Control of a vortex pair using a weak external flow

The problem of controlling the position of a pair of point vortices using a strain field or the field of a single source/sink is considered using singular control methods and dynamical system perturbation theory. We show that averaging over the fast rotation of the vortices around the centre of vorticity reduces the order of the system of evolution equations and allows one to achieve the desired control using a single control field. This article was chosen from Selected Proceedings of the 4th International Workshop on Vortex Flows and Related Numerical Methods (UC Santa-Barbara, 17-20 March 2002) ed E Meiburg, G H Cottet, A Ghoniem and P Koumoutsakos.