| The observational characteristics of a core-collapse supernova, such as its lightcurve and spectrum, as well as its final nucleosynthesis, are modified by the post-explosion hydrodynamics of the remnant. After a massive star explodes as a supernova, a reverse shock forms and triggers the growth of the Rayleigh-Taylor instability, which mixes together the layers that composed the presupernova star. This mixing determines the final nucleosynthesis of the star, since core collapse supernovae leave behind stellar remnants in the form of black holes or neutron stars that accrete a certain amount of matter. Detailed multidimensional calculations are required to resolve the Rayleigh-Taylor instability. This thesis presents simulations of the post-explosion hydrodynamics of core-collapse supernovae modeled in two-dimensional (2D) axisymmetric coordinates using the FLASH code, and in 2D axisymmetric and three-dimensional (3D) Cartesian coordinates using the CASTRO code. Non-rotating progenitor models, as well as progenitor models in which rotationally-induced mixing was included in a parameterized way, are examined. Models at zero, 10-4 Z⊙ , and solar metallicity are simulated, at a range of masses from 15 to 40 M⊙ and explosion energies from 0.5 to 2.4 x 1051 ergs. It is found that Rayleigh-Taylor mixing is generally more vigorous in lower mass stars than higher mass stars, in larger, redder stars than more compact bluer stars, and in higher energy explosions than lower energy explosions. The rotation rate, for the moderate rotation rates examined in this thesis, is found to have little effect on the outcome of the simulations. For simulations in which the Rayleigh-Taylor instabilities become nonlinear and begin to interact with one another, the final width of the mixed region is the same between 2D and 3D simulations. While the growth rate is initially faster in 3D than in 2D, owing to artificial drag forces arising from 2D geometry, 3D simulations mix more completely, reducing their Atwood number and thus their growth rate relative to 3D. An inverse cascade in the Rayleigh-Taylor instability cannot produce large-scale asymmetries even in 3D; instead, these must arise from the explosion itself. |
