Flow pattern dynamics in convecting liquid helium

Abstract

We present experimental data which correlate thermal measurements and flow visualization in convecting liquid 4He. For a small range R(C)<R<R1 of the Rayleigh number R above the convection threshold value R(C) a robust stationary pattern is observed. This pattern exhibits periodic pulsation when R>R1, generating thermal oscillations as in earlier reports. At higher R values the time dependence becomes aperiodic with the surprising appearance of spiral-defect chaos at an aspect ratio smaller than has previously been reported.

Unstructured finite element method for the solution of the Boussinesq problem in three dimensions

“…In the remainder of this subsection, we focus on the natural convective patterns that occur in cavities. Such patterns have been extensively studied in cylindrical cell containers [14,49,[52][53][54] for low-Pr fluids. By contrast, there seem to have relatively few attempts to numerically simulate flows in such geometries (some examples include [55][56][57]).…”

Reentrant and whirling hexagons in non-Boussinesq convection

“…In recent years exciting results have been obtained for the stability and dynamics of structures that are connected with roll convection. In particular, the spiral-defect chaos obtained in convection of fluids with low Prandtl number [2,3,4,5,6,7] and domain chaos [8,9,10,11] driven by the Küppers-Lortz instability [12] in rotating systems have attracted notable interest. In most of these investigations the systems have been kept close to the Oberbeck-Boussinesq approximation by minimizing the dependence of the fluid parameters on the temperature to avoid the appearance of cellular or hexagonal structures.…”