Convective instability in a stratified ideal gas containing an acoustic field

Koulakis, John P.; Putterman, Seth

doi:10.1017/jfm.2021.83

Cited by 6 publications

(6 citation statements)

References 27 publications

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“…[15] and quantitatively fits previous numerical simulations (see also Ref. [16] in the limit of small temperature gradients). It suggests a new procedure based on stationary waves to acoustically enhance heat transfers in the absence of natural convection, e.g.…”

supporting

confidence: 88%

“…The theoretical approach of such setups remains challenging and requires numerical simulations accounting for two-way coupling between the acoustic waves and the streaming flow [11,15]. Second, similar large-amplitude streaming flows should be expected wherever stationary acoustic waves develop in inhomogeneous fluids, as for instance in thermoacoustic devices [20] and in acoustically-trapped spherical plasma bulbs [16,21].…”

mentioning

confidence: 99%

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Cooling by Baroclinic Acoustic Streaming

Michel

Gissinger

2021

Phys. Rev. Applied

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supporting

confidence: 88%

mentioning

confidence: 99%

Cooling by Baroclinic Acoustic Streaming

Michel

Gissinger

2021

Phys. Rev. Applied

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“…Other applications of our theory could also concern (rotating) fluids that are not in isothermal nor isentropic equilibrium (e.g. with a conductive temperature profile due to internal heating 6,17 ), for which wave Eq. ( 7) is appropriate.…”

Section: Discussionmentioning

confidence: 99%

“…Slight variations of temperature (e.g. in the room, or due to acoustic transducers 17 ) may indeed break the assumption of isothermal equilibrium, such that Eq. ( 13) may lead to inaccurate predictions.…”

Section: B Parameter Regimes For Experimentsmentioning

confidence: 99%

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Acoustic modes of rapidly rotating ellipsoids subject to centrifugal gravity

Vidal,

Cébron

2021

Preprint

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The acoustic modes of a rotating fluid-filled cavity can be used to determine the effective rotation rate of a fluid (since the resonant frequencies are modified by the flows). To be accurate, this method requires a prior knowledge of the acoustic modes in rotating fluids. Contrary to the Coriolis force, centrifugal gravity has received much less attention in the experimental context. Motivated by on-going experiments in rotating ellipsoids, we study how global rotation and buoyancy modify the acoustic modes of fluid-filled ellipsoids in isothermal (or isentropic) hydrostatic equilibrium. We go beyond the standard acoustic equation, which neglects solid-body rotation and gravity, by deriving an exact wave equation for the acoustic velocity. We then solve the wave problem using a polynomial spectral method in ellipsoids, which is compared with finite-element solutions of the primitive fluid-dynamic equations. We show that the centrifugal acceleration has measurable effects on the acoustic frequencies when M Ω 0.3, where M Ω is the rotational Mach number defined as the ratio of the sonic and rotational time scales. Such a regime can be reached with experiments rotating at a few tens of Hz, by replacing air with a highly compressible gas (e.g. SF 6 or C 4 F 8 ).

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Aspect-ratio-dependent heat transport by baroclinic acoustic streaming

Massih,

Mushthaq,

Michel

et al. 2024

J. Fluid Mech.

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Standing acoustic waves have been known to generate Eulerian time-mean ‘streaming’ flows at least since the seminal investigation of Lord Rayleigh in the 1880s. Nevertheless, a recent body of numerical and experimental evidence has shown that inhomogeneities in the ambient density distribution lead to much faster flows than arise in classical Rayleigh streaming. The emergence of these unusually strong flows creates new opportunities to enhance heat transfer in systems in which convective cooling cannot otherwise be easily achieved. To assess this possibility, a theoretical study of acoustic streaming in an ideal gas confined in a rectangular channel with top and bottom walls maintained at fixed but differing temperatures is performed. A two time scale system of equations is utilized to efficiently capture the coupling between the fast acoustic waves and the slowly evolving streaming flow, enabling strongly nonlinear regimes to be accessed. A large suite of numerical simulations is carried out to probe the streaming dynamics, to highlight the critical role played by baroclinically generated wave vorticity and to quantify the additional heat flux induced by the standing acoustic wave. Proper treatment of the two-way coupling between the waves and mean flow is found to be essential for convergence to a self-consistent steady state, and the variation of the resulting acoustically enhanced steady-state heat flux with both the amplitude of the acoustic wave and the $O(1)$ aspect ratio of the channel is documented. For certain parameters, heat fluxes almost two orders of magnitude larger than those realizable by conduction alone can be attained.

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Convective instability in a stratified ideal gas containing an acoustic field

Abstract: Abstract

Cited by 6 publications

References 27 publications

Cooling by Baroclinic Acoustic Streaming

Cooling by Baroclinic Acoustic Streaming

Acoustic modes of rapidly rotating ellipsoids subject to centrifugal gravity

Aspect-ratio-dependent heat transport by baroclinic acoustic streaming

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