Numerical study of the effects of aspect ratio and Reynolds number on the flow over a rectangular cylinder with rounded corners

The numerical investigation of flow over a cylinder is conducted using the momentum exchange-based immersed boundary-lattice Boltzmann method (IB-LBM). The cross-section of the cylinder resembles a rectangle-like, with an aspect ratios ARs denoted as L/W, where L and W represent the dimensions in the length and width directions, respectively. The focus is to investigate the effect of Reynolds number Re (=40–180), aspect ratio L/W (=1.0–4.0) on the critical Reynolds number, flow topology, drag & lift force, and Strouhal number (St). Numerical simulations results demonstrate that the fluid dynamics involved are strongly sensitive to both aspect ratios and Re, leading to three distinct wake flow patterns, namely steady-state, transition-state, and Karman vortex streets mode. The critical Reynolds number and vortex shedding frequencies exhibit a higher sensitivity to aspect ratio L/W compared to Re. Increasing AR from 1.0 to 4.0 stabilizes the flow and results in an elevated critical Re value of 44.0–87.5. The time-mean drag coefficient decreases with increasing Re, St monotonically increases with Re at all aspect ratio values. Additionally, drag coefficient of a rectangular-like cylinder with rounded corners exhibits a relatively lower value compared to that of a rectangular cylinder, while St number demonstrates an increased trend. •Flow investigated around a rectangular cylinder with round corners using IB-LBM.•Three distinct wake flow patterns identified depending on the Reynolds number.•Flow characteristics and force coefficients depend on Re number and aspect ratios.•Aspect ratios significantly impacts vortex shedding frequencies and critical Reynolds number.