波浪破碎下湍流混合的实验研究

波浪破碎过程产生的湍流动量和能量垂向输运对于加快海洋上混合层中垂向混合具有显著效果.采用二维实验室水槽中对波浪破碎过程进行模拟.对采集的波浪振幅时间序列采用希尔伯特变换定位破碎波位置,波浪的破碎率随有效波高的增加而增大,波浪谱分析得到的波浪基本周期与有效周期结果相似.实验中采用粒子图像测速技术(particle ima...

TURBULENT MIXING DURING WAVE BREAKING: AN EXPERIMENTAL STUDY

The vertical transport of turbulent momentum and energy generated by wave breaking has a significant effect on accelerating vertical mixing in the mixing layer of the upper ocean. The wave breaking process was simulated in a two-dimensional laboratory flume. Hilbert transform was used to locate the position of breaking wave in the sampled wave amplitude time series. The breaking rate of wave increased with the increase of effective wave height. The wave basic period obtained by wave spectrum analysis was similar to that of effective period. With the increase in significant wave height, the wave breaking rate increased in square form, and the wave spectra show that the wave periods were similar to the significant wave heights. The spatial distribution of the turbulent kinetic dissipation rate was calculated from the data of particle image velocimetry (PIV). The observations showed that the phase of wave had a close relationship with turbulence intensity, reaching maximum at wave crest. The phenomenon that the vertical profile of the turbulent dissipation rate stayed unchanged in the upper crest layer was called "turbulence saturation" and the turbulence by wave breaking reached 70%-90% of the depth of wave height. The calculation of the turbulent diffusivity coefficient increased exponentially with depth in the upper ocean layer and then stabilized. The data collected from the acoustic Doppler velocimeter (ADV) was compared with that of the PIV at the same location, and showed the same magnitude. Therefore, the results of the experiments show high accuracy for turbulence.