Ahmad El Sayed: Numerical modelling of turbulent non-premixed combustion
Turbulent combustion is a fast-growing research area, vital to the advancement of various industrial sectors, such as energy production and transportation, and to the design of combustion devices, such as engines, turbines, and burners. The underlying physics of turbulent combustion are complicated in nature due to the strongly coupled interactions between turbulence and chemistry. The inherent fundamentals of these interactions can only be understood through detailed knowledge of chemical kinetics and fluid dynamics. Turbulent combustion modelling is the branch of computational fluid dynamics devoted to the numerical modelling of turbulence-chemistry interactions in reacting flows. The talk first provides an overview of the structures and properties of premixed and non-premixed flames. The conservation equations supplementing the Navier-Stokes equations are presented for both laminar and turbulent reacting flows, and the difficulties associated with the direct averaging of the chemical reaction rate in the latter flows are addressed. A number of models suited for the modelling of non-premixed combustion are presented, with emphasis on the Conditional Moment Closure (CMC) and the Stationary Laminar Flamelet Model (SLFM). The modelling of scalar mixing is these two modelling approaches is of critical importance for accurate predictions. CMC results obtained for a lifted hydrogen/nitrogen jet flame using classical and advanced mixing models are presented. The importance of mixing in multi-stream flames is assessed in the context of the SLFM.