Through rigid model pressure measurement wind tunnel tests and numerical simulations, this study systematically investigates the aerodynamic characteristics of two side-by-side rectangular cylinders with different width–thickness ratios (B/D = 1/4–1/1) at different spacing ratios. This study provides a detailed analysis of the effects of width–thickness ratio and spacing ratio on aerodynamic parameters of two side-by-side rectangular cylinders, including the mean drag/lift coefficients, fluctuating lift coefficient, and Strouhal number. It also addresses the classification of flow regimes into the biased flow regime and the coupled vortex street regime and explains the underlying flow field mechanisms. Experimental results indicate that as the width–thickness ratio of two rectangular cylinders decreases, the range of spacing ratios at which the biased flow phenomenon occurs gradually increases. Under the biased flow regime, significant differences are observed in the mean drag coefficients between two rectangular cylinders. Particularly when B/D = 1/2 and 1/4, the maximum difference reaches 1.0 in both cases. The Strouhal number exhibits a sudden jump, particularly reaching an increase in 0.22 when B/D = 1/3. Under the coupled vortex street regime, except for two rectangular cylinders with width–thickness ratio of 1/2, which exhibit significant amplification effects in both mean drag coefficient and fluctuating lift coefficient, the values of other width–thickness ratios remain essentially consistent with those of single rectangular cylinder. Vortex shedding is fully developed, characterized by large and distinct peaks in the Fourier amplitude spectrum, while the Strouhal number matches that of a single rectangular cylinder.
Yang et al. (Sun,) studied this question.