Enstrophy Cascade in Decaying Two-Dimensional Quantum Turbulence

摘要

We report evidence for an enstrophy cascade in large-scale point-vortex simulations of decaying two-dimensional quantumturbulence. Devising a method to generate quantum vortex configurations with kinetic energy narrowly localized near a single length scale, the dynamics are found to be well characterized by a superfluid Reynolds number Res that depends only on the number of vortices and the initial kinetic energy scale. Under free evolution the vortices exhibit features of a classical enstrophy cascade, including a k(-3) power-law kinetic energy spectrum, and constant enstrophy flux associated with inertial transport to small scales. Clear signatures of the cascade emerge for N greater than or similar to 500 vortices. Simulating up to very large Reynolds numbers (N = 32 768 vortices), additional features of the classical theory are observed: the Kraichnan-Batchelor constant is found to converge to C' approximate to 1.6, and the width of the k-3 range scales as Re-s(1/2).