Experimental Study On Hydrodynamic Performance Of Single Pontoon-Mooring Line Floating Breakwater

In recent years, the application of pontoon-mooring line floating breakwaters has been more and more brought to engineering and research people's attention because of their simple structure, inexpensive cost, and nice flexibility to groundwork, easy relocation and so on. But At present the research for dynamics hydrodynamic performance of pontoon floating breakwaters, especially for mooring force characteristic are on the initial stage and the transmission rate of such breakwater to long waves (W/L<0.17) is still high, which is the main reason that restricts the floating breakwater to work as a permanent wave attenuation equipment, so it is necessary to optimize it.Laboratory physical model tests were performed to study the hydrodynamic performances of eleven kinds of pontoon models, influence of model parameters (mooring relative lie length Lt/Ls, stiffness of mooring chain k, angle between mooring axes and horizontal at the jointα, relative draft S/d and so on) on hydrodynamic performances are discussed with 2D in regular waves.Wave Attenuation Performance of Models: With the increase of relative width, the transmission coefficient is descended at first and ascended latter with any influence of model parameters. There is a best relative width which gives birth to the smallest transmission coefficient. Bedises, wave height associates with different influence of model parameters have different results for wave attenuation performances.Motion Responses of Models: With the increase of relative width, Sway and heave are descended at all times, however Roll is descended at first and ascended at the middle phase then descended at last. Wave height associates with different influence of model parameters have different results for motion responses.Mooring forces Characteristics: With different influence of model parameters, Mooring forces(including offside mooring force, onside mooring force and total mooring force) have not the same rules. The characteristic of onside mooring force is similar to the characteristic of offside mooring force, but the numerical values are less than offside mooring force; The characteristic of total mooring force is similar to the characteristic of offside mooring force as well and the numerical values are equal to offside mooring force mostally.As a type of ocean structures'fense establishment, pontoon-mooring structure's floating breakwater has been the most concerned about its wave attenuation performances and mooring force's characteristics in the engineering domain. It is required that this structure have good wave attenuation performances and the better mooring force's characteristics. For this reasons relativity analysis for wave attenuation performances and mooring force's characteristics are discussed with the influence of model parameters in the present paper.The results indicates that we can obtain the structure which include good wave attenuation performances and the better mooring force's characteristics with minishing the angle between mooring axes and horizontal at the joint or adding the relative draft. For mooring relative lie length and the position of mooring joint, we should link to relative width to optimize the model. However, changing the stiffness of mooring chain to optimize the model is a contravention for good wave attenuation performances and the better mooring force's characteristics.