Oscillating foil-based wind harvesting systems utilize the phenomenon of limit-cycle oscillation (or constrained flutter) to generate power, and these systems are capable of generating enough power to support the average household electricity usage of 900 KWH per month. In this project, researchers aim to address one of the most challenging aspects of this renewable energy technology, in which significant gaps still exist in understanding methods to actively maintain limit cycle oscillations and achieve continual power generation in the realistic, time-varying operational environments that foils would encounter in Nature. To this end, the project will investigate new active flow control methods, which are shown to achieve well-controlled flutter-induced wind energy extraction characteristics in realistic operating environments. To achieve the highest possible net power output, the project researchers will employ low-auxiliary power actuators embedded in the foil, which are known to be effective in conventional flow control applications. The proposed closed-loop active flow control systems will be tested and refined using high-fidelity computational fluid dynamics simulations and experimental wind tunnel tests. The developed active flow control methods could be successfully employed in further optimization studies of the wind energy extraction technology, which could offer several potential benefits (including low noise, low wind speed requirements, and compactness), compared to the traditional wind turbine designs. The project further offers the potential to enhance the practical performance of oscillating foil-based wind harvesting systems, thus making them more amenable to widespread implementation. The project integrates research and education through the creation of a multidisciplinary research and development group, in which aerospace engineering and engineering physics undergraduate and graduate students work in teams to develop conceptual designs for physics-based control methods for wind energy harvesting systems. Project team leaders will follow the tradition of promoting equal opportunities for underrepresented groups when nominating students for the project.
To perform the proposed investigations, control-oriented, reduced-order mathematical models will first be formulated for oscillating foil-based wind energy harvesting systems, which incorporate detailed dynamic models of the power generation system, foil-mounted flow actuators, fluid flow dynamics, and the aeroelastic effects of the oscillating foil. New methods of nonlinear, closed-loop active flow control will then be developed and rigorously analyzed, which are proven to influence the foil-surface fluid flow velocity/pressure field in such a way that the energy harvested by the oscillating foil is maximized over a wide range of wind velocities and unexpected gusts. The project will utilize detailed mathematical analytical methods to investigate and rigorously quantify the range of operating conditions within which the newly developed active flow control systems can reliably maintain foil oscillations. An additional aim of this research project is to develop feedback control designs that are practically implementable, requiring no function approximators, minimal computational complexity, and few sensor measurements. Oscillating foil-based wind harvesting systems promise performance levels comparable to that of rotary wind turbine systems, while benefiting from low wind-speed environments. To design reliable and practical oscillating foil-based energy generation systems, detailed mathematical modeling and active control of the fluid-structure interaction dynamics must be rigorously investigated and clearly understood. The experimental validation aspect of the project will be performed in collaboration with Dr. Oksana Stalnov, of the Technion-Israel Institute of Technology in Haifa, Israel, using their wind tunnel facility.
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.
