Experimental study on aerodynamic characteristics of two square cylinders at various incidence angles

Wind tunnel tests are conducted to study the aerodynamic characteristics of two identical square cylinders with variations in the incidence angle at a Reynolds number of Re = 8.0 x 10(4). The center-to-center spacing (P) ranges from 1.25 to 5.0 times the width of the cylinders (B), and the incidence angle (alpha) varies from 0 degrees to 90 degrees. The spacing ratio significantly influences the aerodynamics. When the two cylinders are very close, they can be treated as one bluff body for which the vortex sheds only at the wake of the downstream cylinder. With an increasing spacing ratio, the flow finally separates individually from the two cylinders and creates two related vortex shedding patterns. The interference effects of the two cylinders on the aerodynamics changes with an increasing spacing ratio. According to the aerodynamics, the arrangement of two identical square cylinders can be classified by the spacing ratio into three states: closely spaced (P/B < 1.5), moderately spaced (1.5 <= P/B <= 3) and widely spaced (3 < P/B <= 5). The characteristics of the aerodynamics and mechanism of interference effects in the three states are discussed, considering the influence of the incidence angles.