RUI: Collaborative Research: Optimized design principles inspired by compliant natural propulsors.

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High efficiency is a fundamental design goal of vehicles moving through both air and water. Although most human designs of propulsors such as wings or propellers are rigid, natural propulsors are generally flexible. Propulsive efficiencies of natural flyers and swimmers are typically higher than human-designed vehicles of similar weight and dimensions. However, attempts to emulate flexible animal designs have met with limited success. Recent comparative animal studies have demonstrated startlingly consistent patterns of bending kinematics among a broad diversity of swimmers and flyers constructed from very different materials and of very different physical dimensions. These patterns encompass cilia to whale flukes and fluid regimes from water to air. This project will use computational fluid dynamics and particle image velocimetry to measure fluid velocities to investigate the mechanical and fluid dynamic details that enable high force production by flexible natural propulsors. K-12 outreach activities are planned at the universities and at the Cabrillo Aquarium in San Pedro, CA and undergraduate and graduate student involvement is core to the research project. The goal of this project is to develop a set of design rules that govern force production by flexible propulsors. To achieve this goal, experiments and computations will be used to investigate: a) bending kinematics of propulsors as control surfaces of vorticity, pressure fields and thrust, b) the hydrodynamic basis of vortex-vortex interactions that generate pressure fields and thrust and c) the advantageous limits of bending kinematics. Each of these will be investigated using a combination of experiments (particle image velocimetry) with natural organisms and computational fluid dynamic models. The results of this project will define the necessary design criteria that enable performance enhancement by bending propulsors of different types and across a range of fluid regimes. While contributing to interpretation of the natural world, the results will also contribute to novel engineered designs ranging from biomedical applications (cilia) to vehicle design (swimming, flight).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.