LEBUの乱流摩擦抵抗低減の数値計算

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概要

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• Large Eddy Break Up (LEBU) is one of the promising ways to reduce ship frictional resistance because of its simple structure and passive action. There are, however, several questions about the effect of LEBU such as exact amount of the drag reduction, persistence of the effect or effectiveness in high Reynolds number (Re) flow. The valid mechanism of drag reduction by LEBU has not yet been made clear, too. The present study aims to answer these questions by computational fluid dynamics. A finite volume method with the k-ε turbulent model and the SIMPLE argorithm is employed to calculate viscous flows on a flat plate with and without LEBU under zero pressure gradient. After comparing the computed flow fields and frictional resistance with wind tunnel results at low Re, the effect of LEBU in high Re flow is predicted by computations at Re=10^9. Possible mechanism of drag reduction by LEBU is also discussed. The following conclusions are obtained: (1) Computed flow fields and frictional drag behind the LEBU agree well with the wind tunnel results. (2) Estimated amount of drag reduction by LEBU is about 15% at maximum and the effect persists until about 100δ downstream from LEBU regardless of Re. (3) Continuous drag reduction effect is realized by the 2nd and 3rd LEBU located at the point where the upstream LEBU effect vanishes. (4) Because LEBU modifies the eddy scale, the structure of boundary layer is altered then the Reynolds stress near the wall is reduced.

• 社団法人日本船舶海洋工学会の論文
• 1989-08-25

著者

• 白勢 康

  IHI

• 白勢 康

  石川島播磨重工業(株)技術研究所

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