When doing a gas solid euler-euler setup withn CFX PRE I choose "air at 25C" as the continuous phase. When I specify my "solid" material, I'm aware of I should use a continuum phase for the solid part. But should I choose a "material Group" = "Constant property gases" for the dispersed solid phase or should I choose "Constant Property Liquids"? What's the difference? What I have done is taken the data for water and altered them to my need by specifying the proper density and reduce the viscosity to 1e-12.

Difference between solids and liquids? Try diving in an empty swimming pool, you will feel the difference