Prediction and Guideline for Evaluation of Flow-Induced In-Line Oscillation of a Cylindrical Structure in the Bubbly Flow of the Pipe System.

本研究为日本机械工程师学会标准JSME S 012 -1998“管道中圆柱形结构的流致振动评估指南”的支持和发展提供了重要数据。在水洞中对实际工业装置中使用的热电偶等悬臂圆柱模型的流致顺向振荡进行了实验研究，在水（单相流）中对热电偶等悬臂圆柱模型的自由振荡进行了实验研究：测量了圆柱在1.0 ~ 4.0不同折合速度下的响应尖端振幅。悬臂圆柱体由安装在水洞壁上的板簧支撑。圆柱体的纵横比从5变化到21，以研究纵横比对响应幅度的影响。结果表明，长径比为5和10的圆柱只出现一个激励区，而长径比为14和10的圆柱只出现一个激励区， ...更多信息 D21显示两个激发区。因此，纵横比强烈地影响第二激发区域的振幅。端部效应的影响也进行了研究，使用与端板连接的自由端的圆柱。由于带端板的悬臂柱即使在高宽比为5时也存在两个激励区，因此悬臂柱自由端的绕流产生了端部效应。采用在尾流中设置隔板的圆柱体作为研究对象，研究了圆柱体的振动机理。振幅比正常圆柱大，尤其是在降速2.3到3.0时，附端板的圆柱显示出第二激励区，即交替涡抑制了该范围内的振幅。每个激励区域的最大振幅与减小的倾卸参数成比例地减小，并且第一激励的振幅对该参数更敏感。当折合倾卸参数大于2.5，纵横比分别为10和21时，振幅在每个激励区都受到抑制。悬臂梁模型在两相流中的自由振荡试验：作为两相流中悬臂圆柱模型流致顺向振荡的基础研究，当两相流通过垂直管道中的面积突然膨胀区域时，使用电阻率探针测量气泡直径和气泡速度。在这项研究中，两个不同的径向空隙分布在管道中被认为是。一种是滑动流区，发生在气泡直径小于5 mm时。另一种为取心流型，即气泡直径大于5 mm时的取心流型。并通过水洞两相流自由振荡试验，测量了圆柱的响应幅值。通过与水介质中的振动结果进行比较，发现两相流对流激振动有明显的抑制作用。少

This study are for providing important data to support and develop "Guideline for Evaluation of Flow-Induced Vibration of a Cylindrical Structure in a Pipe" by the Japan Society of Mechanical Engineers, Standard JSME S012-1998. Flow-induced in-line oscillation of a cantilevered circular cylinder model like a thermocouple that is actually used in industrial plants has been experimentally studied by free-oscillation tests in a water tunnel.Free- oscillation test for a cantilevered model like a thermocouple in a water (a single- phase flow): The response tip amplitudes of a circular cylinder were measured at varying reduced velocity from 1.0 to 4.0. A cantilevered cylinder was supported by plate spring mounted on the water tunnel wall. The aspect ratio of a cylinder was varied from 5 to 21 to investigate the effect of aspect ratio on the response amplitude. It is found that the cylinders with aspect ratio of 5 and 10 show one excitation region, but the cylinders with aspect ratio of 14 an … More d 21 showed two excitation regions. The aspect ratio, therefore, strongly affects the amplitude of the second excitation region. The influence of end-effect also was investigated using cylinders with an end plate attached on the free end. Because the cylinders with an end plate show two excitation regions even if the cylinder has an aspect ratio of 5, the flow around the free end of cantilevered cylinder makes the end-effect. The mechanism of vibration was investigated using a cylinder with a splitter plate in wake to prevent the alternate vortices. The amplitude is bigger than normal cylinder especially at the reduced velocity from 2.3 to 3.0 where the cylinder attached an end plate shows the second excitation region; that is to say, the alternate vortices suppress the amplitude in this range. The maximum amplitude of each excitation region decreases in proportion to the reduced dumping parameter and the amplitude of the first excitation is more sensitive to that parameter. The amplitudes are suppressed in each excitation region when the reduced dumping parameter is greater than 2.5 with each aspect ratio of 10 and 21.Free- oscillation test for a cantilevered model in two-phase flow: As the fundamental study on flow-induced in-line oscillation of a cantilevered circular cylinder model in two-phase flow, the variations of void fraction, bubble diameter and bubble velocity are measured using an electrical resistivity probe when two-phase flow goes through the region of sudden area expansion in the vertical pipe. In this study two different radial void distributions in the pipe are considered. One is called as sliding flow regime, which occurs when the bubble diameters are less than 5mm. The other is termed as coring flow regime, which takes place when the bubble diameters are greater than 5mm. And the response amplitudes of a circular cylinder have been measured by the free-oscillation tests in the two-phase flow in a water tunnel. Comparing the response amplitudes with the results in a water, we found that the flow-induced vibration are suppressed by the two phase flow. Less