Publication Date
2025
Document Type
Thesis
Committee Members
Mitch Wolff, Ph.D. (Advisor); George Huang, Ph.D., P.E. (Committee Member); Christopher Marks, Ph.D. (Committee Member)
Degree Name
Master of Science in Mechanical Engineering (MSME)
Abstract
A variety of aerodynamic devices operate at low Reynolds number conditions, such as unmanned aerial vehicles and low-pressure turbines in gas turbine engines. At low Reynolds numbers, many airfoils experience laminar boundary layer separation as the fow lacks the energy to overcome the adverse pressure gradient. Researchers have documented a variety of methods which can suppress laminar separation, and now focus on ways to reduce energy requirements to provide efective fow control. Aspects of fow control strategy such as actuator location and pulsing at frequencies which exploit natural instabilities in the fow can reduce energy requirements. In a study by Gross et al. (Gross, Marks, and Sondergaard, 2024, ”Laminar Separation Control for Eppler 387 Airfoil Based on Resolvent Analysis,” AIAA J., 62:4, 1487-1502) a resolvent analysis was used to determine an optimal actuation frequency and location to reduce the laminar boundary layer separation bubble on an Eppler 387 airfoil. The gain curve provides a narrow range of frequencies which should provide signifcant ”no-cost” amplifcation exploited by the actuators. A subsequent numerical fow control study showed a 20%, and 4% increase to the lift-to-drag ratio at 0% and 1% freestream turbulence intensity. Two methods of fow control were used to investigate if the efects of the gain curve translate to airfoil performance. A test article embedded with synthetic jets, and a test article with an adjustable Helmholtz resonator were constructed to achieve this goal. Experiments were performed at AFRL’s Low Speed Wind Tunnel Facility to assess the change in the pressure coefcient and section drag over a range of actuation frequencies. The results of the synthetic jet implementation showed slight frequency dependence where the largest improvement shifted to a higher actuation frequency compared to the numerical analysis. The resonator implementation showed little frequency dependence except in limited edge cases. Both active and passive strategies used demonstrated that energy requirements were low enough for passive methods to achieve significant performance improvements.
Page Count
101
Department or Program
Department of Mechanical and Materials Engineering
Year Degree Awarded
2025
Copyright
Copyright 2025, all rights reserved. My ETD will be available under the "Fair Use" terms of copyright law.
ORCID ID
0009-0009-4847-4284
