非定常绕流主动控制的数值分析

Numerical analysis on active control for unsteady flow around cylinder

为抑制圆体后尾流区涡脱落,降低流动阻力;在主圆柱体后方以上下对称方式各设置一旋转小圆柱体,以此实现对流场的控制。采用数值模拟方法,对采用此控制策略下的二维非稳态圆柱绕流尾流流动特性进行了分析研究;考察了Re=200时,附属小圆柱旋转速度α及旋转方向对主圆柱尾流流动特性的影响。数值模拟结果表明:当上部小圆柱顺时针旋转、下部小圆柱逆时针旋转时,可以抑制涡脱落并降低流动阻力;当α=2.4时即可实现对主圆柱体尾流区涡脱落的抑制效果;同时阻力系数和升力系数得到较大幅度降低,圆柱绕流的尾流流动特性被完全改变,有效控制了尾流区的不稳定性;而当上部小圆柱逆时针旋转、下部小圆柱顺时针旋转时,会导致尾流涡量增强,阻力及升力系数增大。

In order to suppress vortex shedding and reduce drag,an active control is implemented by two symmetrical affiliated cylinders with fixed rotation,which are located right behind the main cylinder.Numerical study on this active control is employed for the two-dimensional unsteady flow around the cylinder.Numerical simulations are performed in a range of rotation speed α and different directions of rotation at Reynolds number of 200.The numerical simulation result indicates that when the upper small cylinder spins clockwise and the bottom cylinder spins counterclockwise,the purpose can be achieved.When α equals to 2.4,vortex shedding of wake fluid of the main cylinder is suppressed completely.When the rotation directions of two affiliated cylinders are different,the vorticity is reinforced and the drag and lift coefficients are increased.