Some Observations of Ultrasonic Absorption in Water of Ship Yard Dock

Abstract

The air bubbles occur in various forms in the sea, and they are generated also in wakes of ships where they are known to remain for long periods of time. Especially, great amounts of air bubbles are generated in the dock water by pouring water and by discharging currents of tag-boats in which high value of ultrasonic absorption is presumed. Observations of ultrasonic absorption in dock water were carried out in the No.2 Dock of Nagasaki Ship Yard of Mitsubishi Heavy Industry Co., in February 1970. After observations, the absorptions caused by air bubbles and others in dock water were estimated as 0.05dB/m to 0.35dB/m, and 0.13dB/m in average. Those values were far high beyond the predicted one.