Violent breaking wave impacts. Part 3. Effects of scale and aeration
Violent breaking wave impacts. Part 3. Effects of scale and aeration
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DOI：
10.1017/jfm.2014.692
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发表时间：
2015-01
影响因子：
3.7
通讯作者：
H. Bredmose;G. Bullock;A. Hogg
中科院分区：
文献类型：
--
作者：
H. Bredmose;G. Bullock;A. Hogg
摘要本文用解析和数值方法研究了尺度和掺气对破碎波冲击的影响。通过量纲分析，我们表明，弗劳德尺度条件下的冲击压力之前的影响取决于规模和曝气水平。Bagnold-Mitsuyasu比例定律的压缩的空气袋的活塞不可压缩的水重新推导和推广到三维空气袋的任意形状。壁面压力，力和脉冲的数值结果，然后提出了一个翻转通过的影响，低曝气的影响和高曝气的影响，九个尺度和五个级别的初始曝气。其中两种撞击类型会在壁面处形成一个气穴。该论文的研究结果之一是，对于固定的初始曝气，来自翻转冲击的冲击压力大致遵循弗劳德尺度。这也是两种冲击类型的情况下，捕获的空气袋的冲击压力低于318千帕，而冲击压力高于这个值广泛遵循Bagnold-Mitsuyasu标度定律与全尺寸的压力大于弗劳德定律预测的。对于所有的冲击类型，充气的效果被发现，以减少最大的冲击压力，最大的力量和冲动。与Peregrine & Thais（J. Fluid Mech.，第325卷，1996年，第325页。377-397）被发现的翻转通过的冲击压力和一个公平的协议被发现的低和高曝气的影响。基于数值计算结果，提出了一种结合Froude标度和Bagnold-Mitsuyasu定律的修正标度曲线。的实际意义的研究结果进行了讨论，并提请注意物理模型试验的局限性。
Abstract The effects of scale and aeration on violent breaking wave impacts with trapped and entrained air are investigated both analytically and numerically. By dimensional analysis we show that the impact pressures for Froude scaled conditions prior to the impact depend on the scale and aeration level. The Bagnold–Mitsuyasu scaling law for the compression of an air pocket by a piston of incompressible water is rederived and generalised to 3D air pockets of arbitrary shape. Numerical results for wall pressure, force and impulse are then presented for a flip-through impact, a low-aeration impact and a high-aeration impact, for nine scales and five levels of initial aeration. Two of these impact types trap a pocket of air at the wall. Among the findings of the paper is that for fixed initial aeration, impact pressures from the flip-through impact broadly follow Froude scaling. This is also the case for the two impact types with trapped air pockets for impact pressures below 318 kPa, while impact pressures above this value broadly follow the Bagnold–Mitsuyasu scaling law with full-scale pressures greater than those predicted by the Froude law. For all impact types, the effect of aeration is found to reduce the maximum impact pressure, maximum force and impulse. Good agreement with the asymptotic model of Peregrine & Thais (J. Fluid Mech., vol. 325, 1996, pp. 377–397) is found for the flip-through impact pressure and a fair agreement is found for the low- and high-aeration impacts. Based on the numerical results, a modified scaling curve that combines Froude scaling and the Bagnold–Mitsuyasu law is suggested. The practical implications of the findings are discussed and attention is drawn to the limitations of physical model tests.