串列双圆柱流致振动的数值模拟及其耦合机制

NUMERICAL INVESTIGATION ON FLOW-INDUCED VIBRATION OF TWO CYLINDERS IN TANDEM ARRANGEMENTS AND ITS COUPLING MECHANISMS

对雷诺数Re=100条件下串列双圆柱的流致振动进行了数值模拟.圆柱的质量比m*均为2.0,间距比L/D为2.0～5.0.考虑两种工况:(a)上游圆柱固定,下游圆柱可沿横流向自由振动;(b)上、下游圆柱均可沿横流向自由振动.结果表明:无论上游圆柱静止或者振动,下游圆柱横向振幅明显大于单圆柱的.工况(b)的下游圆柱最大振幅要大于工况(a)的,这是由于两圆柱均振动时,两圆柱之间耦合作用增强,上游圆柱的尾流和下游圆柱的振动之间"相互调节"作用显著.对工况(b)的下游圆柱振动和间隙流之间的作用机制进行了详细的研究,发现当上游圆柱脱落的自由剪切层重新附着于下游圆柱上并且完全从间隙之间通过时,下游圆柱的振幅最大.

Flow-induced vibration of two circular cylinders arranged in tandem at Re = 100 is numerically investigated.The mass ratio of the cylinders is 2.0 and the center to center spacing ratio of the cylinders varies from 2.0 to 5.0. Two scenarios are considered:(a) the downstream cylinder is allowed to vibrate freely in the cross-flow direction while the upstream is fixed;(b) both cylinders are allowed to vibrate freely in the cross-flow direction. Results show that no matter the upstream cylinder is fixed or not, the transverse vibration amplitude of the downstream cylinder is obviously larger than an isolated one. For Scenario(a), the transverse amplitude of the downstream cylinder is larger than that of Scenario(b),which can be attributed to the fact below. When both cylinders vibrate freely, a significant 'mutual-adjusting' happens between the wake of the upstream cylinder and the vibration of the downstream one, which intensifies the interaction between the two cylinders. We also investigated the coupling mechanisms of the downstream cylinder vibration and the gap flow of Scenario(b) and found that the vibration amplitude of the downstream cylinder attains its maximum when the reattached shear layer from the upstream cylinder can completely pass through the gap.