Haibo Dong, associate professor in the Mechanical and Aerospace Engineering Department, and his team are closing the knowledge gap regarding aerodynamics of micro air vehicles.
Imagine a vehicle small enough to fly through cracks in concrete while searching for earthquake victims or exploring radioactivity-contaminated buildings. In an effort to create highly maneuverable micro air vehicles (MAVs) that can perform such feats, research scientists have been developing and testing a myriad of MAV prototypes. Surprisingly, progress has been slow as researchers have discovered that many developments in aerodynamics over past decades cannot be applied at the micro level.
Haibo Dong, associate professor in the University of Virginia’s Mechanical and Aerospace Engineering Department, and his team have taken on the exciting challenge of closing this knowledge gap. “What we know about aerodynamics simply isn’t working when we try to design small robotic air vehicles for this type of efficiency, maneuverability, and accuracy. Today’s aerospace engineers will need to examine the fundamental physics and science behind flying and swimming in order to make progress,” Dong said.
Dong’s Flow Simulation Research Lab is challenging current tenets of aerodynamics by studying elite natural flyers of the world, including hummingbirds and dragonflies. These agile flyers are small and out-maneuver even their closest insect relatives—making them the perfect inspiration for MAVs. Using a unique approach that includes high-speed photography, 3D animation, kinematics, fluid dynamics, high speed computing, and computational modeling, the lab’s bio-inspired research has already overcome some of the barriers to progress.
Members of the lab have won several awards for breakthrough research, including most recently the American Physical Society – Division of Fluid Dynamics Gallery of Flow Motion Best Video Award, the American Institute of Aeronautics and Astronautics (AIAA) Foundation Abe M. Zarem Award for Distinguished Achievement—Aeronautics, and the AIAA Foundation Abe M. Zarem Educator Award. Other universities that competed for these awards include Harvard, Carnegie Mellon, and MIT.
What Innovation Looks Like
Competing at the graduate level, Ayodeji Bode-Oke was an undergraduate when he won second place in his region from the AIAA Foundation and later the Abe M. Zarem Award for Distinguished Achievement—Aeronautics for his research, “Optimized Body Deformation in Dragonfly Maneuvers.” Bode-Oke was the first to demonstrate that body deformation (of the dragonfly) could, inherently without considering aerodynamic effects, help minimize energy expenditure or torque during a maneuver. This discovery overturned the prevalent assumption in the aeronautics field that body deformation was unimportant, and thus set new standards for the future design of fuselage for flying drones.
Bode-Oke, a 5th year student, has been in Associate Professor Dong’s lab since his second year at UVA. With Dong as his advisor, he has also worked closely with mentor and fellow lab mate, PhD candidate Samane Zeyghami. “She’s the smartest person I’ve worked with. She makes me feel smart because I bring something to the table.” Bode-Oke credits Zeyghami, who is second author on many of his papers, for her advanced knowledge, scientific rigor, and dedication to guiding and advising him. Bode-Oke says that being in a lab environment that is challenging but also satisfying, from the undergraduate through to the graduate level, has helped him incubate his ideas and gain breadth and depth in his research.
Dong has intentionally created a lab that is collaborative and exciting. “It’s the fun way to do research. No one is left on their own.” Dong started the Computation, Visualization, and Bio-inspiration Lab using grants from the National Science Foundation (NSF) and Air Force Office of Scientific Research (AFOSR), which conduct biological fluid dynamic research with an integrated experimental and computational approach. Dr. Dong received the AIAA Abe M. Zarem Educator award for being an outstanding educator.
Pioneering Research in Aerodynamics
Although sometimes it seems that the vivid flow simulation graphics are more artistic than scientific, the unique methodology used by the Flow Simulation Research Group is based entirely upon science. Its integrated approach captures the intricate and extensive details of flight in nature, uncovering information hidden in air currents and vortices of moving wings—details that have not been previously observed or studied. Since the fundamentals must be revisited, researchers collect as much data as possible so as not to eliminate any possible discoveries about the relationships of mass, movement, airflow, and other properties.
To produce the models that have been the catalyst for this pioneering work, first researchers must catch the object of bio-inspiration. The favored place on UVA grounds to capture dragonflies is the pond near Dell Field. Then, the researchers must carefully place colored dots onto the dragonflies’ transparent wings so that they can be tracked on a digital camera output. Next, the insect is transported to the a space where motion-triggered, high-speed cameras await the flight of the dragonfly. A photogrammetry system consisting of three high-speed cameras (1 Mpix at 1000 fps,) synchronized and calibrated in three-dimensions, enables sufficient and instantaneous data acquisition.
After the data has been collected, it is used to reconstruct an animation in Autodesk Maya and conduct kinematics analysis in an in-house 3D software program (SMOKA). This program uses kinematic equations to compute wing/body motions, flapping/pitching angles, body deformation, wing morphing, and more. Then, using in-house code, an immersed-boundary method-based high-fidelity flow solver developed by Dr. Dong and others, fluid dynamic equations are plugged into all of the flight and kinematics data. This procedure involves so much data that super-computers are required in order to process it. IBM NeXtScale computer clusters totaling 200 cores, 1TB of RAM, plus a file server with 150 TB of disk capacity with InfiniBand architecture, are used. The output is a computational model that provides a high-definition, data-dense, visual simulation of motion and flow field data.
Because the movements and flow fields are now “visible,” researchers have a solid model to analyze and study them in order to find possible flow control mechanisms that insects and birds might use to adjust their flight forces quickly and efficiently. Also under investigation are the possible connections between flight forces and the wing modifications that insects make to accomplish specific maneuvers. The 3D computational flow simulation and analysis tools include direct numerical simulation (DNS), flow visualization through Eulerian vorticity and Lagrangian coherent structure, and instantaneous locomotive force computation via CFD methods and Lagrangian wake dynamics.
With this research, information to produce the next generation of MAVs starts to become available.
“Our hope is that by researching the efficiencies of insect flight we are contributing to the design of small flexible winged robots and lead to an innovative design of flying robots and perhaps extend it to other aircraft designs as well,” Dong said.
Dong is also teaming with Mechanical Engineering Professor Hillary Bart-Smith for more bio-inspired research using this same methodology. Footage from other camera-capture sources can be plugged into the flow simulation computational modeling process. The graphic to the left is an example of the output using swimming orcas.
Bart-Smith is leading her second MURI (Multi-University Research Initiative) program funded by the Office of Naval Research. The project is titled “Bio-inspired Flexible Propulsors for Fast, Efficient Swimming: What Physics Are We Missing?” It is a collaboration between the University of Virginia, Princeton, Harvard, Lehigh University, and West Chester University.