Term of Award

Fall 2025

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Mechanical Engineering

Committee Chair

Mosfequr Rahman

Committee Member 1

David Calamas

Committee Member 2

Hossain Ahmed

Abstract

Electric Vehicles, despite many advantages over their gasoline-powered counterparts, have the following main challenges towards mass adoption – the charging infrastructure and the range of the vehicle. Among the myriads of factors affecting the range, the coefficient of drag and the required power to overcome it are noteworthy. This study aims to investigate the effect of rear underbody slant angle on a common, simplified hatchback-shaped Electric Vehicle. The rear underbody slant angles (upward) assessed were 0°, 5°, 10°, and 15° and they were subjected to three freestream velocities representative of urban (16 m/s), highway (25 m/s) and interstate (40 m/s) driving conditions. Followed by CAD model development and mesh generation, the computational investigation was executed using a steady RANS SST k-ω model to evaluate the impact of each angle configuration with variation in freestream velocities. The model tended to overpredict CD by 5.9% when compared against a benchmark model reported in literature.

Results for drag shows weak Reynolds number sensitivity and a repeatable ordering of angles. Across all velocities, the 0° configuration has the lowest CD, which may serve as a reference. Among the remaining geometries, the 15° underbody slant angle is consistently closest to the 0° reference, followed by 10° and 5° configuration, which led to the highest drag coefficient. At 40 m/s, the CD for 0°, 5°, 10°, and 15° angles were reported to be 0.384928, 0.389318, 0.388762 and 0.387725 respectively. Negative lift (downforce) increases substantially with underbody angle and with speed. Using CL < 0 for downforce, the ranking remains stable across all velocities with 10° being the most negative (highest downforce), 15° a close second, 5° third, and 0° being the least negative (lowest downforce). Power requirements rise proportionally as the velocities increase, however, at a particular velocity, the differences between each configuration are small with 15° underbody angle being the closest to baseline value. Overall, if maximum downforce is required, the 10° version of the model offers the most speed robust solution, meanwhile, the 15° variation offers a balance between reduced drag and generated downforce with minimal penalty in downforce

Research Data and Supplementary Material

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