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 、2 ) ， 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
此能減少消耗之功率並不多。 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 ' 1.35L ' 1.5L ~ 1.65L ' 1.75L ' 2L, 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 = 1.5L downstream-wise was 45% less than
that when swimming alone. However, with spacing s = 1.25L, 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 1.5L. Thus, the benefit of energy saving in
group swimming became less distinct.