Numerical study of flow characteristics around different arrays of cylinders at subcritical Reynolds number

Abstract

The flow characteristics around three newly designed arrays (1 × 3,2 × 3, and 3 × 3) of circular cylinders were numerically studied and compared with large eddy simulation (LES) methods at the Re = 3900. It was found that no recirculation zone existed in the spacing ratio range of L/D = 2.0–3.0 and the critical spacing ratio (L/D)c was equal to 4.0 in the 1 × 3 array of cylinders, while the recirculation zones were presented at L/D = 1.5–6.0 and (L/D)c = 3.5 in the 2 × 3 and 3 × 3 arrays. The length Lr/D of recirculation zone in the three arrays was found to be about 40 % longer, and the minimum velocity to be 50 % smaller compared to a single isolated cylinder. The maximum drag coefficient in the 3 × 3 array was increased by approximately 60 % and the maximum fluctuating lift coefficient by 40 % compared with that of the 1 × 3 array. Three primary types of the wake patterns in all the three arrays were found to be the reattached flow with "U" shape of streamwise velocity distribution, the narrow wake impingement flow with shallow "V" shape, and the coshedding flow with deep "V" shape, respectively.