Numerical simulation of the unsteady wake behind an airfoil

The unsteady wake behind an airfoil is simulated numerically by a system of discrete vortex cores, also called point vortices. In common with previously developed procedures, at each time step a core is added to the wake at the trailing edge, and the cores already in the wake are convected at the local particle velocity. The innovation of the present method is that, as the cores begin to separate, more cores are added to the system and the circulations around the individual cores are reduced according to a linear interpolation routine. The spacing between cores is maintained approximately while the total circulation around the wake and airfoil is maintained exactly. In several examples, one finds qualitative agreement between computed wake shapes and flow visualization. The method shows promise as a means of simulating unsteady, closely coupled aerodynamic interference.