Straight fiber bundles with non-uniform porosity: Shell-side hydrodynamics and mass transfer in cross flow

This study explores fully developed shell-side hydrodynamics and mass transfer past straight fiber bundles with non-uniform porosity in cross-flow. Simplified geometries made up by checkerboard arrays of alternately high and low porosity regions are considered. Simulations are performed for two domain sizes: a small geometry (26 fibers) and a large geometry (104 fibers). In the small geometry, the Darcy friction coefficient (fT) exhibits hydraulic isotropy at low transverse flow Reynolds numbers (ReT) but becomes dependent on the flow attack angle (θ) at higher ReT. In the large geometry, this dependency is observed at lower ReT. A non-uniform porosity reduces fT at almost all ReT and θ in the small geometry, with the large geometry exhibiting a more complex behavior. Regarding mass transfer, up to ReT≈1-10 (depending on θ), a non-uniform porosity leads to lower Sherwood numbers compared to regular square arrays. However, at higher ReT, it enhances mass transfer.