Numerical analysis of raindrops effect on downforce generating multi-element wing

The study of aerodynamic devices behaviour in different conditions had always been of fundamental importance since the first investigations on wings icing. In parallel, heavy rain conditions have also received significant attention, with great experimental efforts dedicated to their analysis. Such condition can alter, to varying degrees, the aerodynamic performances of wings by affecting efficiency, shifting the transition point and leading, in some cases, to premature flow separation. The present thesis aims to report a numerical investigation of wings behaviour in rain conditions. The study setup considers a wing initially wetted by some droplets and evaluates the coupled evolution of the airflow and the water phase. The research was made using multiphase CFD more specifically adopting Volume Of Fluid (VOF) method, that is the most common modelling approach for free-surface flow simulations. Single-phase and multi-phase simulations were performed on OpenFOAM employing its different solvers, respectively pimpleFoam and interFoam. Particular attention was observed to aerodynamic performance variations, especially in terms of transition and separation behaviour. In particular, to capture also transitional flow features the transitional turbulence model k- ω SSTLM (γ– Reθ) was adopted. The work was focussed,at first, on the introduction of a numerical modelling tech nique for this case, tuning the solver parameters and defining the initial conditions; then the attention shifted on studying water droplets effects on wing profiles of in terest. The profiles were analyzed in low Reynolds number and different wings were addressed. Following the first simulations on single-element profiles the core simulations where done on a bi-plane wing; its configuration was studied to have a pressure distribu tion that could be closer to real racing applications. The free simulation parameters, changed across the different cases, were surface wetting conditions, Reynolds number and airfoil geometry. In conclusion, the analyzed configurations showed that the presence of droplets leads to an overall degradation of aerodynamic performances, with a reduction in suction capability and an efficiency decrease. Furthermore, water droplets promote earlier flow transition and for the most of the cases also earlier separation. In multi-element wing configurations,