Visualization of the Starting Vortex Shed by a Cylinder Accelerating in Superfluid Helium-4: Preliminary Results

Abstract

A cylinder of elliptical cross-section is accelerated from rest in superfluid helium-4, a unique cryogenic liquid, characterized by very small values of kinematic viscosity. The starting vortex generated by the cylinder is visualized using the particle tracking velocimetry technique, at different values of fluid temperature and cylinder acceleration. The vortex trajectory and strength are estimated from the particles’ positions and velocities, in view of comparing the behaviour of the shed vortices in various experimental conditions. We specifically find that the vortex trajectory does not appear to depend appreciably on the fluid temperature and cylinder acceleration magnitude, while the latter seems to influence significantly the vortex strength. Overall, the preliminary results presented here show that further studies are required to assess in a quantitative way similarities and differences with analogous flows of Newtonian fluids.