Flow through a Tube with an Annual Porous Medium Layer

Abstract

In this study, the boundary conditions necessary for continuum numerical modeling of flow involving a porous-medium-free-fluid interface are examined. In a region within the free flow adjacent to a porous medium interface, the momentum dispersion persists due to the extension of the spatial velocity fluctuation into the free flow. Consequently, at elevated flow rates, the viscous response to flow of the fluid in the region adjacent to a porous medium has to be modified due to the presence of such spatial velocity fluctuations caused by the porous medium. This influence decays exponentially and extends several pore sizes into the free fluid. Experimental and numerical studies have shown that, at moderately high flow rates, the pressure drop through a porous bed is a quadratic function of the flow discharge rate. For flow through a straight tube containing no porous structures, the pressure drop is linearly related to the flow discharge rate in the laminar regime. However, experimental observation shows that when fluid flows through a tube with an annular porous medium ring, the qualitative trend of the pressure drop is similar to flow through a porous medium. This behavior confirms our expectations on the existence of momentum dispersion. An exponential decay model is proposed to account for the momentum dispersion variation.