On Resistance of a Submerged Lifting Body which Generates Downward Lifting Force

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  • 鉛直下向き揚力を発生する没水揚力体の抵抗について
  • エンチョク シタムキ ヨウリョク オ ハッセイスル ボッスイ ヨウリョクタイ

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Experiments and the linear wave theory have suggested that the wave-making resistance of a submerged body can be reduced by downward lifting force. Although much studies have been done on submerged lifting bodies, all of them are focused on those generating the upward lifting force. The free surface phenomenon of downward lifting force is worthy to be studied for practical applications.<BR>In the present study, numerical simulation is carried out to investigate the characteristics of drag of a lifting body submerged near the free surface. The simulation is done by a direct boundary element method where fully non-linear free surface boundary condition for the submerged lifting body is considered. To simulate the flow around a lifting body, a wake sheet is extended from the trailing edge so as to satisfy the Kutta condition.<BR>Through the computations, it is found that the downward lifting force reduces the drag of a submerged lifting body, and the minimum value of drag appears when the lifting force is produced downward. The computations for various submergence depths have revealed that there exists a depth where the drag is minimum.<BR>The method of optimization is introduced in order to obtain the optimum profile with minimum drag. At a result of iterative optimization, the drag is remarkably reduced compared with that of the initial profile.

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