CONVECTION IN 3HE-4HE MIXTURES WITH LARGE NEGATIVE SEPARATION RATIOS

The authors describe convection experiments on two dilute liquid mixtures of 3He in 4He with cylindrical Rayleigh-Benard geometry in the separation ratio range -1.8<S<-0.06. Measurements of the critical Rayleigh number are in agreement with linear theory in the range -1.4<S<-0.06. For S<-1.4 experimental critical Rayleigh numbers are smaller than those predicted by linear theory. In the range -1.8<S<-0.95 heat transport is time dependent with characteristic times an order of magnitude larger than those predicted by linear theory. In the range -0.95<S<-0.06 time dependence is not detected. Heat transport data indicate that the bifurcation to the initial convecting state is backward over the whole range of S. They derive two coupled amplitude equations based on Linz and Lucke's (1988) eight-mode travelling wave model and compare the properties of the equations with their own experimental results.