Recent advances of hybrid RANS/LES with Reynolds-stress background modelling

Kurzfassung

The combination of statistical RANS modelling with turbulence resolving LES methods (hybrid RANS/LES) enables the efficient simulation of complex, industry-relevant flows (e.g. aircrafts in high-lift configuration). In such a hybrid form, the respective RANS model mainly serves as wall model in the near-wall regions and as background model in the LES regions away from the wall. Pure RANS models that are based on differential Reynolds-stress modelling (RSM), achieve a higher accuracy for flows with rotation, streamline curvature and secondary motion compared to simpler turbulence models (e.g. eddy-viscosity models). It is expected that this accuracy advantage is still present when combined with an LES method. Recently, in [1] the robust SSG/LRR RSM-RANS model was combined with the IDDES method, a well-established representative of hybrid RANS/LES. However, so far it was not explicitly demonstrated that this newly developed RSM-IDDES captures the aforementioned complex flow phenomena properly. This study aims to fill this gap by addressing the capability of the RSM-IDDES to resolve secondary motions arising in turbulent corner flows, such as those occurring in the intersection regions of aircraft components (e.g. between nacelle, pylon and wing). Furthermore, in order to limit the computational cost of elaborate scale resolving simulations, we focus on improving the efficiency of the RSM-IDDES. To this end, two different wall function approaches are coupled to the RSM-IDDES, principally allowing a significant coarsening of the wall-normal resolution of the corresponding computational grid.