The effect of arrangement of two circular cylinders on the maximum efficiency of Vortex-Induced Vibration power using a Scale-Adaptive Simulation model

2014 ◽  
Vol 49 ◽  
pp. 654-666 ◽  
Author(s):  
Javad Farrokhi Derakhshandeh ◽  
Maziar Arjomandi ◽  
Bassam Dally ◽  
Benjamin Cazzolato
Keyword(s):  
Simulation Model ◽  
Circular Cylinders ◽  
Maximum Efficiency ◽  
Vortex Induced Vibration ◽  
Adaptive Simulation

Surface Roughness Effects on Circular Cylinders at High Reynolds Numbers

2002 ◽  
Author(s):  
M. Eaddy ◽  
W. H. Melbourne ◽  
J. Sheridan
Keyword(s):  
Surface Roughness ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Flow Induced Vibration ◽  
Roughness Effects ◽  
Vortex Induced Vibration ◽  
Smooth Cylinder ◽  
Lift Forces ◽  
High Reynolds ◽  
Effect Of Surface

The problem of flow-induced vibration has been studied extensively. However, much of this research has focused on the smooth cylinder to gain an understanding of the mechanisms that cause vortex-induced vibration. In this paper results of an investigation of the effect of surface roughness on the cross-wind forces are presented. Measurements of the sectional RMS fluctuating lift forces and the axial correlation of the pressures for Reynolds numbers from 1 × 105 to 1.4 × 106 are given. It was found that surface roughness significantly increased the axial correlation of the pressures to similar values found at high subcritical Reynolds numbers. There was little effect of the surface roughness on the sectional lift forces. The improved correlation of the vortex shedding means rough cylinders will be subject to larger cross-wind forces and an increased possibility of vortex-induced vibration compared to smooth cylinders.

scholarly journals Scale Adaptive Simulation Model for the Darrieus Wind Turbine

2016 ◽  
Vol 753 ◽  
pp. 022050 ◽  
Author(s):  
K Rogowski ◽  
M O L Hansen ◽  
R Maroński ◽  
P Lichota
Keyword(s):  
Simulation Model ◽  
Wind Turbine ◽  
Adaptive Simulation

Experimental Study About the Influence of the Free End Effects on Vortex-Induced Vibration of Floating Cylinder With Low Aspect of Ratio

2016 ◽  
Author(s):  
Dennis M. Gambarine ◽  
Felipe P. Figueiredo ◽  
André L. C. Fujarra ◽  
Rodolfo T. Gonçalves
Keyword(s):  
Degrees Of Freedom ◽  
Transverse Direction ◽  
Lift Coefficient ◽  
Circular Cylinders ◽  
Force Coefficient ◽  
End Effects ◽  
Recirculation Bubble ◽  
Vortex Induced Vibration ◽  
Visualization Experiments ◽  
Structural Mass

Experiments regarding free-end effects on vortex-induced vibration (VIV) of floating circular cylinders with low aspect ratio were carried out in a towing tank. Four cylinders with low aspect of ratio, L/D = 2 (Length / Diameter) were tested with different free end corner shape types, namely by the relation between chamfer rounding radius (r) divided by the radius of cylinder (R) (r/R = 0.0, 0.25, 0.5 and 1.0). For the initial case, r/R = 0.0 represents flat tip and r/R = 1.0 the hemispherical tip. The aims were to understand the effect of different free-end types on VIV behavior of cylinders. The floating circular cylinders, i.e. unit mass ratio m* = 1(structural mass/displaced fluid mass) were elastically supported by a set of linear springs to provide low structural damping on the system and allow six degrees of freedom. The range of Reynolds number covered 3,000 ≤ Re ≤ 20,000. To conclude, cylinder with r/R = 0.25, shows lower amplitudes in transverse direction. The same occurs for the cylinder r/R = 0, but for amplitudes of vibration in in-line direction. Behaviors of the vibration frequencies in in-line and transverse direction don’t have significantly differences. Regarding force coefficient, flat tip cylinder (r/R = 0) presents higher values compared to the others however, for the lift coefficient, results converge in similar values for the same velocities that were observed higher transverse amplitudes. The visualization experiments show an expressive reduction of the recirculation bubble for r/R = 0.5 model compared with the flat tip, can therefore justify the lower values for this model obtained in draft amplitudes and drag coefficient compared with the flat tip model.

Experimental Study on Vortex-Induced Vibration of Floating Circular Cylinders With Low Aspect Ratio

2014 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
André L. C. Fujarra
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
Water Channel ◽  
Circular Cylinders ◽  
Structural Damping ◽  
End Effects ◽  
Vortex Induced Vibration ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Ratio Range

Experiments regarding vortex-induced vibration on floating circular cylinders with low aspect ratio were carried out in a recirculation water channel. The floating circular cylinders were elastic supported by a set of linear springs to provide low structural damping on the system. Eight different aspect ratios were tested, namely L/D = 0.2, 0.3, 0.4, 0.5, 0.75, 1.0, 1.5 and 2.0. These aspect ratios were selected to cover the aspect ratio range of the main offshore circular platforms, such as spar and monocolumn. The aims were understanding the VIM of such platforms; due to this, the cylinders were floating, or m* = 1. The range of Reynolds number covered 2,800 < Re < 55,400. The amplitude results showed a decrease in amplitude with decreasing aspect ratio in both directions. The frequency results confirm a different behavior for cylinders with L/D ≤ 0.5; in these cases, the cylinder free-end effects were predominant. The resonant behaviour was no longer observed for L/D ≤ 0.2. The decrease in Strouhal number with decreasing aspect ratio is also verified. All the results presented here complement the work presented previously for stationary circular cylinder with low aspect ratio presented by Gonçalves et al. (2013), Experimental Study on Flow around Circular Cylinders with Low Aspect Ratio, OMAE2013-10454.

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