Effect of the fluctuating fluid flow in a bidisperse porous medium on the matter propagation in it

An unsteady process of matter extraction from a porous body is considered. The body is modeled by a system of semi-infinite capillary tubes connected with a system of closed-end channels, so that the matter transfer rate in the flow (large-size channels) is composed of two components. The first is a constant velocity component, while the second is a time-periodic addition to the former component, which is assumed to have a small amplitude. Analytical dependences for the matter concentration in the porous body are derived both in the main approximation and with account of the correction for the periodic forcing of the system.