  We present high-resolution, full-star simulations of the post-ignition phase
of Type Ia supernovae using the compressible hydrodynamics code Castro. Initial
conditions, including the turbulent velocity field and ignition site, are
imported directly from a simulation of the last few hours of presupernova
convection using a low Mach number code, Maestro. Adaptive mesh refinement
allows the initial burning front to be modeled with an effective resolution of
36,864^3 zones (~136 m/zone). The initial rise and expansion of the
deflagration front are tracked until burning reaches the star's edge and the
role of the background turbulence on the flame is investigated. The effect of
artificially moving the ignition location closer to the star's center is
explored. The degree to which turbulence affects the burning front decreases
with increasing ignition radius since the buoyancy force is stronger at larger
radii. Even central ignition --- in the presence of a background convective
flow field --- is rapidly carried off-center as the flame is carried by the
flow field. We compare our results to analytic models for burning thermals, and
find that they reproduce the general trends of the bubble's size and mass, but
underpredict the amount of buoyant acceleration due to simplifying assumptions
of the bubble's properties. Overall, we find that the amount of mass that burns
prior to flame break out is small, consistent with a "gravitationally confined
detonation" occurring at a later epoch, but additional burning will occur
following breakout that may modify this conclusion.
