The Presence of a Substrate Strengthens The Jet Generated by Upside-Down Jellyfish
The Presence of a Substrate Strengthens The Jet Generated by Upside-Down Jellyfish
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DOI：
10.3389/fmars.2022.847061
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发表时间：
2022-05-12
影响因子：
3.7
通讯作者：
Santhanakrishnan, Arvind
中科院分区：
文献类型：
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作者：
Battista, Nicholas;Gaddam, Manikantam G.;Santhanakrishnan, Arvind
倒立水母（仙后座水母属，Cassiopea）在世界各地海洋温暖且浅的区域普遍存在。它们在水母中是独特的，因为它们倒立在基质上，将口腕向上伸展。这种构造使它们能够沿着基质持续拉动水流，使其通过口腕进入水体上层，以进行进食、营养和气体交换以及废物排出。尽管水母伞状体脉动的流体动力学在很多情况下都得到了研究，但基质的存在与否如何改变仙后座水母所产生的整体流动模式尚不清楚。在本文中，我们使用三维（3D）粒子追踪测速技术和三维浸入边界模拟来描述倒立水母所产生的水流。在这两种情况下，都去除了口腕，这使我们能够分离基质的影响。实验结果用于验证数值模拟，数值模拟表明基质的存在增强了漩涡的产生，进而提高了所产生射流的向上速度。此外，基质的存在创造了一种流动模式，即伞状体内部的水体在每个脉冲周期都会被喷射出去。这些结果表明，倒立水母将其伞状体压在海底的这种位置对于增强垂直水流以及增加每个脉冲期间所抽取的水体体积是有益的。
Upside-down jellyfish, Cassiopea, are prevalent in warm and shallow parts of the oceans throughout the world. They are unique among jellyfish in that they rest upside down against the substrate and extend their oral arms upwards. This configuration allows them to continually pull water along the substrate, through their oral arms, and up into the water column for feeding, nutrient and gas exchange, and waste removal. Although the hydrodynamics of the pulsation of jellyfish bells has been studied in many contexts, it is not clear how the presence or absence of the substrate alters the bulk flow patterns generated by Cassiopea medusae. In this paper, we use three-dimensional (3D) particle tracking velocimetry and 3D immersed boundary simulations to characterize the flow generated by upside-down jellyfish. In both cases, the oral arms are removed, which allows us to isolate the effect of the substrate. The experimental results are used to validate numerical simulations, and the numerical simulations show that the presence of the substrate enhances the generation of vortices, which in turn augments the upward velocities of the resulting jets. Furthermore, the presence of the substrate creates a flow pattern where the water volume within the bell is ejected with each pulse cycle. These results suggest that the positioning of the upside-down jellyfish such that its bell is pressed against the ocean floor is beneficial for augmenting vertical flow and increasing the volume of water sampled during each pulse.