The Generation Of Freak Waves And Its Behaviors

The problem of freak waves becomes an issue of principal interest due to their potentially devastating effect. However, as the short research history on freak wave and scarcity of actual field measurements of freak wave, researchers thirst for regenerating freak wave by experiment or numerical simulation, then getting its basic behaviors, the cause of the occurrence, the inside and outside configuration.In present paper, wave train containing a freak wave is simulated and be converted to the signal that can control the wave maker so that the controllable freak wave can be generate in the laboratory. The wave gauges recorded the process of the freak wave generation. The basic behavior of freak waves generated on vary conditions are also studied. The subject is as follow:·As a beginning of this thesis, the appeared field, definitions, basic behaviors, the cause of the occurrence and the research condition are summarized.·In the second part, freak wave are simulated by several models such as adjusting theinitial phases of the wave components, two and three wave trains superposition models. The result shows that wave train containing the freak waves all can be simulated by these models. Comparing three records with each other, the three wave trains superposition model is the most efficient.·Freak waves are generated in the laboratory in four methods.At first, the normal irregular wave distortion at the slope is observed in order to research the possibility of appearance of freak wave by the circumstance change of the real sea. The result shows that the normal irregular wave distortion at the slope can generate freak wave, however, it's not efficient and hard to control.The second method converts the wave train, which adjusts 1/3 initial phases of the wave components to the same, controls the wave maker, generates freak wave in the laboratory. 1/3 wave components with same phases strengthened the energy, more large waves appear in the experiment, however, it can hardly control the generation time and location of the freak wave.The third method adopts the Kriebel's method, displaces the corresponding part of the wave make procedure by two wave trains superposition method. The result shows that this method can control the generate time and location, but the generative wave can not consistent with the definition. We improve Kriebel's experiment method by adjusting the initial phases of the wave components and iterate the signals. Using the improved method, the freak wave can be generated in the laboratory at certain time and certain location, however, it may influence the significant wave height and is not efficient.The fourth is three wave trains superposition model in improved method . The result shows that it can generate freak waves more efficiently and factually while using the same energy as two wave trains superposition model. It can not only generate the freak waves in the real sea field efficiently, but also hardly influence the basic character of the wave train. The freak waves can be generated at certain time, certain location and certain scale, by adjusting the significant wave height and the energy given to the transient wave trains.·We simulate the recorded freak waves in the three wave trains superposition model whose result is perfect.·The generation, evolvement process and behaviors of the freak waves are studiedbased on the achievement of controllable technology. The result shows a huge trough can distort after the generation of the freak wave, and another freak wave will appear during 2 average period. The generative freak wave will last under one and a half significant period. The period of freak wave exceeds average period, but is shorter than the significant period.