Numerical simulation on flows past porous bluff bodies

Abstract

Flow past bluff porous bodies has attracted relatively less attention so far although such flow occurs widely in industries and everyday life. In the present study, computational fluid dynamics is applied to investigate this type of problems. The coupling flow in both porous medium and homogenous fluid regions is solved by a finite volume method based on the body-fitted and multi-block grids. At the porous-fluid interface, a shear stress jump condition that includes both the viscous and inertial effects is imposed, together with a continuity of normal stress. The steady flows are simulated in a wide range of the Reynolds and Darcy numbers. Three most commonly used shapes of the bluff body in the literature, that is, circular cylinder, square cylinder and sphere, are examined. Several interesting flow phenomena, which are different from those of flow past a solid bluff body, are revealed by the present simulations. It is found that the recirculating wake existing downstream of a porous bluff body may be completely detached from the body in a certain range of parameters. In a certain range of Darcy number, the wake may initially increase in size with an increase in Reynolds number but then decrease in size and eventually disappear when the Reynolds number is sufficiently large. There is only one "separation" point along the horizontal axis of the porous bluff body, but not a pair of separation points on the surface of the solid one. The present findings may provide a starting point for re-evaluating the flow around and through a porous bluff body and stimulate new studies to understand the underlying mechanics of the new flow phenomena which have not been answered here. © 2011 by Nova Science Publishers, Inc. All rights reserved.