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The time step constraint in radiation hydrodynamics
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Astronomy. University of Colorado, USA.ORCID iD: 0000-0002-7304-021X
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Colorado, USA.
Number of Authors: 22019 (English)In: Geophysical and Astrophysical Fluid Dynamics, ISSN 0309-1929, E-ISSN 1029-0419Article in journal (Refereed) Epub ahead of print
Abstract [en]

Explicit radiation hydrodynamic simulations of the atmospheres of massive stars and of convection in accretion discs around white dwarfs suffer from prohibitively short time steps due to radiation. This constraint is related to the cooling time rather than the radiative pressure, which also becomes important in hot stars and discs. We show that the radiative time step constraint is governed by the minimum of the sum of the optically thick and thin contributions rather than the smaller one of the two. In simulations with the Pencil Code, their weighting fractions are found empirically. In three-dimensional convective accretion disc simulations, the Deardorff term is found to be the main contributor to the enthalpy flux rather than the superadiabatic gradient. We conclude with a discussion of how the radiative time step problem could be mitigated in certain types of investigations.

Place, publisher, year, edition, pages
2019.
Keywords [en]
Numerical stability, radiative cooling, convection, accretion discs, hot stars
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-175783DOI: 10.1080/03091929.2019.1676894ISI: 000491590900001OAI: oai:DiVA.org:su-175783DiVA, id: diva2:1372215
Available from: 2019-11-22 Created: 2019-11-22 Last updated: 2019-11-22

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