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Experimental Studies of Flow Control Techniques for Future Aircraft


Oshima, Emile Kazuo (2023) Experimental Studies of Flow Control Techniques for Future Aircraft. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/fpcj-w268.


From the signing of the Paris Agreement to the COVID-19 outbreak, the past decade has truly challenged the aviation industry to adapt. New technologies need to be developed constantly to meet the increasing commercial and defense demands for more efficient, quiet, safe, and agile aircraft. To keep up with these rapidly changing times, an approach that marries a fundamental understanding of aerodynamics with systems design and optimization is necessary. This thesis explores two promising concepts for controlling flow over next-generation aircraft: active control on a swept wing for airplane applications, and passive control on a rotating blade for drone applications. In each, force measurements are combined with advanced flow visualization techniques to create a research framework that is both data-driven and physics-informed.

In Part I, a comprehensive wind tunnel campaign is carried out on a swept wing model of modular geometry equipped with an array of sweeping jet actuators, which have demonstrated tremendous promise for flow control authority in both laboratory settings and full-scale flight tests. The flow physics and performance of the wing is investigated first without actuation, revealing separation behaviors at both the leading and trailing edges that are crucial to consider when flow control is applied. This paves the way for an optimization study in a newly proposed framework that relies on fluid power coefficients rather than the momentum coefficient that has been the accepted parameter of choice for characterizing blowing systems over the past seven decades of active flow control research.

Part II explores the feasibility of a "prop-shroud" concept for small-scale aerial vehicles, in which the shroud is directly attached to the blade tips and thus co-rotates with the propeller. Such a configuration has the potential to provide the various aerodynamic and engineering benefits of a shrouded propeller without the associated costs and complexities of its installation. The hover efficiency of a prop-shroud is shown to be comparable to commercially available drone propellers, even without a rigorous optimization of its geometry. The effect of the co-rotating shroud is then analyzed in detail on the time-averaged, phase-averaged, and unsteady features of the flow field. A model based on vortex formation time is developed, laying out a foundation for future research and understanding.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:aerodynamics, experimental fluid mechanics, active flow control, sweeping jet actuator, wing, propeller, shrouded rotor, particle image velocimetry, tuft visualization, wind tunnel
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Awards:Ernest E. Sechler Memorial Award in Aeronautics, 2023. Rolf D. Buhler Memorial Award in Aeronautics.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gharib, Morteza
Thesis Committee:
  • Colonius, Tim (chair)
  • Dabiri, John O.
  • Bae, H. Jane
  • Wygnanski, Israel J.
  • Gharib, Morteza
Defense Date:16 December 2022
Funding AgencyGrant Number
Center for Autonomous Systems and Technologies at CaltechUNSPECIFIED
Ohio Aerospace InstituteFA8650-16-C-2644
Boeing Company University Innovation Leadership programUNSPECIFIED
Record Number:CaltechTHESIS:02042023-015312785
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Ch 3 adapted for Ch 2 and 4
Oshima, Emile Kazuo0000-0002-1689-3726
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15100
Deposited By: Emile Oshima
Deposited On:17 Feb 2023 17:40
Last Modified:25 Oct 2023 20:51

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