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

Research Project

Project/Area Number	61460115
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	機械力学・制御工学
Research Institution	Science University of Tokyo
Principal Investigator	HARA Fumio (Professor) Science University of Tokyo, 工学部・第一部, 教授 (90084376)
Project Period (FY)	1986 – 1987
Project Status	Completed (Fiscal Year 1987)
Budget Amount *help	¥5,800,000 (Direct Cost: ¥5,800,000) Fiscal Year 1987: ¥1,800,000 (Direct Cost: ¥1,800,000) Fiscal Year 1986: ¥4,000,000 (Direct Cost: ¥4,000,000)
Keywords	Single disk / Double disk / Rotation in water / Vebration / Swirling flow / Buckling mode static deformation / Single-diametor-node-line mode vabration / out-of-phase mode vibration / 回転ディスク / 流体不安定振動 / ヒステリシス特性 / 水中ディスク / レーザドップラ振動計
Research Abstract	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