Statistically Steady Turbulence in Soap Films: Direct Numerical Simulations with Ekman Friction

TL;DR

This paper uses direct numerical simulations to study how walls and Ekman friction influence turbulence in soap films, revealing simple and multiscaling behaviors in velocity and vorticity structures, respectively.

Contribution

It introduces a detailed DNS approach to analyze the effects of walls and Ekman friction on soap film turbulence, including multiscaling analysis and comparison with experiments.

Findings

Velocity structure functions exhibit simple scaling.

Vorticity structure functions show multiscaling.

The Weiss parameter distribution matches experimental data.

Abstract

We present a detailed direct numerical simulation (DNS) designed to investigate the combined effects of walls and Ekman friction on turbulence in forced soap films. We concentrate on the forward-cascade regime and show how to extract the isotropic parts of velocity and vorticity structure functions and thence the ratios of multiscaling exponents. We find that velocity structure functions display simple scaling whereas their vorticity counterparts show multiscaling; and the probability distribution function of the Weiss parameter $\Lambda$, which distinguishes between regions with centers and saddles, is in quantitative agreement with experiments.