Phd in AERONAUTICS AND SPACE ENGINEERING

Thesis title: Interplay of hydrodynamic instabilities and turbulence in premixed flames

This thesis is devoted to the numerical investigation of premixed Flames subject to intrinsic hydrodynamic instabilities as well as turbulence. Laminar as well as turbulent premixed combustion can be largely influenced by the onset of hydrodynamic instabilities which can cause a significant increase in flame corrugation and, as a result, in the turbulent flame speed, especially when low turbulence intensity level are present. Indeed, such instability is responsible for the formation of sharp folds and creases in the flame front and for the wrinkling observed, undergo certain conditions, over the surface of expanding flames. Hydrodynamic instability is a result of thermal expansion across the flame and its role is particularly dominant in large-scale flames, when flames are constrained by domains larger than several hundred times the flame thickness. The understanding of these phenomena and their interaction with turbulence can play a potentially significant role in practical combustion systems such as gas turbines and, more generally, in industrial and domestic burners. The aim of this thesis is to develop a numerical tool capable of simulating the propagation of turbulent premixed flames under the influence hydrodynamic instabilities and gather qualitative and quantitative data on flame properties such as morphology and global propagation.