Kavli Affiliate: Lile Wang
| First 5 Authors: Xiaoyu Zhang, Xiaoyu Zhang, , ,
| Summary:
We present direct numerical simulations demonstrating
deflagration-to-detonation transition (DDT) driven by oxygen flames in Type Ia
supernova progenitors. Using the Castro hydrodynamics code coupled with the
“aprox13” 13-isotope nuclear network, we simulate combustion in isolated fuel
regions where oxygen flames trail carbon flames. In a fiducial one-dimensional
run at $rho_0=3.5times10^7 mathrmg cm^-3$ we observe spontaneous
DDT of the oxygen flame via the Zel’dovich gradient mechanism when the
carbon-oxygen separation reaches $sim 10 mathrmkm$. The oxygen detonation
then captures the carbon flame and triggers a stable carbon detonation.
Systematic one-dimensional parameter scans show that successful carbon DDT
requires upstream densities in the range $(3.1$–$3.6)times10^7 mathrmg
cm^-3$ and a minimum carbon-flame thickness of $gtrsim 20 mathrmm$.
Two-dimensional simulations confirm DDT and demonstrate that the
multidimensional cellular structure of the oxygen detonation can promote carbon
detonation at somewhat lower densities than in one dimension. These results
provide direct numerical evidence that oxygen-flame-driven DDT is physically
plausible in turbulent white-dwarf environments and underscore the importance
of multidimensional effects for Type Ia supernova explosion modeling.
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