Longitudinal Dispersion of Tracer Particles in the Blood Flowing in a Pulmonary Alveolar Sheet

The analysis of G. I. Taylor on the dispersion of solutes in a circular cylindrical tube is extended to the case of flow in a channel bounded by porous layers. Creeping flow in the channel and the porous layers stimulates the blood flow in the alveolar sheets of the lung. Overall perturbation on the longitudinal dispersion due to the porous layers is evaluated. It is shown that the mean coefficient of apparent diffusivity is smaller in a channel bounded by porous layers than that in a channel with impermeable walls for the case that the channel walls are permeable to solvent but not to tracer. For the case that channel walls are permeable to both solvent and tracer, the mean coefficient of apparent diffusivity is nearly the same as that of a channel with impermeable walls.