This project will combine new experimental and computational tools in the design and optimization of biologically-inspired propulsors. For engineering technology to successfully replicate the observed performance of biological systems requires understanding the dynamical role of propulsor flexibility and nonlinear elasticity, characteristics that are ubiquitous in biological propulsion systems. Toward this aim, the PIs will investigate jellyfish swimming as a model system for biological propulsion in general. These animals are a compelling model because they represent one of the simplest examples of a biological propulsor and yet exhibit coupled fluid-structure interactions, large deformations, and nonlinear elasticity. Furthermore, a recently compiled morphological database of over 600 species of jellyfish is available to compare the results of the engineering design optimization with the solutions found in nature. The project objectives are made possible by the recent development of a fully-coupled, two-dimensional, large-deformation, fluid-structure solver that functions within a novel paradigm: material properties and actuation forces are specified instead of propulsor kinematics or inflow boundary conditions. The numerical method will eventually be extended to axisymmetric and three-dimensional configurations. Experimental tools will provide essential new data for validation and refinement of the numerical model, initial inputs to the design optimization, and evaluation of the optimal solutions. Digital particle image velocimetry (DPIV) measurements will be collected both simultaneously and sequentially in multiple planes of the flow field created by free-swimming jellyfish. These data will be evaluated using traditional velocity and vorticity metrics as well as by using new Lagrangian tools from dynamical systems. The collaboration will enable co-design of the experiments and simulations to maximize their mutual utility for understanding biological propulsion and optimizing biologically-inspired engineering designs. A recently developed course on "Biological Propulsion" at Caltech, taught by one of the PIs, will serve as an educational outlet for this research. In order to reach a broader audience, the Illinois group will set up a user-friendly version of the developed code for use in instruction. The Caltech investigator will also continue in his role as Coordinator of the Freshmen Summer Institute (FSI) Research Program at Caltech, which introduces underrepresented incoming freshman to the environment of a research university. Finally, both PIs will mentor undergraduate and graduate students in the day-to-day research activities.
