Two-phase flows

Large-eddy simulation (LES) is becoming a standard tool for combustion system analysis since it has extensively demonstrated its ability to predict mean and unsteady reactive gaseous flows in complex geometries. Therefore, LES seems a natural candidate for the investigation of the complex physical phenomena involved in reacting two-phase flows, for which two numerical strategies can be applied:

• In Euler-Lagrange (EL) simulations, the gas is modeled by a classical Eulerian approach whereas particles are tracked in a Lagrangian framework.
• Euler-Euler (EE) simulations use the Eulerian description for the gaseous and the dispersed phases.

The Euler-Lagrange approach is commonly used as individual droplet physical mechanisms can be easily implemented: polydispersion of a spray, crossing trajectories, bouncing on walls, group and wake combustion of droplets. However, the large number of tracked particles in real applications and their localisation in the vicinity of the injector lead to load balancing issues since the droplets are only present on few processors. Thus, the Euler-Euler approach is sometimes preferred as the parallellisation of the liquid phase solver is identical to the gas solver. However, modelling aspects are generally more difficult to treat in the Euler-Euler framework.