Sway stabilization of Doppler Sodar Isolator for Offshore Wind Observation

Abstract

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.