Date Approved

8-19-2025

Graduate Degree Type

Thesis

Degree Name

Engineering (M.S.E.)

Degree Program

School of Engineering

First Advisor

Sanjivan Manoharan

Second Advisor

Ryan Krauss

Third Advisor

Brian Krug

Academic Year

2024/2025

Abstract

This study investigates the effects of passive flow control techniques on aerodynamic hysteresis primarily in NACA 2412 (cambered) and 0012 (symmetric) wings. Computational Fluid Dynamics (CFD) was used to design and evaluate three passive techniques, including outward-facing dimples, leading-edge tubercles, and rectangular vortex generators, prior to experimental validation. These techniques demonstrated improvements in aerodynamic performance in CFD simulations and were therefore selected for wind tunnel testing to analyze their aerodynamic performance and influence on hysteresis behavior. A custom, cost-effective experimental setup was designed and developed to facilitate efficient angle-of-attack control and data acquisition. It incorporates a three-axis force sensor, stepper motor, and Arduino Uno to automate testing and collect high-resolution force measurements. The airfoils were tested at low to moderate Reynolds numbers of 1.32x105, 1.98x105, 2.64x105, and 3.24x105. Results indicate that airfoil geometry and Reynolds number strongly affect the size and behavior of the hysteresis loops. While all passive flow control techniques modified the hysteresis characteristics, they did not consistently improve aerodynamic performance. Among them, the leading-edge tubercles were most effective at reducing the size of the hysteresis loop across all airfoils and Reynolds numbers but did not consistently enhance lift or delay stall. Dimples and rectangular vortex generators also influenced hysteresis but showed similarly inconsistent effects on overall aerodynamic performance. These findings suggest that while passive modifications affect post-stall behavior, their aerodynamic benefits are highly dependent on both Reynolds number and airfoil geometry.

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