Friction-Enhanced Lifetime of Bundled Quantum Vortices

Abstract

We show that a toroidal bundle of quantized vortex rings in superfluid helium generates a large-scale wake in the normal fluid which reduces the overall friction experienced by the bundle, thus greatly enhancing its lifetime, as observed in experiments. This collective effect is similar to the drag reduction observed in systems of active, hydrodynamically cooperative agents such as bacteria in aqueous suspensions, fungal spores in the atmosphere, and cyclists in pelotons.