scholarly journals Vortex- and Wake-Induced Vibrations of a Circular Cylinder Placed in the Proximity of Two Fixed Cylinders

2022 ◽  
Author(s):  
Yoshiki Nishi ◽  
Yuga Shigeyoshi
Keyword(s):  
Circular Cylinder ◽  
Water Channel ◽  
High Amplitude ◽  
Circular Cylinders ◽  
Circulating Water ◽  
Vortex Induced Vibrations ◽  
Vortex Streets ◽  
Cylinder Model ◽  
Karman Vortex ◽  
Second Peak

Abstract Purpose This study aims to understand the vibratory response of a circular cylinder placed in proximity to other fixed bodies. Methods A circular cylinder model was placed in a circulating water channel and was supported elastically to vibrate in the water. Another two circular cylinders were fixed upstream of the vibrating cylinder. The temporal displacement variations of the vibrating cylinder were measured and processed by a frequency analysis. Results When the inline spacings were small, two amplitude peaks appeared in the reduced velocity range 3.0–13.0. When the inline spacings were large, the amplitude response showed a single peak. Conclusion For small inline spacings, the first peak was attributed to high-amplitude vibrations forced by Karman vortex streets shed from the upstream cylinders. The second peak arose from interactions of the wakes of the upstream cylinder with the vibrating cylinder. When the inline spacing increased, the vortex-induced vibrations resembled those of an isolated cylinder.

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.

Interference Between a Square and a Circular Cylinder

2015 ◽  
Author(s):  
Nithin S. Kumar ◽  
R. Ajith Kumar ◽  
Jayalakshmi Mohan
Keyword(s):  
Circular Cylinder ◽  
Flow Visualization ◽  
Shear Layer ◽  
Flow Pattern ◽  
Water Channel ◽  
Flow Patterns ◽  
Observation Time ◽  
Square Cylinder ◽  
Circulating Water ◽  
Layer Flow

The flow visualization studies around a square cylinder (upstream) and a circular cylinder arranged in tandem configuration is studied experimentally to identify the interference flow patterns. Flow visualization studies are carried out in a re-circulating water channel. The investigations are carried out for tandem arrangement varying the center-to-center distance (L) between the cylinders; L/B ratio is varied from 1 to 5 where B is the characteristic length. Experiments were conduct at a Reynolds number of 2100 (based on B). The results are also obtained for two tandem square cylinder configuration. The flow patterns observed are: Alternate Shear Layer Reattachment with and without gap flow, Simultanous shear layer reattachment and detached shear layer flow pattern. The time of persistence (in percentage) for each flow pattern is estimated over a sufficiently long period of observation time to identify the most influential, predominant flow pattern. Though these patterns are identical for square-square and square-circular tandem configurations, their order of predominance is different for both the configurations.

Response of a Circular Cylinder Fitted With Permeable Meshes Acting as VIV Suppressors

2014 ◽  
Author(s):  
Murilo M. Cicolin ◽  
Gustavo R. S. Assi
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Dynamic Response ◽  
Flow Direction ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Vortex Induced Vibrations ◽  
Different Types ◽  
Cylindrical Tubes ◽  
Low Mass

Experiments have been carried out on models of rigid circular cylinders fitted with three different types of permeable meshes to investigate their effectiveness in the suppression of vortex-induced vibrations (VIV). Measurements of the dynamic response are presented for models with low mass and damping which are free to respond in the cross-flow direction. Results for two meshes made of ropes and cylindrical tubes are compared with the VIV response of a bare cylinder and that of a known suppressor called the “ventilated trousers” (VT). All three meshes achieved an average 50% reduction of the response when compared with that of the bare cylinder. The sparse mesh configuration presented a similar behaviour to the VT, while the dense mesh produced considerable VIV response for an indefinitely long range of reduced velocity. Reynolds number ranged from 1,000 to 10,000 and reduced velocity was varied between 2 and 13.

Fluctuating Lift Forces of the Karman Vortex Streets on Single Circular Cylinders and in Tube Bundles: Part 1—The Vortex Street Geometry of the Single Circular Cylinder

1972 ◽  
Vol 94 (2) ◽  
pp. 603-610 ◽  
Author(s):  
Y. N. Chen
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Vortex Street ◽  
Circular Cylinders ◽  
Number Range ◽  
Pressure Drag ◽  
Minimum Drag ◽  
Vortex Streets ◽  
Karman Vortex ◽  
Better Than

The geometry of the vortex street for single circular cylinders will be calculated from the measured values given by numerous investigators about the steady pressure drag coefficient and the Strouhal number, whereby the Kronauer minimum drag criterion comes into use. The calculated results will be compared with the experimentally determined ones. A good agreement can be achieved between both. The Bearman-Strouhal number SB = fh/Us will also be computed as a function of the Reynolds number. Furthermore a new wake number C = fh2/Γ will be introduced. It will be shown that this new number is universally much better than the Bearman one. It remains constant at 0.165 for an ideal flow over the whole Reynolds number range up to the highest value of 107 ever measured hitherto.

A Basic Research on the VIV Response of Rotating Circular Cylinder in Flow

2011 ◽  
Author(s):  
Chang-Kyu Rheem ◽  
Koichiro Kato
Keyword(s):  
Circular Cylinder ◽  
Natural Frequency ◽  
Vortex Shedding ◽  
Oscillation Amplitude ◽  
Water Channel ◽  
Basic Research ◽  
Rotation Frequency ◽  
Circular Cylinders ◽  
Discrete Vortex ◽  
Rotating Circular Cylinder

The characteristics of VIV response of rotating circular cylinders in flow had been investigated by both experiment and numerical simulation. In the experiment, the motions of a flexible circular cylinder pipe installed in a circulation water channel were measured. In simulation, a Discrete Vortex Method had been used to estimate hydrodynamic forces acting on a rigid circular cylinder. When a cylinder rotates in flow, a rotation frequency becomes important added to natural frequency and vortex shedding frequency. The deflection of a flexble pipe peaked when the frequency ratio of rotation frequency to natural frequency was between 1.0 and 1.5. This is similar to increment of oscillation amplitude by a resonance of natural vibration and vortex shedding. The peak oscillation frequency of a rotating circular cylinder in flow decreased with increase in rotation number. The main axis of cylinder oscillation turned in the rotation direction.

Effect of Marine Growth on an Elastically Mounted Circular Cylinder

2008 ◽  
Author(s):  
Kjetil Skaugset ◽  
Rolf Baarholm
Keyword(s):  
Circular Cylinder ◽  
Dynamic Response ◽  
Parametric Study ◽  
Circular Cylinders ◽  
Laboratory Environment ◽  
Marine Risers ◽  
Vortex Induced Vibrations ◽  
Helical Strakes ◽  
Viv Suppression

The Riser and Mooring project of the Norwegian Deepwater Programme (NDP) has undertaken a parametric study on the influence of marine growth on the effectiveness of helical strakes to suppress vortex-induced vibrations on circular cylinders. Helical strakes are one of the most commonly used devices to suppress vortex-induced vibrations (VIV) on marine risers. The aim is provide guidance on the effect marine growth has on the dynamic response of a riser fitted with such VIV suppression devices. The tests were conducted at MARINTEK in a controlled laboratory environment. Artificial marine growth was modelled, manufactured and tested. Both hard and soft marine growth of various heights and coverages were tested. The present paper discusses some results obtained in this test campaign.

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