Numerical study on reducing aerodynamic drag and noise of circular cylinders with non-uniform porous coatings

This paper presents a numerical study on the flow and noise control of circular cylinders with nonuniform porous coating over the circumference in the subcritical flow regime (Re = 4.7 x 10(4)). A numerical method is employed that combines three-dimensional large eddy simulation (LES) with Ffowcs Williams-Hawkings (FW-H) acoustic analogy, and is validated by comparing with available experimental and numerical data of flow over circular cylinders. The numerical results show that applying high-porosity material in the separation zone is most effective on reducing aerodynamic drag and noise. This partial high-porosity coating enhances the slip velocity at the porous-fluid interface, stabilizes shear layers detached from the cylinder, and hence suppresses vortex shedding, as well as raising the base pressure on the leeward side and reducing drag. A high-porosity coating with a 60 degrees circumferential coverage of the separation zone is found to be a cost-effective configuration in controlling both drag and noise. Varying the porosity on the leeward side of a cylinder, however, shows slight differences on flow and acoustic characteristics. This study is expected to provide some useful information for porous coated cylinders aimed at flow and noise control towards practical applications with constrains on coating area. (c) 2020 Elsevier Masson SAS. All rights reserved.