For suppression device of aerodynamic vibration, there is a technique of installing the additional members such as fairing, flap and horizontal plate in a current bridge design. The horizontal plate was focused as the additional members, which is a simple structure and highly effective to suppress aerodynamic vibration.
However, at the present time, its detail mechanism is not yet elucidated on suppressing aerodynamic vibration. Therefore, the examination of a basic section was conducted at first to obtain the basic effect of the horizontal plate on suppression of aerodynamic vibrations. In this study, the flow visualization, the measurements of the aerodynamic response in torsional vibration and three components of aerodynamic force, and the wind speed measurement by PIV were conducted. As a result of three tests, it was confirmed that aerodynamic instability could be improved by installing the horizontal plates in the appropriate position.
In order to observe offshore wind with Doppler sodar on oscillating boats, the pendulum-type isolator to keep the horizontal state of the Doppler sodar was developed. The oscillation of the isolator pendulum itself was attempted to be suppressed by attaching additional masses to decrease the natural frequency of the pendulum and installing a damping system to dissipate the oscillation energy. As a result, the pendulum oscillation was suppressed sufficiently when the additional masses were attached above the rotation center of the isolator pendulum. In addition, the friction damper using sponge-like material suppressed the pendulum oscillation effectively.
The offshore wind observation using the Doppler sodar with the developed isolation system verified that the vertical profiles of the observed wind speeds follow the power law or logarithmic law. In addition, the wind speeds and wind directions observed by the Doppler sodar have good correlations with those of the cup anemometer & wind vane at the onshore site.