A consideration on drag reduction by air lubrication using integral type boundary layer computation

概要

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The present paper is aimed to illuminate the effect of bubbles in reducing frictional resistance which was confirmed by the results of full scale experiment carried out in 2008 by using the cement carrier Pacific Seagull. Obtained results from the experiment show that the resistance reduction in cases of ballast condition and full load condition were 11% and 6%,respectively. Boundary layer method of integral type is utilized in this paper with the assumption that local skin friction is reduced by the injected bubbles.Axial velocity distribution and momentum thickness are computed for with and without bubbles cases. Calculated results show that reduction rate of local skin friction has the distribution although the same constant reduction rate is applied to the local skin friction law. It means the boundary layer development is different for with and without air bubbles. It could also show the difference of velocity distribution at propeller plane which was observed in full scale experiment indirectly by thrust measurement.