The effect of anisotropic permeability on the flow past structured porous square cylinders

When flow passes twodimensional porous cylinders, the downstream flow structure is altered by the mutual interplay between longitudinal and lateral bleedings. Based on previous studies with isotropic porous cylinders, the bleeding jets and the resulting downstream flow are dominated by cylinder permeability. To further understand the permeability effect on the flow characteristics of twodimensional porous cylinders, this study investigates the downstream flow pattern of anisotropic porous square cylinders with a periodic and scalable structure based on a simple cubic lattice. The cylinders were designed to exhibit different permeability in longitudinal and lateral directions by manipulating the number of struts on each side of the unit cell. A high resolution stereolithographic 3D printer was used to fabricate the porous cylinders. The downstream flow pattern behind the cylinder was visualized in the $x$-$y$ plane by performing particle-image velocimetry (PIV) measurements, utilizing two high-resolution PIV cameras in tandem to maximize the streamwise field of view (FOV). The Reynolds number, based on the cylinder diameter, was set to O(10^4). Experimental results were systematically analyzed along with the data from isotropic cases in the previous study.