Channel-confined wake structure interactions between two permeable side-by-side bars of a square cross-section

The current research focuses on the laminar flow through permeable side-by-side bars of a square cross section in a channel-confined domain. Vorticity generation on the leeward sides of the permeable bodies further necessitates the study for a better understanding of underlying physics. Reynolds number (Re) and Darcy number (Da) are varied from 5 to 150 and 10-6 to 10-2, respectively, at transverse gap ratios s/d = 2.5-10. In the perspective of periodic unsteady flow, critical Re for the onset of vortex shedding is analyzed. Streamlines, vorticity, pressure coefficient distribution, and velocity profiles are discussed to identify the wake patterns. In lower permeability level, vortex-shedding from the permeable square cylinders is observed either in synchronized antiphase mode or a single large vortex street with a synchronized in-phase pattern in the near wake. A steady-state wake pattern symmetric and flocked toward the centerline is observed for all s/d at a higher permeability level regardless of Re. Wake patterns are not altered for Da = 10-6 to 10-3; instead, prompt extermination of the two vortex streets downstream is observed at Da = 10-3 as compared to Da = 10-6. The impact of s/d, Re, and permeability on the drag is examined. A jump in the flow characteristics and drag forces is noticed at higher Re for the midrange Da remarkably at lower s/d. For the extent of high permeability, the drag coefficient asymptotically gets closer to zero.