PDF methods provide a means of calculating the properties of turbulent reacting flobs. They have been successfully applied to many turbulent flames, including some with finite-rate kinetic effects. Here the methods are reviewed with an emphasis on computational issues and on their application to turbulent combustion.

The scalar structure of the overfire (fuel-lean) region of sooting turbulent diffusion flames was investigated, considering ethylene and acetylene burning in air. Measurements and predictions are reported of the mean concentrations of major gas species and mean soot volume fractions. Predictions were based on the conserved-scaiar formalism in conjunction with the laminar flamelet approximation....

A novel computational methodology, termed “Irregularly Portioned Lagrangian Monte Carlo” (IPLMC) is developed for large eddy simulation (LES) of turbulent flows. This methodology is intended for use in the filtered density function (FDF) formulation and is particularly suitable for simulation of chemically reacting flows on massively parallel platforms. The IPLMC facilitates efficient simulatio...

Combustion kinetics ...................................................................................................................................... 1 Physical mixing and its effects on ignition, propagation and extinction ...................................................... 2 Mixing ...........................................................................................................

Methods of using stochastic simulations to treat nonlinear interactions in turbulent combustion processes are described emphasizing the use of statistical time-series techniques to analyze the turbulence-radiation interactions of nonpremixed flames. Three aspects of the problem are considered, as follows: the statistics of scalar properties in turbulent flames, the formulation of algorithms to ...

Instantaneous two-dimensional measurements of reaction rate, mixture fraction, and temperature are demonstrated in turbulent partially premixed methane/air jet flames. The forward reaction rate of the reaction CO OH ⇒ CO2 H is measured by simultaneous OH laser-induced fluorescence (LIF) and two-photon CO LIF. The product of the two LIF signals is shown to be proportional to the reaction rate. T...

An idealized model for turbulent premixed flames is introduced. It consists of a scalar advection-reaction-diffusion equation that describes the interaction of a thin flame with a turbulentlike flow field acting on two separate scales. Rigorous asymptotic results as well as affordable and reliable direct numerical simulations are available to predict the effective large scale behavior of the id...

Two combustion models for turbulent premixed combustion in the flamelet regime are developed for unsteady simulations. The first model is a convensional G equation flamelet model and the main issues discussed are the subgrid closure. The second model is based on the Linear-Eddy Model. Both models are used in simulation of turbulent stagnation point flames. The heat release and turbulence intens...

The mechanism of flame propagation in fuel beds of wildland fires is important to understand in order to quantify fire spread rates. Fires spread by radiative and convective heating and often require direct flame contact to achieve ignition. The flame interface in an advancing fire is unsteady and turbulent, making study of intermittent flames in complex fuels difficult. A vertical wall fire, i...

A semi-implicit preconditioned iterative method is proposed for the time-integration of the stiff chemistry in simulations of unsteady reacting flows, such as turbulent flames, using detailed chemical kinetic mechanisms. Emphasis is placed on the simultaneous treatment of convection, diffusion, and chemistry, without using operator splitting techniques. The preconditioner corresponds to an appr...