modifying the fluidised bed geometry
 

dear all,
i am studying about two phase flow. the geometry of my case will be different from the fluidised bed. i need to modify its geometry. currently, i am studying about the polyMesh folder. the flow motion is from left face to right face in my context and the bottom face is a fixed wall. the left faces and right faces are representative volume of a continuum. the top face is open to the atmosphere. there is heat transfer from the bottom wall to this geometry. please suggest me about the necessary changes that i have to make in the geometry of fluidised bed.
thank you.
annier