Vortex Formation with a Snapping Shrimp Claw
Vortex Formation with a Snapping Shrimp Claw
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DOI：
10.1371/journal.pone.0077120
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发表时间：
2013-11-14
期刊：
影响因子：
3.7
通讯作者：
Bleckmann, Horst
中科院分区：
文献类型：
--
作者：
Hess, David;Bruecker, Christoph;Bleckmann, Horst
虾用一只超大的爪子产生高速空泡水射流，用于捕猎、防御和交流。本研究是对射流产生的实验研究。采用放大透明模型再现了捕虾爪的闭合，研究了捕虾（Alpheus-bellulus）。采用高速粒子图像测速技术（HS-PIV）和流动可视化技术对模型内部流动进行了研究。在爪合过程中，在柱塞和套筒之间形成通道状腔，在孔口处具有喷嘴型轮廓。关闭该机构导致形成一个无因次形成数T*近似为4的先导涡环。这表明爪可能以最高的效率工作，即最大的涡流强度是通过最小的流体体积喷射来实现的。随着轴向重入射流的形成而产生的旋涡空化是水射流穿透深度大的合理解释。这是虾用爪子引起的水流可以到达的地方。在这种空化过程中，空化涡的空心圆柱形核心产生轴向重入射流，将锋面进一步向下游推进，其长度可超过初始射流穿透深度数倍。
Snapping shrimp use one oversized claw to generate a cavitating high speed water jet for hunting, defence and communication. This work is an experimental investigation about the jet generation. Snapping shrimp (Alpheus-bellulus) were investigated by using an enlarged transparent model reproducing the closure of the snapper claw. Flow inside the model was studied using both High-Speed Particle Image Velocimetry (HS-PIV) and flow visualization. During claw closure a channel-like cavity was formed between the plunger and the socket featuring a nozzle-type contour at the orifice. Closing the mechanism led to the formation of a leading vortex ring with a dimensionless formation number of approximate Delta T*approximate to 4. This indicates that the claw might work at maximum efficiency, i.e. maximum vortex strength was achieved by a minimum of fluid volume ejected. The subsequent vortex cavitation with the formation of an axial reentrant jet is a reasonable explanation for the large penetration depth of the water jet. That snapping shrimp can reach with their claw-induced flow. Within such a cavitation process, an axial reentrant jet is generated in the hollow cylindrical core of the cavitated vortex that pushes the front further downstream and whose length can exceed the initial jet penetration depth by several times.