EDP Sciences
Free Access
Issue
A&A
Volume 370, Number 3, May II 2001
Page(s) 1092 - 1102
Section Physical and chemical processes
DOI https://doi.org/10.1051/0004-6361:20010273


A&A 370, 1092-1102 (2001)
DOI: 10.1051/0004-6361:20010273

Evolution of highly buoyant thermals in a stratified layer

A. Brandenburg1, 2 and J. Hazlehurst3

1  NORDITA, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark
2  Department of Mathematics, University of Newcastle upon Tyne, NE1 7RU, UK
3  Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany

(Received 7 August 2000 / Accepted 7 February 2001)

Abstract
The buoyant rise of thermals (i.e. bubbles of enhanced entropy, but initially in pressure equilibrium) is investigated numerically in three dimensions for the case of an adiabatically stratified layer covering 6-9 pressure scale heights. It is found that these bubbles can travel to large heights before being braked by the excess pressure that builds up in order to drive the gas sideways in the head of the bubble. Until this happens, the momentum of the bubble grows as described by the time-integrated buoyancy force. This validates the simple theory of bubble dynamics whereby the mass entrainment of the bubble provides an effective braking force well before the bubble stops ascending. This is quantified by an entrainment parameter alpha which is calculated from the simulations and is found to be in good agreement with the experimental measurements. This work is discussed in the context of contact binaries whose secondaries could be subject to dissipative heating in the outermost layers.


Key words: hydrodynamics -- turbulence -- stars: binaries: close

Offprint request: A. Brandenburg, brandenb@nordita.dk




© ESO 2001

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.