振動翼流體動力時域計算法之研究

Study on the Time Domain Calculation of Hydrodynamic Forces of Oscillating Foils

吳昌政(Chang-Cheng Wu)

指導教授 ： 邱逢琛

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01679

摘要

本研究著眼於魚類尾鰭推進的力學機制，以穩態小板法為基礎，擴充至二維振動翼非穩態流場計算，建構尾緣渦流模式及數值計算程式，先與Theodorson的二維薄翼振動解析解進行比較，以驗證本方法的正確性。其次，再引用Triantafyllou所進行的二維翼起伏與縱搖耦合運動下的推力係數、功率係數及推進效率之系列實驗分析結果作為比較驗證的依據。各種起伏振幅、名目攻角及史徹赫數的系列計算結果顯示名目攻角越小其效率越高之趨勢。而在名目攻角固定下，起伏振幅越大則推進效率越佳。此外，產生最佳效率的史徹赫數約在0.15附近，此計算結果與Triantafyllou的實驗所顯示，在小攻角狀態不發生前緣剝離渦流的條件下所得到的結果是一致的。但是在大振幅與大攻角的運動狀態下，其推進效率的理論計算值與Triantafyllou的實驗值則有較顯著的差異，其原因在於前緣剝離渦流發生的效應尚未納入本研究的渦流模式中予以適當模擬所致。

關鍵字

史徹赫數 ； 推進效率 ； 尾鰭 ； 振動翼 ； 小板法

並列摘要

Based on the steady panel method, this study explores the mechanism of caudal fin and further explains oscillation foils under two dimensional unsteady flow field. The validity of the presented study method is compared with the theoretical analysis of the two-dimensional flat plate foil from Theodorson, and with the experimental results from Triantafyllou by examining the thrust coefficient, power coefficient, and propulsive efficiency of a two-dimensional foil under heaving and pitching motion. A series of calculation suggests that the smaller the nominal attack angle, the greater the propulsive efficiency. In addition, the results indicate that the best efficiency is yielded when Strouhal number equals approximately 0.15, which agrees to the results from Triantagyllou’s experiment where no leading edge vortex was assumed.
Nevertheless, under large heave amplitude and large attack angle, the propulsive efficiency from the presented study method differs significantly from that of Triantafyllou’s experiment. This is due to the lack of consideration of the leading edge vortex in the wake model presented.

並列關鍵字

panel method ； oscillation foils ； caudal fin ； Strouhal number ； propulsive efficiency

參考文獻

[3] Wu,T.Y. 1961 Swimming of a waving plate. Journal of Fluid Mechanics 10,321~344

[4] Wu,T.Y. 1971a Hydromechanics of swimming propulsion.Part 1.Swimming of a two dimensional flexible plate at variable forward speeds in an inviscid fluid. Journal of Fluid Mechanics 46,337~355.

Wu,T.Y. 1971b Hydromechanics of swimming propulsion.Part 2,Some optimum shape problems. Journal of Fluid Mechanics 46,521~544.

Wu,T.Y. 1971c Hydromechanics of swimming propulsion.Part 3,Swimming and optimum movement of slender fish with side fin. Journal of Fluid Mechanics 46,545~568.

[5] Chopra,M.G 1974 Hydromechanics of lunate-tail swimming propulsion. Journal of Fluid Mechanics 64,375~391.