Abstract

The effects of hydrophobicity on free surface elevation and impact loads are experimentally investigated during the water entry of wedges and cones with various deadrise angles, with particular attention given to the early stages of the impact. As opposed to spheres and cylinders, there is no Froude number dependency and hydrophobicity is not associated only with cavity formation, since a cavity is created at any velocity and at any contact angle in case of wedges and cones. It is observed that the formation of the jet flow, pileups and cavities during the water entry of the objects with constant deadrise angles are modified under the hydrophobic effects. There is no flow separation and the jet root travels faster along the solid surface and larger pileups with larger wetting factors change the chine wetting time resulting in smaller magnitudes when hydrophobicity is present. The slamming coefficient values under hydrophobic effects are measured about 10–25% smaller than the ones obtained with hydrophilic surfaces. Hydrophobic effects are stronger at smaller deadrise angles. It is also shown that the wetted length depends not only on the geometry but also the solid surface characteristics, and the amount of added mass is not proportional to the wetted area and may be decreased with increased wetted width depending on the contact angle.

Graphic abstract

中文翻译：

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疏水作用下恒死角恒定物体入水的实验研究

摘要

在楔形和圆锥形的进水过程中，以不同的死角对疏水性对自由表面高度和冲击载荷的影响进行了实验研究，并特别注意了冲击的早期阶段。与球体和圆柱体相反，不存在Froude数依赖性，并且疏水性不仅仅与腔体形成有关，因为在楔形和圆锥体的情况下，腔体会以任何速度和任何接触角产生。可以观察到，在具有恒定死角的物体进入水的过程中，射流，堆积和腔的形成在疏水作用下被改变​​。没有流动分离，射流根部沿着固体表面移动得更快，并且具有较大润湿因子的较大堆积物会改变脊柱润湿时间，从而在存在疏水性时导致较小的幅度。疏水作用下的砰砰系数值比亲水表面得到的撞击系数小10-25％。在较小的死角处，疏水作用更强。还显示出润湿长度不仅取决于几何形状，而且还取决于固体表面特性，并且增加的质量的量与润湿面积不成比例，并且可以根据接触角随着润湿宽度的增加而减少。疏水作用下的砰砰系数值比亲水表面得到的撞击系数小10-25％。在较小的死角处，疏水作用更强。还显示出润湿长度不仅取决于几何形状，而且还取决于固体表面特性，并且增加的质量的量与润湿面积不成比例，并且可以根据接触角随着润湿宽度的增加而减少。疏水作用下的砰砰系数值比亲水表面得到的撞击系数小10-25％。在较小的死角处，疏水作用更强。还显示出润湿长度不仅取决于几何形状，而且还取决于固体表面特性，并且增加的质量的量与润湿面积不成比例，并且可以根据接触角随着润湿宽度的增加而减少。

图形摘要