Direct Numerical Simulation of 3D Salt Fingers: From Secondary Instability to Chaotic Convection

TL;DR

This paper uses direct numerical simulation to study the evolution of 3D salt fingers, revealing how secondary instabilities lead from initial growth to chaotic convection.

Contribution

It introduces a detailed DNS approach to analyze secondary instabilities in 3D salt fingers, including a newly identified horizontal shear mode.

Findings

Secondary instability involves vertical shear and a new horizontal shear mode.

Salt fingers evolve from initial growth to chaotic convection.

Simulation visualizes the complex instability mechanisms.

Abstract

The amplification and equilibration of three-dimensional salt fingers in unbounded uniform vertical gradients of temperature and salinity is modeled with a Direct Numerical Simulation in a triply periodic computational domain. A fluid dynamics video of the simulation shows that the secondary instability of the fastest growing square-planform finger mode is a combination of the well-known vertical shear instability of two-dimensional fingers [Holyer, 1984] and a new horizontal shear mode.