不同破碎波气液混合区发展特征及其运动特性研究

Study on development characteristics of gas-liquid mixture zones and kinematics of breaking wave with different breaking type

了解波浪破碎速度场的分布特性对于波浪破碎物理机制的研究极为重要,同时,对比研究不同类型破碎产生的气液混合区的演化特征有利于波浪白冠覆盖率模型的完善。在实验室水槽,生成了深水临界波、单次崩破波和单次卷破波,采用图像测速技术获取了波浪破碎图像、波面下水体和气液混合区速度场。结果表明,崩破波的水平向速度u和垂直向速度v在波峰前和波峰后的分布极为不对称,其水平向最大速度u_(max)并不位于峰顶,而是在主导波峰前0.7η_(max)处;卷破波的u_(max)出现在波峰峰顶前端极小的区域内,且该区域与周围区域的速度梯度极大。崩破波和卷破波生成的气液混合区发展特征也存在差异:崩破波的u_(max)值大、影响区域长、混合区厚度较小、各区域影响时间短;而卷破波的各项特征参数与崩破波形成对比。

To understand the internal physical mechanism of wave breaking,it is important to study the distribution characteristics of the particle velocity field under breaking wave.In addition,a comparative study of the evolution characteristics of the gas-liquid mixing zone caused by different types of breaking is beneficial to the improvemen of the whitecap coverage model.In the laboratory wave flume,a critical wave,a single spilling wave,and a single plunging wave are generated in deep water based on the linear phase focusing theory.The velocity fields below the wave surface and the velocity fields in the gas-liquid mixing zone are measured using particle image velocimetry(PIV)and bubble image velocimetry(BIV),respectively.The distribution characteristics of the velocity field at the extreme state of different breaking types are compared and discussed.The results show that the horizontal velocity u and vertical velocity v of the spilling wave are extremely asymmetrical in the front part and back part of the wave crest.In addition,the _(max)imum horizontal velocity u_(max) is not at the top of the wave peak,but at the pre-peak position about 0.7η_(max) front part and back part of the wave crest.In addition,the _(max)imum horizontal velocity of the peak.For plunging wave,the _(max)imum horizontal velocity u_(max) appears at the top and very front of the wave peak with a very small region,and the velocity gradient between this area and the surrounding area is very large.The development characteristics of the gas-liquid mixing zone produced by different wave breaking also have differences For spilling wave,the gas-liquid mixing zone generated by breaking has high horizontal movement speed,long influencing area,short influence time at each location,and small thickness.For plunging wave,the gas-liquid mixing zone has relatively slow horizontal movement speed and larger vertical input,shorter affected area,longer affected time at each location,and greater thickness.small thickness.However,for plunging wave,these characteristic parameters are in contrast with those of the spilling wave.