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.

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.

A visual study of the flow around an oscillating circular cylinder at low Keulegan–Carpenter numbers and low Stokes numbers

1990 ◽  
Vol 211 ◽  
pp. 157-182 ◽  
Author(s):  
M. Tatsuno ◽  
P. W. Bearman
Keyword(s):  
Circular Cylinder ◽  
Flow Visualization ◽  
Flow Separation ◽  
Three Dimensional ◽  
Stokes Number ◽  
Flow Patterns ◽  
Half Cycle ◽  
Visual Study ◽  
Sinusoidal Oscillations ◽  
Dimensional Instability

The structures of the flow induced by a circular cylinder performing sinusoidal oscillations in a fluid at rest are investigated by means of flow visualization. The experiments are carried out at Keulegan–Carpenter numbers between 1.6 and 15 and at Stokes numbers between 5 and 160. Above a certain value of Keulegan–Carpenter number, depending on the Stokes number, some asymmetry appears in the flow separation and the associated vortex development behind the cylinder. The two vortices that are developed in a half cycle differ in strength and may be convected in different directions. This results in a fascinating set of flow patterns. Eight different regimes of flow can be identified within the ranges of Keulegan–Carpenter number and Stokes number studied. Furthermore, most of the resulting flows show a three-dimensional instability along the axis of the cylinder. Measurements of the wavelength of these disturbances are presented.

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.

Flow Around Finite Circular and Square Cylinders in an Open Channel

2009 ◽  
Author(s):  
S. S. Paul ◽  
M. Agelinchaab ◽  
M. F. Tachie
Keyword(s):  
Circular Cylinder ◽  
Proper Orthogonal Decomposition ◽  
Large Scale ◽  
Saddle Points ◽  
Water Channel ◽  
Orthogonal Decomposition ◽  
Square Cylinder ◽  
Square Cylinders ◽  
Pod Analysis ◽  
Proper Orthogonal

An experimental investigation was performed to study the structure of the flow field around finite circular and square cylinders in a water channel. Detailed velocity measurements using a particle image velocimetry (PIV) system and proper orthogonal decomposition (POD) analysis were conducted to examine the structures in the near-wake region. Iso-contours and profiles of mean velocities and some turbulent quantities at various streamwise locations were reported. The proper orthogonal decomposition was applied to provide insight into the structure of the flow. The results show that the vortex in the square cylinder is bigger and extends to cover part of the free end of the cylinder. There is also an up-wash flow from the base of the cylinders to form saddle points. The saddle point in the square cylinder is closer to the free end than in the circular cylinder. The low order reconstructed turbulent intensities from POD show that the square cylinder has more large scale structures than the circular cylinder.

An experimental study of the instability of a stably stratified free shear layer

1975 ◽  
Vol 71 (3) ◽  
pp. 563-575 ◽  
Author(s):  
Yu-Hwa Wang
Keyword(s):  
Flow Field ◽  
Shear Layer ◽  
Richardson Number ◽  
Open Channel ◽  
Salt Water ◽  
Stability Boundary ◽  
Water Channel ◽  
Free Shear Layer ◽  
Circulating Water ◽  
The Stability

A stably stratified free shear layer is created in a continuously circulating water channel in the laboratory. Two streams of salt water of different concentrations are brought together at the entrance to the open channel and a layered uniform flow field with a distinct sharp interface is produced in the test section. The maximum density difference between the two layers is Δρx = 0·0065ρw, where ρw is the density of water. The velocity of each layer can be adjusted at will to create free shear across the interface. At the end of the open channel, a mechanical device to separate the layers for recirculation is provided. The resulting flow field has a viscous region approximately 15 times larger than the scale of the salinity diffusion layer. Visual observations are made with hydrogen bubbles and dye traces. Interfacial waves are initiated by artificial excitation. The perturbation frequencies range from 0·476 to 10·40Hz. The measured wavelengths range from 0·46 to 3·02 cm. Damped waves as well as growing waves are observed at various exciting frequencies. Velocity profiles and instantaneous velocities are measured by a hot-film anemometer designed for use in salt water. Experimental values of the Richardson number, the dominant parameter characterizing the instability process, range from 1·23 to 14·45. The stability boundary is determined experimentally. Comparisons with Hazel's numerical results and the earlier results of Scotti & Corcos for low values of the Richardson number are also made.

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