A direct numerical study of a model of superflow, the nonlinear Schrödinger equation, and simple analytical arguments shows a very striking phenomenon: The flow around a disk creates a drag force beyond a well-defined threshold velocity, linked to the emission of vortices from the perimeter of the disk.

• Received 2 April 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.1644