Investigation of Buoy Hydrodynamic Damping Based on Model Testing Data Series of Indonesia Tsunami Buoy

Abstract

Due to the recent Tsunami event in Indonesia in 2018, the Ina-TEWS program has been started again by the Indonesian Government. A new design has been manufactured and already deployed to the Indonesian water. This design is named Buoy G – 3. The tsunami early warning system (TEWS) consists of a tsunami buoy, an ocean bottom unit (OBU), a satellite and a ground station. The changes of the water pressure due to the seismic movement prior to the tsunami event will be acquired by OBU and sent the reading to the tsunami buoy by acoustic signal. Then, tsunami buoy transmits the signal to the ground station via satellite. The continuously link between OBU – Buoy – Satellite makes the buoy motions especially roll/pitch has to be restricted. Because of these the hydrodynamic motion damping assessment of this tsunami buoy becomes so important. This paper describes a hydrodynamic damping analysis for roll/pitch of the tsunami buoy that based on model testing data series of Indonesian Tsunami Buoy G-1 to G-3. The data analysis will be presented on graphics that show the aspect ratio of buoy diameter over draft (D/T) and form ratio of buoy displacement over weight of the cylindrical submerged form (Δ/W) against damping ratio (β). This study finds that by using the linear damping approximation the higher the aspect ratio D/T the larger roll/pitch damping ratio β, but also the higher ratio of Δ/W the smaller roll/pitch damping ratio β.