Large-eddy simulations of flow past cruciform circular cylinders in subcritical Reynolds numbers

Abstract

Large-eddy simulation (LES) technique is adopted to analyze the subcritical flow around the cruciform cylinders, and then the influence of the Reynolds number and the blockage ratio on the flow pattern and the hydrodynamic force is numerically investigated in details. A recirculation flow is observed at the rear of the intersection center and an up-flow is induced along the spanwise direction. Under the action of the up-flow, the vortex formation region of the spanwise cylinder is stretched and the vortex-induced vibration (VIV) caused by the Kármán vortex shedding is suppressed. In addition, the wake region of the cruciform cylinders can be divided into three regions: the recirculation region, the transition region and the Kármán vortex region. Three types of flow pattern of the cruciform cylinders, which are the cylinder-dominated pattern, the mixed pattern and the orthogonal solid pattern, can be identified for different blockage ratios. Furthermore, the drag coefficient, the root-mean-square (r.m.s.) of the lift fluctuation and the Strouhal number of the cruciform cylinders are calculated and compared with that of the isolated cylinder.