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Abstract
The twodegreeoffreedom (2DOF) vortexinduced vibration (VIV) of a circular cylinder with varying inline to crossflow natural frequency ratios (f* = fnx/fny) is studied using a threedimensional (3D) computational fluid dynamics (CFD) approach. Numerical simulation is carried out for a constant mass ratio of 2 at a fixed Reynolds number Re = 500. The reduced velocity ranges from 2 to 12. Three natural frequency ratios are considered, i.e., f* = 1, 1.5 and 2. The structural damping is set to zero to maximise the response of the cylinder. The main objective of this study is to investigate the effect of f* on the 2DOF VIV responses and the 3D characteristics of the flow. It is discovered that there is a significant increase in the vibration amplitude, and the peak amplitude shifts to a higher reduced velocity when f* increases from 1 to 2. A singlepeak crossflow response is observed for the identical inline and crossflow mass ratios when f* = 2. Dual resonance is found to exist over the range of f* studied. The preferable trajectories of the cylinder in the lockin range are counterclockwise figureeight orbits. Oblique figureeight trajectories appear at Vr = 6, 7 and 8 when f* = 1. The third harmonic component which is observed in the lift fluctuation increases with f*. The correlation decreases in the lockin range and reaches its minimum value around the transition region between the lockin and postlockin ranges. Three vortex shedding modes (2S, P + S and 2P) appear in the present simulation. A dominant P + S mode is associated with the oblique figureeight trajectories. Variation of vortex shedding flows along the cylinder is observed leading to the poor correlation of the sectional lift forces.
Original language  English 

Pages (fromto)  162182 
Number of pages  21 
Journal  Journal of Fluids and Structures 
Volume  73 
Early online date  29 Jun 2017 
DOIs  
Publication status  Published  31 Aug 2017 
Keywords
 threedimensional (3D)
 computational fluid dynamics (CFD)
 vortexinduced vibration (VIV)
 twodegreeoffreedom (2DOF)
 natural frequency ratio
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 1 Finished

E Infrastructure Bid  Capital Equipment Bid
Littlejohn, D., Fedorov, M., Mulheran, P. & Reese, J.
EPSRC (Engineering and Physical Sciences Research Council)
20/01/12 → 31/03/12
Project: Research