The ideal flip-through impact: experimental and numerical investigation
The ideal flip-through impact: experimental and numerical investigation
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DOI：
10.1007/s10665-009-9354-3
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发表时间：
2010-06
影响因子：
1.3
通讯作者：
H. Bredmose;A. Hunt-Raby;R. Jayaratne;G. Bullock
中科院分区：
文献类型：
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作者：
H. Bredmose;A. Hunt-Raby;R. Jayaratne;G. Bullock
比较了物理实验和数值计算的结果，以了解翻转型波浪对垂直面（典型的海堤或防波堤）的影响。物理波是通过将聚焦波组技术应用于 JONSWAP 频谱的振幅而生成的，调整焦点位置以产生近乎破碎的波冲击，而没有明显的空气夹带或截留。由此产生的影响的详细信息以高速视频、压力传感器和波计记录的形式呈现。通过应用线性波浪分析模型和完全非线性势流求解器，可以实现波浪变换和影响的数值再现。尽管存在更先进的模型，但后一种模型类型的使用很有趣，因为（1）它被 Cooker 和 Peregrine 应用（第 22 届国际海岸工程会议论文集，164-176，1990）在其最初的翻转撞击数值发现中以及（2）势流模型背后的假设仍然相当有效，直到翻转射流开始分解成液滴。在本研究中，势流模型已通过 Schwarz-Christoffel 等角映射进行了扩展，以允许分段线性形状的土丘几何形状。此外，还添加了特殊的波浪生成技术，以促进水槽中长二阶波的充分数值再现。势流计算得出的自由表面高程与产生翻转冲击波的波规数据非常吻合。实验视频帧与相应的数值自由表面轮廓重叠，显示出与撞击前的流动收缩的良好匹配。讨论了射流形成阶段实验与数值解之间的偏差，并且对稍弱冲击的计算说明了冲击压力对冲击波形状的强烈敏感性。概述了通过使用更先进的模型来改进数值描述的方法。
Results from a physical experiment and a numerical computation are compared for a flip-through type wave impact on a vertical face, typical of a seawall or breakwater. The physical wave was generated by application of the focused-wave group technique to the amplitudes of a JONSWAP spectrum, with the focus location adjusted to produce a near-breaking wave impact with no discernible air entrainment or entrapment. Details of the resultant impact are presented in the form of high-speed video, pressure transducer and wave gauge records. Numerical reproduction of the wave transformation and impact is achieved by application of a linear wave-analysis model and a fully nonlinear potential-flow solver. Although more advanced models exist, use of the latter model type is interesting as (1) it was applied by Cooker and Peregrine (Proceedings of the 22nd International Conference on Coastal Engineering, 164–176, 1990) in their original numerical discovery of the flip-through impact and (2) the assumptions behind the potential-flow model remain reasonably valid, until the flip-through jet begins to break into droplets. In the present study, the potential-flow model has been extended with the Schwarz–Christoffel conformal mapping, to allow a piece-wise linearly shaped mound geometry. Further, an ad-hoc wave-generation technique has been added, to facilitate an adequate numerical reproduction of long second-order waves in the flume. Free-surface elevations from the potential-flow computations show good agreement with wave gauge data for the wave that produces the flip-through impact. Experimental video frames with the corresponding numerical free-surface profiles overlaid show an excellent match for the flow contraction prior to impact. The deviations between the experiment and numerical solution that occur at the stage of jet formation are discussed and a computation of a slightly weaker impact illustrate the strong sensitivity of impact pressures to the shape of the impacting wave. Ways of improving the numerical description by use of more advanced models are outlined.