Assessment of temperature fluctuation models for RANS simulations of hypersonic reacting flows

Turbulence-chemistry interactions play an important role in various fluid flow problems. In a hypersonic boundary layer, these interactions can alter the surface heating rate of the vehicle by modifying the temperature profile across the layer. The effect of these interactions is accounted for in a Reynolds-averaged Navier Stokes (RANS) simulation using a probability density function (PDF) of the temperature distribution. In this paper, two presumed PDF models are considered, namely, the Martin and Candler model and the Gaffney et al. model, and their accuracy is assessed by comparing to direct numerical simulation (DNS) of homogeneous isotropic turbulence. The Martin and Candler model reproduces the turbulence-chemistry interactions in the flow correctly whereas the Gaffney model overpredicts the temperature fluctuations.