Wave-Current Interaction with a Vertical Cylinder in Cross Flow: A Semi-Analytical Approach

2009 ◽  
Author(s):  
I.K. Chatjigeorgiou ◽  
S.A. Mavrakos ◽  
N.I. Xiros
Keyword(s):  
Analytical Approach ◽  
Cross Flow ◽  
Vertical Cylinder ◽  
Current Interaction

Wave-current interaction effects on waves and their loads on a vertical cylinder

2021 ◽  
pp. 103832
Author(s):  
Amin Ghadirian ◽  
Malene Hovgaard Vested ◽  
Stefan Carstensen ◽  
Erik Damgaard Christiensen ◽  
Henrik Bredmose
Keyword(s):  
Vertical Cylinder ◽  
Interaction Effects ◽  
Current Interaction

Wave interaction with a vertical cylinder: spanwise flow patterns and loading

2002 ◽  
Vol 460 ◽  
pp. 93-129 ◽  
Author(s):  
Y. YANG ◽  
D. ROCKWELL
Keyword(s):  
Free Surface ◽  
Flow Velocity ◽  
Large Scale ◽  
Cross Flow ◽  
Vertical Cylinder ◽  
Two Dimensional ◽  
Streamwise Vorticity ◽  
Near Wake ◽  
Cross Flow Velocity ◽  
The Moment

A vertical cylinder is located in a free-surface wave, and a two-camera version of high-image-density particle image velocimetry is employed to characterize the spanwise modes of the flow structure in terms of instantaneous velocity and vorticity. These modes are classified according to organized patterns of velocity in the near wake, and are further interpreted in terms of distinctive arrangements of streamwise vorticity concentrations.At low Keulegan–Carpenter number, which corresponds to small wave height, locally two-dimensional vortices having small scale and circulation tend to form as a symmetrical pair and remain attached, or in close proximity, to the surface of the cylinder. Along the span of the cylinder, the near wake shows either a sinuous S or a unidirectional U mode. The spanwise wavelength λ of the S modes, relative to the cylinder diameter D, lies in the range 1 [lsim ] λ/D [lsim ] 4:5. These values of λ/D represent the spacing between extrema of patterns of cross flow velocity, as well as between clusters of streamwise vorticity of like sign. As the free surface is approached, the value of λ/D scales with the ratio of the minor to major axes of the elliptical particle trajectory of the wave.At moderate values of the Keulegan–Carpenter number, locally two-dimensional vortices having large scale and circulation are shed from the cylinder in an asymmetric arrangement. The corresponding spanwise mode represents the phase variation of this shedding along the span of the cylinder. These sinuous S modes involve large-scale distortions of patterns of both cross flow velocity and streamwise vorticity, which have wavelengths in the range 10 [lsim ] λ/D [lsim ] 110, in contrast to the spacing between individual concentrations of vorticity, which is 1:5D to 4D. Remarkably, it is possible to attain a unidirectional U mode, whereby the phase of the locally two-dimensional vortex shedding is preserved along the entire extent of the cylinder. Signatures of the moments due to the transverse and in-line forces on the cylinder were acquired simultaneously with the patterns of instantaneous velocity and vorticity. Severe modulations of the moment due to the transverse force are associated with spontaneous transformations between basic forms of the sinuous S and unidirectional U modes. The overall form of the signature of the moment due to the in-line force is, however, not generally affected by the spontaneous transformation between modes, but distortion of its peaks is evident.

Aerodynamic Influence of Endwall Fences Located in the Vicinity of the Leading Edge-Endwall Junction of Nozzle Guide Vanes

2011 ◽  
Author(s):  
Zeki Ozgur Gokce ◽  
Cengiz Camci
Keyword(s):  
Total Pressure ◽  
Numerical Study ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Vertical Cylinder ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Horseshoe Vortices ◽  
Nozzle Guide

Secondary flow characteristics like horseshoe vortices and related total pressure losses decrease turbine efficiency. Computerized simulations of potentially favorable modifications in turbine systems could provide a fast, numerical and inexpensive method of evaluating their effects on flow properties: This paper consists of a comparative numerical study of the flow characteristics of a domain containing a vertical cylinder subjected to cross flow and upstream endwall modifications. Analyzing the flow around a turbine nozzle guide vane (NGV) could be simplified by modeling it as a vertical cylinder with a diameter proportional to the leading edge diameter of the blade, and adding upstream endwall fences of varying dimensions and alignments could attenuate the development of a horseshoe vortex. A commercial computational fluid dynamics (CFD) software package, Fluent, was used for the numerical analysis. To validate the modeling strategy, experimental data previously reported in the literature for conventional cylinders in cross flow were compared to the current predictions. A grid independence study was also performed. The lateral distance between the two legs of the horseshoe vortex downstream of the cylinder was decreased by 7% to 14%. All fence types effectively changed the location of the main horseshoe vortex roll-up. The height of the fence was more influential than the length of the fence in modifying flow characteristics. The existence of the fences slightly increased the mass-averaged total pressure loss far downstream of the cylinder; however, beneficial near-fence flow characteristics were observed in all cases. Also, it was noted that an endwall fence could possibly result in decreased interaction between the horseshoe vortices created by consecutive blades in a row of NGV blades, which would be expected to result in improved flow conditions within actual turbine passages.

Experimental study on the solitary wave-current interaction and the combined forces on a vertical cylinder

2021 ◽  
Vol 236 ◽  
pp. 109569
Author(s):  
Zhiying Yang ◽  
Bo Huang ◽  
Azhen Kang ◽  
Bing Zhu ◽  
Jiayi Han ◽  
...  
Keyword(s):  
Experimental Study ◽  
Solitary Wave ◽  
Vertical Cylinder ◽  
Current Interaction

Experimental Investigation of Vortex-Induced Vibration on an Inclined Circular Cylinder

2007 ◽  
Author(s):  
Andre´ L. C. Fujarra ◽  
Ju´lio R. Meneghini ◽  
Ricardo Franciss ◽  
Guilherme R. Franzini ◽  
Ivan Korkischko
Keyword(s):  
Circular Cylinder ◽  
Flow Direction ◽  
Water Channel ◽  
Cross Flow ◽  
Vertical Cylinder ◽  
Elastic Base ◽  
Cylinder Axis ◽  
Vortex Induced Vibrations ◽  
Uniform Current ◽  
Drag And Lift

This paper presents experimental results of vortex-induced oscillations of an inclined circular cylinder mounted on an elastic base. Models are mounted on an air-bearing elastic base, instrumented with strain gages, accelerometers and a load cell. The experiments were carried out on a water channel facility at NDF-EPUSP. The elastic base has low structural damping and is free to oscillate only in the cross-flow direction. The cylinder axis is inclined in relation to the current. New measurements on the dynamic response oscillations of this inclined cylinder, due to vortex-induced vibrations (VIV), are compared with previous experiments on a vertical cylinder. VIV is investigated by conducting experiments in two ways: first, the cylinder is maintained vertical on the elastic base, with a uniform current normal to its axis, and the response curve is obtained; subsequently, the investigation is carried out changing the angle of inclination from 0 to 45 degrees in relation to vertical. The results for a vertical cylinder are in accordance with other literature measurements for mass ratio m*=2. For the inclined model, using the decomposition of the flow on the direction normal to cylinder axis, the results for amplitude, drag and lift coefficients are consistent with the vertical cylinder.

scholarly journals Application of Control Rods for Passively Suppressing Cross-Flow VIV of an Inclined Flexible Cylinder

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Wanhai Xu ◽  
Wenqi Qin ◽  
Yan Lu
Keyword(s):  
Inclination Angle ◽  
Cross Flow ◽  
Vertical Cylinder ◽  
Outer Wall ◽  
Dominant Frequency ◽  
Dominant Mode ◽  
Water Tank ◽  
Flexible Cylinder ◽  
Control Rod ◽  
Control Rods

Laboratory experiments were conducted to investigate the cross-flow (CF) vortex-induced vibration (VIV) suppression effectiveness of an inclined flexible cylinder by using control rods. 4 control rods with a diameter of 0.25D (where D is the diameter of the main cylinder) and outer wall distance between the control rod and the main cylinder of 0.50D were attached to the main cylinder. The uniform flow was simulated by towing the cylinder models along a water tank. The corresponding flow velocity ranged from 0.05 to 1.00 m/s with an interval of 0.05 m/s. Two inclination angle cases (a = 0° and 45°) were selected in the experiment. The inclination angle a referred to the angle between the main cylinder axis and the plane orthogonal to the oncoming flow. The experimental results indicate that the control rods can effectively mitigate the CF VIV responses, such as the bending strain, displacement amplitude, dominant frequency, and dominant mode, of both the vertical (a = 0°) and inclined (a = 45°) flexible cylinders. The suppression effectiveness of the control rods on the 45° inclined cylinder is as good as that on the vertical cylinder, and the average suppressing efficiency of the control rods is even better on the 45° inclined cylinder.

The Dynamics of TAT Process

2014 ◽  
Vol 35 (2) ◽  
pp. 103-133 ◽  
Author(s):  
Benoît Verdon ◽  
Catherine Chabert ◽  
Catherine Azoulay ◽  
Michèle Emmanuelli ◽  
Françoise Neau ◽  
...  
Keyword(s):  
Defense Mechanisms ◽  
Analytical Approach ◽  
Therapeutic Process ◽  
Practice Research ◽  
Rorschach Test ◽  
Mental Functioning ◽  
Projective Tests ◽  
The Subject ◽  
Latent Content ◽  
Rigorous Method

After many years of clinical practice, research and the teaching of projective tests, Shentoub and her colleagues (Debray, Brelet, Chabert & al.) put forward an original and rigorous method of analysis and interpretation of the TAT protocols in terms of psychoanalysis and clinical psychopathology. They developed the TAT process theory in order to understand how the subject builds a narrative. Our article will emphasize the source of the analytical approach developed by V. Shentoub in the 1950s to current research; the necessity of marking the boundary between the manifest and latent content in the cards; the procedure for analyzing the narrative, supported by an analysis sheet for understanding the stories' structure and identifying the defense mechanisms; and how developing hypotheses about how the mental functions are organized, as well as their potential psychopathological characteristics; and the formulation of a diagnosis in psychodynamic terms. In conjunction with the analysis and interpretation of the Rorschach test, this approach allows us to develop an overview of the subject's mental functioning, taking into account both the psychopathological elements that may threaten the subject and the potential for a therapeutic process. We will illustrate this by comparing neurotic, borderline, and psychotic personalities.

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