scholarly journals The Hydrodynamic Behavior of Vortex Shedding behind Circular Cylinder in the Presence of Group Focused Waves

Fluids ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 4
Author(s):  
Iskander Abroug ◽  
Nizar Abcha ◽  
Fahd Mejri ◽  
Emma Turki ◽  
Elena Ojeda
Keyword(s):  
Circular Cylinder ◽  
Wavelet Analysis ◽  
Vortex Shedding ◽  
Intermediate Water ◽  
Hydrodynamic Behavior ◽  
Powerful Approach ◽  
Wave Trains ◽  
Lock In ◽  
Subharmonic Frequency ◽  
Approach Time

Vortex shedding behind an elastically mounted circular cylinder in the presence of group focused waves propagating upstream was investigated using a classical approach (time series and FFT) and nonclassical approach (complex 2D Morlet wavelets). Wavelet analysis emerged as a novel solution in this regard. Our results include wave trains with different nonlinearities propagating in different water depths and derived from three types of spectra (Pierson–Moskowitz, JONSWAP (γ = 3.3 or γ = 7)). It was found that the generated wave trains could modify regimes of shedding behind the cylinder, and subharmonic frequency lock-in could arise in particular situations. The occurrence of a lock-in regime in the case of wave trains propagating in intermediate water locations was shown experimentally even for small nonlinearities. Moreover, the application of time-localized wavelet analysis was found to be a powerful approach. In fact, the frequency lock-in regime and its duration could be readily identified from the wavelet-based energy and its corresponding ridges.

Flow Past Oscillating Cylinders

1993 ◽  
Vol 115 (4) ◽  
pp. 197-205 ◽  
Author(s):  
R. W. Yeung ◽  
M. Vaidhyanathan
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Vortex Method ◽  
Boundary Integral ◽  
Preliminary Evaluation ◽  
Computational Results ◽  
Variable Boundary ◽  
Marine Risers ◽  
Boundary Integral Formulation ◽  
Lock In

The phenomenon of vortex shedding by oscillating cylinders is a complex one. Its understanding is, however, of utmost importance in marine-related engineering, particularly in connection with motions of deep submersibles and marine risers. In this paper, computational results are presented so that the behavior of the shedding as a function of certain parameter space can be elucidated. A methodology based on the random vortex method and a complex-variable boundary-integral formulation is used to study both forced and vortex-induced oscillations of a circular cylinder. Preliminary evaluation of this method indicates that it has been successful in predicting a number of experimentally observed behavior, among which the phenomena of “lock-in” associated with oscillations of the cylinder are well captured.

Synchronized Vibrations of a Circular Cylinder in Cross Flow at Supercritical Reynolds Numbers1

2003 ◽  
Vol 125 (1) ◽  
pp. 97-108 ◽  
Author(s):  
Tsutomu Kawamura ◽  
Toshitsugu Nakao ◽  
Masanori Takahashi ◽  
Masaaki Hayashi ◽  
Kouichi Murayama ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Excited Vibration ◽  
Karman Vortex ◽  
Lock In

Synchronized vibrations of a circular cylinder in a water cross flow at supercritical Reynolds numbers were measured. Turbulence intensities were varied to investigate the effect of the Strouhal number on the synchronization range. Self-excited vibration in the drag direction due to symmetrical vortex shedding began only when the Strouhal number was about 0.29, at a reduced velocity of 1.1. The reduced velocities at the beginning of lock-in vibrations caused by Karman vortex shedding decreased from 1.5 to 1.1 in the drag direction and from 2.7 to 2.2 in the lift direction, as the Strouhal number increased from 0.29 to 0.48.

Calculation of the Vibration of an Elastically Mounted Cylinder Using Experimental Data From Forced Oscillation

1983 ◽  
Vol 105 (2) ◽  
pp. 225-229 ◽  
Author(s):  
T. Staubli
Keyword(s):  
Experimental Data ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Forced Oscillation ◽  
Structure Interaction ◽  
Fluid Forces ◽  
Sinusoidal Motion ◽  
Nonlinear Relation ◽  
Lock In ◽  
Excitation Method

Several methods for investigating the fluid-structure interaction of bodies vibrating due to vortex shedding are compared briefly. The advantage of employing a forced-displacement excitation method is asserted. This method has been adopted to measure the response of the fluid forces acting on an oscillating circular cylinder in crossflow. With the results of these measurements, and a calculation based on the assumption of sinusoidal motion, the vibrations of a freely oscillating cylinder are predicted in the lock-in range. It is shown that hysteresis effects, which are observed in experiments with elastically mounted cylinders of certain damping and mass ratios, are caused by the nonlinear relation between the fluid force and the amplitude of oscillation.

Studying Three-Dimensionality of Vortex Shedding Behind a Circular Cylinder with Mems Sensors

2007 ◽  
Vol 23 (2) ◽  
pp. 107-116 ◽  
Author(s):  
J. K. Tu ◽  
J. J. Miau ◽  
Y. J. Wang ◽  
G. B. Lee ◽  
C. Lin
Keyword(s):  
Aspect Ratio ◽  
Circular Cylinder ◽  
Wavelet Analysis ◽  
Vortex Shedding ◽  
Reynolds Numbers ◽  
Splitter Plate ◽  
Mems Sensors ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

AbstractExperiments were made with 14 MEMS sensors situated along the span of a circular cylinder whose aspect ratio was 5. The signals of the MEMS sensors were sampled simultaneously as flow over the cylinder at Reynolds numbers of 104. The results of Wavelet analysis of the signals indicate that the percentage of time during which strong three-dimensionality of vortex shedding was detected is about 10%.As noted, strong three-dimensionality took place when the fluctuating amplitude of the signals was severely modulated and the vortex shedding frequency reduced appeared abnormally high or low. Further noted was that the addition of a splitter plate of 0.5 or one diameter in length behind the circular cylinder was not able to suppress the three-dimensionality of the flow.

An experimental study of pressure fluctuations on fixed and oscillating square-section cylinders

1982 ◽  
Vol 119 ◽  
pp. 297-321 ◽  
Author(s):  
P. W. Bearman ◽  
E. D. Obasaju
Keyword(s):  
Experimental Study ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Vortex Shedding ◽  
Pressure Fluctuations ◽  
The Body ◽  
Front Face ◽  
Side Face ◽  
Lock In ◽  
Fixed Cylinder

Measurements are presented of the pressure fluctuations acting on a stationary squaresection cylinder, with the front face normal to the flow, and one forced to oscillate, transverse to a flow, at amplitudes up to 25% of the length of a side. The range of reduced velocities investigated, 4–13, includes the vortex lock-in regime. At lock-in the amplification of the coefficient of fluctuating lift is found to be much less than that found for a circular cylinder. The variation of the phase angle, between lift and displacement, is also different from that measured on a circular cylinder, and vortex-induced oscillations are possible only at the high-reduced-velocity end of the lock-in range. At reduced velocities sufficiently far below lock-in the natural vortex-shedding mode is suppressed and vortices are found to form over the side faces at the body frequency. Intermittent reattachment occurs over the side faces and, for an amplitude of oscillation equal to 10% of the length of a side face, the time-mean drag coefficient can be reduced to 60% of its fixed-cylinder value.

scholarly journals Vortex Shedding from a Circular Cylinder with Spiral Fin

2008 ◽  
Vol 3 (6) ◽  
pp. 787-795 ◽  
Author(s):  
Hiromitsu HAMAKAWA ◽  
Keisuke NAKASHIMA ◽  
Tomohiro KUDO ◽  
Eiichi NISHIDA ◽  
Tohru FUKANO
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding

Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

1980 ◽  
Vol 101 (4) ◽  
pp. 721-735 ◽  
Author(s):  
Masaru Kiya ◽  
Hisataka Tamura ◽  
Mikio Arie
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Shear Flow ◽  
Vortex Shedding ◽  
Transverse Velocity ◽  
Number Range ◽  
Uniform Shear ◽  
Reynolds Number Range ◽  
Moderate Reynolds Number ◽  
Shear Parameter

The frequency of vortex shedding from a circular cylinder in a uniform shear flow and the flow patterns around it were experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter and the approaching velocity at its centre, ranged from 35 to 1500. The shear parameter, which is the transverse velocity gradient of the shear flow non-dimensionalized by the above two quantities, was varied from 0 to 0·25. The critical Reynolds number beyond which vortex shedding from the cylinder occurred was found to be higher than that for a uniform stream and increased approximately linearly with increasing shear parameter when it was larger than about 0·06. In the Reynolds-number range 43 < Re < 220, the vortex shedding disappeared for sufficiently large shear parameters. Moreover, in the Reynolds-number range 100 < Re < 1000, the Strouhal number increased as the shear parameter increased beyond about 0·1.

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