旋转圆柱绕流流场特性分析

ANALYSIS OF FLOW CHARACTERISTICS AROUND A ROTATING CYLINDER

对雷诺数Re=20000~90000、相对转速α=0~0.72的旋转圆柱后方流场进行了实验测量,分析了旋转圆柱后方不同剖面处的速度分布规律和湍流度分布规律.采用LES方法对旋转圆柱绕流问题进行了数值模拟,分析旋转圆柱周围流场特性和自由剪切层变化规律,最后通过理论模型对流场变化进行分析,得出如下结论:当圆柱逆时针旋转时,同一雷诺数下随着相对转速的增加,旋转圆柱尾迹区域下方速度突变处的位置随着相对转速的增加而上移,而上方速度突变处的位置不变,雷诺数的增加使旋转圆柱尾迹区域下方速度突变处位置有小幅度的下移.通过数值模拟发现,圆柱旋转之后,圆柱后方下侧涡的位置明显上移,且幅度较大.下方的自由剪切层有明显的上移,上方的自由剪切层位置变化较小.最后通过理论分析发现,圆柱后侧下方涡位置的上移对圆柱升力影响十分显著,在高雷诺数、低相对转速的条件下,旋转圆柱后侧下方涡位置的改变对旋转圆柱的升力、尾流区自由剪切层的变化起到了重要的影响.

The flow field behind a rotating cylinder with Reynolds number Re=20000~90000 and relative speedα=0~0.72 was measured experimentally,and the velocity distribution and turbulence distribution at different sections behind the rotating cylinder were analyzed.The flow around a rotating cylinder is numerically simulated by LES method,and the characteristics of the flow field around a rotating cylinder are analyzed.Finally,the theoretical model is used to analyze the flow field variation and came to the following conclusions:When the cylinder rotates counterclockwise,with the increase of the relative speed at the same Reynolds number,the position of the velocity mutation below the wake region of the rotating cylinder moves up with the increase of the relative speed,while the position of the velocity mutation above remains unchanged.With the increase of Reynolds number,the position of velocity mutation below the wake region of the rotating cylinder moves down to a small extent.Through numerical simulation,it is found that the position of the lower vortex behind the cylinder moves up obviously after the cylinder rotates,and the amplitude is large.The lower free shear layer has obvious upward movement,while the upper free shear layer has little change in position.Finally,through theoretical analysis,it is found that the upward movement of the lower vortex on the rear side of the rotating cylinder has a significant effect on the lift force of the rotating cylinder.Under the condition of high Reynolds number and low relative speed,the change of the lower vortex position on the rear side of the rotating cylinder has an important effect on the lift force of the rotating cylinder and the change of the free shear layer in the wake region.