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標題: | 魚類群游以及槽道效應的節能表現探討 Investigation of Power Saving on Fish School and Channel Effect |
作者: | Wei Shih-Chieh 魏士傑 |
指導教授: | 楊鏡堂(Jing-Tang Yang) |
關鍵字: | 群魚游動,三維排列,自身推進,槽道效應,來流速度, fish school,three dimensional arrangement,self-propelled,channel effect,incoming flow velocity, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 本文研究鰺魚式推進的魚類游動排列相對位置與耗能的關係。由於魚類群游的研究難以量測能量消耗,而流場的分析又需要足夠大的區域以避免壁面效應的影響,因此對於魚類群游的探討多以模擬進行。近年來研究以二維數值模擬居多,即使有三維模擬也多數聚焦於固定來流,鮮少有自推進的相關研究,因此本研究除了自身推進外,亦使用三維模擬為探討模型,以期更貼近真實魚類游動的現象。 本文首先以固定來流與固定魚身的方式模擬在前後魚列距為0.3倍魚身長,模擬結果顯示下游魚隻的平均游動功率係數與文獻中相符,證實本文模擬的可靠度。接著以自推進設定上游兩隻魚帶領下游一隻魚的方式,固定上游魚隻排距為0.3倍魚身長,並以0.3倍、0.4倍、0.5倍為上下游魚隻的列距模擬群魚游動。經計算,在初始位置為0.4倍以及0.5倍的游動時會產生節能的現象。分析流場後發現,前方魚隻在擺尾時尾部壓力與單一魚隻有些許不同進而使其產生節能效益。而游動速率方面,因為渦漩強度不夠,加上無法透過調整動作以完整捕獲上游魚隻產生的逆卡門渦街能量,自身推進的魚隻穩態速度與單一魚隻相差甚少,顯示跟隨魚隻並無回收利用領頭魚隻的能量。 當魚類併排游動時會產生槽道效應。流體流過兩隻魚中間時,由於流道變窄而加速形成低壓,本文發現此低壓可以幫助擺尾向此處的魚隻節能,但不會造成擺離此處的魚隻額外的耗能。改變不同的來流速度後,流速越大會使群魚游動的耗能越低,且流場相對高低壓的生成時間產生差異,致使一週期內的耗能峰值與谷值有些許的相位差。而調整魚隻不同的排距後,併排魚隻中間的低壓區會隨著排距增加而減弱,由此證明槽道效應在魚隻的併排游動中確實扮演重要的節能角色。本文的結果可應用於未來群體水下載具的發展以及風機擺設的研究,在尾流中如何能讓風機提升發電量。 In this study, the relationship between the relative position of fish school and power consumption of carangiform locomotion fish is discussed. The power consumption is hard to measure through experiment, and the analysis of the flow field needs a large enough area to avoid the influence of wall effect, as a result, the study of fish school swimming is mostly carried out by simulation. In recent years, most researches on fish swimming are two-dimensional numerical simulations, though some of them may be three-dimensional, there are still few self-propelled related researches. Therefore, in addition to self-propulsion, this study also applies three-dimensional simulation as model, in order to get closer to the phenomenon of real fish swimming. This article first sets the distance between upstream fish and downstream fish as 0.3 times fish body length. The result shows that the power consumption of the downstream fish is consistence with the literature, confirm the reliability of my simulation. Then setting the self-propelled simulation with upstream two parallel fish to lead one downstream fish, fix the distance between upstream fish as 0.3 times fish body length, and use 0.3 times, 0.4 times, and 0.5 times as the upstream and downstream fish distance to simulate a school of fish swimming. The result shows that when the distance between upstream and downstream fish is 0.4 and 0.5 times body length, the total power consumption may reduce compared to single fish, we find that there’s a little difference pressure distribution between upstream fish tail and single fish tail, this may be the reason why energy is saved. In terms of swimming velocity, because the vortex strength is not enough, and the energy of reverse Kármán vortex street generated by the upstream fish cannot be fully captured by downstream fish, the steady-state velocity of those fish swim in school is almost the same as single fish, indicating that downstream fish did not benefit from swimming in fish school. The channel effect happens when fish swim side by side. When the fluid flows between two fish, it accelerates and form a low pressure area due to the narrowing of the flow channel. This article find that the low pressure area can help those fishes swinging their tails to it save energy, while not causing additional energy consumption for those fishes swinging their tail away. After changing different incoming flow velocity, we found that the higher the flow velocity, the lower the power consumption. The generation time of the relative high and low pressure of the flow field are also different, causing some phase lag on the peak and valley of power consumption. After adjusting the size of the channel, the low pressure area in the middle of the channel will decrease as the distance increases, which proves that the channel effect does play an important energy-saving role in the side-by-side swimming of the fish. The results of this article can be applied to the future development of AUV and the research of wind turbines layout, helpinging the wind turbines increase the power generation in the wake. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/49820 |
DOI: | 10.6342/NTU202003017 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
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