Aerodynamic Optimization Using Add-On Devices: Comparison between CFD and Wind Tunnel Experimental Test

JUNO is an urban concept vehicle (developed at the Politecnico of Torino), equipped by an ethanol combustion engine, designed to obtain low consumptions and reduced environmental impact. For these goals the main requirements that were considered during the designing process were mass reduction and aerodynamic optimization, at first on the shape of the car body and then, thanks to add-on devices. JUNO's aerodynamic development follows a defined workflow: geometry definition and modelling, CFD simulations and analysis, and finally geometry changes and CFD new verification. In this paper the results of the CFD simulations (using STARCCM#x0002B; and RANS k-?) with a corresponding 1/1 scale wind tunnel tests made using the real vehicle. Particularly, the results in term of: total drag coefficient (Cx), total lift coefficient (Cz), the total pressure in the side and rear analyzing twenty different aerodynamics configurations made up of different combination of some aerodynamics add-on devices. From the analysis of the results is emerged that CFD simulations using RANS k-? methods are able to predict the trend of total drag coefficient and its absolute value. Regarding the trend and the absolute value for lift coefficient, much larger deviation than Cx has been identified. For total pressure scene, there is a high similarity between the two ways of testing, especially on the side and on the central rear zone. The CFD results simulations, RANS k-? model is correct to develop and test symmetrical wide body. The obtained results are in good agreement with experimental wind tunnel results but, with particular attention to geometry, that suddenly change the way of air-flow.