UT Formula SAE Drag

Photo of Chisom Agada, Will Choi, Nida Kahn Students: Chisom Agada, Will Choi, Nida Kahn

Sponsor: The University of Texas Society of Automotive Engineers

Date: Fall 2009

Requirements:
When decreasing aerodynamic drag, a decrease in down force usually follows. A lower coefficient of drag is crucial in a straight section of the track where acceleration is the key component of the racecar being tested; however, down force allows the car to negotiate tight corners at high velocities. The team's main task is to reduce drag, but it would be in the best interest of the sponsor and the SAE Team to strike a balance between decreased drag and decreased down force. Another major constraint imposed by the Formula SAE Team is the dimensional restrictions set by the rulebook, which are primarily intended to ensure safety for the driver. The Formula SAE Team also wanted an aesthetically pleasing design without compromising the performance so they could attract more sponsors.

Problem:
The goal of this project is to design and modify a skin for the existing frame of the UT Formula SAE car. The FSAE team did not perform aerodynamic analysis on their previous year's models, so it is this design team's responsibility to provide the FSAE team with computational fluid dynamic (CFD) analysis verifying the new body design's reduction in drag.

Solution:
After comparing an Ahmed body with and without wings we concluded that the winged Ahmed body has a high pressure region along the top side of the rear wing and a low pressure region on the bottom side. The formation of these opposing pressure regions creates downforce because the low pressure region acts like a vacuum and pulls the car towards the ground. The front wing helps guide the airflow over the Ahmed body; this results in less flow separation at the curves of the body thus keeping the pressure consistent along the top side. A higher overall pressure on the top surface of the car results in downforce that reduces lift. In conclusion the front and rear wings generated 407% more drag and 75% more downforce. Although the winged Ahmed body has aerodynamic benefits, the specific wing geometry given to us from the FSAE team produces so much drag that its inclusion in the final body design is undesirable.

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