Postcritical flow around a circular cylinder by the vortex method

Unsteady flow around a circular cylinder at postcritical Reynolds numbers is simulated by the vortex method with a boundary-layer turbulence model. In the fractional step scheme, the vortex-in-cell method with a polar mesh is used for the convection of point vortices and random walks are superimposed to simulate turbulent mixing in the boundary region. The eddy viscosity is determined from the vorticity distribution through an algebraic turbulence model. Transport of vorticity, in a spatially varying viscosity field, requires theoretical development of the random-walk method. Convergence tests for the symmetric early stages of impulsively started flow are used to determine appropriate numerical parameters. The computation is then advanced to longer times, allowing the flow to reach a stationary, nearly periodic state. The mean pressure distribution and the vortex shedding frequency compare reasonably with experimental data. © 1989 Academic Press Limited.