摘要
本文主要探討魚類的操控式游動，先觀測錦鯉在穩定來流下水洞中的游行動作並採用粒子影像測速儀技術量測流場結構，再利用一階梯擋體後方所產生特殊形式之流場，了解魚類為了減少自身能耗如何改變其運動模態。研究主軸是以比較錦鯉在有無階梯擋體水洞中游動時作動方式以及流場分布的不同之處。動作分析主要是以尾擺頻率、胸鰭擺動頻率、魚體側邊擺動振幅、前進速度與一個週期間瞬時時速度為重點；而流場定量分析著重於探討錦鯉在階梯擋梯後方時「特殊」運動機制之原因。 錦鯉在無階梯擋體水洞中游動時主要以尾鰭配合身體擺動產生推進力前進游動，錦鯉在階梯擋體後方時，則是以胸鰭擺動為其停在定點主要推力來源。實驗結果顯示：胸鰭擺動的頻率較尾鰭擺動的頻率小、魚體側邊擺動振幅之分析可得在擋體後方之錦鯉軀幹幾乎不會擺動，即錦鯉此時並非靠魚體擺動來抵抗水流。故錦鯉在遭遇一速度快至難以抵抗的來流時，在階梯擋體後方時相較於無階梯擋體時的游動是相對的能耗較少。 當錦鯉在無階梯擋體水洞中游動時會在尾鰭後方產生反向卡門渦流來提供高速游動所需的推進力，此時錦鯉的運動模態是一種BCF 模式。當錦鯉停在階梯擋體後方定點受一來流阻力以胸鰭作動時，會在尾鰭附近形成一股中心射流指向上游的噴流來抵抗來流，此噴流為卡門渦流，對錦鯉來說是產生一向後的力而非推進力；再由渦漩環衝理論模型計算流體推力大小，其值約與流體流經錦鯉在無階梯擋體停在定點時所受的阻力大小相同。故此推力並非錦鯉靠胸鰭擺動產生的尾流結構而使錦鯉有停在某一定點的推進力，而是錦鯉藉由胸鰭的擺動來整合其周遭因來流流經階梯擋體後方所產生的渦流，利用渦流中的能量流而減少自身游動時的能量消耗。未來希望可用於改善目前水上及水下人造載具推進機構之高耗能、低機動性與穩定性差等缺點。
關鍵字
魚類 節能並列摘要
The objective of this study is to investigate the swimming maneuvers of a fish. The experiments are carried out using the high speed camera to do motion analysis and particle image velocimetry (PIV) to do quantitative analysis between colored carp swimming in free stream and behind the step. To know how can colored crap change swimming locomotion decreasing energy consumption. The comparison of swimming locomotion and flow field structure between colored crap swimming in free stream and behind the step is a main part of this study. Colored crap use the propulsion modes of caudal fin and body undulatory motions when swimming in free stream. On the other hand, when swimming behind the step, it use pectoral fins as the main propulsion source to stay. The swimming locomotion analysis shows that the tail-beat frequency is larger than pectoral beat frequency, and the lateral body amplitudes of colored crap swimming in free stream is larger than behind the step. The qualitative flow visualization shows that the production of vortex ring between colored crap swimming in free stream and behind the step is so different. When colored crap swimming in free stream, it choose BCF mode to swim forward. When colored crap swimming behind the step, the direction of the central jet force is different from the central jet of reverse Karman vortex . Besides, we use vortex ring model calculating the value of the central jet force when it swimming behind the step. These values are close to the drag force that it stay in free stream. The experimental results indicate that colored crap know how to manipulate the interaction between the fins and the environmental flow field to decrease the energy consumption when swimming in fast flow.