Modélisation de la transition laminaire-turbulent par rugosité et bulbe de décollement laminaire sur les aubes de turbomachines

摘要

The goal of this thesis is to enhance laminar-turbulent transition modeling on high-lift lowpressure turbine blades. The presented transition modeling method relies on the Menter and Langtry transition model used in a RANS framework in the elsA solver.Once the model’s limits were clearly identified through a parametric study, we moved on to modification of the model. To do so, an optimization method was developed that allows recalibration of the model’s inner correlation functions. This new version of the model allows us to obtain modeling gains of about 20% on the VKI T106C cases through better capture of the separation-induced transition process.These previous computations correspond to ideal cases, for which surfaces may be considered as being smooth. However, we also have the need to consider more realistic surfaces for which roughness may influence the flow. Indeed, among those effects, is the potential influence of surface roughness on transition. In particular, if surface roughness induces transition up-stream of the smooth separation point, the separation bubble will be suppressed. Considering our efforts on modeling separation-induced transition with the Langtry model, it seemed natural to add roughness-induced transition modeling capacities to it. To do so, we implemented in the Langtry model a method developed by Stripf et al. to take into account surface roughness.Finally, the use of the Langtry transition model was extended to the k-l of Smith turbulence model. Indeed, this turbulence model is widely used in turbomachinery. In order that our works on transition modeling over turbine blades be more widely usable, we have completed this thesis by proposing an evolution of the transition model so that it may be used alongside the k-l model.