Turbulent Oxygen Flames in Type Ia Supernovae

In previous studies, we examined turbulence-flame interactions in carbonburning thermonuclear flames in Type Ia supernovae. In this study, we consider turbulence-flame interactions in the trailing oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen flame. Scaling arguments analogous to the carbon flames are presented and then compared against three-dimensional simulations for a range of Damköhler numbers (Da16) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when Da16 < 1, and the flame burns inductively some distance behind the carbon flame. However, for Da16 > 1, turbulence enhances heat transfer and drives the propagation of a flame that is narrower than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbonoxygen turbulent flame with complex compound structure. The simulations do not appear to support the possibility of a transition to detonation in the oxygen flame, but do not preclude it either. Subject headings: supernovae: general — white dwarfs — hydrodynamics — nuclear reactions, nucleosynthesis, abundances — conduction — methods: numerical — turbulence — distributed flames