Aerodynamic force characteristics and flow field mechanism of multiple square cylinders in a tandem arrangement

Abstract

Wind tunnel tests and large eddy simulations were employed to obtain the aerodynamic coefficients and flow fields of two and three tandem square cylinders across various spacing ratios. The spacing ratio L/D, defined as the ratio of the center-to-center spacing between adjacent square cylinders to their width, ranges from 1.2 to 8. By analyzing these results, the aerodynamic force characteristics and their generation mechanism of the three tandem square cylinders at a high Reynolds number (Re = 3.2 × 104) were revealed. By comparing the results of the two and three tandem square cylinders, the effect of adding a third square cylinder behind the two tandem square cylinders on its aerodynamic characteristics was clarified. The results show that unlike the two tandem square cylinders, the three tandem square cylinders exhibit two critical spacing ratios, (L/D)cr1 = 2.5–3 and (L/D)cr2 = 3.5–4, respectively. Based on these two critical spacing ratios, the flow around the three tandem square cylinders is identified as single blunt body, reattachment, and co-shedding regimes. In the single blunt body and reattachment regimes, the addition of a third square cylinder behind significantly alters the flow around the two tandem square cylinders, leading to reduced mean drag coefficients, fluctuating lift coefficients, and Strouhal numbers, along with an increased critical spacing ratio. In the co-shedding regime, this addition has little effect on the flow.