Numerically Modelling the Effect of the Drag Crisis on Vortex Induced Vibration of a Circular Cylinder

This paper presents work using commercially available computational fluid dynamics (CFD) software that provides evidence of the effect that the drag crisis has on the dynamic response of a bluff object excited by vortex induced vibration (VIV) from normal flow. Results are presented of simulations of flow past a stationary circular section. A dynamic Large Eddy Simulation (LES) turbulence formulation is used to ensure important features of the drag crisis are captured. Further simulations are presented where the cylinder is free to oscillate in two directions, parallel and normal to the direction of flow. Emphasis is given to the role that the drag crisis phenomenon plays on the locus of oscillations. Key findings are that the drag crisis increases the response by allowing more energy to go into the system on the upstream stroke of the oscillations and that a reversal of drag can occur in both upstream and downstream movements. This suggests the drag crisis phenomenon can affect fatigue performance.