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Access Type

Campus Access

Document Type


Degree Program

Mechanical Engineering

Degree Type

Master of Science in Mechanical Engineering (M.S.M.E.)

Year Degree Awarded


Month Degree Awarded



wind turbine, blade, flutter, flexible, large-scale


There is a growing interest in extracting more power per turbine by increasing the rotor size in offshore wind turbines. As a result, the turbine blades will become longer and therefore more flexible and a flexible blade is susceptible to flow-induced instabilities, such as classical flutter. In order to design and build stable large wind turbine blades, the onset of instability should be considered in the design process. To observe flow-induced instabilities in wind turbine blades, a small-scale flexible blade was built based on NREL 5MW reference wind turbine blade. The blade was placed in the test section of a wind tunnel and its tip displacement was measured using a non-contacting displacement measurement device. The blade was non-rotating and was subjected to uniform incoming flow. For a range of blade angles of attack, instability was observed beyond a critical wind speed. The amplitude of oscillations increases for wind speeds higher than the critical speed, and the frequency of oscillations remains constant. Flow visualizations and force measurements are conducted and the influence of various system parameters including the angle of attack and the blade twist was examined.


First Advisor

Yahya Modarres-Sadeghi