Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21733708p&link_type=abstract
American Astronomical Society, AAS Meeting #217, #337.08; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
Turbulent thermonuclear burning fronts are presently believed to be the key component of the explosion mechanism powering type Ia supernovae (SNIa). Rapid increase in intensity of turbulent motions inside the white dwarf in the course of the explosion causes wrinkling of the flame, which significantly increases its surface area and, thus, accelerates the flame. This creates tightly packed flame configurations with high local flame curvature. Furthermore, small-scale turbulence begins to penetrate the flame, thus modifying its structure and altering its properties. Even in the thin reaction zone regime, i.e., when turbulence has disrupted only the preheat zone of the flame, the turbulent flame may be significantly different locally from a planar laminar burning front. Large-scale numerical modeling of SNIa requires the use of subgrid-scale models which accurately reproduce local properties, and in particular the local speed, of the turbulent flame formed in the presence of intense turbulence.
We present results of the direct numerical simulations aimed at studying the mechanisms which control the turbulent flame speed in the thin reaction zone regime. Simulations were performed using the massively parallel reactive-flow code Athena-RFX. The increase of the flame surface area is the primary process responsible for accelerating the flame. We find, however, a significant additional increase in flame speed at high turbulent intensities. Such accelerated burning is the result of flame collisions in a tightly packed turbulent flame. Failure to account for this process in subgrid models can lead to the underestimation of the turbulent flame speed by as much as 30-50%. Finally, we discuss the implications of these results for the process of the deflagration-to-detonation transition.
This work was supported in part by the Naval Research Laboratory, the Office of Naval Research, the Air Force Office of Scientific Research, and by the National Science Foundation through the TeraGrid resources.
Oran Elaine S.
Poludnenko Alexei Y.
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