Internally heated convection and Rayleigh-B\'enard convection

TL;DR

This paper reviews the fundamental features, models, and recent experimental and numerical findings of Rayleigh-Bénard and internally heated convection, highlighting differences in boundary conditions and heat transport properties.

Contribution

It provides a comprehensive comparison of IH and RB convection models, including new bounds and stability thresholds, and summarizes recent experimental and numerical results.

Findings

Different boundary conditions significantly affect convection behavior.

Bounds on mean temperatures and convective transport are established.

Numerical and experimental results enhance understanding of heat transfer in convection.

Abstract

This work reviews basic features of both Rayleigh-B\'enard (RB) convection and internally heated (IH) convection, along with findings on IH convection from laboratory experiments and numerical simulations. In the first chapter, six canonical models of convection are described: three configurations of IH convection driven by constant and uniform volumetric heating, and three configurations of RB convection driven by the boundary conditions. The IH models are distinguished by differing pairs of thermal boundary conditions: top and bottom boundaries of equal temperature, an insulating bottom with heat flux fixed at the top, and an insulating bottom with temperature fixed at the top. The RB models also are distinguished by whether temperatures or heat fluxes are fixed at the top and bottom boundaries. Integral quantities important to heat transport are discussed, including the mean fluid temperature, the mean temperature difference between the boundaries, and the mean convective heat transport. Integral relations and bounds are presented, and further bounds are conjectured for the IH cases. The second chapter presents results that can be derived mathematically from the governing equations: linear and nonlinear stability thresholds of static states, and parameter-dependent bounds. Known bounds are on mean temperatures in IH convection and on convective transport in RB convection. The third chapter reviews numerical simulations and laboratory experiments on IH convection, emphasizing quantitative results.