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Title: RAYLEIGH–TAYLOR UNSTABLE FLAMES—FAST OR FASTER?

Abstract

Rayleigh–Taylor (RT) unstable flames play a key role in the explosions of supernovae Ia. However, the dynamics of these flames are still not well understood. RT unstable flames are affected by both the RT instability of the flame front and by RT-generated turbulence. The coexistence of these factors complicates the choice of flame speed subgrid models for full-star Type Ia simulations. Both processes can stretch and wrinkle the flame surface, increasing its area and, therefore, the burning rate. In past research, subgrid models have been based on either the RT instability or turbulence setting the flame speed. We evaluate both models, checking their assumptions and their ability to correctly predict the turbulent flame speed. Specifically, we analyze a large parameter study of 3D direct numerical simulations of RT unstable model flames. This study varies both the simulation domain width and the gravity in order to probe a wide range of flame behaviors. We show that RT unstable flames are different from traditional turbulent flames: they are thinner rather than thicker when turbulence is stronger. We also show that none of the several different types of turbulent flame speed models accurately predicts measured flame speeds. In addition, we find that themore » RT flame speed model only correctly predicts the measured flame speed in a certain parameter regime. Finally, we propose that the formation of cusps may be the factor causing the flame to propagate more quickly than predicted by the RT model.« less

Authors:
 [1]
  1. Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and the Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States)
Publication Date:
OSTI Identifier:
22522503
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 803; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; FLAMES; GRAVITATION; HYDRODYNAMICS; PROBES; RAYLEIGH-TAYLOR INSTABILITY; SUPERNOVAE; SURFACES; TURBULENCE; VELOCITY; WHITE DWARF STARS

Citation Formats

Hicks, E. P., E-mail: eph2001@columbia.edu. RAYLEIGH–TAYLOR UNSTABLE FLAMES—FAST OR FASTER?. United States: N. p., 2015. Web. doi:10.1088/0004-637X/803/2/72.
Hicks, E. P., E-mail: eph2001@columbia.edu. RAYLEIGH–TAYLOR UNSTABLE FLAMES—FAST OR FASTER?. United States. doi:10.1088/0004-637X/803/2/72.
Hicks, E. P., E-mail: eph2001@columbia.edu. Mon . "RAYLEIGH–TAYLOR UNSTABLE FLAMES—FAST OR FASTER?". United States. doi:10.1088/0004-637X/803/2/72.
@article{osti_22522503,
title = {RAYLEIGH–TAYLOR UNSTABLE FLAMES—FAST OR FASTER?},
author = {Hicks, E. P., E-mail: eph2001@columbia.edu},
abstractNote = {Rayleigh–Taylor (RT) unstable flames play a key role in the explosions of supernovae Ia. However, the dynamics of these flames are still not well understood. RT unstable flames are affected by both the RT instability of the flame front and by RT-generated turbulence. The coexistence of these factors complicates the choice of flame speed subgrid models for full-star Type Ia simulations. Both processes can stretch and wrinkle the flame surface, increasing its area and, therefore, the burning rate. In past research, subgrid models have been based on either the RT instability or turbulence setting the flame speed. We evaluate both models, checking their assumptions and their ability to correctly predict the turbulent flame speed. Specifically, we analyze a large parameter study of 3D direct numerical simulations of RT unstable model flames. This study varies both the simulation domain width and the gravity in order to probe a wide range of flame behaviors. We show that RT unstable flames are different from traditional turbulent flames: they are thinner rather than thicker when turbulence is stronger. We also show that none of the several different types of turbulent flame speed models accurately predicts measured flame speeds. In addition, we find that the RT flame speed model only correctly predicts the measured flame speed in a certain parameter regime. Finally, we propose that the formation of cusps may be the factor causing the flame to propagate more quickly than predicted by the RT model.},
doi = {10.1088/0004-637X/803/2/72},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 803,
place = {United States},
year = {2015},
month = {4}
}