Spatial and temporal patterns of water flow generated by suction-feeding bluegill sunfish Lepomis macrochirus resolved by Particle Image Velocimetry
Spatial and temporal patterns of water flow generated by suction-feeding bluegill sunfish Lepomis macrochirus resolved by Particle Image Velocimetry
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DOI：
10.1242/jeb.01708
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发表时间：
2005-07-01
影响因子：
2.8
通讯作者：
Wainwright, PC
中科院分区：
文献类型：
--
作者：
Day, SW;Higham, TE;Wainwright, PC
吸食鱼在头部外部产生一个流场，以便将猎物吸入口中。到目前为止，有很少的经验测量的特点吸食流体力学，特别是在鱼的前面的水的速度的时间和空间模式。为了表征吸食蓝鳃太阳鱼Lepomis macrochirus前方的流动，使用粒子图像测速仪（PIV）进行了高空间（< 1 mm）和时间（500 Hz）分辨率的测量。在与PIV分离的分析中，高速视频序列用于在每次喂食期间视觉跟踪每个种子颗粒的新方法，以直接确定鱼摄取的总水包裹。PIV测量和粒子跟踪显示，水是从嘴周围吸来的。流体速度随着离嘴的距离而迅速降低，并且仅在鱼的大约1个嘴直径内是显著的（>嘴处速度的5%）。吸入式给料器在扩大该流场方面几乎没有收获，即使在口部开口处流体速度的显著增加也是如此。相反，嘴部处流速增加的主要优点可能是在非常靠近嘴部的空间内产生的力的大小增加。缩放后的速度场的基础上的大小的嘴开口和测量的流体速度在一个固定的位置，测量的速度分布为所有的饲料是非常相似的彼此，使流体速度的大小作为从捕食者嘴的距离的函数的函数关系，并示出是准确的运动学变量的范围内测试。这种关系描述了速度场都沿着中心线的鱼和沿着横断面躺在一个角度的中心线内的正中矢状面和额状面。时间分辨的流体速度测量gape运动学的比较表明，峰值流体速度与95%的峰值gape同时发生，表明蓝鳃金龟几乎同时最大化所产生的力和这些力作用的区域的大小。在每次撞击期间的峰值流体速度的大小作为到峰值张开的时间的增加的函数而减小（r（2）=0.87），表明颊腔扩张速率与最大产生的流体速度之间的强关系。
The suction-feeding fish generates a flow field external to its head in order to draw prey into the mouth. To date there are very few empirical measurements that characterize the fluid mechanics of suction feeding, particularly the temporal and spatial patterns of water velocity in front of the fish. To characterize the flow in front of suction-feeding bluegill sunfish Lepomis macrochirus, measurements with high spatial (< 1 mm) and temporal (500 Hz) resolution were taken using Particle Image Velocimetry (PIV). In an analysis separate from the PIV, high-speed video sequences were used for a novel method of visually tracking every seed particle for the duration of each feeding in order to determine directly the total parcel of water that the fish ingests. PIV measurements and particle tracking show that water is drawn from all around the mouth. Fluid velocity decreases rapidly with distance from the mouth and is only significant (> 5% of speed at the mouth) within roughly 1 mouth diameter of the fish. Suction feeders gain little in terms of extending this flow field by even substantial increases in the fluid speed at the mouth opening. Instead, the chief advantage of increased flow speed at the mouth may be the increased magnitude of generated forces within the space very close to the mouth. After scaling of the velocity field based on size of the mouth opening and the measured fluid speed at a fixed position, the measured velocity profiles for all feedings are very similar to one another, so that a functional relationship for the magnitude of fluid speed as a function of distance from the predator mouth is presented and shown to be accurate over the range of kinematic variables tested. This relationship describes the velocity field both along the centerline of the fish and along transects lying at an angle to the centerline within both the mid-sagittal and frontal planes. Comparison of the time-resolved fluid velocity measurements to gape kinematics demonstrate that peak fluid speed occurs simultaneously with 95% of peak gape, showing that the bluegill maximizes nearly simultaneously both the generated forces and size of the region over which these forces act. The magnitude of peak fluid speed during each strike decreases as a function of increasing time to peak gape (r(2)=0.87), demonstrating a strong relationship between the rate of buccal cavity expansion and maximum generated How speed.