scholarly journals Flow-Induced Vibration of Bluff Bodies. Experiments on Flow-Induced In-Line Oscillation of a Circular Cylinder in a Water Tunnel. 2nd Report, Influence of the Aspect Ratio of a Cantilevered Circular Cylinder.

2001 ◽  
Vol 44 (4) ◽  
pp. 705-711 ◽  
Author(s):  
Akira NAKAMURA ◽  
Atsushi OKAJIMA ◽  
Takashi KOSUGI
Keyword(s):  
Aspect Ratio ◽  
Circular Cylinder ◽  
Water Tunnel ◽  
Bluff Bodies ◽  
Flow Induced Vibration

Flow-Induced In-Line Oscillation of a Circular Cylinder in a Water Tunnel

2001 ◽  
Vol 124 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Atsushi Okajima ◽  
Takashi Kosugi ◽  
Akira Nakamura
Keyword(s):  
Circular Cylinder ◽  
Free Oscillation ◽  
Water Tunnel ◽  
Hysteresis Phenomenon ◽  
Two Dimensional ◽  
Flow Induced Vibration ◽  
Excitation Region ◽  
Damping Parameter ◽  
Resonance Flow ◽  
Velocity Region

Flow-induced in-line oscillation of a circular cylinder has been experimentally studied by free-oscillation tests in a water tunnel. Response amplitudes of a circular cylinder have been measured for determining the values of the reduced mass-damping parameter of less than 1.0. In the free-oscillation tests, the cylinder models were spring-mounted so as to oscillate as a two-dimensional rigid cylinder in the water tunnel. Two types of excitation phenomena appear at approximately half of the resonance flow velocity. The response amplitudes are sensitive to the reduced mass-damping parameter during the in-line oscillation of the first excitation region with a symmetric vortex street, and the alternate vortices are periodically shed, locking-in with the vibration of the cylinder in the second excitation region. A hysteresis phenomenon is observed to appear in the in-line oscillation of the latter region. A cantilevered circular cylinder with a finite length aspect ratio of 10 was tested for fluid-elastic characteristics of the cylinder, and these characteristics are found to be quite different from those of the two-dimensional cylinder, having only one wide velocity region of excitation. The results of this study are providing important supporting data for the recent publication “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.

Spring-Arrangement Effect on Flow-Induced Vibration of a Circular Cylinder

2021 ◽  
Author(s):  
Koki Yamada ◽  
Yuga Shigeyoshi ◽  
Shuangjing Chen ◽  
Yoshiki Nishi
Keyword(s):  
Circular Cylinder ◽  
Dynamic Model ◽  
Geometric Nonlinearity ◽  
Water Channel ◽  
Fluid Flows ◽  
Flow Induced Vibration ◽  
Theoretical Evaluation ◽  
Circulating Water ◽  
Linear Dynamic ◽  
Elastically Supported

Abstract Purpose This study elucidated the effect of an inclined spring arrangement on the flow-induced vibration of a circular cylinder to understand if the effect enhances the harnessing of the energy of fluid flows. Method An experiment was conducted on a circulating water channel. A circular cylinder was partially submerged. It was elastically supported by two springs whose longitudinal directions were varied. With the speed of the water flow varied, the vibrations of the circular cylinder were measured. The measured vibrations were interpreted by la linear dynamic model. Results and discussion In a few cases, a jump in response amplitudes from zero to the maximum was observed with the spring inclination at reduced velocities of 6 to 7, whereas gradually increasing response amplitudes were observed in other cases. The inclined spring arrangement achieved greater velocity amplitudes than in cases without spring inclination. A theoretical evaluation of the measured responses indicates that the effect of the inclined springs was caused by geometric nonlinearity; the effect would be more prominent by employing a longer moment lever.

scholarly journals Effect of Cylinder Gap Ratio on The Wake of a Circular Cylinder Enclosed by Various Perforated Shrouds

CFD letters ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 51-68
Author(s):  
Nurul Azihan Ramli ◽  
Azlin Mohd Azmi ◽  
Ahmad Hussein Abdul Hamid ◽  
Zainal Abidin Kamarul Baharin ◽  
Tongming Zhou
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Control Method ◽  
Lift Coefficient ◽  
Base Case ◽  
Bluff Bodies ◽  
Ansys Fluent ◽  
Gap Ratio ◽  
Spacing Ratio

Flow over bluff bodies produces vortex shedding in their wake regions, leading to structural failure from the flow-induced forces. In this study, a passive flow control method was explored to suppress the vortex shedding from a circular cylinder that causes many problems in engineering applications. Perforated shrouds were used to control the vortex shedding of a circular cylinder at Reynolds number, Re = 200. The shrouds were of non-uniform and uniform holes with 67% porosity. The spacing gap ratio between the shroud and the cylinder was set at 1.2, 1.5, 2, and 2.2. The analysis was conducted using ANSYS Fluent using a viscous laminar model. The outcomes of the simulation of the base case were validated with existing studies. The drag coefficient, Cd, lift coefficient, Cl and the Strouhal number, St, as well as vorticity contours, velocity contours, and pressure contours were examined. Vortex shedding behind the shrouded cylinders was observed to be suppressed and delayed farther downstream with increasing gap ratio. The effect was significant for spacing ratio greater than 2.0. The effect of hole types: uniform and non-uniform holes, was also effective at these spacing ratios for the chosen Reynolds number of 200. Specifically, a spacing ratio of 1.2 enhanced further the vortex intensity and should be avoided.

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