or fluent writes
"error:eval:invalide function"
"error object : #[free(1 cells)]"
please help me