Convection in a Binary Mixture Heated from Below

Abstract

Heat-transport measurements in a bulk normal-fluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixture heated from below and over the range $-0.02\mathrm{}\lesssim \psi \lesssim 0.02$ of the separation ratio $\psi$ reveal a forward bifurcation with an initial slope $S\cong 0$ of the Nusselt number for large $\psi$, and a backward bifurcation for $\psi <{\psi }_b\cong 0.006$. At ${\psi }_b$, $S\cong 1$. The critical line $\Delta T_c\left(\psi \right)$ has two branches which meet at $\psi \cong -0.003\mathrm{}$, and which we attribute to the expected stationary and Hopf bifurcation lines. However, stable oscillations bifurcating from the conduction state exist only for $\psi \lesssim -0.015\mathrm{}$.