Projects per year
Abstract
The effects of transverse rotation on the vortexinduced vibration (VIV) of a sphere in a uniform flow are investigated numerically. The one degreeoffreedom sphere motion is constrained to the crossstream direction, with the rotation axis orthogonal to flow and vibration directions. For the current simulations, the Reynolds number of the flow, , and the mass ratio of the sphere, , were fixed at 300 and 2.865, respectively, while the reduced velocity of the flow was varied over the range , where, is the upstream velocity of the flow, is the sphere diameter, is the fluid viscosity, is the system natural frequency and and are solid and fluid densities, respectively. The effect of sphere rotation on VIV was studied over a wide range of nondimensional rotation rates: , with the angular velocity. The flow satisfied the incompressible NavierStokes equations while the coupled sphere motion was modelled by a springmassdamper system, under zero damping. For zero rotation, the sphere oscillated symmetrically through its initial position with a maximum amplitude of approximately 0.4 diameters. Under forced rotation, it oscillated about a new timemean position. Rotation also resulted in a decreased oscillation amplitude and a narrowed synchronisation range. VIV was suppressed completely for 1.3]]>. Within the synchronisation range for each rotation rate, the drag force coefficient increased while the lift force coefficient decreased from their respective preoscillatory values. The increment of the drag force coefficient and the decrement of the lift force coefficient reduced with increasing reduced velocity as well as with increasing rotation rate. In terms of wake dynamics, in the synchronisation range at zero rotation, two equalstrength trails of interlaced hairpintype vortex loops were formed behind the sphere. Under rotation, the streamwise vorticity trail on the advancing side of the sphere became stronger than the trail in the retreating side, consistent with wake deflection due to the Magnus effect. This symmetry breaking appears to be associated with the reduction in the observed amplitude response and the narrowing of the synchronisation range. In terms of variation with Reynolds number, the sphere oscillation amplitude was found to increase over the range at for each of , 0.75 and 1.5. The VIV response depends strongly on Reynolds number, with predictions indicating that VIV will persist for higher rotation rates at higher Reynolds numbers.
Original language  English 

Pages (fromto)  786820 
Number of pages  35 
Journal  Journal of Fluid Mechanics 
Volume  847 
DOIs  
Publication status  Published  25 Jul 2018 
Keywords
 aerodynamics
 flowstructure interactions
Projects
 1 Finished

Wake Transitions and FluidStructure Interactions of Rotating Bluff Bodies
Hourigan, K., Lo Jacono, D., Sheridan, J., Thompson, M. & Leweke, T.
Australian Research Council (ARC), Monash University, CNRS  Centre National de la Recherche Scientifique (French National Centre for Scientific Research), Université PaulSabatier (Paul Sabatier University)
1/01/15 → 6/11/18
Project: Research