Small, autonomous flying drones, also called uninhabited air vehicles or UAVs, have the potential to greatly expand our ability to gather information in complex environments where larger vehicles cannot operate. Their missions include delivering medical supplies in the urban canopy, search and rescue in disaster sites such as collapsed structures, collecting climate-change data in forests, and inspecting facilities such as wind turbines. To succeed, they must be highly maneuverable and handle gusts within the atmospheric boundary layer, as well as air disturbances from structures. These UAVs fly in a low-to-moderate Reynolds number regime where the flow may separate over their wings and roll up into vortices associated with unsteady forces, particularly during maneuvers and gusts. Moreover, their wings typically have low aspect ratios (ARs), making the flow highly 3D. Recent research has examined strategies to manage canonical gust types, e.g., wing pitching through a transverse gust to offset the variations in the effective angle of attack. This talk focuses on the use of a simple morphing-tip planform or shape, roughly inspired by birds or bats, to alleviate the lift-force changes from streamwise (headwind or tailwind) gusts. It rotates in-plane from a leading-edge pivot and employs sweep to promote vortex attachment. Scaled experiments are done on a low-AR translating wing in a water towing tank, which surges forward or decelerates to emulate gusts. The motorized panel is retracted or extended, respectively, to help offset lift variations from simple step-up or step-down changes in streamwise velocity. A transducer measures the unsteady lift, and dye visualization is used to visualize the separated flow including vortex structures. Recent 3D velocimetry measurements will be shown which quantitatively characterize the flow, to help explain the tip-panel performance.
Dr. Matthew Ringuette
He has a B.S. in Aeronautical & Mechanical Engineering from Rensselaer Polytechnic Institute (RPI), and both his M.S. and Ph.D. in Aeronautics from Caltech, graduating in 2004. He then worked as a postdoctoral researcher at Princeton University, and in 2008 joined the faculty in the MAE Department at the University at Buffalo (UB). His research interests are experimental fluid mechanics, vortex dynamics, unsteady aerodynamics, and bio-inspired propulsion, with applications to autonomous air and underwater vehicles, as well as high-speed flow. In 2010 he received the AFOSR YIP Award. He is currently an Associate Professor and was Director of Undergraduate Studies in Aerospace Engineering from 2014 to 2020.