Rayleigh–Bénard convection driven by a long wavelength heating

Asgarian, Ali; Hossain, M. Z.; Floryan, J. M.

doi:10.1007/s00162-015-0379-0

Cited by 12 publications

(1 citation statement)

References 18 publications

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“…Abourida, Hasnaoui & Douamna (1999) showed that the system's overall heat transfer could be enhanced or reduced by proper choices of the time-variable heating modes at the top and bottom boundaries. Other studies have modified the Rayleigh–Bénard cells in a horizontal fluid layer with heating from the top and bottom using spatially sinusoidal boundary conditions (Asgarian, Hossain & Floryan 2016; Floryan, Shadman & Hossain 2018), wherein a higher heat transfer rate is observed for specific phase differences between the top and bottom boundary conditions. Similarly, for vertical enclosures with differentially heated sidewalls, the flow and thermal performance have been modified mechanically by vibrating boundaries or with the inclusion of rigid and flexible fins (Yucel & Turkoglu 1998; Xu 2006; Lappa 2016).…”

Section: Introductionmentioning

confidence: 99%

Natural convection in vertical enclosures with conjugate boundary conditions

2022

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A numerical investigation and reduced-order modelling of natural convection in a cavity with differentially heated sidewalls is discussed. The effect of conjugate boundary conditions on the cavity's heat transfer and natural flow circulation with varying aspect ratios and Rayleigh numbers is examined. Validation of the canonical differentially heated cavity reveals that a modification to the definition of the Rayleigh number (Ra) is required to reconcile the $Nu\sim Ra^{1/4}$ scaling (where Nu is the Nusselt number) and validity of previously proposed correlations for the heat transfer in vertical enclosures. Dynamic mode decomposition is used to uncover the underlying time-dependent flow structures and the results are compared with stability bifurcation studies in the literature. A flow mode previously associated with smaller aspect ratio cavities is identified as the unstable mode for a larger aspect ratio of 4. The effect of conjugate boundary conditions is scaled based on the ratio of the internal and external boundary layers, wherein higher external Reynolds numbers aid in the heat transfer as the Nusselt number approaches the isothermal limit. A reduced-order theoretical model is proposed to predict the Nusselt number for the conjugate boundary conditions. The performance of conjugate boundary conditions is connected to the flow stability, with the parallel-flow configuration acting in a destabilizing manner while the counterflow configuration has a stabilizing effect and results in the highest heat transfer. We also found that relatively large heat transfer can be achieved with substantially lower external actuation with intermediate aspect ratios, translating to less power in practice.

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