Rayleigh-Taylor Unstable Flames

Type Ia supernovae are extremely bright stellar explosions whose light curves can be calibrated for use as standard candles in cosmology. Researchers simulating these explosions have a problem: the driver of the explosion, a flame less than 1cm wide, is so much smaller than the size of star that it can't be resolved in the simulations. So, full-star simulations of Type Ia supernovae must include a subgrid model that sets the flame speed below a certain scale. These subgrid models take into account the complex small-scale effects of the gravitationally-driven Rayleigh-Taylor (RT) instability, turbulence generated by the RT instability, and burning on the flame speed. Two main types of subgrid models are currently in use: turbulence-based models and RT-based models. The choice of subgrid model affects the full-star simulation outcome, yet there is no agreement about which models are most accurate. In this project, we simulate RT unstable flames using the spectral element code Nek5000 and compare measurements from these simulations to the predictions of different flame speed models. Currently, our main focus is on processes (like flame curvature) that can affect the local burning rate.

Publications

  • E. P. Hicks, Rayleigh-Taylor Unstable Flames -- Fast or Faster?, 2015, The Astrophysical Journal, 803, 72. pdf
  • E. P. Hicks, A shear instability mechanism for the pulsations of Rayleigh–Taylor unstable model flames, 2014, Journal of Fluid Mechanics, 748, 618-640. pdf
  • E. P. Hicks and R. Rosner, Gravitationally Unstable Flames: Rayleigh-Taylor Stretching Versus Turbulent Wrinkling, 2013, The Astrophysical Journal, 771, 135. pdf
  • Elizabeth Hicks and Robert Rosner, The effects of burning on the development of 2D turbulence, 2010, Physica Scripta, Vol. 2010, T142, 01404.