Vortex shedding in a highly porous structure

•We investigate the flow in a continuous milli-reactor with highly porous inserts.•Vortex shedding emerges from ligaments and interconnections of ligaments (nodes).•Shedding frequencies are smaller behind nodes than behind ligaments.•Smaller wake lengths are observed behind ligaments than behind nodes.•Vortex shedding is identified as transport mechanism for mixing and heat transfer.

Highly porous media (with a porosity ≥85%≥85%), like metal foams, fins or designed porous inserts are widely used in industrial flow applications. Motivated by the use of highly porous inserts in continuous chemical reactors, the time dependent behavior of flows through a highly porous structure is investigated experimentally and numerically for Reynolds numbers ReD=33 and 330 (based on the ligament diameter and the bulk velocity). The experimental studies are based on the Particle Image Velocimetry (PIV), whereas the numerical studies are conducted by using the Large Eddy Simulation (LES) approach with the dynamic Lagrangian subgrid closure. The vortex shedding phenomena is observed for both values of Reynolds number. It is demonstrated that the length of the wake and the orientation of the shedded vortices are dependent on the position within the highly porous structure.