UPThèses

In industrial situation, the computation of unsteady and three-dimensional characteristics of complex flows, is often necessary. Large-eddy simulation demands prohibitive computational costs, peculiarly near walls. One of the objectives of hybrid methods, is to optimize the computational cost, by simulating certain areas of flows in RANS mode, and in LES mode elsewhere. The latter centres generally around spatial filtering of the studied variables, while RANS corresponds to a temporal average, in most flows. The PITM approach (Partially Integrated Transport Model), developed in homogeneous turbulence, is a theoretically justified hybrid method. Its transposition to the temporal context was done previously, showing that, under certain hypotheses, both spatial and temporal versions are formally identical. The PITM method has however difficulties in controlling the resolution level. This thesis suggests a dynamic approach to fix that point. Secondly, the temporal version of PITM, the T-PITM, is compared to DES (Detached Eddy Simulation), a popular but empirical hybrid method. It is shown that both methods produce similar results, providing DES an indirect theoretical justification. The underlying RANS model is the elliptic blending Reynolds-stress model (EB-RSM), accounting for wall effects, using neither damping functions nor wall laws.