Feedback Mechanism of Combinated Vibration Phenomenon of Fluid-Structure and Its Control

本研究旨在探讨流固耦合振动现象的反馈机理及其控制。采用具有基本结构形态的不同深度比的矩形棱镜。通过自由振动和强制振动试验，研究了矩形棱镜旋转振动的响应特性。在矩形棱镜的上、下游分别安装t形板和分流板，实现了对流激振动的抑制。主要结果可以总结如下。(1)除尾缘附近外，棱柱侧面的脉动压力是由棱柱前缘周期性撞击前缘涡脱落产生的。(2) B/H=3时棱镜的流激振动是由前缘涡和尾流涡的碰撞引起的。t型板抑制碰撞前缘涡的产生，分流板抑制尾流涡的产生。(3)带分色板的棱镜与普通棱镜的波动矩基本相同。然而，与普通棱镜相比，带有t型板的棱镜的波动力矩大大减小。因此，人们认识到，棱镜的流激振动强烈地依赖于碰撞的前缘涡，而不是尾流涡。(4)在强迫振荡频率Sv<1.0范围内，平面棱镜和带分流板棱镜的脉动力矩做功为正，流激振动发散。另一方面，在Sv=0 ~ 0.06范围内，t型板棱镜的功几乎为零。振动会收敛，因为在Sv=0.23的范围内，功是负的。(5)通过对具有前缘涡撞击的平面矩形棱镜的自由振动试验，发现其存在低速扭转颤振、涡激振和高速扭转颤振三种流激振动。(6)在棱镜的下游加装分流板抑制了涡流的激发。在上游加装t型板可抑制低速和高速扭转颤振及涡激振。因此，用t型板抑制前缘撞击涡时，对棱镜流激振动的抑制效果最好。少

The objective of this study to investigate the feedback mechanism of combined vibration phenomenon of fluid-structure and its control. The rectangular prism with various ratio of depth having a fundamental structure configuration is adopted. The response characteristics of rotary oscillation of the rectangular prism are investigated on the free and forced vibration test. The suppression of the flow-induced vibrations is established by a T-shape plate and a splitter plate attached to the upstream and downstream of rectangular prism. The main results can be summarized as follows.(1) The fluctuating pressure on side surface of the prism except near the trailing edge is generated by impinging leading-edge vortex shed periodically from the leading edge of the prism.(2) Flow-induced vibrations of a prism with B/H=3 is induced by impinging leading-edge vortex and wake vortices. The T-shape plate suppresses the generation of impinging leading-edge vortex and the splitter plate suppresses the g … More eneration of the wake vortices.(3) The fluctuating moment of the prism with splitter plate is almost same to the plain prism. However, the fluctuating moment of the prism with T-shape plate greatly decreases in comparison with the plain prism. Therefore, it is recognized that flow-induced vibrations of the prism are strongly dependent on the impinging leading-edge vortices rather than the wake vortices.(4) The work done by fluctuating moment of the plain prism and the prism with splitter plate becomes a positive within forced oscillation frequency Sv<1.0 and flow-induced vibration diverges. On the other hand, the work of the prism with T-shape plate becomes almost zero value in the range of Sv=0 to 0.06. And the vibration converges because the work is negative in the range to Sv=0.23.(5) From the free-vibration test for the plain rectangular prism with impinging leading-edge vortices, it is found that there exists three types of flow-induced vibration, I.e., low-speed torsion flutter, vortex excitation and high-speed torsion flutter.(6) The vortex excitation is suppressed when the splitter plate is attached at the downstream of a prism. The low-speed and the high-speed torsion flutter and the vortex excitation are suppressed when the T-shape plate is attached at the upstream side. Therefore, suppression of the flow-induced vibrations of the prism is done with the most effectiveness when the impinging leading-edge vortices are suppressed with the T-shape plate. Less