ABSTRACT
This chapter shows that flow of a very dense suspension is similar to the limiting case of relative motion of fluid through a moving porous solid or packed bed. It discusses detailed treatment of flow through porous media, packed beds and moving beds, flow of granular solids, and fluidized beds are fields of studies by themselves. This is also the order of complexity from considering phase Interactions; the two simple extremes appear to be dilute suspensions on the one end and fixed dense beds on the other. In the case of a dense gas-solid suspension, plugs of solids were observed in horizontal pipe flow by Y. Tsuji and Y. Morikawa with fluidization assisted by a subpipe. A basic difference of a bed of solids from a suspension is the stress existing within the bed. The density of fluidized bed changes due to expansion of the bed.
