Small-scale interaction of turbulence with thermonuclear flames in type ia supernovae

Microscopic turbulence-flame interactions of thermonuclear fusion flames occurring in Type Ia supernovae were studied by means of incompressible direct numerical simulations with a highly simplified flame description. The flame is treated asa single diffusive scalar field with a nonlinear source term. It is characterized by its Prandtl number, Pr much less than 1, and laminar flame speed, S-1am. We find that if S-1am greater than or equal to u', where u' is the rms amplitude of turbulent velocity fluctuations, the local flame propagation speed does not significantly deviate from S-1am even in the presence of velocity fluctuations on scales below the laminar flame thickness. This result is interpreted in the context of subgrid-scale modeling of supernova explosions and the mechanism for deflagration-detonation transitions.