Computation of flow through a fluid-sediment interface in a benthic chamber

In this paper we present a single-domain approach for the solution of flow in a composite region made up of a purl fluid layer and an underlying saturated porous layer. As an example, we compute the unsteady, axisymmetric flow and scalar transport in a stationary cylindrical container with a rotating lid, filled to the midheight with a porous material and to the top with water. A generalized equation known as the Brinkman-extended Darcy equation is solved inside the porous medium, along with the incompressible Navier-Stokes equations in the upper fluid layer. Comparisons with experimental data previously obtained by the authors for flow in the same geometry show good agreement, thus verifying the accuracy of the present computations. The results indicate that a single-domain approach can provide good predictions of interfacial flow, thereby obviating the need for ad hoc interface conditions. The existence of a thin Brinkman layer below the interface is observed. Radial profiles of computed velocity components adjacent to the interface show remarkable similarity, despite vast differences in magnitudes, showing that good matching between the two different flows has been achieved by the present single-domain approach. (C) 1999 American Institute of Physics. [S1070-6631(99)03006-8].