Turbulent Thermal Convection - Selected Topics of Computational and Experimental Fluid Mechanics - page 36

Turbulent Thermal Convection

Enrico Fonda and Katepalli R. Sreenivasan

Abstract Turbulent thermal convection is a phenomenon of crucial importance in
understanding the heat transport and dynamics of several natural and engineering
flows. Real world systems such as the Earth's atmosphere—its oceans as well as
the interior—and the interior of stars such as the Sun, are all affected to various
degrees by thermal convection. The simplified physical model used to understand
this ubiquitous heat transport mechanism is the Rayleigh-Bénard convection, which
is a fluid flow driven by a temperature difference between the top and bottom plates of
an experimental cell with adiabatic sidewalls. Despite the long history of the subject
and the recent progress in theoretical, numerical and experimental domains, many
questions remain unresolved. We report some recent results and discuss a few open
issues.

1 Introduction

The density of fluids in general decreases with increasing temperature. A temperature
difference can then drive a flow via buoyancy force. This ubiquitous phenomenon,
called convection, has a history that goes back to the 18th century with the work of
Hadley, Lomonosov, Thompson and others, but is still the subject of active research
(e.g., Ahlers et al. 2009a ; Lohse and Xia 2010 ; Chillà and Schumacher 2012 ;Xia
2013 ). The possibility that convection greatly enhances heat transport compared to
thermal conduction makes it basic for heat transfer engineering—for example, ovens,
nuclear reactors, ventilation systems, crystallization processes and casting. In natural
phenomena, motion due to non-uniform heating is perhaps the most widespread kind
of fluid motion in the universe.