École Nationale Supérieure de
Techniques Avancées

Résumé

The presented study is the result of a 3-month internship conducted remotely with Imperial College London. It is the continuation of the work of François Chantriaux, who did his thesis on this subject in 2017. The subject of this internship is the numerical analysis of a set of experimental data of turbulent reacting flows, augmented using insights gained from an associated DNS (Direct Numerical Simulations) database. These turbulent flows are characterized by the presence of a flame. This work aimed at identifying the relative importance of different lengthscales of turbulent structures on two phenomena, both studied with the use of a bandpass filter applied in the wave number space, allowing to select a given length scale for the flow. The first is the stretching of the flame by different sizes of straining structures. This is particularly interesting in the context of Large Eddy Simulations (LES). Indeed, in LES, we wish to avoid computing the scales that have a small impact on the reaction or on the flow, in order to gain computational efficiency. It is found that the flame is stretched the most strongly by eddies whose size is between 1.68 and 2.0 times the thermal flame thickness. The second phenomenon is the alignment between vortical structures and straining structures, which depends on the considered lenghtscales of the structures.