Study on Drag Reduction of a Car Prototype for Fuel-Saving Competition

This paper discusses the optimal aerodynamic shape design for the vehicle model participating in the Shell Eco-Marathon. The design of the vehicle's body is developed based on the chassis structure and regulations of the competition. Simultaneously, the NACA 2421 Airfoil profile is used to construct the vehicle body shape to reduce the aerodynamic drag. Three series of numerical simulations were conducted to determine the optimal values of the diffuser angle and the body side profile for the minimum aerodynamic drag. The first simulation series was performed on a three-dimensional vehicle model with different diffuser angles to find the angle that yields the smallest aerodynamic drag value. In the second series of simulations, the optimization focused on the body side profile of the vehicle model with different heights of the NACA 2421 profile sections of 0.5H, 0.6H, and 0.7H, in which H is the total height of the upper side of the NACA 2421 airfoil's profile, while the optimal diffuser angle is fixed. The last simulation series investigated the aerodynamic drag on the vehicle model with the optimal diffuser angle and body side shape at different velocities. The results show that the model with a diffuser angle of 15° and a body side profile of the NACA 2421 profile section with the height of 0.6H produces the minimum aerodynamic drag. The optimal drag coefficients of the vehicle model vary in the range of 0.150 to 0.129 along with the velocities of 20 to 50 km/h, respectively. The study showed that applying the NACA 2421 profile to the vehicle profile design for reducing fuel consumption has obtained significant achievements.