Collaborative Research: Development of Low Order Modeling Methods for Oscillating Foil Energy Harvesting based on Experimental and Computational Fluid Dynamics

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Alternative energy systems based on oscillating motion of hydro- or aerodynamic foils hold promise for future development of both large- and small-scale renewable energy resources that currently remain mostly untapped, such as tides, rivers, and small wind farms. Oscillating systems offer important advantages over rotary turbines because they can operate at relatively low frequencies, are environmentally friendly, and their designs can be more aerodynamically efficient due to lower blade stress. One key fundamental challenge associated with the development and optimization of these energy harvesters is the need for a better understanding of nonlinear fluid dynamic mechanisms that significantly impact device performance. The goal of this project is to combine experimental and computational analyses to investigate critical underlying flow physics and to develop low order theoretical models which can accurately predict the power extraction potential of these devices. The project will engage K-12 outreach through the Oregon State University SMILE and SEYES programs, which bring pre-collegiate students to the OSU campus for research experiences. In particular, hands-on wind tunnel demonstrations, created with the help of university URISE and STEM fellowships to undergraduate students, will expose elementary and high school students to aerodynamics research. Finally, an open access textbook, largely based on the elements of this project, will be made available to a national network of over 50 universities. Specific goals of this project are to develop a thorough understanding of how large-scale, low Reynolds number viscous flows can be accurately and efficiently evaluated using a global impulse-based model. This model will be developed through careful scaling of experimental and computational flow field data to account for kinematic oscillatory motion. The derivative moment transformation technique will be applied to phase-averaged flow dynamics to arrive at transient force predictions. The methodologies to be used include phase-resolved particle image velocimetry and advanced hybrid RANS-LES computational modeling to provide detailed time-dependent flow analysis. The primary technical objective is to elucidate the ?life cycle? evolution of large-scale vortical structures inherent in these flows and to correctly model their dynamics. In addition to improving fundamental understanding of the complex dynamics of oscillating foil systems, the low order models will be developed for a wide range of oscillating foil kinematic conditions.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.