Simulating a Variable Density Jet with Negative Turbulent Kinetic Energy Production

Experiments with a variable density, turbulent jet in coflow by Charonko & Prestridge (2017) have observed negative turbulent kinetic energy production. While backscattering of energy is known to occur in turbulent flows exhibiting a conventional forward cascade, in this variable density jet a net transfer of energy from the fluctuations to the mean flow takes place as demonstrated by Lai, Charonko, & Prestridge (2018). It is a challenge to represent this kind of jet using many Reynolds-Averaged Navier-Stokes (RANS) models available in the literature. Prior simulations with established RANS methods have shown excessive spreading of the jet relative to the experiment. One promising method which could potentially overcome this challenge is a recently developed de-mix capable RANS model for compressible, variable density flows, based on the Besnard-Harlow-Rauenzahn (BHR) family of models. BHR-4 differs from previous BHR models in that it evolves additional turbulent correlations associated with fluctuations in species mass fraction. This work simulates the variable density jet using the BHR-4 model and compares the results to earlier versions of BHR in order to see if these additional turbulent correlations better represent the jet.