The understanding of vortex-induced vibrations of bodies such as a circular cylinder is well developed, but little is discussed about vortex-induced vibrations of wing-like structures exposed to a cross flow. Such structures are characteristic of stationary large scale wind turbine blades exposed to the cross flow in the wind. Wind tunnel experiments have been carried out on a blade modeled as a flat plate to investigate vortex shedding, frequency response, vortex-induced vibrations and synchronization (a.k.a., lock-in) behavior. Measurements are conducted in a low speed wind tunnel, with test Reynolds Number ranging from 2.1 × 10~4 to 2 × 10~5. Lock-in is observed which is revealed by large amplitude vibration and the frequency synchronization of vortex shedding and the structural frequency. Frequency measurements were taken with sweeps in wind velocities, and a hysteresis effect associated with the lock-in flow velocity was found, depending upon sweeps of increasing or decreasing wind speeds. The relationships between the natural frequency of the structure, the response frequency of a structure in a flow, the Strouhal frequency related to the vortex shedding frequency from a fixed body, and the vortex shedding frequency associated with the vibrating body are considered, as well as the lock-in behavior that may occur.
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