Date of Award

Fall 2001

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Oktay Baysal

Committee Member

Colin Britcher

Committee Member

Drew Landman

Call Number for Print

Special Collections; LD4331.E535 M44 2001

Abstract

Since the goal of NASCAR racing is to win and since drag is a force the vehicle must overcome, a thorough understanding of the drag generating airflow around and through the automobile is greatly desired. The external airflow contributes to most of the drag that a car experiences and most of the downforce the vehicle produces. Therefore, an estimate of the vehicle's performance may be evaluated using a computational aerodynamics model. This thesis presents a computational fluid dynamic (CFD) analysis of a NASCAR Winston Cup series race car to investigate the salient flow characteristics.

Before a computational analysis could be performed, a computer model had to be developed. This model was created from the measurements of the car obtained by using a laser triangulation system. Once a computer-aided drafting (CAD) model of the actual car was developed, the model was simplified by the removal of the tires, roof strakes, and modification of the spoiler.

The first computational part of the project was to determine an optimal mesh density. Henceforth, a mesh refinement study was performed. The mesh refinement study explored five cases with volume meshes ranging from 400,000 to 2,500,000 elements. The primary criteria used to determine the optimal density was the convergence of the computed drag coefficient. From this analysis, the case with 2,000,000 elements was selected as being optimal; hence this best mesh density was designated as the baseline case.

Qualitative and quantitative results were extracted from the computational results obtained from the baseline case. Qualitative results included flow visualization of the wake in the form of streamline and vector plots. Graphical plots of pressure and velocity distributions were also prepared to visualize flow characteristics. Quantitative results included forces to measure lift and drag and the body surface pressure distribution to determine the centerline pressure coefficient. When the computational results are compared to the experimental results, the CFD drag forces are expectedly lower than the experimental forces. This result is attributable to the differences between the CFD model and the actual car. For reference purposes, the results obtained using the meshes other than the baseline mesh are presented in an appendix.

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DOI

10.25777/6mxe-rh15

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