The flame born in the deep interior of a white dwarf that becomes a Type Ia supernova is subject to several instabilities, the combination of which determines the observational characteristics of the explosion. We briefly review these instabilities and discuss the length scales for which each dominates. Their cumulative effect is to accelerate the speed of the flame beyond its laminar value, bu...

Large 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...

A consistent formulation of the G-equation approach for LES is developed. The unfiltered G-equation is valid only at the instantaneous flame front location. Hence, in a filtering procedure applied to derive the appropriate LES equation, only the instantaneous unfiltered flame surface can be considered. A new filter kernel is provided, which averages along the flame surface. The filter kernel is...

A recent numerical study of turbulence-flame interactions in lean premixed hydrogen, where the Lewis number was approximately 0.36, observed that flames at different equivalence ratios presented significantly different behavior despite having the same Karlovitz and Damköhler numbers. This differing behavior is due to the thermodiffusively-unstable nature of low Lewis number flames. In more than...

The unsteady flamelet model is applied in numerical simulations of a steady, turbulent, nitrogen-diluted hydrogen-air diffusion flame. An unsteady flamelet is solved interactively with a CFD solver for the turbulent flow and the mixture fraction field. Transient effects occurring in steady jet diffusion flames are discussed in terms of the relevant timescales. It is shown that radiation can be ...

Detailed studies of flame-vortex interactions are extremely valuable to improve our understanding of turbulent combustion regimes. Combined experimental and numerical studies have already been performed in the premixed case during previous investigations. Therefore, we decided to carry out a detailed experimental investigation on the regimes observed during interaction of a vortex ring and a no...

Raman scattering from nitrogen in laminar (Re 4 1600) and turbulent (Re 4 15,000) non-premixed flames of diluted methane has been investigated as a means of complementing the two-scalar mixturefraction computation based on measurements of fuel mass fraction and temperature (nFT). Using a diluent consisting of argon and oxygen with an overall volumetric dilution ratio of 3/1 (diluent/fuel) allow...

High speed planar laser induced fluorescence (PLIF) imaging of the OH radical is presented in a turbulent nonpremixed methane-air flame. Sequences of up to eight successive PLIF images could be resolved sequentially at several kHz repetition rates. Turbulent flow phenomena such as vortex formation and air entrainment in the flow could be visualised and their development tracked in real time. Tu...