Study on Mechanism for Unstable Vibrations of an Axisymmetric Body in a Cavitating Leakage Flow
Project/Area Number |
09650265
|
Research Category |
Grant-in-Aid for Scientific Research (C)
|
Allocation Type | Single-year Grants |
Section | 一般 |
Research Field |
Dynamics/Control
|
Research Institution | Tokyo University of Agriculture & Technology |
Principal Investigator |
ARAI Masaaki Tokyo University of Agriculture and Technology, Faculty of Technology, Assis. Prof., 工学部, 助手 (50092474)
|
Project Period (FY) |
1997 – 1999
|
Project Status |
Completed (Fiscal Year 1999)
|
Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1999: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥1,500,000 (Direct Cost: ¥1,500,000)
|
Keywords | Vibration Coupled with Fluid Motion / Fluid Force / Cavitation / Stability / Leakage Flow / Axisymmetric Body / Axisyvnmetric Body / Vibration Coupled with Fluid Motion / Stability / leakage Flow / Dileution Coupled with Fluid Motion / Cauitution |
Research Abstract |
In order to find out the similarity law for the occurrence of the unstable vibrations, the stabilities of the systems were examined by changing outside diameter of the center body, annular width and length of the annular passage. From the waveforms of the displacement of the center body and the outer wall surface pressure, it is found that the unstable vibration of the center body is the self-excited vibration supplied the positive work caused by the fluid-dynamic force. The experimental results show that the similarity law for the self-excited vibration corresponds to nondimensional pressure loss coefficient β and cavitation number σ. When the self-excited vibrations occur, the β and σ become about 2 and 0.3, respectively. From the observation of the leakage flow, the cavitation bubbles in the passage disappear in the vicinity of the exit when the self-excited vibrations occur. That is, the system attains dynamic instability because the leakage passage is deformed by the cavitation bub
… More
bles. In order to observe the cross section of the leakage flow, the leakage models are made of the thin plates. From the still photographs of the models, the leakage flow separates at the right-angles of the inlet, and the cavitation bubbles result in the wake because the pressure at the vena-contracta is lower than the saturation vapor pressure. Moreover, in the case of dynamic instability, the bubbles are destroyed in the vicinity of the exit. In this case, the divergent passage is approximately formed by the cavitation bubbles and the area ratio of the exit to the inlet AィイD1rィエD1 is about 3. Using the value of AィイD1rィエD1, the stabilities of the systems in the case of the coupled vibrations are examined theoretically. On the other hands, the stability analysis for the system combining translational and rotational vibrations have been reported by the authors. In that case, the theoretical result shows that the system attains the dynamic instability. Therefore, as the divergent passage is approximately formed by the cavitation bubbles, the self-excited vibrations occur Less
|
Report
(4 results)
Research Products
(6 results)