Astronomy and Astrophysics – Astronomy
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...210.1511g&link_type=abstract
American Astronomical Society Meeting 210, #15.11; Bulletin of the American Astronomical Society, Vol. 39, p.114
Astronomy and Astrophysics
Astronomy
Scientific paper
We study shock-flame interactions on small scales as a possible mechanism for deflagration-to-detonation transition (DDT) in an exploding carbon-oxygen white dwarf. Thermonuclear flames are modeled using reactive Navier-Stokes equations coupled with a 13-species alpha-network. Two-dimensional numerical simulations that resolve carbon and oxygen burning scales show that shock-flame interactions produce turbulent flames through Richtmyer-Meshkov instabilities and accelerate shocks. This may result in DDT when shocks become strong enough to produce hot spots in unburned carbon-oxygen mixture.
In contrast to terrestrial chemical systems, for which similar phenomena are well known, we observe an additional mechanism for shock acceleration related to different length scales of carbon and oxygen burning in a white dwarf. The slow oxygen burning can release almost as much energy as the fast carbon burning, and occurs in a hot material where carbon is already depleted. Shocks that propagate through the hot and relatively thick oxygen burning zone can pick up energy and even produce detonations driven only by the oxygen burning. When this oxygen detonation enters the cold unburned material, it can ignite it and produce a regular carbon-oxygen detonation. Our simulations show this can occur for densities below 8x10^7 g/cm^3. For higher densities, shocks produced by oxygen detonations are too weak to ignite carbon.
This work was supported in part by the NASA ATP program (NRA NNH05ZDA001N-AT) and by the Naval Research Laboratory (NRL) through the Office of Naval Research.
Gamezo Vadim N.
Oran Elaine S.
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