Convective instabilities of a normal liquid−43He mixture

Abstract

We report studies of Nusselt number N versus Rayleigh number R for a normal liquid ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He mixture with ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ mass concentration c=0.038, confined in cylindrical containers with aspect ratios, Γ (radius/height) of 5.5≤Γ≤10.2. These data were obtained for separation ratios Ψ of -0.2≲Ψ≲0.1. For Ψ>0, the data are consistent with predictions that the slope RdN/dR is small just above the onset of convection and then increases with R. For Ψ≃0, N is a concave function of R with N∝(R-$R_{\mathrm{cs}{)}^{1/2}}$. Contrary to predictions for a horizontally infinite layer, no oscillations at onset were found for Ψ<0. Above the onset of convection when Ψ<0, we observed additional transitions which are beyond the scope of current theory.