Because of their small size and agility, quadrotors could revolutionize search-and-rescue or terrain-mapping missions. However, to do so, they have to operate in confined spaces such as rubble corridors or glacial crevasses. Existing models for how quadrotors behave near obstacles are based on helicopter theories, which are inaccurate at the smaller scales of quadrotors. We therefore built a flow-mapping arena to study how micro-scale quadrotors interact with nearby boundaries. We discovered, for example, that dueling vortices appear beneath micro-quadrotors as they land at an angle.
Cyber Physical Systems (CPS) is an emerging field. Existing CPS Education Programs typically have just a couple classes, and they often consist of previously offered classes. Along with others in the UVA Link Lab, we are creating a stand-alone graduate curriculum for CPS that consists of teaching core classes, in-depth classes, and professional development skills. New classes focus on the intersection of the physical and cyber and explicitly relate the technical material in the classes to CPS applications. (This work came out of the CPS National Research Traineeship at UVA, directed by Jack Stankovic).
The dorsal and anal fins of fish interact with the tail fins to produce higher thrust and efficiency. We focused on thin elongated dorsal fins, like those of jackfish. We discovered that dorsal fins can act like the wing strakes of fighter jets, promoting flow attachment on a main lifting surface (wing/tail) by inducing spanwise flow and reducing the effective angle of attack. Beyond a critical sharpness, the effect is more costly than beneficial, meaning dorsal fins may be optimal when they are slightly blunted rather than razor sharp. See a video of the results here. (This work was done in collaboration with the Flow Simulation Research Group at the University of Virginia.)
Fish flap their tails asymmetrically to maneuver around obstacles. In contrast, classic fish tail models assume symmetric motions in a uniform flow. We tested how well these classic models work for maneuvering tails. In some cases, the models work well: even 2D wakeless models were able to predict the phase of high frequency lateral displacements. As for predicting overshoot and settling time, only a semi-empirical model was accurate to within 10%.
Fish and birds experience different forces when they swim/fly near a flat surface (e.g. seabed, solid ground, still lake). We discovered that the vertical forces they feel switch from negative (downward) to positive (upward) at a particular distance from the surface. In other words, there’s a stable equilibrium altitude where they are neither pushed down nor up. Animals and bio-inspired robots should factor this altitude into their control schemes; ignoring it could lead to high energy costs when swimming/flying near a flat surface. (This work was done in collaboration with the Biofluids Research Lab at Lehigh University.)