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O. E. B. Messer (University of Chicago)
Simulations of Type Ia supernovae are characterized by vastly disparate spatial scales, spanning some 12 orders of magnitude. This large dynamic range cannot be captured in any modern direct numerical simulation. Therefore, a subgrid model is used to describe unresolved physical processes taking place on the smallest scales. All modern Type Ia supernova simulations currently use steady-state subgrid models. In particular, velocity perturbations are assumed to stem from either a Kolmogorov cascade from larger scales (Reinecke et al. 2002) or are generated by local Rayleigh-Taylor instabilities (Khokhlov 1995). In all of these descriptions, the effective flame speed is assumed to be a function of the local instantaneous (steady-state) velocity field.
I will describe a series of studies undertaken at the Flash Center at the University of Chicago designed to confirm and extend the RT-based subgrid model of Khokhlov to account for non-steady propagation of the flame front at early times. The aim is to provide an improved implementation for large-scale simulations, as the particulars of any subgrid flame speed model can have profound effects on the total amount of kinetic energy liberated during explosion and the buoyancy of the ash bubbles formed in these calculations. Both of these factors can contribute to the explosion energy and the observed asymmetry of the event.
This work was supported by the U.S. Department of Energy under grant No. BB523820.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.