Simulation of the flow past a circular cylinder in the supercritical regime by blending RANS and variationalmultiscale LES models. Journal of Fluids and Structures, Elsevier, 2014, 47, pp. AbstractA strategy which blends a Variational Multiscale Large Eddy Simulation model (VMS-LES) and a RANS model in a hybrid approach is investigated. A smooth blending function, which is based on the value of a blending parameter, is used for switching from VMS-LES to RANS. Different definitions of the blending parameter are investigated. The capabilities of the novel hybrid approach are appraised in the simulation of the flow around a circular cylinder at a Reynolds number 1.4 · 10 5 , based on the freestream velocity and on the cylinder diameter, in presence of turbulent boundary-layer due to turbulent inflow conditions. A second study at Reynolds numbers from 6.7 · 10 5 to 1.25 · 10 6 is also presented. The effect of using the VMS-LES approach in the hybrid model is evaluated. Results are compared to those of other RANS, LES and hybrid simulations in the literature and with experimental data

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The present article focuses on the improvement of the two components of hybrid RANS/LES models. In the LES component, a Variational Multiscale (VMS) formulation [17] is introduced with the dynamic control of Germano et al, [11]. In the RANS component, an Organised Eddy Simulation (OES) model is used, [4,39]. The impact of these modifications on several critical flows past bluff bodies is analysed. These are the flow past cylinder at Re = 140, 000 entering the critical regime because of blockage ratio confinement, a flow past a cylinder at Re = 1, 000, 000, as well as the flow past a tandem cylinder at Re = 166, 000.Key words: hybrid turbulence models, RANS, VMS-LES, OES, DDES, bluff body flows.VMS-and OES-based hybrid simulations of bluff body flows and the existence of asymmetric forces on the cylinder surface (Bearman, 1965;Schewe, 1983). The passage to the critical and supercritical regime highly interests the aeronautics design and from a fundamental research point of view, the reasons of vortex shedding disappearance in a specific supercritical Reynolds number range. The numerical simulation of the drag crisis and of the supercritical regime remain important CFD challenges. The supercritical regime offers the possibility of the boundary layer treatment as fully turbulent, which is a simpler situation in respect for turbulence modelling issues than the transitional regime corresponding to the drag crisis. In this context, LES approaches and advanced URANS and hybrid RANS-LES methods can be adapted in order to capture the boundary layer nature and the transition location. LES methods need a quite high number of degrees of freedom (of order 100-500 Million for the single cylinder's problem, Rolfo-Revell et al, (2013) [34], Rodriguez et al, 2013 [18]), whereas hybrid methods are generally more economic as seen in the collected articles of the 4th Hybrid RANS-LES methods symposium (Girimaji et al, 2015 [1]). The objective of the present article is to offer reliable hybrid methods needing relatively economic grids.