Dissipation enhancement from a single vortex reconnection in superfluid helium

Abstract

We investigate a single vortex reconnection event in superfluid helium at finite temperatures using the vortex filament model. The reconnection induces Kelvin waves which strongly increase energy dissipation. We evaluate the mutual friction dissipation from the reconnection and show that the dissipation power has universal form, which is seen by scaling both time (measured from the reconnection event) and power by the mutual friction parameter alpha. This observation allows us to conclude that the Kelvin-wave cascade is not important in the energy dissipation process within the range alpha > 0.001. Rather, the energy is directly transferred from Kelvin waves to the normal component. Moreover, while the excited Kelvin waves greatly enhance energy dissipation, no similar change is seen in angular momentum from the reconnection event. This result has similarities with recent 3He-B measurements. Our results also confirm another earlier observation that the minimum distance between vortices scales approximately as d ~ sqrt(|t-trec|), both before and after the reconnection event.