MOMENTUM TRANSPORT MECHANISM FOR WATER-FLOW OVER POROUS-MEDIA

The momentum transport phenomena at the interface of the porous medium and fluid have been numerically investigated. The single domain appro ach is used with matching boundary conditions; that is, the Brinkman-F orchheimer-extended Darcy equation is used for the present study. Five typical porous media found in natural and engineered systems are sele cted in order to cover a wide range of the Darcy number (6.25 x 10(-4) less than or equal to Da less than or equal to 5.90 x 10(-11)). In ad dition, six different Reynolds numbers (10 less than or equal to R les s than or equal to 1,000) are tested for each case. When Da > 10(-7), the results showed the importance of viscous shear in the channel flui d. The viscous shear propagates across the interface into the porous m edium and forms a transition region of disturbed flow in the porous me dium. The depth of penetration is only dependent on the Darcy number o f the porous medium rather than the Reynolds number and the shape of v elocity profile. In the vicinity of the interface, it is clear that Da rcy's law is inappropriate to describe flow in a permeable wall fractu re or flow over porous media.