Project Title:

A New Subgrid Model for Large-Eddy Simulations of Mixing and Chemical Reaction in

02.01-9500
900757
A New Subgrid Model for Large-Eddy Simulations of Mixing and Chemical Reaction in

Abstract:

Turbulent Flows
Conventional, turbulent-mixing models based on gradient-diffusion assumptions are
not capable of accurately predicting mixing and reaction rates in most practical
combustion devices. Furthermore, at the small scales, most conventional models make
no distinction between turbulent conversion and molecular diffusion. This distinction
is critical for the accurate description of the mixing process. In addition, it is
known that turbulent mixing and entrainment processes in shear flows are dominated
by unsteady, large-scale, vortical motions. The spatial and temporal evolution of
these large-scale structures cannot be modeled and must be explicitly computed for
accurate predictions. Phase I will explore subgrid modeling techniques for use in
large-eddy simulation (LES) of reacting flows. In particular, a model for mixing
and chemical reactions at the subgrid level, in both low- and high-speed flows, will
be developed based on Kerstein's linear-eddy approach. LES of incompressible, two-dimensional
mixing layers will be performed and the results will be compared with high-resolution
direct numerical simulations and available experimental data to assess the proposed
subgrid model. In Phase II, this model would be extended to study three-dimensional,
compressible reacting flows with heat release.
A predictive capability for unsteady simulation of combustion in both low- and high-speed
flows with full coupling between the chemical heat release and the fluid dynamic
flow field can be utilized for a variety of purposes by both government and industry.
turbulent mixing, large-eddy simulation, chemical reactions, subgrid modeling, supersonic
flows, multispecies mixing, linear eddy, compressible flows