Large Eddy Simulation

Large Eddy Simulation has a long history dating back to the infancy of the research efforts
in computational climate science by Smagorinsky (1963

), Lilly (1967) and
Deardorff (1964). Large Eddy Simulation (LES) is a technique that
allows for computationally feasible modeling of turbulent fluid motion. The main assumption behind LES is that while large scales of turbulence (the

*large eddies*) are specific to the geometry and boundary conditions, the smallest scales are universal. As such, the smallest scales are

*problem independent*
and can be modeled, while the large scales need to be resolved. Also,
large scales contain most of the kinetic energy, while the smallest
scales, despite controlling dissipation, are responsible for a tiny
fraction of the overall turbulent fluctuations. The recent increase in
affordability and availability of computing power has allowed to apply
LES to the simulation of flow in complex geometries of interest relevant
to engineering applications.

## Filtered Density Function

In the last decade, LES of turbulent combustion has become
computationally affordable. Large-eddy simulation coupled with a
Filtered Density Function (FDF) approach has been considered as a
promising method to capture the interaction between hydrodynamics and
chemical kinetics, making it possible to predict the occurrence of slow
chemistry effects, extinction, and possibly reignition. Recently, FDF
methods have also been applied to the modeling of particulates (soot)
formation in turbulent non-premixed combustion.

The Reactive Flow Modeling Laboratory at KAUST is involved in large
scale simulations of non-equilibrium turbulent non-premixed flames using
hybrid LES / FDF approaches.