Small-scale interaction of turbulence with thermonuclear flames in type iasupernovae

Microscopic turbulence-flame interactions of thermonuclear fusion flames oc curring in Type Ia supernovae were studied by means of incompressible direc t numerical simulations with a highly simplified flame description. The fla me is treated asa single diffusive scalar field with a nonlinear source ter m. It is characterized by its Prandtl number, Pr much less than 1, and lami nar 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 thi ckness. This result is interpreted in the context of subgrid-scale modeling of supernova explosions and the mechanism for deflagration-detonation tran sitions.