Time Scaling in the Convection Onset of Supercritical 3He

Abstract

A review is presented of the laboratory experiments and simulations of the convection onset of a supercritical fluid, 3He, in a Rayleigh-Benard cell after the start of a steady heat flow q from the bottom wall at the time t=0. The experiments were conducted at several temperatures along the critical isochore and over a wide range of q and measured the temperature drop ΔT(t) across the fluid layer. It was empirically found that the various characteristic times t i observed in the profile of ΔT(t), and also in the convection growth determined by numerical simulations, could each be expressed by t i /τ D as function of the Rayleigh number, where τ D is the diffusive relaxation time. This scaled representation is to be expected, as has been shown in a general demonstration by Michael Cross (unpublished) and its implications are discussed. A comparison of the profiles ΔT(t) from experiments and simulations are presented and various unresolved discrepancies will be discussed.