Turbulence-condensate interaction in two dimensions

TL;DR

This paper experimentally investigates how a large-scale coherent flow, or spectral condensate, influences turbulence in thin fluid layers, revealing significant modifications to velocity moments and implications for atmospheric turbulence energy flux analysis.

Contribution

It demonstrates experimentally that spectral condensates alter turbulence statistics and affect energy flux measurements, providing new insights into turbulence-condensate interactions.

Findings

Condensate modifies third-order velocity moments over a wide scale range.

Presence of condensate can change the sign of the third moment in inverse cascade.

Condensate increases the velocity flatness, indicating more intense fluctuations.

Abstract

We present experimental results on turbulence generated in thin fluid layers in the presence of a large-scale coherent flow, or a spectral condensate. It is shown that the condensate modifies the third-order velocity moment in a much wider interval of scales than the second one. The modification may include the change of sign of the third moment in the inverse cascade. This observation may help resolve a controversy on the energy flux in mesoscale atmospheric turbulence (10-500 km): to recover a correct energy flux from the third velocity moment one needs first to subtract the coherent flow. We find that the condensate also increases the velocity flatness.