Experiment And Numerical Simulation Study On Air Bubbles Breakwater

Breakwater is a common kind of coastal engineering structures, as the important hydraulic structures to provide protection for many coastal activities from waves, and it is playing special and important role in mainly for providing stable and safe area to shipping. In deep waters, the traditional breakwaters can not be fit for the construction with execrable circumstance, furthermore, the traditional breakwater construction cost is expensive, the technology is complex and the construction is difficult, so it can't adapt to deep water harbour development needs. Therefore, reasonable and reliable structure and feasible construction method to assure the functionsofuse and reduce the cost are important for the world port engineering.Air bubbles breakwater is one of special breakwaters, so it has several specific characters of the mobile breakwater compared with stable breakwaters, such as mobility, temporality, cheapness, etc. it can not be restricted by the water depth and geological conditions, and it can easily be anchored by chain or through the precast bodies into water. Besides thses, it is pointed out as a special merit of the air bubbles breakwater form environment point of view not interrupt the exchange of water and the sediment of sands in harbors and facilities of air discharge are placed on the sea bottom. In addition, air bubbles breakwater has the other advantages, for the light weight, simple structure and low cost. Therefore, it has good application prospects in water transportation, aquaculture and military domain.This paper presents the experiment investigation and numerical simulation of the wave dissipating performance in air bubbles breakwater. In the physical model experiments, a set of air bubbles breakwater wave elimination performance test research plan are designed based on similarity criterion of gravity. In the proceeding of tests, the wave dissipating performance of air bubbles breakwater with different incident wave elements, the different air amount and the different orifice diameter under the condition of different length scales are studied, and the reflection action of wave motion are analysis at the same time. According to the arrangement of test data and analysis, same conclusions are given for the wave dissipating performance of air bubbles breakwater.Firstly, in the numerical simulation aspect, the two-phase fluid of water and air is assumed as a variable density fluid, the air is incompressible, the continuity equation, the Reynolds average equations and the standard k-εequations are selected as the governing equations, and the interface of water and air was traced by the VOF method and the finite volume method is used for solve the equations. The additional mass source was added to the continuity equation by the Macro of UDF. The single air bubble and the air bubbles curtain characteristics in calm water are conducted by numerical simulation, which give the further explanation that the wave dissipating mechanism of air bubbles breakwater is the horizontal flow caused by air bubbles curtain in water.Secondly, it is presented the 2-d numerical wave tank with the wave generation by pushing plate, and using UDF for wave elimination process at the end of wave tank, the air bubbles curtain is realized in the wave tank at the meanwhile, so the mathematical model of air bubbles breakwater is finished. By using the same wave elements and test cases, the wave dissipating performance of air bubbles breakwater are studied, then the numerical simulation results and experimental results are analyzed in this paper, it is aimed to certify the mathematical model rationality of the air bubbles breakwater. In addition, the effects of air compressibility on air bubbles breakwater wave damping performance are studied in this paper by numerical simulation, and the related conclusions are given.Thirdly, through the mathematical model establishment of air bubbles breakwater, the influencing factors, which maybe influence the wave dissipating performance of air bubbles breakwater, are studied by numerical simulation. Form two aspects, the incident wave elements and the structural parameters of air bubbles breakwater, are likely to affect the air bubbles breakwater wave elimination properties be simulated in this paper. Combining the given relevant conclusions, it provided reliable and valuable basis for the practical application of air bubbles breakwater.Finally, the relation of the air amount scale and the length scale in the air bubbles breakwater system are studied by numerical simulation and the preliminary discuss are made for the relationship between the air amount scale and the length scale with the prototype method and the extrapolation methodand. Then the comparations with the experimental results are conducted. Forthemore, the two cases with considering air compressibility and without considering air compressibility are also analyzed and discussed for the relationship between the air amount scale and the length scales.