Mound, JE orcid.org/0000-0002-1243-6915 and Davies, CJ orcid.org/0000-0002-1074-3815 (2017) Heat transfer in rapidly rotating convection with heterogeneous thermal boundary conditions. Journal of Fluid Mechanics, 828. pp. 601-629. ISSN 0022-1120
Abstract
Convection in the metallic cores of terrestrial planets is likely to be subjected to lateral variations in heat flux through the outer boundary imposed by creeping flow in the overlying silicate mantles. Boundary anomalies can significantly influence global diagnostics of core convection when the Rayleigh number, Ra, is weakly supercritical; however, little is known about the strongly supercritical regime appropriate for planets. We perform numerical simulations of rapidly rotating convection in a spherical shell geometry and impose two patterns of boundary heat flow heterogeneity: a hemispherical Y¹₁ spherical harmonic pattern; and one derived from seismic tomography of the Earth’s lower mantle. We consider Ekman numbers 10⁻⁴ ≤E≤10⁻⁶, flux-based Rayleigh numbers up to 800 times critical, and a Prandtl number of unity. The amplitude of the lateral variation in heat flux is characterised by q^{∗}_{L} = 0, 2.3, 5.0, the peak-to-peak amplitude of the outer boundary heat flux divided by its mean. We find that the Nusselt number, Nu, can be increased by up to 25% relative to the equivalent homogeneous case due to boundary-induced correlations between the radial velocity and temperature anomalies near the top of the shell. The Nu enhancement tends to become greater as the amplitude and length scale of the boundary heterogeneity are increased and as the system becomes more supercritical. This Ra dependence can steepen the Nu α Ra^{γ} scaling in the rotationally dominated regime, with γ for our most extreme case approximately 20% greater than the equivalent homogeneous scaling. Therefore, it may be important to consider boundary heterogeneity when extrapolating numerical results to planetary conditions.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017, Cambridge University Press. This is an author produced version of a paper published in Journal of Fluid Mechanics. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Bénard convection; geophysical and geological flows; rotating flows |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Funding Information: | Funder Grant number NERC NE/L011328/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 17 Aug 2017 13:52 |
Last Modified: | 05 Feb 2018 01:38 |
Status: | Published |
Publisher: | Cambridge University Press |
Identification Number: | 10.1017/jfm.2017.539 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:120244 |