Interplay between advective, diffusive, and active barriers in Rayleigh-B\'enard flow

TL;DR

This paper investigates how advective, diffusive, and active transport barriers interact in complex 3D turbulent Rayleigh-Bénard flows, using advanced mathematical and numerical methods to visualize and quantify their roles.

Contribution

It systematically compares different types of transport barriers in 3D unsteady flows with thermal and shear features, revealing their interplay in turbulent convection.

Findings

Advective, diffusive, and active barriers are visualized in 3D turbulent flow.

The role of each barrier type varies with Rossby number.

Transport barriers significantly influence heat and momentum transfer.

Abstract

Our understanding of the material organization of complex fluid flows has recently benefited from mathematical developments in the theory of objective coherent structures. These methods have provided a wealth of approaches that identify transport barriers in three-dimensional (3D) turbulent flows. Specifically, theoretical advances have been incorporated into numerical algorithms that extract the most influential advective, diffusive and active barriers to transport from data sets in a frame-indifferent fashion. To date, however, there has been very limited investigation into these objectively-defined transport barriers in 3D unsteady flows with complicated spatiotemporal dynamics. Similarly, no systematic comparison of advective, diffusive and active barriers has been carried out in a 3D flow with both thermal and shear-driven features. In our study, we utilize simulations of turbulent rotating Rayleigh-B\'enard convection to uncover the interplay between advective transport barriers (Lagrangian coherent structures), material barriers to diffusive heat transport and objective Eulerian barriers to momentum transport. For a range of (inverse) Rossby numbers, we visualize each type of barrier and quantify their role as barriers to momentum and heat transport under changes in the relative influence of mechanical and thermal forces.