Aerodynamic Design Improvement of NDSU Solar Car through Computational Fluid Dynamics 2008-01-2251

In the design of solar powered cars aerodynamic efficiency is extremely important. Due to the limited power and energy sources available, the aerodynamic design of the car must provide a low coefficient of drag. In order to identify the major drag source areas in the design and to improve the aerodynamics performance of the current NDSU solar car an extensive computational fluid dynamics (CFD) study was performed using ANSYS CFX 10.0. The study was set into two paths. The first path focused on modifying the current NDSU solar car design in order to reduce the drag force. The second path was to design a completely new solar car with better aerodynamics performance. Through the CFD analysis of all the designs considered major drag source areas were identified as the underbody, the dome, and the nose section of the car. In order to reduce the drag contribution from the underbody the inclusion of fairings enclosing wheels, suspension, brake, and motor components was recommended for all designs. Even though fairings increase the cross sectional area, their overall effect greatly reduced the drag force. It was found through CFD analysis that the individual fairings can decrease the drag force created by the wheels, suspension, brake, and motor components by 50%. Simulations indicated that the nose section of the current solar car had the largest contribution to the drag force. Therefore reducing the drag on the nose was essential in order to increase the efficiency of the car. The nose section was modified to a leaner, pointed, and gradually angled shape. The separated flow region behind the dome in the current car design was eliminated and the aerodynamic characteristics of the dome section were improved by designing a streamlined and low profile dome shape. In all designs the limitations and regulations set forth by the American Solar Car Challenge (ASC) were followed. The results of the analysis for the current NDSU solar car showed that with basic modifications the coefficient of drag could be reduced by approximately 5%. From the analysis of new concept cars a few major recommendations were concluded. The best aerodynamic performance was obtained for a design with three wheels with individual fairings on each wheel, a thin nose section, and a lean a streamlined canopy section. The paper includes details of the computational analysis including the comparison of different designs.