Introduction to Effects of a Steady-State Acceleration Field

Abstract

The two previous parts of this book provided theoretical and experimental results on the hydodynamic behavior of supercritical and near-critical fluids following a parietal thermal disturbance in the absence of any acceleration field, as it is well-known that motion in such hyperdilatable and hyperexpandable fluids is extremely sensistive to gravity (see Sect. 1.8). However, in the past few decades, considerable attention has been focused on hydrodynamic instabilities in supercritical fluid layers—mainly in relation to the situation where the temperature gradient is in the opposite direction to the Earth’s gravitational acceleration, a situation that is referred to as the Rayleigh–Bénard configuration (see Sect. 1.8.3 in Chap. 1 and [1, 16] for more details). Aside from the pioneering work of Busse [8] in 1967, a number of experiments have been performed to explore organized fluid motion close to or in the turbulent regime [2, 5, 6, 9, 14, 15, 17, 18, 21] . Key problems have also been addressed theoretically. Among the results obtained, it is worth noting that the Nusselt number is now known to be related to other characteristic numbers, scaling theories, large-scale temperature fluctuations, pattern formation, spiral turbulence, and the random reversal of macroscopic flows. Readers should also refer to [7] for a review of the state of the art in Rayleigh–Bénard convection in the year 2000, and to Chaps. 4 and 5 of [12] (published in 2006 for the Henri Bénard Centenary Review). More recently, non-Oberbeck–Boussinesq effects in turbulent convection have been studied by Ahlers et al. [3, 4].