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Stability and resonant wave interactions of confined two-layer Rayleigh–Bénard systems

Published online by Cambridge University Press:  06 August 2014

S. V. Diwakar
Affiliation:
Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
Shaligram Tiwari
Affiliation:
Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
Sarit K. Das
Affiliation:
Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
T. Sundararajan*
Affiliation:
Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
*
Email address for correspondence: tsundar@iitm.ac.in

Abstract

The current work analyses the onset characteristics of Rayleigh–Bénard convection in confined two-dimensional two-layer systems. Owing to the interfacial interactions and the possibilities of convection onset in the individual layers, the two-layer systems typically exhibit diverse excitation modes. While the attributes of these modes range from the non-oscillatory mechanical/thermal couplings to the oscillatory standing/travelling waves, their regimes of occurrence are determined by the numerous system parameters and property ratios. In this regard, the current work aims at characterising their respective influence via methodical linear and fully nonlinear analyses, carried out on fluid systems that have been selected using the concept of balanced contrasts. Consequently, the occurrence of oscillatory modes is found to be associated with certain favourable fluid combinations and interfacial heights. The further branching of oscillatory modes into standing and travelling waves seems to additionally rely on the aspect ratio of the confined cavity. Specifically, the modulated travelling waves have been observed to occur (amidst standing wave modes) at discrete aspect ratios for which the onset of oscillatory convection happens at unequal fluid heights. This behaviour corresponds to the typical $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}m$:$n$ resonance where the critical wavenumbers of convection onset in the layers are dissimilar. Based on all of these observations, an attempt has been made in the present work to identify the oscillatory excitation modes with a reduced number of non-dimensional parameters.

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Papers
Copyright
© 2014 Cambridge University Press 

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Diwakar et al. supplementary material

Onset of standing wave oscillations in a two layer system with a*=0.667, ρβα = 4.0 and AR = 2.35

Download Diwakar et al. supplementary material(Video)
Video 5.8 MB

Diwakar et al. supplementary material

Onset of standing wave oscillations in a two layer system with a*=0.667, ρβα = 4.0 and AR = 2.45

Download Diwakar et al. supplementary material(Video)
Video 8.3 MB

Diwakar et al. supplementary material

Onset of quasi-periodic modulated travelling waves in a two layer system with a*=0.667, ρβα = 4.0 and AR = 2.415

Download Diwakar et al. supplementary material(Video)
Video 25.9 MB