ABSTRACT
For an isotropic. homogeneous porous medium. such as a packed bed composed of particulates. both techniques of permeability measurement should give the same permeability value. Differences can. however, sometimes arise. and these are related to the fact that the porous medium in the transient experiment is unsaturated while that in the steady-state experiment is saturated: in the former case. pore impregnation and wetting effects in the vicinity of flow front can change the flow behavior and influence the results ]1.261. More seriously, though, a porous medium may be homogeneous but nonisotropic. In this instance. the permeability may be different in different directions. A flow front whose shape is elliptical rather than circular during radial flow is a clear indication of a nonisotropic porous medium [26]. Such a situation is easy to visualize for fibrous porous media that are relevant to composites processing-as discussed in the next section. the permeability of a fiber bundle in the direction of the fibers can be quite different from the permeability perpendicular to the fibers.
