魚類群游之流體動力學數值模擬研究

Numerical Investigation on Swimming Hydrodynamics of Fish School

李蓮吟(Lian-Yin Lee)

指導教授 ： 湯敬民

淡江大學/工學院/航空太空工程學系碩士班/碩士(2010年)

https://doi.org/10.6846/TKU.2010.00186

摘要

本文以數值模擬之方式研究魚群體游動時的省能機制，當二維流場之Re=5000，經求解二維不可壓縮黏滯性的Navier-Stokes方程式進行數值模擬，本文設定可產生最佳游動效率之史卓荷數為0.3，調整下游魚隻之距離(s =1.25、1.35、1.5、1.65、1.75、2L)，探究下游魚隻最佳之省能位置與機制。本文歸納出之最佳下游位置為s=1.5L，下游魚隻受上游剝離之低壓尾流同向吸力之影響，可較單獨游動時減少45%功率之消耗；s=1.25 L則是減少消耗最少功率之下游位置，下游魚隻僅較單獨游動時減少9%的功率消耗。若下游魚隻之位置超過s=1.5 L(即超過1.5倍身長)，則因低壓尾流受流體黏滯性影響，較消散甚至減弱，下游魚隻受到上游剝離之低壓尾流的影響較少，因此能減少消耗之功率並不多。

關鍵字

魚群 ； 數值模擬 ； 低壓尾流 ； 省能

並列摘要

The objective of this research is to study the energy saving mechanism of group-swimming fish via numerical simulation. Two-dimensional Navior-Stokes equations have been solved in a viscous, incompressible flow with Re = 5000. For better swimming performance, the Strouhal number was set at 0.3. Simulations with various spacing (s = 1.25L、1.35 L、1.5 L、1.65 L、1.75 L、2 L, where L is the length of the fish) between the fish in stream-wise direction have been carried out to find the optimum value. Results showed that, due to the suction effect induced by low pressure wake region caused by tail sweeping of the fish at the upstream side, power consumption of the fish with s = 1.5 L downstream-wise was 45% less than that when swimming alone. However, with spacing s = 1.25 L, the power consumption of the downstream side of the fish was only 9% less than that when swimming alone. Since the low pressure suction effect was dissipated gradually by viscosity, the influence from the upstream side of the fish upon the downstream side of the fish became smaller when the spacing was greater than 1.5 L. Thus, the benefit of energy saving in group swimming became less distinct.

並列關鍵字

Fish school ； Numerical simulation ； Low-pressure wake ； Energy-saving

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