Abstract
Based upon an analysis of the Kozeny-Carman equation, a general expression was developed for the fluid drag on a particle which is different in size from the other particles in the bed. It is expected that the limitations of usage of the general equation derived will be the same as for the Kozeny-Carman equation, except that the porosity dependence on the solid fraction of specified species in the theory should be determined otherwise. An interesting effect of the size ratios on the fluid drag was illustrated by use of past experimental data on packing porosity. The present analysis suggests a way of estimating the fluid drag on a particle in assemblages of solid particles of various sizes.