Turbulent Oxygen Flames in Type Ia Supernovae

TL;DR

This paper investigates how turbulence affects oxygen flames in Type Ia supernovae, examining the potential for transition to detonation and finding turbulence influences flame structure at high Damköhler numbers without clearly causing detonation.

Contribution

It presents a detailed analysis of turbulence-flame interactions in oxygen flames, extending previous work on carbon flames, and explores conditions for possible transition to detonation.

Findings

Turbulence has little effect on oxygen flames when Damköhler number < 1.

At Damköhler number > 1, turbulence enhances heat transfer and narrows the flame.

Simulations do not conclusively support transition to detonation in oxygen flames.

Abstract

In previous studies, we examined turbulence-flame interactions in carbon-burning 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 Damk\"ohler numbers ($\Da_{16}$) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when $\Da_{16}<1$, and the flame burns inductively some distance behind the carbon flame. However, for $\Da_{16}>1$, turbulence enhances heat transfer and drives the propagation of a flame that is {\em narrower} than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbon-oxygen 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.