The dynamic shape factors of two types of polyhedral shaped agglomerates were measured. One type consists of the close packing of 4 to 12 spheres.on a core sphere (close packed agglomerate, dynamic shape factor ks); the other has the same configuration as the above agglomerate except that the central sphere has been removed (hollow agglomerate, kv). The dynamic shape factor kvwas analyzed by using a model agglomerate in which the core void is simulated as a sphere of fluid (kf). Comparison of kv and kf shows that, for hollow agglomerates comprising a number of spheres between 5 and 13, part of the fluid flows through the core void.