Impatto della Turbolenza Ambientale sulla performance Aerodinamica del Veicolo = Environmental Turbulence Impact on Automotive Aerodynamics Performance

In the past years aerodynamics of road vehicles have always been considered as a low impact design feature, mainly submitted to style requirements and poorly affecting car performances, if not on extreme sports car. Recently pursuing always greater car fuel efficiency and thanks to always more powerful CFD software and brute computational power things come to an important change: car’s aerodynamic features are more and more studied and updated. The actual state of the art relies on both CFD simulation correlated with experimental Wind tunnel tests. The point is that car aerodynamic wind tunnels offer a very limited description of real word phenomena. It’s almost impossible to have a high turbulence level, since most of the wind tunnel are actually designed to decrease it, it’s not possible to correctly analyse the effect of crosswind and it’s impossible to reply real world driving conditions such as abrupt wind burst affecting the vehicle. CFD software on the other hand are fully capable to overcome the limits of a classic physical facilities and, even if with some inaccuracies and necessities for a parameter tuning to reach the correlation with reality, are nowadays a powerful and reliable base. This wind of renovation involving vehicle aerodynamics is leading to the research and settelment of new standards able to account in always more realistic way for the true physics of the phenomena. One of the most interesting research fields, as well as key of this thesis Is the representation and analysis of realistic world driving conditions managing parameters such as Atmospheric Boundary Layer, surface roughness impact, vehicle behaviour under steady or unsteady crosswind, turbulence effect. The target is to obtain is a standardised method able to predict in a good way the average Cx coefficient of a vehicle subjected to all the previously mentioned effects while travelling at constant speed.