Underbody aerodynamics: Drag coefficient reduction in road vehicles 2018-36-0291
In the last decades it has been constantly debated about the behaviour of the human being towards a better usage of the natural resources through a restructuring of unsustainable processes. Considering the case for road vehicles, it was noticed a potential for improvement by assigning a more “harmonious” configuration to the underbody of the vehicles, in order to contribute to the reduction of aerodynamic drag. This region of the vehicles is often overlooked by the automakers because it is not easily accessible to the eyes of the consumer. The objective of this paper is, therefore, to improve the aerodynamic performance of the underbody region of a compact hatchback car available in the Brazilian market. This project proposes a new underbody configuration that promotes a more harmonious flow under the vehicle, reducing this way the drag coefficient (Cd) hence improving the fuel consumption. A comparative analysis, therefore, was performed between the standard condition of the underbody (baseline) and the experimental configuration by the fluid flow simulation of the tridimensional models using a Computational Fluid Dynamics (CFD) software. Both analysis can be divided in three main stages: the tridimensional geometry modeling in CAD software, the model discretization (the creation of the computational domain and boundary conditions using a mesh generator) and the fluid flow solution in CFD. Based on the analysis of the results obtained for the fluid flow on the baseline, panels (belly pans) were proposed to cover the underbody of the vehicle. This experimental condition presented a reduction on the local drag coefficient, that is, considering only the underbody, of 28,4% and, considering the complete vehicle, of 13%. The total drag coefficient with the proposed panels was reduced from 0.34 to 0.296, which would make the studied model the vehicle with the lowest Cd of its category (compact hatchback) available in the Brazilian market.