Study of Flow-Induced Vibrations in a Rotating Double Disk Immersed in a Confined Water

本报告讨论了在密闭水中旋转的圆盘振动特性的实验研究。检查了两种类型的磁盘；一个是一个直径350毫米，厚1毫米的单磁盘，另一个是由两个相同的磁盘组成的双磁盘，磁盘间隙为7毫米。双磁盘的大小与单磁盘的大小相同。两个磁盘系统都浸在由护罩封闭的水中。两种系统的罩壁与盘之间的间隙均为7mm。将转速从3rps改变为7rps，我们测量了两对角线处圆盘的位移和叶冠壁面上的压力波动。数据被记录在磁带上，并数字化存储在一台微型计算机中。我们计算了这些数据的平均值、均方根、功率谱密度和相角，得到了以下主要结果：单个圆盘在一定的转速下发生不稳定振动，在较高的转速下，这种振动变为更严重的玻璃化。旋转单盘的振动幅值对转速的增加和减少都有滞后性。圆盘上两个对角线点之间的不稳定振动模态为非相位。转速与圆盘振动主频率之间的关系，以及圆盘位移或静位移均值与转速之间的关系也存在滞后性。对于双盘，我们发现在不同的转速范围内有两个大的振动，但在传动轴的固定部分有孔的双盘没有发现迟滞。双圆盘的不稳定振动与圆盘直径相异双盘发生屈曲型静态变形。从这些实验结果中，我们得出结论，在受限流体中旋转的圆盘会经历两种类型的变形：一种是静态或屈曲模式变形，另外两种是不同主导频率的异相模式振动。少

This report deals with experimental studies of vibration characteristcs of disks rotating in a confined water. Two type of disks were examined; one was a single disk 350 mm in diameter and 1 mm thick, and the other was a double disk consisting of two identical disks having a disk gap of 7 mm. The double disk size was the same as that of a single disk. Both disk systems were immersed in water confined by a shrouds. The gap between the shroud-wall and the disk was 7 mm for both systems. Changing rotation speed from 3 rps to 7rps, we measured the diaplacement of disk at two points diagonal to each other and pressure fluctuation on the shroud wall. Data were recorded on magneic tape and digitized to be stored in a microcumputer. We calculated the mean, root mean square, power spectral density and phase angle for these data and found the following major results:1. A single disk underwent a unstable vibration a a certain rotation speed and this vibration became a more severe vitration at hig … More her rotation speed.2. Vibration amplitude of a rotating single disk had a hysteresis for increasing and decreasing rotation speed.3. The mode of the unstable vibrations was out-of-phase between two diagonal points on the disk.4.The hysteresis was also found in the relationship between rotation speed and the dominant frequency of the disk vibration as well as in that between the mean value of disk displacement or static displacement and rotation speed.5. For a double disk we found two large vibrations for different rotation speed ranges but no hysteresis was found for the double disk having holes at the fixed part to the driving shaft.6.The unstable vibrations in a double disk was out-of-phase with respect to the disk diameter.7 The double disk underwent a buckling mode static deformation.From these experimental results we concluded-that a disk rotating in a confined fluid undergoes therr type of deformations: one is a static, or buckling mode deformation, the other two were out-of-phase mode vibrations with different dominant frequencies. Less