55 / 2019-09-08 17:23:23

Wake interaction and hydrodynamic characteristics of flow past multiple cylinders in a V configuration

wake interaction; hydrodynamic characteristic; multiple cylinders; flow structure

Migrating geese fly in a V formation to save energy for downstream companions, deserving our study and application in engineering. The wake structure of five identical circular cylinders arranged in a V configuration at low Reynolds numbers of 80, 120 and 160 is numerically investigated in this work. Cylinder in-line center-to-center spacing ratios ranging from 1.5 to 8 are considered in simulations that computed for a wide range of intersection angles α=0°–120°. It is found that the first cylinder bears greater drag while the downstream cylinders attain more lift. The differences of hydrodynamic coefficients among the cylinders are enlarged as Re increases. The wake flow is sensitive to the spacing ratio and intersection angle, and bifurcation phenomena occur at certain flow conditions. Wake patterns observed behind the multiple cylinders with varying spacing ratio and intersection angle are presented for each Reynolds number, identified by shear layer reattachment, vortex impingement and wake interference. The hydrodynamic forces, wake recirculation region, vortex formation length, phase lag among vortex shedding from different cylinders are tightly associated with the wake interaction. Finally, the spacing ratio and intersection angle for the V-configuration cylinders are recommended from the perspective of energy harvesting.