A new model for mixing by double-diffusive convection (semi-convection). II. The transport of heat and composition through layers

TL;DR

This paper investigates layered oscillatory double-diffusive convection in stellar and planetary interiors, providing empirical scaling laws for heat and composition transport, and proposing a new 1D model for use in astrophysical simulations.

Contribution

It introduces a new 1D prescription for layered semi-convection based on 3D simulation data, improving modeling of heat and composition transport.

Findings

Layered convection significantly enhances heat and composition transport.

Empirical scaling laws for layered convection transport are derived.

Layer formation occurs spontaneously under certain conditions.

Abstract

Regions of stellar and planetary interiors that are unstable according to the Schwarzschild criterion, but stable according to the Ledoux criterion, are subject to a form of oscillatory double-diffusive (ODD) convection often called "semi-convection". In this series of papers, we use an extensive suite of three-dimensional (3D) numerical simulations to quantify the transport of heat and composition by ODD convection, and ultimately propose a new 1D prescription that can be used in stellar and planetary structure and evolution models. The first paper in this series demonstrated that under certain conditions ODD convection spontaneously transitions from an initially homogeneously turbulent state into a staircase of convective layers, which results in a substantial increase in the transport of heat and composition. Here, we present simulations of ODD convection in this layered regime, we describe the dynamical behavior of the layers, and we derive empirical scaling laws for the transport through layered convection.