Direct numerical simulation of hydrodynamic dispersion in open-cell solid foams.

Highlights • Axial Dispersion in open-cell foams scales non-linearly with the Péclet Number. • Phenomenon equivalent to Taylor dispersion is observed for Darcy flow. • Non-mechanical dispersion is induced by the appearance of stagnant zones. • Hydrodynamic dispersion is governed by chaotic advection at high velocities. • Dispersion coefficients have an inverse dependency on the particle diameter. Abstract Fully resolved simulations of flow and mass transfer in a unit cell of structured open-cell foam catalysts are presented. Numerical studies are conducted on a uniform three-dimensional Cartesian grid where the fluid-solid interface coupling is enforced via a sharp interface Immersed Boundary technique. Several validation cases for the numerical method are presented followed by extensive calculations to quantify hydrodynamic dispersion in open-cell foams. In our study five different porosities of the idealized foam structure, represented by the spatially periodic Kelvin's unit cell, were considered. Dimensionless dispersion coefficients were calculated for varying Péclet numbers and flow directions using volume-averaging theory. Our numerical studies indicate that Taylor dispersion is the dominant mechanism for structured porous media in the Darcy-Brinkman flow regime. [ABSTRACT FROM AUTHOR]