Direct Numerical Simulation of Turbulent Supersonic Shear Layers Under Chemical Nonequilibrium Conditions

Turbulent chemically reacting flows with shock interactions are central to numerous high-speed phenomena, including astrophysical events, scramjet propulsion, etc. This work presents a Direct Numerical Simulation (DNS) investigation into turbulent combustion at high Mach numbers using a newly extended compressible Navier-Stokes solver with reacting flow capabilities. The solver is based on the original CFD code Hybrid [J. Comput. Phys. 229.4 (2010): 1213-1237] and incorporates multiple high-order numerical methods. The DNS adopt a finite-difference discretization of the governing equations on a structured Cartesian grid. A sixth-order central difference scheme in the split form is adopted for the inviscid fluxes and is replaced by a fifth-order WENO using Roe flux splitting and entropy fix near shocks. The viscous fluxes are computed using a conservative discretization that has the resolution characteristics of a sixth-order scheme. Time is advanced by a fourth-order Runge–Kutta method. A dilatation-based artificial viscosity and regularization through diffusive terms are used to stabilize the equations. As part of current work, multispecies transport and chemical reaction equations are added, using conservative skew-symmetric convective forms and production terms. Diffusion follows the Hirschfelder-Curtis formulation. Solver verification includes: (i) Sod shock tube and modified shock tube tests for convection of species, (ii) unsteady diffusion of a smoothed profile for molecular transport, and (iii) hydrogen-oxygen combustion in a constant-pressure reactor for chemical kinetics. Two mechanisms of the kinetics are assessed: a five-step reduced model and a detailed subset of the GRI 3.0 mechanism [http://www.me.berkeley.edu/gri_mech/]. Results show accurate resolution of convection, diffusion, and reaction dynamics, confirming solver fidelity for DNS of chemically reacting supersonic flows.