| Issue |
EAS Publications Series
Volume 63, 2013
New Advances in Stellar Physics: From Microscopic to Macroscopic Processes
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|---|---|---|
| Page(s) | 255 - 262 | |
| Section | Hydrodynamics, Mixing Processes and Transport of Angular Momentum in Stars | |
| DOI | https://doi.org/10.1051/eas/1363029 | |
| Published online | 19 December 2013 | |
G. Alecian, Y. Lebreton, O. Richard and G. Vauclair (eds)
EAS Publications Series, 63 (2013) 255–262
A remark on the vertical transport of large-scale temperature fluctuations by smaller-scale convection
Institute of Astronomy & Department of Applied Mathematics and Theoretical Physics, Madingley Road, Cambridge, CB3 0HA, UK
A simple mixing-length discussion of vertical diffusive transport of a scalar by small-scale turbulent convection is presented, likening it to the microscopic transport in a classical gas. If the scalar is passive, the transport is governed by the well known telegraph equation. Temperature, on the other hand, influences the dynamics of the small-scale motion by modifying the buoyancy that drives the turbulent eddies; it leads to a rather more complicated equation, which, for relatively rapid variation reduces to the same wave equation as for a passive scalar, with maximal propagation speed comparable with the rms vertical eddy velocity; but in the slow diffusive limit it reduces, for good reason, to the classical diffusion equation with a diffusivity enhanced by a factor 3/2 over that pertaining to a passive scalar.
© EAS, EDP Sciences, 2013