density UDF problem
 

How can I use UDF to define the mixture density when I used a species transport equations to solve the combustion questions?

the fluent default choice is imcompressible-ideal-gas. the choice must define the operating pressure,but my operating pressure is growing but not the comprssible flow.

when I use the UDF to define my mixture density(use the function C_YI(c,t,i),the fluent solver can't be initilized. the error message is FLUNT received fatal sigal(ACCESS_VIOLATION) need your help!thanks!