Separation scaling for viscous vortex reconnection

TL;DR

This study reveals that viscous vortex reconnection in classical fluids exhibits a universal 1/2 power-law scaling of the minimum separation distance, similar to quantum vortices, depending on initial conditions and Reynolds number.

Contribution

It is the first report of 1/2 scaling in viscous vortex reconnection, demonstrating a universal behavior across classical and quantum fluids.

Findings

Minimum separation distance follows 1/2 power-law scaling.

Scaling depends on initial vortex configuration and Reynolds number.

Universal reconnection route suggested for classical and quantum vortices.

Abstract

Reconnection plays a significant role in the dynamics of plasmas, polymers and macromolecules, as well as in numerous laminar and turbulent flow phenomena in both classical and quantum fluids. Extensive studies in quantum vortex reconnection show that the minimum separation distance {\delta} between interacting vortices follows a 1/2 scaling. Due to the complex nature of the dynamics (e.g., the formation of bridges and threads as well as successive reconnections and avalanche), such scaling has never been reported for (classical) viscous vortex reconnection. Using the direct numerical simulation of the Navier-Stokes equations, we study viscous reconnection of slender vortices, whose core size is much smaller than the radius of the vortex curvature. For separations that are large compared to the vortex core size, we discover that {\delta}(t) between the two interacting viscous vortices surprisingly also follows the 1/2 power scaling for both pre- and post-reconnection events. The prefactors in this 1/2-power law are found to depend not only on the initial configuration but also on the vortex Reynolds number (or viscosity). Our finding in the viscous reconnection, complementing numerous works on quantum vortex reconnection, suggests that there is indeed a universal route for reconnection -- an essential result for understanding the various facets of the viscous vortex reconnection phenomena and their potential modeling, as well as possibly explaining turbulence cascade physics.