Experimental and numerical investigations of incidence angle and cross-sectional aspect ratio effects for the flow over wall-mounted rectangular cylinders

In this study, both experimental and numerical methods (large eddy simulation, LES) are used to investigate the flow over wall-mounted rectangular cylinders with various cross-sectional aspect ratios (CR = 1–4, representing the ratio of the sides of the cylinder cross section) and incidence angles (α = 0°–90°). The Reynolds number is defined using the free-stream velocity and the projected width of the cylinder in the flow direction, i.e., Rew = (12–48) × 103. The experimental results of surface pressure and the Strouhal number (obtained through hot wire measurements) are used to validate the numerical results. This comparison shows a good agreement between both experimental and numerical results. A single frequency is found for all positions along the cylinder height and also at the other places employed for any given CR and α. The experimental and LES results of the present study confirmed this finding. It is observed that there is a maximum Strouhal number (Sta) at a specific angle (critical angle, αc) for each CR, i.e., αc = 15°, 10°, 5°, and 0° for CR = 1, 2, 3, and 4, respectively. Interestingly, for any CR, where St reaches its maximum value at the critical angle, the drag coefficient (C¯D) reaches its minimum value due to the formation of the maximum length of the separation bubble on the lateral surface, as well as the creation of a narrow-width wake flow.