Bleeding flow characteristics downstream of meta-structured porous cylinders

Flow past porous bluff bodies has received considerable attention due to their enhanced aerodynamic performance, which includes reduction in drag, noise, and vibration. These improvements are primarily attributed to a key structural feature: bleeding flow through the porous medium. Despite its significance, the structural characteristics of bleeding flow remain poorly understood, particularly at high Reynolds numbers relevant to practical aerospace applications. The objective of this study is to experimentally investigate the structural evolution and key features of bleeding flow downstream of porous square cylinders. A unique structural design was employed to isolate the effect of permeability, allowing it to be treated as an independent and equivalent control parameter and facilitating analysis from a meta-structural perspective.

To this end, PIV measurements were performed in a wind tunnel at Re ∼ 3.1 × 10⁴ to characterize the flow field. The permeability of the isotropic porous structures was carefully measured using a circular duct system. The bleeding characteristics were then systematically investigated across a wide range of permeability, and an analytical model was developed based on the Darcy-Brinkman-Forchheimer framework.