**AAS 200th meeting, Albuquerque, NM, June 2002**

*Session 14. Supernovae*

Display, Monday, June 3, 2002, 9:20am-6:30pm, SW Exhibit Hall
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## [14.01] Three-Dimensional Numerical Simulations of Type Ia Supernovae: Numerical Convergence for Deflagration Stage

*V.N. Gamezo, A.M. Khokhlov, E.S. Oran (Lab. for Computational Physics and Fluid Dynamics, Naval Research Laboratory)*

We consider a Type Ia supernova explosion originating as a
deflagration in the center of a carbon-oxygen
Chandrasekhar-mass white dwarf (WD) with initial composition
0.5C+0.5O, central density 2.0 \times 10^{9} g/cm^{3} and
initial radius 2.1 \times 10^{8} cm. A three-dimensional
(3D) numerical model is based on reactive Euler equations of
fluid dynamics coupled with an equation of state for a
degenerate matter and a simplified kinetics of energy
release. The energy-release model provides the correct
propagation velocity for a laminar flame and takes into
account carbon burning, as well as nuclear statistical
quasi-equilibrium and equilibrium relaxations. The model for
the turbulent burning on scales that are not resolved in the
simulations is based on the assumption that burning on small
scales is driven by the gravity-induced Rayleigh-Taylor (RT)
instability. We performed 3D calculations for the first 1.9
seconds of explosion using an adaptively refined structured
mesh. For the highest-resolution case, the minimum cell size
was 2.6 \times 10^{5} cm, and the mesh consisted of 10^{8}
computational cells by the end of the simulation. The flame,
started as a sphere with the radius 3 \times 10^{6} cm,
becomes very convoluted due to the RT and Kelvin-Helmholtz
instabilities on resolved scales and develops multiple
buoyant plumes. As the plumes grow, the unburnt material
either sinks towards the center or expands more slowly than
the burnt material inside the plumes. The material burns at
all distances from the center even when the larger flame
plumes reach the outer layers of the star. By 1.9 seconds,
some of these plumes approach the surface of the expanding
WD that extends to (5-6) \times 10^{8} cm from the center.
About 50% of the material burns out releasing 1.3 \times
10^{51} ergs of nuclear energy. The expansion velocity at
the surface reaches 1.2 \times 10^{9} cm/s and continues
to grow. A convergence study shows that at high resolutions,
the results become practically independent on the
computational cell size and insensitive to subgrid model
parameters.

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Bulletin of the American Astronomical Society, **34**

© 2002. The American Astronomical Soceity.