| dc.description.abstract | While airplane design has been carefully crafted, there is always room for improvement. One debated topic within the aerospace industry is which fixed airfoil winglet design best increases lift while decreasing drag. A winglet, the sole purpose of which is to keep high- pressure air below the wing and low-pressure air on top, is the upright flap that exists on the end of airplane wings. Optimization of winglet design has substantial bearing on the future of flight, given that a joint venture between Aviation Partners and Boeing reported a 4-billion-dollar worldwide savings due to their motionless winglet. Advantages of an optimized design include reducing fuel usage, CO2 emissions, and noise by up to 6% each while also increasing the range and payload capability. Throughout my research, I have striven to understand the effectiveness of current winglet designs in reducing wing tip vortices. My testing procedure resulted in over 250 data points collected, comprising of lift force and drag force measurements for four different winglet prototypes at various speeds and angles of attack. The purpose of this extensive experimental procedure was to create the most widespread picture of the performance of each winglet configuration in a simulated takeoff, cruise, and land cycle. Data analysis of the wind tunnel data revealed that no one winglet configuration is best for all velocities and angles of attack. It became clear that conventional winglets, while they do help to reduce wing tip vortices, are a negotiation of numerous conflicting requirements, resulting in less than optimal effectiveness throughout the flight envelope. Specifically, the tradeoff is between diminished induced drag and increased profile drag. This revelation led to my conceptual formulation of the morphing winglet, capable of modifying shape and orientation to optimize the desired performance metric (such as aerodynamics) at each flight condition. Not only do the benefits of morphing winglets include improved aerodynamic efficiency and an expanded flight envelope, but they have the potential to increase control maneuverability through a variable center of gravity and moment of inertia. Beyond the creation of an optimization scheme, I performed an investigation into all major subsystems (aerodynamics, structures, mechanisms, and controls) of morphing winglet design. Morphing winglet behavior is inherently multidisciplinary (coupled structural and aerodynamic effects), and thus morphing winglet design requires multidisciplinary design optimization (MDO) in order to determine the optimum wingtip geometry -- a function of the performance metric and the multitude of constraints. I conducted a literature review that provided theory and design recommendations that I implemented into CAD design. Servo actuated hinges drive the motion of the morphing winglet inside the wing skin. Future work lies in assessing the gain of the morphing winglet relative to a static winglet, followed by the execution of a cost-benefit analysis of the morphing wingtip device, which would weigh the gain against the incurred penalties, such as weight and complexity. Morphing potential includes not only adaptation to the flight environment (velocity, angle of attack, air density) but also to the mission goal and associated performance metric. When this is achieved, aircraft with morphing winglets will significantly outperform fixed winglet designs across a wide spectrum of requirements. All things considered, this thesis has laid the groundwork for future research, which could impact the aerospace sector on a global scale. | |
