Influence of inflow acceleration on the aerodynamic characteristics of a square cylinder

Large-Eddy Simulations were conducted to investigate accelerated flows around a square cylinder. The study explores flow characteristics for Gaussian-type accelerations of the inflow within the range of Reynolds numbers Re=1.720×104 to Re=6.536×104. Three different inflow acceleration intensities within the same range of Re have been considered. For all analyzed acceleration values, time cells with a constant frequency in vortex shedding were identified in agreement with the experimental findings of Brusco et al. (2022a). The temporal behavior of the vorticity field indicates that vortex packets are shed at a constant frequency within these cells. Moving from one cell to another, there is a discontinuity in the vortex-shedding mechanism, leading to an unsteady but more symmetrical wake and a reduction in crossflow-force fluctuations. Subsequently, vortex shedding restarts at a higher frequency. As acceleration intensity increases, the time length of the constant-frequency time cells decreases. A similar behavior of the Strouhal number with the Reynolds number is obtained for all acceleration intensities.