Tadd T. Truscott, Jeffrey M. Aristoff, Alexandra H. Techet
备注：
American Physical Society Division of Fluid Dynamics Gallery of Fluid Motion Video Entry Replaced previous version because abstract had LaTex markup and was too long
The hydrodynamics associated with water-entry of spheres can be highly variable with respect to the material and kinematic properties of the sphere. This series of five fluid dynamics videos illustrates several subtle but interesting variations. The first series of videos contrasts the nature of impact between a hydrophilic and hydrophobic sphere, and illustrates how surface coating can affect whether or not an air cavity is formed. The second video series illustrates how spin and surface treatments can alter the splash and cavity formation following water entry. The spinning sphere causes a wedge of fluid to be drawn into the cavity due to the no-slip condition and follows a curved trajectory. The non-spinning sphere has two distinct surface treatments on the left and right hemispheres: the left hemisphere is hydrophobic and the right hemisphere is hydrophilic . Interestingly, the cavity formation for the half-and-half sphere has many similarities to that of the spinning sphere especially when viewed from above. The third video series compares two millimetric nylon spheres impacting at slightly different impact speeds (Uo = 40 and 45 cm/s); the faster sphere fully penetrates the free surface, forming a cavity, whereas the slower sphere does not. The fourth series shows the instability of an elongated water-entry cavity formed by a millimetric steel sphere with a hydrophobic coating impacting at Uo = 600 cm/s. The elongated cavity forms multiple pinch-off points along its decent. Finally, a millimetric steel sphere with a hydrophobic coating breaks the free surface with an impact speed of Uo = 350 cm/s. The cavity pinches-off below the surface, generating a Worthington jet that pinches into droplets owing to the Rayleigh-Plateau instability.
Acoustic Signatures of Pinch-Off Cavities During Water-Entry
College of Shipbuilding Engineering, Harbin Engineering University（哈尔滨工程大学船舶工程学院）；Nanhai Institute of Harbin Engineering University（哈尔滨工程大学南海研究院）；Southampton Ocean Engineering Joint Institute, Harbin Engineering University（哈尔滨工程大学南安普顿海洋工程联合学院）；National Key Lab of Ship Structural Safety, Harbin Engineering University（哈尔滨工程大学船舶结构安全国家重点实验室）
Water entry of small hydrophobic spheres on an axisymmetric wavefield
Brown University（布朗大学）；Georgia Institute of Technology（佐治亚理工学院）；École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院）；Naval Undersea Warfare Center（海军水下战中心）
A two-dimensional analytical model of vertical water entry for asymmetric bodies with flow separation
考虑了非对称二维物体垂直入水时的分离流动。只要没有流动分离，线性化的Wagner理论与修正的Logvinovich模型相结合，已被证明可以在入水过程中提供计算快速和可靠的砰击载荷估计。Tassin等人（2014年）引入了Fictionary Body Continuation（FBC）概念，作为将Wagner模型的使用扩展到分离流配置的一种方式，但他们只考虑对称体。在本研究中，我们调查的能力，FBC的概念，提供准确的估计砰击载荷的非对称机构。在这种情况下，流动分离可能不会同时发生在主体的两侧。在中间阶段，砰击载荷由局部流分离引起的局部压降和润湿面积的持续膨胀之间的竞争决定。作为该模型的第一个基准，我们考虑了一个倾斜的平板的水进入和比较FBC估计与非线性模型的结果。然后，我们考虑的情况下，箔和比较FBC的结果与计算流体动力学的预测。在这两种情况下，我们发现，FBC模型是能够提供可靠的估计砰击载荷。
