Computer simulation study of the effective viscosity in Brinkman’s equation

Brinkman’s equation is often used to match solutions of Stokes’ equation to solutions of Darcy’s law at free‐fluid:porous medium interfaces by the introduction of an effective viscosity parameter, μe. Theoretical predictions of the dependence of μe on the porosity of the porous medium have given conflicting results. A finite difference solution of Stokes’ equation in three dimensions was used to study fluid flow near the interface between a free fluid and a porous medium. It was found that in order to match solutions of Brinkman’s equation to the numerical solutions, the value of μe had to be greater than the free‐fluid viscosity. Within numerical precision, the effective viscosity μe was monotonically increasing with decreasing porosity. Good fits to the numerical fluid velocity profiles were obtained for porosities ranging from 50% to 80%.

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