An exploration of physical mechanism for dynamic permeability using a microscopic computational fluid dynamic model

Abstract

Dynamic permeability is a frequency-dependent parameter in the Darcy model for analyzing the porous-flow problem with time-varying pressure. Until now, physical mechanisms behind the associated correlation are still unclear. To uncover the physics, we built a microscopic flow model in which a temporal-sinusoidal pressure difference was applied in the axial flow direction with frequency ranging from one to ten thousand Hertz. Flow phenomenon was found by parallelly comparing the velocity field and negative-pressure-gradient field. Results show that alternating the sign of pressure difference within a time on the order of step-response time constant can restrict the flow development causing a lessening effect on the dynamic permeability. A triangle-wave case shows that the phase angle of dynamic permeability results from the temporal-variation rate of pressure difference. Further physical phenomenon study, such as those with deformation or oscillation of solid medium, can be made based upon the current approach.