5 OREGON STATE ENGINEERING more flexible and affordable alternative, Robertson explains. “We want to be able to test the technology quickly, accurately, and inexpensively without the need to build multimilliondollar machines and test them in the ocean,” he said. Robertson is the co-principal investigator of a study to explore the effectiveness of coupling physical experiments with numerical modeling. The resulting hybrid simulation was used to evaluate the performance of a floating wind turbine model at the Hinsdale wave lab. “There’s no reason researchers can’t come here to test a variety of different floating platform configurations to understand their performance characteristics.” In the study, Robertson and his colleagues built a 1/50 scale model of a floating wind platform. The model includes the turbine mast but not the blades. They subjected the tripodal, semi-submersible design to a range of sea conditions in the wave lab’s multidirectional wave tank. Results of the open-source study, funded by the U.S. Department of Energy, will be made available to anyone. “We first needed to determine what hydrodynamic tests to run in the wave tank. Then we had to figure out the best ways to measure and characterize the model’s responses so that the results could be used to predict how a full-scale floating platform would behave in the open ocean,” Lomonaco said. But something different was needed to determine the impact of wind. Because aerodynamic and hydrodynamic forces are measured using different scales that cannot be reconciled in physical models, wind forces had to be generated numerically. To accomplish that, the researchers employed a robotic arm to manipulate the mast of the scaled-down wind turbine that arises from the floating platform, explained Ted Brekken, a professor of electrical and computer engineering who focused on internal control systems for the study. “The water is much deeper off the West Coast; the waves are larger, longer, and more energetic — those factors have to be considered when designing and testing floating platforms. The designs used in the North Sea may be suitable for those locations, but they may not be optimal for our area.” Pedro Lomonaco, director of Oregon State’s O.H. Hinsdale Wave Research Lab and research team member
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