Study on the Angular Oscillation of a Rigid Blade in the Liquid Flow

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  • 流水中における剛性平板翼の振動に関する研究
  • 流水中における剛性平板翼の揺動に関する研究
  • リュウスイチュウ ニ オケル ゴウセイ ヘイバンヨク ノ ヨウドウ ニカンスル

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Abstract

The present study on the angular oscillation of a rigid blade in the liquid flow primarly aims at investigation of the fluid force exerted on the moving body, in succession to the former study on the linear oscillation in the still fluid, particularly focussed on propulsive performance of the flapping wing. The range of experiments covers four kinds of test blade of rectangular shape with different aspect-ratios. It results from the experiment that the fluid force varies in quasi-sinusoidal form, with a phase lag denoted by δ relative to the oscillation angle of the body. δ increased with advance ratio denoted by α, as confirmed by simple analysis. Formulae of propulsive efficiency for general use in terms of above-mentioned α and δ are deduced for the rigid blade and elastic blade. There-from it is explained how the efficiency generally depends on α and δ and the poorquality of the rigid blade as propeller is attributed to high value of δ which amounts to as much as nearly 90°. Also, it is revealed that α for the present case is far smaller compared with aquatic animals and it deteriorates the efficiency.

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