define three phase flow of air-water-sand
 

dear friends
I am modeling three phase flow (air,water,sand) with eulerian model in Fluent6.3.26.
that is a free surface and fluiduzed bed problem. I want to define water velocity as velocity-inlet in boundary condition panel and patch the zone of sand.
and I want sand to be stationary untill the water puor to it.
but I don't know how to define sand in boundary condition, and Is it important to take each of the phases as primary and secondary?
I am in urgent need.
please help me