Axial Leakage Flow-Induced Vibration of the Elastic Rod as the Axisymmetric Continuous Flexible Beam

2001 ◽  
Vol 123 (4) ◽  
pp. 421-428 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Atsuhiko Shintani
Keyword(s):  
Rigid Bodies ◽  
Flexible Body ◽  
Flexible Beam ◽  
Leakage Flow ◽  
Root Locus ◽  
Argand Diagram ◽  
Elastic Rod ◽  
Flow Induced Vibration ◽  
Critical Flow Velocity ◽  
Evaluation Methodologies

The evaluation methodologies for the flow-induced vibration instability of a long flexible rod due to axial leakage-flow are reported. In the previous papers, the axisymmetric rods are regarded as rigid bodies, not as continuous bodies. In this paper, we deal with the rod as a continuous flexible body. The equations for the fluid and the structure are coupled analytically and the added mass, added damping, and added stiffness are derived by considering unsteady pressure acting on the rod. The relation between the axial velocity and the unstable phenomena is clarified. Concerning the critical flow velocity, the root locus (Argand diagram) is shown. We compared our results with the experimental results which one of the authors reported before.

A Study on Leakage Flow Induced Vibration From Engineering Viewpoint

2015 ◽  
Author(s):  
Fumio Inada
Keyword(s):  
Damping Ratio ◽  
Axial Flow ◽  
Engineering System ◽  
Dimensional System ◽  
Leakage Flow ◽  
Fluid Inertia ◽  
Flow Induced Vibration ◽  
One Dimensional ◽  
Annular Gap ◽  
Excited Vibration

Leakage-flow-induced vibration for a relatively short gap is studied analytically to provide useful information to design structures that include a leakage flow. The relationship between the analysis of a one-dimensional system and that of an annular gap is explained first. Then, the mechanism of flutter-type instability is reproduced from previous study after correcting an error. Finally, the self-excited vibration potential of an engineering system is shown from sample calculations. It is shown that an axial flow becomes dominant in the short-gap approximation, and in this case, the analysis of a one-dimensional flow can be expanded to that of an annular flow. The result that negative damping can occur in the case of a divergent passage owing to the delay induced by fluid inertia was obtained from a previous study. It was suggested analytically that the damping ratio could become negative and its absolute value could become more than 10% in a system that is frequently encountered in a plant, if the natural frequency decreases. The value could be sufficient to generate self-excited vibration.

Axial Leakage Flow-Induced Vibration of Thin Cylindrical Shell With Respect to Circumferential Vibration

2002 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Atsuhiko Shintani ◽  
Masakazu Ono
Keyword(s):  
Cylindrical Shell ◽  
Equations Of Motion ◽  
Fluid Pressure ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Thin Cylindrical Shell ◽  
Flow Induced Vibration ◽  
Navier Stokes Equation ◽  
Coupled Equations ◽  
Unstable Vibration

In this paper, the dynamic stability of a thin cylindrical shell subjected to axial leakage flow is discussed. In this paper, the third part of a study of the axial leakage flow-induced vibration of a thin cylindrical shell, we focus on circumferential vibration, that is, the ovaling vibration of a shell. The coupled equations of motion between shell and liquid are obtained by using Donnell’s shell theory and the Navier-Stokes equation. The added mass, added damping and added stiffness in the coupled equations of motion are described by utilizing the unsteady fluid pressure acting on the shell. The relations between axial velocity and the unstable vibration phenomena are clarified concerning the circumferential vibration of a shell. Numerical parametric studies are done for various dimensions of a shell and an axial leakage flow.

Axial Leakage Flow-Induced Vibration of a Thin Cylindrical Shell With Respect to Axisymmetric Vibration

2003 ◽  
Vol 125 (2) ◽  
pp. 151-157 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Atsuhiko Shintani ◽  
Masakazu Ono
Keyword(s):  
Cylindrical Shell ◽  
Axial Flow ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Axisymmetric Vibration ◽  
Thin Cylindrical Shell ◽  
Flow Induced Vibration ◽  
Navier Stokes Equation ◽  
Coupled Equations ◽  
Stiffness Matrices

In this paper, the stability of a thin cylindrical shell subjected to axial leakage flow is discussed. In this paper, the first part of a study of the axial leakage flow-induced vibration of a thin cylindrical shell, we focus on axisymmetric vibration, that is, the ringlike vibration of a shell. The coupled equations between a shell and a fluid are obtained by using the Donnell’s shell theory and the Navier-Stokes equation. The added mass, added damping and added stiffness matrices in the coupled equations are described by utilizing unsteady fluid forces on a shell. The influence of the axial flow velocity on the unstable phenomena is clarified concerning axisymmetric vibration mode of shell. The numerical calculations are performed taking the dimensions of shell and fluid as parameters.

Spatial motion of rigid bodies connected by an elastic rod

1988 ◽  
Vol 24 (6) ◽  
pp. 630-633
Author(s):  
V. V. Kravets ◽  
E. P. Kryshko
Keyword(s):  
Rigid Bodies ◽  
Spatial Motion ◽  
Elastic Rod

Active Feedback Control of Leakage-Flow-Induced Sheet Flutter by Injection and Suction of Fluid at Inlet or Outlet of Passage

2006 ◽  
Author(s):  
Masahiro Watanabe ◽  
Yutaka Koyama
Keyword(s):  
Feedback Control ◽  
Flow Velocity ◽  
The Self ◽  
Control Technique ◽  
Critical Flow ◽  
Leakage Flow ◽  
Critical Flow Velocity ◽  
Active Feedback ◽  
Narrow Passage ◽  
Active Feedback Control

This paper proposes and develops a new non-contact active feedback control of leakage-flow-induced sheet flutter in a narrow passage, by injection and suction of fluid at inlet or outlet of the passage. The strategy of this active control technique is that the active feedback, which is by the activation of the injection/suction of the fluid at the inlet or outlet of the passage, suppresses the original source of the self-exciting fluid force acting on the structure, i.e., cancels the self-excited feedback mechanism. In this paper, the effective suppression of the leakage-flow-induced sheet flutter by the active feedback control technique is demonstrated experimentally. A flexible sheet, as a controlled object, is subjected to fluid flow in a narrow passage. The leakage-flow-induced flutter occurs to the flexible sheet in the translational motion over the critical flow velocity. The leakage-flow-induced sheet flutter is actively controlled and suppressed by the activation of injection/suction of the fluid at the inlet or outlet of the passage. The critical flow velocity under the controlled condition is examined with varying the controller gain and phase-shift between the injection/suction of the fluid and the sensor (vibration displacement) signal of the flexible sheet. As a result, it is indicated experimentally that the active feedback control technique increases the critical flow velocity, and suppress the leakage-flow-induced sheet flutter effectively. Moreover, the control performance is examined experimentally, and stabilization mechanism by the active feedback control is discussed.

scholarly journals Experimental Investigation on Flow-Induced Vibration of Fuel Rods in Supercritical Water Loop

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Licun Wu ◽  
Daogang Lu ◽  
Yu Liu
Keyword(s):  
Fuel Assembly ◽  
Flow Rate ◽  
Supercritical Water ◽  
Vibrational Energy ◽  
Experimental Result ◽  
Small Scale ◽  
Leakage Flow ◽  
Flow Induced Vibration ◽  
Fuel Rods ◽  
Vibration Experiment

The supercritical water-cooled reactor (SCWR) is one of the most promising Generation IV reactors. In order to make the fuel qualification test for SCWR, a research plan is proposed to test a small scale fuel assembly in a supercritical water loop. To ensure the structure safety of fuel assembly in the loop, a flow-induced vibration experiment was carried out to investigate the vibration behavior of fuel rods, especially the vibration caused by leakage flow. From the experiment result, it can be found that: the vibration of rods is mainly caused by turbulence when flow rate is low. However, the effects of leakage flow become obvious as flow rate increases, which could changes the distribution of vibrational energy in spectrum, increasing the vibrational energy in high-frequency band. That is detrimental to the structure safety of fuel rods. Therefore, it is more reasonable to improve the design by using the spacers with blind hole, which can eliminate the leakage flow, to assemble the fuel rods in supercritical water loop. On the other hand, the experimental result could provide a benchmark for the theoretical studies to validate the applicability of boundary condition set for the leakage-flow-induced vibration.

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