Title: Windows Opening Influence on the Drag Coefficient of a Hatchback Vehicle
text: Aerodynamics plays a key role in nowadays vehicle development, aiming efficiency on fuel consumption, which leads to a green technology. Several initiatives around the world are regulating emissions and efficiency of vehicles such as EURO for European Marketing and the INOVAR Auto Project to be implemented in Brazil on 2017. In order to meet requirements in terms of performance, especially on aerodynamics, automakers are focusing on aero-efficient exterior designs and also adding deflectors, covers, active spoilers and several other features to meet the drag coefficient. Usually, the aerodynamics properties of a vehicle are measured in both CFD simulations and wind tunnels, which provide controlled conditions for the test that could be easily reproduced. During the real operations conditions, external factors can affect the flow over the vehicle such as cross wind in open highways. The aerodynamic behavior of the vehicle can also be affected by the influence of the user such as by opening the windows in order to cool down the cabin, which is the main topic of this paper. In this work, 12 different window-opening combinations are presented and the drag values compared with a baseline model, considering fully closed windows. The study was conducted using CFD simulations of a current production hatchback vehicle, with two passenger inside and full interior cabin representation. Results show drag increment for all presented cases, compared with baseline configuration, which also implies in fuel consumption increase. Further studies on cabin cooling effects and passenger’s thermal comfort are conducted in order to complement this paper.