1. Scaling behaviour of small-scale dynamos driven by Rayleigh-Bénard convection.
- Author
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Yan, M., Tobias, S. M., and Calkins, M. A.
- Subjects
RAYLEIGH-Benard convection ,ELECTRIC generators ,NUSSELT number ,PLANE geometry ,KINETIC energy ,PRANDTL number - Abstract
A numerical investigation of convection-driven dynamos is carried out in the plane layer geometry. Dynamos with different magnetic Prandtl numbers Pm are simulated over a broad range of the Rayleigh number Ra. The heat transport, as characterized by the Nusselt number Nu, shows an initial departure from the heat transport scaling of non-magnetic Rayleigh-Bénard convection (RBC) as the magnetic field grows in magnitude; as Ra is increased further, the data suggest that Nu grows approximately as Ra
2/7 , but with a smaller prefactor in comparison with RBC. Viscous (u) and ohmic (B) dissipation contribute approximately equally to Nu at the highest Ra investigated; both ohmic and viscous dissipation approach a Reynolds-number-dependent scaling of the form Rea, where a ≈ 2.8. The ratio of magnetic to kinetic energy approaches a Pm-dependent constant as Ra is increased, with the constant value increasing with Pm. The ohmic dissipation length scale depends on Ra in such a way that it is always smaller, and decreases more rapidly with increasing Ra, than the viscous dissipation length scale for all investigated values of Pm. [ABSTRACT FROM AUTHOR]- Published
- 2021
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