Large eddy simulation of flow around a rectangular cylinder at low subsonic and transonic speeds

Flow characteristics around a rectangular cylinder with different aspect ratios at low subsonic and transonic speeds were studied by large eddy simulation. At Re=22000, large eddy simulations were performed for flows around a rectangular cylinder with aspect ratios of 1:1, 2;1, 3:1 and 4:1 at Ma = 0.1 and 0.75 respectively, to study the effects of the aspect ratio and the compressibility on the flow characteristics. At Ma =0.1, the Strouhal number decreases first and then increases and finally deceases with the increase of the aspect ratio. Flow reattachment is observed for the cases with aspect ratios of 3:1 and 4:1. Complex three-dimensional flow structures were observed in the wake. At Ma =0.75, the Strouhal number and the turbulence intensities decrease with the increase of the aspect ratio. It is also observed that there are two kinds of mechanisms about the formation of the local supersonic zones in the near wake region.