Formation of a Direct Kolmogorov-like Cascade of Second Sound Waves in He II

TL;DR

This paper reports the observation of a steady-state energy cascade of second sound waves in superfluid helium, revealing nonlocal energy transfer and power-law amplitude distribution, with implications for studying acoustic turbulence.

Contribution

It demonstrates the formation of a Kolmogorov-like cascade in second sound waves in He II through combined experimental and numerical analysis.

Findings

Energy cascade involves nonlocal flux in spectral space

Wave amplitude distribution follows a power law

Numerical results agree with experimental data

Abstract

Based on measurements of nonlinear second sound resonances in a high-quality resonator, we have observed a steady-state wave energy cascade in He II involving a flux of energy through the spectral range towards high frequencies. We show that the energy balance in the wave system is nonlocal in K-space and that the frequency scales of energy pumping and dissipation are widely separated. The wave amplitude distribution follows a power law over a wide range of frequencies. Numerical computations yield results in agreement with the experimental observations. We suggest that second sound cascades of this kind may be useful for model studies of acoustic turbulence.