Analysis of Multiple Scalar Large-Eddy Simulation/Probability Density Function Formulation for Turbulent Spray Combustion

A large eddy simulation (LES)/probability density function (PDF) method is proposed for modeling turbulent spray combustion. The PDF method has the advantage that the chemical source term appears closed but requires models for the small scale mixing process. The transport equation for the joint-scalar PDF is high dimensional and solved using a Lagrangian technique. A stable and consistent numerical algorithm for the LES/PDF approach is presented. An evaporating spray experiment is used to verify the numerical implementation. To understand the modeling issues in the PDF method, direct numerical simulation of a spray flame and an equivalent gaseous flame are carried out. It is demonstrated that currently used models for the scalar time scale are reasonably accurate in the spray flame.