Transition from hexagons to rolls in convection in fluids under non-Boussinesq conditions

Year: 1992

Authors: Pampaloni E., Perez Garcia C., Albavetti L., Ciliberto S.

Autors Affiliation: Departamento de Fisica, Universidad de Navarrra, Pamplona, Spain;
Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, Italy

Abstract: The transition between hexagons and rolls in convective patterns has been studied. The transition thresholds and changes in the Nusselt number are discussed theoretically in terms of calculations made by Busse (1967 a) and with amplitude equations. Experiments have been done in a shallow layer of pure water under non-Boussinesq conditions using complementary techniques: shadowgraph (qualitative), optical (based on the deflections of a laser beam) and calorimetric. The experimental values of the critical Rayleigh number R(c) and the critical wavenumber k(c) are in agreement with theoretical ones. However, theory and experiments show some discrepancies in the slopes of the non-dimensional convective heat flow curve and in the thresholds of the hysteretic hexagons rolls transition. These discrepancies are discussed in terms of lateral effects and of the presence of defects in the pattern.

Journal/Review: JOURNAL OF FLUID MECHANICS

Volume: 234      Pages from: 393  to: 416

KeyWords: RAYLEIGH-BENARD CONVECTION; WAVE-NUMBER SELECTION; HEAT-TRANSPORT; AMPLITUDE EQUATION; SPATIAL VARIATION
DOI: 10.1017/S0022112092000831

Citations: 28
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