Study of the Effect of Undertray Geometry Variations in Formula Student Cars on Downforce and Drag Coefficient Using Computational Fluid Dynamics Methods

Abstract

Undertray is the term for the venturi tunnel under the car body, which can increase the traction and acceleration of a racing car due to increased downforce. This research aims to find the optimal undertray geometry for formula student racing vehicles. The modification carried out in the research compared three undertray geometry variation designs to produce a design with the highest downforce value and the lowest drag coefficient. Testing was conducted using Computational Fluid Dynamics (CFD) by giving each design a wind speed of 80 km/hour, 90 km/hour, and 100 km/hour. After testing, the values for downforce, drag coefficient, turbulence kinetic energy contour, pressure, speed, and streamline behavior were obtained. As a result, the drag coefficient value is not too influenced by changes in speed but is more influenced by the shape of the undertray geometry. In contrast, the downforce value increases in direct proportion to the increase in car speed. The optimization also compared the effect of adding a diffuser with the same geometry to each undertray design. The research results show that adding a diffuser reduces the drag coefficient by 0.28% and downforce by 1.103%. Meanwhile, adding an undertray increases downforce by 102.3% for student formula cars compared to not using an undertray tunnel. The simulation results show that the most optimal design to use is the undertray 3 design with a diffuser because it has proportional drag and downforce coefficient values compared to without an undertray. Even though the results of this research show that the most considerable downforce value is produced by undertray design 1 with a diffuser, the coefficient of drag value for design 1 has the highest value, so the design is not proportional to use.