The onset and saturation of the Faraday instability in miscible fluids in a rotating environment

TL;DR

This study explores how rotation affects the onset and development of the Faraday instability in miscible fluids, revealing that Coriolis forces delay instability onset but have less impact at higher forcing amplitudes, with saturation behavior depending on the ratio of Coriolis to forcing frequency.

Contribution

It provides a combined theoretical and numerical analysis of the influence of rotation on Faraday instability in miscible fluids, highlighting the stabilizing effect of Coriolis force and the conditions for saturation of turbulent mixing.

Findings

Coriolis force stabilizes flow and delays sub-harmonic instability onset.

At higher forcing amplitudes, rotation's stabilizing effect diminishes.

Turbulent mixing zone size saturates when (f/ω)^2<0.25, otherwise it grows continuously.

Abstract

We investigate the influence of rotation on the onset and saturation of the Faraday instability in a vertically oscillating two-layer miscible fluid using a theoretical model and direct numerical simulations (DNS). Our analytical approach utilizes the Floquet analysis to solve a set of the Mathieu equations obtained from the linear stability analysis. The solution of the Mathieu equations comprises stable and harmonic, and sub-harmonic unstable regions in a three-dimensional stability diagram. We find that the Coriolis force stabilizes the flow and delays the onset of the sub-harmonic instability responsible for turbulent mixing at lower forcing amplitudes. However, at higher forcing amplitudes, the flow is energetic enough to mitigate the stabilizing effect of rotation, and the evolution of the turbulent mixing zone is similar in both rotating and non-rotating environments. These results are corroborated by DNS at different Coriolis frequencies and forcing amplitudes. We also observe that for $\left(f/\omega\right)^2<0.25$, where $f$ is the Coriolis frequency, and $\omega$ is the forcing frequency, the instability, and the turbulent mixing zone size-$L$ saturates. When $\left(f/\omega\right)^2\geq0.25$, the turbulent mixing zone size-$L$ never saturates and continues to grow.