scholarly journals Dynamics of the Tip Vortices in the Wake Behind a Circular Cylinder of Finite Length

2020 ◽  
Vol 328 ◽  
pp. 05008
Author(s):  
Václav Uruba ◽  
Pavel Procházka
Keyword(s):  
Circular Cylinder ◽  
Finite Length ◽  
Ground Plane ◽  
Cross Flow ◽  
Cylinder Axis ◽  
Thin Boundary Layer ◽  
Time Resolved ◽  
Vortical Structures ◽  
Tip Vortices ◽  
Piv Technique

The dynamics of the tip vortices in the wake behind a wall-mounted finite-length circular cylinder of the aspect ratio 2 was studied experimentally using time resolved stereo PIV technique. The cylinder was mounted normal to a ground plane and it was subjected to a cross-flow with thin boundary layer developed on the wall, the Reynolds number based on inflow velocity and cylinder diameter was 9.7 thousands. The dynamics of tip vortices were analysed using the POD method applied to the plane perpendicular to the flow close to the cylinder. Besides the decaying power spectrum, slower that the Kolmogorov-type one, the two distinct frequencies were detected on Strouhal numbers 0.09 and 0.15. These frequencies could be linked to the vortical structures dynamics in the wake. The frequency Sh = 0.15 corresponds to predominantly spanwise vortices dynamics with anti-symmetrical patterns with respect to the cylinder axis, while the frequency Sh = 0.09 corresponds to mainly streamwise vortical structures dynamics with symmetrical patterns respectively. Thus, the von Kármán vortex street was detected on Strouhal frequency 0.15.

scholarly journals Near Wake behind Circular Cylinder of Finite Length on Ground Plane.

1997 ◽  
Vol 63 (613) ◽  
pp. 2923-2929
Author(s):  
Shiki OKAMOTO ◽  
Kazumi TSUNODA ◽  
Eiji OKADA ◽  
Junichi FUJITA
Keyword(s):  
Circular Cylinder ◽  
Finite Length ◽  
Ground Plane ◽  
Near Wake

scholarly journals Validation of large eddy simulation of flow behind a circular cylinder

2021 ◽  
Vol 345 ◽  
pp. 00013
Author(s):  
Martin Isoz ◽  
Tomáš Hlavatý ◽  
Václav Uruba ◽  
Pavel Procházka
Keyword(s):  
Mathematical Model ◽  
Circular Cylinder ◽  
Large Eddy Simulation ◽  
Dynamical Behavior ◽  
Cross Flow ◽  
Numerical Data ◽  
Time Resolved ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mathematical Model

The flow in the wake behind a circular cylinder in a cross-flow at Reynolds number of 4815 was studied both experimentally and via mathematical modeling. The mathematical model was performed as a Large Eddy Simulation (LES), while the experiments were carried out using the time-resolved variant of the Particle Image Velocimetry (PIV) method. Both the simulation and experiment took into account the dynamical aspects of the studied phenomenon, which enabled a detailed validation of the mathematical model. The overall statistical properties of the simulated flow were validated via comparing the time-averaged measured and computed velocity and vorticity fields. To validate the dynamical behavior, the velocity spectra were examined first. Next, the Proper Orthogonal Decomposition (POD) of the spatio-temporal velocity data was performed on both the experimental and numerical data and a comparison of the obtained energetic modes was carried out. All the performed validations have shown a satisfactory agreement between the simulation and the experiment.

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.

Experimental Investigation of Cavitation Behind a Circular Cylinder in Cross-Flow

2017 ◽  
Vol 9 (3) ◽  
Author(s):  
Pankaj Kumar ◽  
Shamit Bakshi ◽  
Dhiman Chatterjee
Keyword(s):  
Circular Cylinder ◽  
Growth Phase ◽  
Cross Flow ◽  
Cavitation Number ◽  
Self Similarity ◽  
Time Resolved ◽  
Expansion Phase ◽  
Cavity Collapse ◽  
Number Dynamics ◽  
Gradual Expansion

Cavitation behind a circular cylinder is studied with the aid of highly time-resolved images at a constant Reynolds number of 64,000. Apart from recording the overall cavitation activity behind the cylinder, the study also delves into the dynamics of individual cavities. The length of cavity scales with cavitation number and this scaling is similar to the existing results obtained in flow regimes different from that presented here. Dynamics of individual cavities show distinct phases of cavity formation, growth, and collapse. At lower cavitation numbers, cavity collapse was followed by a rebounce. Variation of area normalized by the length of cavity shows self similarity in the growth phase of cavities for different cavitation numbers. Thus, the cavity length is the suitable length scale for dynamics of cavities, at least for the growth phase. The cavity lifetime scales inversely with the square of cavitation number. Dynamics of individual small cavity captured at higher frame rates was found to be similar to that of an isolated bubble. In this case, a rapid collapse follow a more gradual expansion phase, unlike that shown by larger cavities.

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