Dissipative Vortex Binaries in Compact Fluid Domains with Geometric Corrections

TL;DR

This paper analyzes dissipative vortex binaries in a doubly periodic fluid domain, revealing how dissipation and geometry influence vortex dynamics, including spirals, collapses, and angular drifts.

Contribution

It introduces a dissipative extension of vortex-binary motion with analytical solutions and geometric corrections, highlighting new behaviors in periodic fluid systems.

Findings

Equal same-sign vortices spiral outward.

Opposite-sign pairs (dipoles) collapse in planar limit.

On the torus, dipole orientation drifts slowly due to geometry.

Abstract

We study a dissipative extension of vortex-binary motion in a doubly periodic fluid domain. The underlying conservative system admits an exact integrable reduction to a single complex relative coordinate. Dissipation is introduced via a minimal rotated-velocity (mutual-friction) term, as motivated by finite-temperature superfluid dynamics, converting the Hamiltonian evolution into a mixed symplectic--gradient flow with monotonic energy decay for quantized vortices. In the local regime, the dissipative binary remains analytically solvable and admits closed-form solutions, with systematic corrections arising from the toroidal geometry. Equal same-sign vortices execute outward spiraling motion, while equal opposite-sign pairs (dipoles) undergo finite-time collapse in the planar limit. On the torus, however, the dipole orientation is no longer invariant: the geometry induces a slow angular drift, even in regimes where planar dynamics would preserve alignment. For unequal opposite-sign pairs, dissipation induces coupled contraction and rotation, leading to a finite-time nonlinear chirp characterized by $\dot{\omega}\propto\omega^2$, in contrast with electromagnetic and gravitational inspirals where $\dot{\omega}\propto \omega^{3}$ and $\dot{\omega}\propto \omega^{11/3}$. These results highlight the interplay between Hamiltonian structure, dissipation, and geometry in periodic fluid systems.