An effort has been made in this paper to numerically estimate the critical rotational speeds for which the steady separation bubble completely disappears behind a circular cylinder. The cylinder is subjected to an unconfined free stream flow, however, fictitious confining boundaries are considered for computational convenience. The Reynolds numbers computed from the free stream flow velocity are considered in the range of 10–40. In this range of Reynolds number, the flow around a stationary circular cylinder remains steady and separated with the formation of a recirculation zone through counter-rotating vortices (separation bubble) behind the body. Rotational motion is provided to the cylinder that causes stabilization of the flow field. The separation bubble vanishes and an attached type flow feature is observed. The rotational speeds at which the recirculating zone behind the cylinder completely vanishes in the said range of Reynolds number are considered as the critical rotation rates. The aerodynamic coefficients are obtained for the specific operating conditions and a regime diagram is produced depicting the separated and the attached flows.

本文已作出努力，以数值方式估算了临界旋转速度，对于该临界旋转速度，稳定的分离气泡在圆柱体后完全消失了。圆柱体承受无限制的自由流，但是，为计算方便起见，考虑了虚拟限制边界。根据自由流的流速计算出的雷诺数在10–40的范围内。在此雷诺数范围内，固定圆柱周围的流动保持稳定并通过在身体后方的反向旋转涡流（分离气泡）形成再循环区而分离。旋转运动提供给气缸，导致流场稳定。分离气泡消失，观察到附着型流动特征。在所述雷诺数的所述范围内，汽缸后方的再循环区域完全消失的转速被认为是临界转速。获得了针对特定工况的空气动力学系数，并绘制了状态图，描绘了分离后的气流和附着的气流。