A hydrodynamic analysis of fish swimming speed: wake structure and locomotor force in slow and fast labriform swimmers.
A hydrodynamic analysis of fish swimming speed: wake structure and locomotor force in slow and fast labriform swimmers.
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发表时间：
2000-08
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通讯作者：
E. G. Drucker;G. Lauder
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作者：
E. G. Drucker;G. Lauder
过去对鱼类游动速度种间差异的研究主要集中在限制运动肌肉产生动力的内在生理机制上。在本文中，我们探讨的问题，为什么有些鱼能够比别人游得更快，从流体动力学的角度来看，使用数字粒子图像测速技术，允许测量流体速度和估计的尾动量和机械力的运动。我们调查的结构和强度的尾流在三维空间中，以确定如何在两个物种的水动力变化，显着不同的最大游泳速度。黑鲈鱼（Embiotoca jacksoni）和蓝鳃太阳鱼（Lepomis macrochirus）在低速时仅使用胸鳍，在高速时切换到胸鳍和尾鳍联合运动。E. jacksoni的游泳速度是同样大小的L的两倍。仅使用胸鳍的长臂猿。在所有速度下，黑鲈胸鳍尾流由两个腹侧相连的涡环组成。当速度从1.0增加到3.0 L s（-）（1）时，其中L是总的机身长度，在鳍下冲程上形成的涡环重新定向，以使力越来越多地向下游，平行于运动方向。随着速度的增加，横向力与下游力的比值从0.93下降到0.07。与此相反，太阳鱼胸鳍产生一个单一的涡环每拍鳍在低游泳速度和一对相连的涡环（一个环只有部分完成，并附在身体上）在最大的唇状速度。在一个生物相关的游泳速度范围内，蓝鳃太阳鱼产生相对较大的横向力与成对的鳍：横向力与下游力的比率在所有速度下保持在1.0或以上。通过增加尾流动量，并将这种动量定向在更有利于推力而不是侧向力的方向上，黑鲈能够以两倍于蓝鳃太阳鱼的速度游泳。在太阳鱼，没有一个重新定向的脱落涡，胸鳍肌肉的功率输出的增加将有最大运动速度的影响不大。我们提出了两个假设有关运动的稳定性，机动性和结构的涡流尾流。首先，在低速时，两种物种所表现出的大的侧向力对于稳定性可能是必要的。第二，我们提出了一个潜在的水动力平衡之间的速度和机动性，出现作为一个几何后果的涡流环脱落胸鳍的方向。蓝鳃翻车鱼可能更容易弯曲，因为它们能够在左右鳍之间产生大的中外侧力不对称。
Past study of interspecific variation in the swimming speed of fishes has focused on internal physiological mechanisms that may limit the ability of locomotor muscle to generate power. In this paper, we approach the question of why some fishes are able to swim faster than others from a hydrodynamic perspective, using the technique of digital particle image velocimetry which allows measurement of fluid velocity and estimation of wake momentum and mechanical forces for locomotion. We investigate the structure and strength of the wake in three dimensions to determine how hydrodynamic force varies in two species that differ markedly in maximum swimming speed. Black surfperch (Embiotoca jacksoni) and bluegill sunfish (Lepomis macrochirus) swim at low speeds using their pectoral fins exclusively, and at higher speeds switch to combined pectoral and caudal fin locomotion. E. jacksoni can swim twice as fast as similarly sized L. macrochirus using the pectoral fins alone. The pectoral fin wake of black surfperch at all speeds consists of two distinct vortex rings linked ventrally. As speed increases from 1.0 to 3.0 L s(-)(1), where L is total body length, the vortex ring formed on the fin downstroke reorients to direct force increasingly downstream, parallel to the direction of locomotion. The ratio of laterally to downstream-directed force declines from 0.93 to 0.07 as speed increases. In contrast, the sunfish pectoral fin generates a single vortex ring per fin beat at low swimming speeds and a pair of linked vortex rings (with one ring only partially complete and attached to the body) at maximal labriform speeds. Across a biologically relevant range of swimming speeds, bluegill sunfish generate relatively large lateral forces with the paired fins: the ratio of lateral to downstream force remains at or above 1.0 at all speeds. By increasing wake momentum and by orienting this momentum in a direction more favorable for thrust than for lateral force, black surfperch are able to swim at twice the speed of bluegill sunfish using the pectoral fins. In sunfish, without a reorientation of shed vortices, increases in power output of pectoral fin muscle would have little effect on maximum locomotor speed. We present two hypotheses relating locomotor stability, maneuverability and the structure of the vortex wake. First, at low speeds, the large lateral forces exhibited by both species may be necessary for stability. Second, we propose a potential hydrodynamic trade-off between speed and maneuverability that arises as a geometric consequence of the orientation of vortex rings shed by the pectoral fins. Bluegill sunfish may be more maneuverable because of their ability to generate large mediolateral force asymmetries between the left- and right-side fins.