Large eddy simulation of coherent structures in rectangular methane non-premixed flame

Abstract

a b s t r a c tLarge eddy simulation of a three-dimensional spatially developing transitional free methane non-premixed flame is performed. The solver of the governing equations is based upon a projection method. The Smagorinsky model is utilized for the turbulent subgrid scale terms. A global reaction mechanism is applied for the simulation of methane/air combustion. Simulation results clearly illustrate the coherent structure of the rectangular non-premixed flame, consisting of three distinct zones in the near field. Periodic characteristics of the coherent structures in the rectangular non-premixed flame are discussed. The predicted structure of the flame is in good agreement with the experimental results. Distributions of species concentrations across the flame surfaces are illustrated and typical flame structures in the far field are analyzed. Local mass fraction analysis and flow visualization indicate that the black spots of the flames are due to strong entrainment of oxygen into the central jet by streamwise vortices, and breaking up of the flame is caused by an enormous amount of entrainment of streamwise vortices as well as stretching of spanwise vortices at the bottom of the flame.

LES of convective heat transfer and incompressible fluid flow past a square cylinder

“…The effect of SGS on large scale motions must be considered carefully. As discussed in the literature [39][40][41][42][43][44][45][46], the sub-grid stress is postulated usually to be proportional to the local filtered strain rate, with a factor called subgrid viscosity. This is analogous to Newtonian constitutive relationship for laminar flows, implying that these SGS models have not ascertained satisfactorily the validity of the range of Reynolds numbers.…”

“…For turbulent flow simulations, three strategies, phenomenological modeling [35,36], DNS [37], and LES [38], are usually employed. In recent years, as reported widely [38][39][40][41][42][43][44][45][46], LES has become a viable and popular simulation tool.…”