Experimental investigation of the turbulent flow around/behind the structured porous square cylinders.

When the flow past two-dimensional porous cylinders, the downstream wake is structurally modified by the mutual interplay between longitudinal and lateral bleedings that penetrates through the porous cylinders. To gain a better understanding of the complex flow characteristics behind the two-dimensional porous cylinders, the current study aims to explore the structural pattern around the porous square cylinders with a periodic and scalable structure. The present porous cylinders (D=24-40 mm, where D represents the cylinder diameter) were fabricated based on a simple cubic lattice by a high-resolution 3D printer with varying porosity and permeability.

To visualize the downstream flow pattern behind the cylinder, particle-image velocimetry (PIV) measurements were performed in the x-y plane, utilizing two high-resolution PIV cameras in tandem to maximize the streamwise field of view (FOV). The Reynolds number based on the cylinder diameter is set to O(10⁴). Permeability, as the key control parameter in this study, was carefully acquired by measuring differential pressures, upstream and downstream of porous media versus superficial velocity in an open-loop pipe flow system.