ABSTRACT
Permeation is fl uid fl ow through interstices among many discrete particles. Flows of groundwater, crude oil, and natural gas are typical permeations taking place in nature. This type of fl ow is widely utilized in industrial processes in which both particles and fl uid fl ow play important roles simultaneously, such as a catalytic reaction, fi ltration, and so on. Thanks to the extensive number of studies on porous media since D’arcy, macroscopic fl ow characteristics in a porous medium can be evaluated fairly well, although the microscopic fl ow pattern inside the medium is complex and not amenable to rigorous solution by the Navier-Stokes equation. In this section, general theories developed to explain resistance to fl ow through a porous medium are described, and the resistances of granular and fi brous packed beds are outlined as typical examples of high and low packing densities, respectively.
