Experimental Study on Wave Breaking in Relation to Coastal Processes

流动显示和图像分析的实验技术已被应用于波浪破碎的研究以及数值计算的拉格朗日框架。利用高速录像机和以分散的聚苯乙烯微珠为示踪剂的A-D转换器组成的测量系统，可以精确地获得波浪破碎条件下的瞬时速度场。解决了基于拉格朗日描述的数值分析在设计速度和压力解方法方面的技术困难。这些技术的应用为波浪破碎现象提供了新的途径，得出结论：在波峰附近出现低压区是最直接和最明显的破碎指标。水平速度分量和垂直速度分量的增加分别在行波式和立式破碎器中造成了这种灾难。另外，还进行了一系列波浪水槽实验，以宏观地研究陡峭海滩上的波浪破碎和由此产生的涡流。试验数据表明，根据深水波浪的陡度和底坡，对溢流型、俯冲型、崩落型和涌浪型破碎机进行了明确的划分。根据破碎波的波高和速度，在底斜率和雷诺数的不同范围内，也发现了斜卷和水平卷的存在。

Experimental techniques of flow visualization and picture analysis have been applied to the investigation of wave breaking as well as the Lagrangian framework for numerical computation. Instantaneous velocity fields under wave wave breaking conditions could precisely be obtained by utilizing a measuring system of a high-speed VTR camera and an A-D converter with scattered polystyrene beads as tracers. Technical difficulties that accompany numerical analyses based on the Lagrangian description were coped with in devising both velocity and pressure solution methods.Application of these techniques permitted new approaches to wave breaking phenomena, leading to the conclusion that occurrence of low pressure region in the vicinity of a wave crest is the most direct and apparent breaking index. Increases in horizontal and vertical velocity components respectively cause such catastrophes in progressive and standing breakers.Another series of wave-tank experiments were conducted for macroscopic investigation of wave breaking on a steep beach and resultant vortices. The experimental data indicates that the demarcation of spilling, plunging, collapsing and surging breakers is clearly made in terms of the deepwater wave steepness and bottom slope. It was also found that oblique and horizontal voltices occur in different ranges of the bottom slope and Reynolds number defined by using the breaking wave height and celerity