Hexagons and spiral defect chaos in non-Boussinesq convection at low Prandtl numbers

Madruga Sánchez, Santiago and Riecke, Hermann (2007). Hexagons and spiral defect chaos in non-Boussinesq convection at low Prandtl numbers. "Physical Review e", v. 75 ; pp.. ISSN 1539-3755. https://doi.org/10.1103/PhysRevE.75.026210.

Description

Title: Hexagons and spiral defect chaos in non-Boussinesq convection at low Prandtl numbers
Author/s:
  • Madruga Sánchez, Santiago
  • Riecke, Hermann
Item Type: Article
Título de Revista/Publicación: Physical Review e
Date: 2007
ISSN: 1539-3755
Volume: 75
Subjects:
Faculty: E.T.S.I. Aeronáuticos (UPM)
Department: Fundamentos Matemáticos de la Tecnología Aeronáutica [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

We study the stability and dynamics of non-Boussinesq convection in pure gases ?CO2 and SF6? with Prandtl numbers near Pr? 1 and in a H2-Xe mixture with Pr= 0.17. Focusing on the strongly nonlinear regime we employ Galerkin stability analyses and direct numerical simulations of the Navier-Stokes equations. For Pr ? 1 and intermediate non-Boussinesq effects we find reentrance of stable hexagons as the Rayleigh number is increased. For stronger non-Boussinesq effects the usual, transverse side-band instability is superseded by a longitudinal side-band instability. Moreover, the hexagons do not exhibit any amplitude instability to rolls. Seemingly, this result contradicts the experimentally observed transition from hexagons to rolls. We resolve this discrepancy by including the effect of the lateral walls. Non-Boussinesq effects modify the spiral defect chaos observed for larger Rayleigh numbers. For convection in SF6 we find that non-Boussinesq effects strongly increase the number of small, compact convection cells and with it enhance the cellular character of the patterns. In H2-Xe, closer to threshold, we find instead an enhanced tendency toward roll-like structures. In both cases the number of spirals and of targetlike components is reduced. We quantify these effects using recently developed diagnostics of the geometric properties of the patterns.

More information

Item ID: 21708
DC Identifier: http://oa.upm.es/21708/
OAI Identifier: oai:oa.upm.es:21708
DOI: 10.1103/PhysRevE.75.026210
Deposited by: Memoria Investigacion
Deposited on: 11 Mar 2014 16:33
Last Modified: 21 Apr 2016 12:26
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