Large Eddy Simulation of flow past a circular cylinder in the drag crisis regime: effect of aspect ratio and the existence of multiple states

In this work, we present Large Eddy Simulation of flow past a three-dimensional circular cylinder in the drag crisis regime, 1×10⁴≤ Reynolds number≤ 4×10⁵. A stabilized Finite Element Method is used to solve the incompressible Navier Stokes equations. The Sigma model is implemented to model the effects of the sub-grid scales in the flow. First, we investigate the effect of aspect ratio of the cylinder on drag crisis. It is found that critical Reynolds number for the onset of drag crisis is sensitive to the aspect ratio of the cylinder. The drag crisis occurs at a lower Reynolds number for a cylinder with a small aspect ratio compared to one with large aspect ratio. The existence of multiple solutions in the drag crisis regime is explored by carrying out computations with different initial conditions. It is found that multiple states exist near the onset and also towards the end of drag crisis. Multiple states are identified in the variation of time-averaged coefficient of drag and lift, rms of coefficient of lift and vortex shedding frequency with Reynolds number.