Numerical Simulation of In-Line and Cross-Flow Oscillations of a Cylinder

The flow-induced vibration of a circular cylinder is simulated numerically. The finite element method is used to solve the three-dimensional incompressible Navier-Stokes equations, and the flow field is coupled with the cylinder motion. The oscillation of the cylinder in the in-line direction is shown when the reduced velocity, Ur, is smaller than 4.0. Symmetric vortices are seen for Ur≤2.5 and alternative vortices appear for Ur≥2.9, while the cylinder motion is damped at around Ur=2.6. It is found that the cross-flow oscillation of the cylinder is dominant under the alternative vortex condition. The drag and lift coefficients increase and the vortex field become finer both in space and time by the cross-flow oscillation.