A Calculation of Air Bubble Locus around Ship Hulls

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The air bubbles, which entrained to the ship bottom from tho bow, disturb reliable sound operation of underwater acoustic instruments on the bottom. This paper deals with a method to calculate air bubble locus around ship hulls and a guidance for the design of ship hull forms with less bubble entrainment and the arrangement of acoustic instruments. The size of bubbles studied is between 250μm and 550μm in radius. Because sound wave used in operation of the acoustic instruments is considered to be in resonance with the pulsation of the bubbles described above, and then the reliability of the instruments deteriorate remarkably. Firstly, a method to calculate air bubble locus around ship hulls was investigated. Secondly, the model test was carried out to observe bubble locus around ship model. Finally, the calculation method was applied to the design of ship hull forms. The method is based on an equation of bubble locus formulated by adding the rising velocity due to buoyancy of air bubble to the equation of stream line around a ship hull. As a result, bubble locus calculated by the present method agrees well with the observation in model tests. It is also shown that the U-shaped bow form with bulbous bow is less bubble entrainment to the ship bottom than the V-shaped bow form with normal bow.
社団法人日本船舶海洋工学会の論文
1991-03-29