Computer Model of Vortex Shedding from a Cylinder

A mathematical model of unsteady flow around a cylinder gives lift, drag, and velocity fluctuations in reasonable agreement with experimental results. Vorticity is represented by element Rankine vortices, which are superimposed on the potential flow around a cylinder to form the boundary layers and separated shear layers. The solution advances timewise from assumed initial conditions. At each time step, every element vortex is moved through a distance equal to the product of its instantaneous translational velocity and a small time increment, determined after stability tests. Concentrated clouds of vorticity form and are shed from the cylinder, with accompanying fluctuations in lift and drag. The total number of element vortices in the model is minimized by replacing each cloud by a single equivalent vortex. Because feedback from the formation region to the separation points is present in the model, it is potentially well-suited to studies of flow around oscillating cylinders.