Direct simulations for wall modeling of multicomponent reacting compressible turbulent flows

Abstract

A study of multicomponent reacting channel flows with significant heat transfer and low Mach number has been performed using a set of direct and wall-resolved large-eddy simulations (LES). The Reynolds number based on the channel half-height and the mean friction velocity is Reτ=300 for DNS and Reτ=1000 for wall-resolved LES. Two temperature ratios based on the mean centerline temperature Tc and the temperature at the wall, Tw, are investigated: Tc/Tw=1.1 for DNS and Tc/Tw=3 for wall-resolved LES. The mass/momentum/energy balances are investigated, specially showing the changes induced by multicomponent terms of the Navier–Stokes equations. Concerning the flow dynamics, the data support the validity of the Van Driest transformation for compressible reacting flows. Concerning heat transfer, two multicomponent terms arise in the energy conservation balance: the laminar species diffusion which appears to be negligible in the turbulent core and the turbulent flux of chemical enthalpy which cannot be neglected. The data also show that the mean composition of the mixture is at equilibrium state; a model for the turbulent flux of chemical enthalpy is then proposed and validated. Finally, models for the total shear stress and the total heat flux are formulated and integrated in the wall normal direction to retrieve an analytical law of the wall. This wall model is tested favorably against the simulation database.