Numerical simulation of water impact of solid bodies with vertical and oblique entries
Numerical simulation of water impact of solid bodies with vertical and oblique entries
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DOI：
10.1016/j.oceaneng.2013.11.021
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发表时间：
2014
影响因子：
5
通讯作者：
H. Gu;L. Qian;D. Causon;C. Mingham;P. Lin
中科院分区：
文献类型：
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作者：
H. Gu;L. Qian;D. Causon;C. Mingham;P. Lin
基于纳维-斯托克斯方程（NSE）在固定笛卡尔网格上的解，通过双流体自由表面代码模拟了各种形状和配置的固体物体进入水时的水动力冲击的流动问题。数值模型中利用水平集函数捕捉自由表面，并采用部分单元法结合局部相对速度法来模拟运动体。首先使用半圆柱体和对称楔子垂直进入的冲击力和表面压力分布方面的实验数据和其他数值结果对该代码进行了验证。然后模拟了楔子倾斜入水的配置，并将碰撞过程中预测的自由表面轮廓与实验结果进行了比较，显示出良好的一致性。最后，模拟了一系列涉及不同横跟角的楔块垂直和倾斜入水的测试，并将结果与已发表的数值结果进行了比较。研究发现，本模型预测的表面压力分布和力与基于势流理论的其他数值结果总体上非常吻合。然而，由于当前模型基于 NSE 的解，因此更加稳健，因此可以预测，例如，当水平速度占主导地位时，薄流射流（喷雾）从楔形表面的形成和分离，以及倾斜进水情况下的相关通风现象。还值得注意的是，由于势流理论对非分离流的固有限制，可能会导致楔形尖端处的负压被高估。
The flow problem of hydrodynamic impact during water entry of solid objects of various shapes and configurations is simulated by a two-fluid free surface code based on the solution of the Navier–Stokes equations (NSE) on a fixed Cartesian grid. In the numerical model the free surface is captured by the level set function, and the partial cell method combined with a local relative velocity approach is applied to the simulation of moving bodies. The code is firstly validated using experimental data and other numerical results in terms of the impact forces and surface pressure distributions for the vertical entry of a semi-circular cylinder and a symmetric wedge. Then configurations of oblique water entry of a wedge are simulated and the predicted free surface profiles during impact are compared with experimental results showing a good agreement. Finally, a series of tests involving vertical and oblique water entry of wedges with different heel angles are simulated and the results compared with published numerical results. It is found that the surface pressure distributions and forces predicted by the present model generally agree very well with other numerical results based on the potential flow theory. However, as the current model is based on the solution of the NSE, it is more robust and can therefore predict, for example, the formation and separation of the thin flow jets (spray) from surface of the wedge and associated ventilation phenomena for the cases of oblique water entry when the horizontal velocity is dominant. It is also noted that the potential flow theory can result in over-estimated negative pressures at the tip of the wedge due to its inherent restriction to nonseparated flows.