free wake

The following vortex sheet computations were motivated by the soap-film experiments of Yves Couder.
A body moving in fluid at uniform speed creates a free sinusoidal wake which can be modeled by a suitably perturbed vortex sheet. In this case, the wake is symmetric about the horizontal centerline. The final state resembles a classical Karman vortex street.

If the body oscillates in the streamwise direction, the vortices form an array of dipoles which propagate on one side of the centerline.

With a different streamwise oscillation, dipoles form and propagate on both sides of the centerline.


Y. Couder and C. Basdevant (1986) Experimental and numerical study of vortex couples in two-dimensional flows, J. Fluid Mech. 173, 225-251

Krasny, R. (1991) Vortex sheet computations: roll-up, wakes, separation, Proc. AMS-SIAM Sem. on ``Vortex Dynamics and Vortex Methods", C. Anderson & C. Greengard (eds.), Lects. Appl. Math. 28, 385-402, AMS