Numerical simulations of internal wave generation by convection in water
Name
PhysRevE.91.063016.pdf
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2.93 MB
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Author(s)
Lecoanet, Daniel
Le Bars, Michael
Vasil, Geoffrey M.
Brown, Benjamin P.
Quataert, Eliot
Oishi, Jeffrey S.
Burns, Keaton James
Date Issued
June 2015
Journal
Physical Review E
Publisher
American Physical Society
Citation
Lecoanet, Daniel, Michael Le Bars, Keaton J. Burns, Geoffrey M. Vasil, Benjamin P. Brown, Eliot Quataert, and Jeffrey S. Oishi. "Numerical simulations of internal wave generation by convection in water." Phys. Rev. E 91, 063016 (June 2015). © 2015 American Physical Society
Version
Final published version
Abstract
Water's density maximum at 4[superscript ∘]C makes it well suited to study internal gravity wave excitation by convection: an increasing temperature profile is unstable to convection below 4[superscript ∘]C, but stably stratified above 4[superscript ∘]C. We present numerical simulations of a waterlike fluid near its density maximum in a two-dimensional domain. We successfully model the damping of waves in the simulations using linear theory, provided we do not take the weak damping limit typically used in the literature. To isolate the physical mechanism exciting internal waves, we use the spectral code dedalus to run several simplified model simulations of our more detailed simulation. We use data from the full simulation as source terms in two simplified models of internal-wave excitation by convection: bulk excitation by convective Reynolds stresses, and interface forcing via the mechanical oscillator effect. We find excellent agreement between the waves generated in the full simulation and the simplified simulation implementing the bulk excitation mechanism. The interface forcing simulations overexcite high-frequency waves because they assume the excitation is by the “impulsive” penetration of plumes, which spreads energy to high frequencies. However, we find that the real excitation is instead by the “sweeping” motion of plumes parallel to the interface. Our results imply that the bulk excitation mechanism is a very accurate heuristic for internal-wave generation by convection.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
http://dx.doi.org/10.1103/PhysRevE.91.063016
