The simulation of vortex shedding from an oscillating circular cylinder

The interaction between cylinder oscillation and the shedding of vortices is investigated numerically in this paper. The near wake structure is presented for different values of reduced velocity of a circular cylinder free to oscillate transversely. The method used for the simulation is based on the Vortex-in-Cell formulation incorporating viscous diffusion. The Navier-Stokes equations are solved through the vorticity-velocity formulation, assuming that the now is two-dimensional. The operator-splitting technique, where convection and diffusion of vorticity are treated separately, is used. The convection part is modelled in a lagrangian way, assuming that the vorticity field is carried on a large number of discrete vortices, while the diffusion part is calculated through the finite-volume method. The calculations are carried out on an unstructured mesh, using the finite-volume technique to solve Poisson's equation for the stream-function and the diffusion equation for the vorticity. Vorticity is created due to the no-slip condition on the cylinder wall, and the mesh is finer close to it in order to have a better description of the boundary-layer. The mesh is also refined behind the cylinder, in order to have a good description of the vortex dynamics in the near-wake region.