Seth Musser (MIT) gives a webinar on Flying in a superfluid: starting flow past an airfoil.

In typical fluids like air or water viscosity plays a crucial role in flight. It allows for the development of a boundary layer that separates from an airfoil when it is accelerated from rest; this separation forms the starting vortex that allows for the generation of lift. It is then interesting to ask what happens in a fluid, like a superfluid, that does not possess any viscosity whatsoever. To investigate this we study the development of superfluid flow around an airfoil accelerated to a finite velocity from rest. Using both simulations of the Gross-Pitaevskii equation and analytical calculations we find striking similarities to viscous flows: from the production of starting vortices to the convergence of the airfoil circulation onto a quantized version of the classical Kutta-Joukowski circulation. Using a phenomenological argument we predict the number of vortices nucleated by a given foil and find good agreement with numerics. Finally we analyze the lift and drag acting on the airfoil. Our simulations suggest that flight is indeed possible in a superfluid despite its lack of viscosity.