NASCAR Truck Aerodynamic Analysis and Improvement

Abstract

The NASCAR Truck Aerodynamic Improvement team is tasked with providing aerodynamic analysis and improvement to Ford Performance and their factory supported team Brad Keselowski Racing for their Ford F-150 race trucks. A Ford F-150 race truck is a “stock” truck that has some modifications for racing speed and safety. Ford Performance, reached out to an MSOE student and asked if a Senior Design team and project could be assembled to provide them with some aerodynamic analysis and improvements that would not require them to build and test using a trial-and-error type method resulting in expensive, and real, testing. The purpose of this project was to conduct a computational fluid dynamic analysis on the truck and make design changes to the truck that will provide more down force on the front two tires. The areas of the truck that were studied included the side panels, deck lid, rear quarter panels, and frontal geometry. There were also constraints put in place by the NASCAR rulebook on the vehicle specifications. These rules limit the design changes that were made to the truck. The model was originally sent as a laser scanned STL file. This file needed to be heavily edited in order to be imported into the CFD program. The programs used to edit this file include Geomagic, Autodesk Fusion 360, and SolidWorks. Through using these programs, the laser scan file was modified to a usable format. Upon conclusion of the CFD simulations using ANSYS Fluent, it was found that the truck with no geometry changes displayed a drag coefficient of 0.489 and a lift coefficient of −0.815. These results were found after 10,000 iterations of testing. The standard deviation in the drag and lift coefficients were 0.00743 and 0.01660 respectively. All statistical calculations along with the averaged solutions were calculated using the data after the 2,500th iteration. This is because the nature of the CFD solutions tend to fluctuate greatly at first and then slowly converge with more iterations. After the 2,500th iteration, a relatively steady state in the solutions is met where the residuals are converging to a single value or the fluctuation in the solutions is repetitive. The following design changes were made in attempt to increase the down force on the truck. A rib was added to the side panel in order to increase the downforce on the truck. The side panel was also modified with a cut. The contour on the rear deck lid was smoothed in order to decrease drag on the truck. Slots were cut out of the shell of the truck behind the rear wheels on both sides of the truck. These slots were angled in an attempt to create down force on the rear wheels. The front splitter was lowered closer to the ground in attempt to increase air velocity moving under the truck. This higher velocity air would create a lower pressure region under the car which would increase down force. All of these modifications were applied to the initial truck body and tested using the same setup as the baseline. The most successful design change was the rear deck lid modification which resulted in a drag coefficient of 0.472 and a lift coefficient of −0.816. This is a 3.48% decrease in the drag coefficient and a 0.12% decrease in the lift coefficient (or 0.12% increase in downforce). The results of this project were purely simulation based; any real modifications and field testing made will be performed by Brad Keselowski Racing and Ford Performance.