Investigation On The Structure Type And Performance Of The Special Breakwater

With the development of the international trade and the increase of vessel size, the construction of harbors steps into the deep water area. As the important hydraulic structures to provide protection for many coastal activities from waves, the traditional breakwaters can not be fit for the construction in deep water with execrable circumstance. They may be very expensive at locations of relative deep water, and difficult for installing with complicate technique. Therefore, the tendency of deep water breakwaters are towards to the new type of permeable, dissipating and multifunctional structures. It is very significant in science and application to explore the special breakwaters with good performance of dissipating waves, which can be fit for the construction in deep water, poor foundation and high demanding of water circulation.In this dissertation, based on the model test in physical wave flumes, and by certain theoretical analysis, the structure type and the performance of the thress kind of special wave attenuators are investigated respectively:Air bubbles breakwater-The model tests with scale of 1:30 , 1:15 and 1:10 are conducted in the wave flumes of the State Key Laboratory of Coastal and Offshore Engineering. The similarity scale of air amount and the performance of the air bubbles breakwater are explored. By the extrapolation method, the approximate relation of the model scale of air amount is presented. The factors of incident wave period, air amount and the arrangement of the pipes, are analyzed in detail. The test results indicate that the air bubbles breakwater can dissipate waves well when the wave period is relative short, while nearly ineffectively for long period waves.New open type breakwater- Based on the concept of wave energy conversion, a new kind of open type breakwater is proposed, which can absorb and utilize the wave energy to dissipate waves. The effects of some factors, such as the configuration insides, the geometrical parameters and the relative width (the ratio of the width to the wave length), on the performance of the breakwater are discussed based on a series of regular wave tests in the wave flume. The hydrodynamic characteristics of the new open type breakwater are analyzed in detail, and thestructure is optimized to improve the performance of the breakwater to effectively dissipate the waves of long period. The results of the physical model tests indicate that the transmission coefficient significantly decreases by about twenty percent at the range of relative width from 0.1 to 0.2, compared with the traditional open type breakwaters.Multiple-layer breakwater-Based on the idea of disturbing the wave motion in the upright direction and reducing the horizontal wave force, a new kind of multiple-layer breakwater is proposed in the paper, which simply consists of several horizontal plates. The breakwater's performance of dissipating waves has been investigated in detail in the regular wave tests. The factors identified with the characteristics of the breakwater are discussed, such as the relative width, the relative gap, and the wave steepness. By linear wave theory and the eigenfunction method, a numerical model is set up to explore the performance of the multiple-layer breakwater, and the wave force acted on the structure is investigated further by the numerical model. The results of the numerical are compared with the experiments. It is demonstrated that the multiple-layer breakwater has good performance of dissipating waves. When the relative width is about 0.25, the transmission coefficient can significantly drop below 0.5. At the same time, the reflection coefficient is small than 0.4 in general.The similarity relations and performance of the air bubbles breakwater presented in the paper are useful for the further investigation on the system of air bubbles breakwater. And the new kind of open type breakwater and the multiple-layer breakwater proposed in the paper are the development the structure type of the traditional breakwater. With the advantages of well dissipating wave...