02.1 - Aerodynamics - CFD Methods and Validation
EFFECTS OF SOME NUMERICAL FORMULATION ASPECTS IN HIGH-LIFT CONFIGURATION SIMULATIONS
E.D.V. Bigarellaš, P.A.G. Ciloniš, L.C. Scalabrinš; šEmbraer S.A., Brazil
High-lift configurations can exercise all levels of theoretical and numerical formulation complexities in CFD simulations. Starting with the geometry, high-lift configurations are generally complex, with multiple trailing edges, coves, surfaces close to each other, fluid dynamic features far from the wall, like vortices and wakes, and other aspects which render mesh generation a science in itself. The resulting, daily-production mesh may present large stretching, which poses numerical difficulties for spatial and temporal discretisation. Furthermore, a broad spectrum of velocity distribution may be found, with the incoming flow being usually low subsonic, with large, even lower speed regions in the volume and close to the wall, and near-supersonic pockets in leading edge regions. Such flow topology also poses difficulties for spatial and temporal integration in terms of numerical stiffness an robustness. Apart from these aspects, boundary layers, developing wakes, boundary-layer and wake interactions, separation pockets and vortices, like nacelle chins, require adequate turbulence modelling capability, at least under an ad-hoc engineering point of view. This paper addresses some spatial, temporal and numerical-formulation aspects of high-lift flow phenomena, for a mesh generated with daily-production, industry best-practice setup, and a turbulence model setup suitable for high-lift simulations. The effects of preconditioning, restarting from previous angle of attack, and gradient computation are addressed.