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，开发了以下两种弹性结构流激振动特性评估系统；第一种是弹性结构在静止气流中运动的情况，如地面试验操作下的卫星天线；第二种是弹性结构在一维泄漏流作用下的振动情况，如热交换器管和电磁盘文件的载荷臂。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、频率和板的边缘结构的函数。针对第二种情况，设计并制作了两种实验装置，用于测量一维泄漏流作用在弹性支承刚性板和悬臂弹性梁上的不稳定流体力。不稳定流体力的测量方法如下：(1)通过增加安装在通道入口的压电异型致动器产生的额外流体力来抑制不稳定振动；(2)计算致动器的输入功率。最后，对“泄漏流量近似”的有效性进行了深入的分析和实验检验，并首次发现当通道长度与通道宽度之比小于10时，该近似是有效的。

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.