DEVELOPMENT OF THE SYSTEM FOR EVALUATING THE CHARACTERISTICS OF FLOW INDUCED VIBRATION OF ELASTIC STRUCTURES IN CONNECTION WITH ADVANCED SYSTEMS

在本项目中，开发了以下两种情况下的弹性结构流激振动特性评估系统：第一种情况是弹性结构在静止气流中运动的情况，如卫星天线在地面试验操作中；第二种情况是弹性结构在一维泄漏流作用下振动的情况，如换热器管和电磁磁盘文件的负载臂。对于第一种情况，通过观察弹性支承板的阻尼自由振动波形，发现流体力的特征是幅值、频率和板的边缘形状的函数。对于第二种情况，设计制作了两种不稳定流体力的实验装置，分别测量了弹性支承刚性板和悬臂弹性梁在一维渗流作用下的不稳定流体力。通过以下步骤测量不稳定流体力：(1)通过增加安装在通道入口处的压电式致动器产生的附加流体力来抑制不稳定振动；(2)计入致动器的输入功率。最后，从理论和实验两个方面对“泄漏流近似”的正确性进行了深入的检验，首次发现该近似在流道长度与流道宽度之比小于10时是有效的。

In this project, the system for evaluating the characteristics of flow-induced vibration of the following two cases of elastic structures was developed ; the first one is the case where elastic structures are moving in quiescent air flow such as antennas of satellites under ground test operations ; the second one is the case where elastic structures are vibrating subjected to one-dimensional leakage flow such as heat exchanger tubes and the load arms of electromagnetic disk files. As for the first case, the characteristics of the fluid force were found to be the function of amplitudes, frequencies, the configuration of edges of plates from the observation of the wave form of damped free vibrations of elastically supported plates. As for the second case, two types of experimental apparatus were designed and made for measuring the unstable fluid force acting on the elastically supported rigid plate and the cantilever elastic beam subjected to one-dimensional leakage flow. The unstable fluid force was measured by the following procedure ; (1) suppressing the unstable vibrations by adding additional fluid forces created by a piezo bymorph actuator installed at the inlet of the passage, (2) accounting the power input of the actuator. Finally, the validity of "the leakage flow approximation" was examined intensively both analytically and experimentally and the fact that this approximation is valid when the ratio between the channel length and the channel width is less than 10 was first found.