Low-Temperature Studies of the Rayieigh-Bénard Instability and Turbulence

Low-temperature techniques were applied to the study of a hydrodynamic instability. High-precision results for the Nusselt number N as a function of the Rayleigh number R for liquid and gaseous helium revealed no singularities in $N(R)$, except at the convective threshold Rc. For R>2.19Rc, a new turbulent state was found and characterized by measuring the frequency spectrum and the amplitude of $N(R)$.