I worked with fluent before but my geometries were comparatively simple i.e. a cylinder or a rectangular and etc. I used "porous media model" to simulate a packed bed of thousands spheres but now I have to model a slice of that and just a packed bed of few spheres. This time I want to use CFX, since heat generation is a function of time and indeed temperature is a function of time. I heard CFX is more convenient on this issue than Fluent. I worked with CFX too but just for modelling simple problems (assignments ). many thanks Peter for your swift and complete responses.