NSF Award
2421489
This award supports research that enables a new dynamic model for fluid-structure interaction (FSI) systems with a focus on large wind turbine blades, thereby promoting the progress of science, and advancing prosperity and welfare. The project will promote safe design of next-generation offshore wind turbine structures by enabling slender and lighter blade designs. The research will provide indications about various wind turbine blade aeroelastic instability thresholds along with the most appropriate simulation and analysis approaches for novel designs of longer and therefore more efficient wind turbine blades. Although flow-induced instabilities have been predicted to occur for such new wind turbine blade designs, predictions are often based on deterministic models without the influence of flow turbulence and load variability. This project will address this critical gap by combining experimental measurements and theoretical modeling to derive a novel model that accounts for the influence of turbulence on the onset of instability and post-critical behaviors. This research is timely since the current energy plan of the United States strongly emphasizes the need for alternative and sustainable energy production by offshore wind energy. Integrated research and educational initiatives will complement the research. The findings of this research will be disseminated, at different levels, by integrating the research into the outreach programs for K-12 students and teachers, creating new modules for different courses, hosting high school classes, and broadening research opportunities for students from under-represented minority groups.<br/><br/>This research aims to make fundamental contributions to accelerate the use of stochastic and probabilistic structural dynamics to examine pre- and post-critical behavior of fully-coupled FSI systems with asymmetric structures and subjected to three-dimensional flows that can undergo nonlinear dynamic instabilities. It will achieve this goal by producing models that describe turbulence effects and more accurately considering the aeroelastic loads, which are relevant to highly flexible and asymmetric structures, such as a wind turbine blade. The existing aeroelastic load models are mainly for basic-shape airfoils (symmetric, small thickness idealized surfaces), and their flow parameters are based on experiments conducted on airfoil cross sections that represent long structures, under two-dimensional flow conditions. The researched modeling will include the asymmetries, twists and variable thicknesses that are typical of modern wind turbine blades but also applicable to a wider range of structures similar to wind turbine blades. These asymmetries and twists result in a highly three-dimensional turbulent flow. Several series of experiments will be conducted both at small and large scales. Information on flow forces and turbulence intensities for each case will be collected to inform a semi-empirical stochastic model for the onset and post-critical instability of the structure. The model will account for three-dimensional “rotationally sampled” flow features and will be validated at two separate experimental scales. These two sets of aeroelastic experiments will enable model verification for larger and full-scale structures.<br/><br/>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.
