仿生彈性鰭及血鸚鵡魚推進原理之分析

The Propulsion Principle of Biomimetic Deformable Fins and Blood Parrot Cichlid

郭子凡(Tzu-Fan Kuo)

指導教授 ： 楊鏡堂

國立清華大學/工學院/動力機械工程學系/碩士(2007年)

https://doi.org/10.6843/NTHU.2007.00243

摘要

本文探究血鸚鵡魚尾鰭運動之高效率推進模態與機制，研究重點是以尾鰭所產生之流場結構、推進力量與能量效率作為研究主軸，並探討人造可變形鰭及非可變形鰭之流體力學參數差異，希望擷取高度可變形鰭在運動與效能上之長處，加上與真實魚鰭流場之動力相似理論分析比較，歸納出能與真實魚鰭性能相匹配之最佳參數。實驗分析分為血鸚鵡尾鰭及人造仿生魚鰭兩部份。人造及真實魚鰭皆以高速攝影機記錄其流場結構，採用粒子影像測速儀及立體粒子影像測速儀(stereoscopic digital particle image velocimetry, SDPIV) 做定量之分析。並比較血鸚鵡尾鰭與高性能人造魚鰭的流場拓樸結構差異。血鸚鵡尾鰭流場定性觀測顯示垂直尾鰭波浪模態可分為三種不同的運動模態，(1)前進下沉；(2)前進上浮； (3)停滯。PIV流場的量測顯示尾鰭波浪擺動推進前進下沉時，尾鰭上緣及下緣各產生一渦流環，且上緣渦流環中心噴流力量大於下緣渦流環。從粒子影像測速儀量測及流場觀察中發現，硬板之速度向量場較軟板混亂且無明顯特徵流場。結果顯示軟鰭在高效率能在不同的頻率擺動下都能保持；當材料為PET，當形狀為矩形，展弦比為1時，史卓荷數(Strouhal number)可得與生物最佳推進參數接近的0.38；血鸚鵡尾鰭的拓樸流場結構與最佳性能參數人工魚鰭的拓樸結構比較結果中顯示，兩者有很大的相似性。這些結果顯示高度可變形之鰭片有接近於真實尾鰭對於推進力量與效能的極大優勢。

關鍵字

尾鰭運動 ； 可變形鰭

並列摘要

The objective of this study is to investigate how can blood parrot cichlid perform highly efficient and maneuverable swimming locomotion in the water and to design a biomimetic fin which is consistent with the dynamic performance of the caudal fin of blood parrot cichlid. The comparison of propulsive performance between deformable and rigid fins is a main part of this study. Besides, the experiments are carried out using both living fish and artificial mechanism mimicking fish tai and a new experimental technique, stereoscopic digital particle image velocimetry (SDPIV), is manipulated to do quantitative analysis. At last we compare the topology flow structure between caudal fin of blood parrot cichlid and the best performance artificial fin. The qualitative flow visualization of caudal fin shows that there are three locomotion types of caudal fin maneuvering. (1) pure forward swimming and forward-sinking, (2) pure forward swimming and forward-rising, (3) position holding. The flow field measurement by using PIV shows that vortex pairs were generated by both the dorsal and ventral parts of the caudal fin and the central jet force of the upper vortex ring is larger than that of the lower one during forward-sinking. The flow field of PET fin is more stable and its flow topology is simpler. PET fin can produce larger propulsive force than PVC fin and PET fin maintains its high propulsion efficiency at different oscillation frequency, while the PVC fin can not. PET fin (rectangle, AR=1) has the best performance in propulsion force, efficiency；its flow field has the similarity with flow field induced by the caudal fin. The topological flow field structure induced by blood parrot’s caudal fin and the best performance artificial fin have many similarities. The experimental results show that highly deformable fin have advantages in maneuverability and efficiency.

並列關鍵字

motion of caudal fin ； deformable fin

參考文獻

Askew, G. N. and Marsh, R. L., 1997, “The effects of length trajectory on the mechanical power output of mouse skeletal muscles,” Journal of Experimental. Biology, Vol. 200, pp. 3119-3131.

Bearman, P. W., Owen, J. C., 1998, “Reduction of bluff-body drag and suppression of vortex shedding by the introduction of wavy separation lines,” Journal of Fluid Structural, Vol. 12, pp. 123-130.

Bushnell, D. M. and Moore, K. J., 1991, “Drag reduction in nature,” Annual Review of fluid mechanics, Vol. 23, pp. 65-79.

Drucker, E. G. and Lauder, G. V., 2000, “A hydrodynamic analysis of fish swimming speed: wake structure and locomotor force in slow and fast labriform swimmers,” Journal of Experimental Biology, Vol. 203, pp. 2379-2393.

Fish, F. E. and Battle, J. M., 1995, “Hydrodynamic design of the humpback whale flipper,” Journal of Morphology, Vol. 225, pp. 51-60.