Dynamics of water entry
Dynamics of water entry
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DOI：
10.1017/jfm.2018.273
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发表时间：
2017-07
影响因子：
3.7
通讯作者：
L. Vincent;Tingben Xiao;Daniel Yohann;Sunghwan Jung;E. Kanso
中科院分区：
文献类型：
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作者：
L. Vincent;Tingben Xiao;Daniel Yohann;Sunghwan Jung;E. Kanso
潜水在入水过程中产生大的压力，伴随着空腔的产生和从自由水面喷射的水飞溅。为了尽量减少冲击力，潜水员在冲击时流线型。在这里，我们调查的影响力和飞溅的演变楔形物进入水作为一个功能的楔形物开口角。随着楔角的减小，观察到从冲击到平滑进入的逐渐过渡。在浸没之后，楔形物经历比浸没的楔形物小得多的拖曳力（小两倍）。我们的实验结果相比，现有的力模型引入基于经验的校正。我们的实验特征的形状的空腔和飞溅所创建的楔形，并发现它们是独立的入口速度在短时间内，但飞溅表现出明显的变化在稍后的时间在形状。我们提出了一个一维模型的飞溅，考虑到重力，表面张力和空气动力。该模型表明，在与实验数据相结合，飞溅的形状是由一个不稳定的文丘里吸力之间的相互作用，由于飞溅和水面之间的空气冲和稳定的力，由于表面张力。总之，这些发现可以指导未来的研究，旨在了解和结合水进入的各个阶段的机制，应用于工程和生物相关的问题，包括海军工程，疾病传播或平台潜水。
Diving induces large pressure during water entry accompanied by the creation of cavity and water splash ejected from the free water surface. To minimize impact forces, divers streamline their shape at impact. Here, we investigate the impact forces and splash evolution of wedges entering water as a function of the wedge opening angle. A gradual transition from impactful to smooth entry is observed as the wedge angle decreases. After submersion, the wedge experiences significantly smaller drag forces (two-fold smaller) than immersed wedges. Our experimental findings compare favourably with existing force models upon the introduction of empirically based corrections. We experimentally characterize the shapes of the cavity and splash created by the wedge and find that they are independent of the entry velocity at short times, but that the splash exhibits distinct variations in shape at later times. We propose a one-dimensional model of the splash that takes into account gravity, surface tension and aerodynamic forces. The model shows, in conjunction with experimental data, that the splash shape is dominated by the interplay between a destabilizing Venturi-suction force due to air rushing between the splash and the water surface and a stabilizing force due to surface tension. Taken together, these findings could direct future research aimed at understanding and combining the mechanisms underlying all stages of water entry in application to engineering and bio-related problems, including naval engineering, disease spreading or platform diving.