Experimental Study On Hydrodynamic Characteristics Of Comb-type Breakwater-OWC Wave Energy Converter Integrated System

Oscillating water column wave energy converter has simple structure and high reliability,which is the most widely used wave energy converter.Compared with the traditional tank breakwater structure,comb-type breakwater can reduce the foundation stress and wave load before the breakwater,save on construction materials,and promote the exchange of water bodies inside and outside the port area.The integrated system of wave energy converter and offshore structure can share the basic unit,reduce the construction cost,improve the survivability of the wave energy converter.As the most promising wave power generation integration system,OWC wave energy converter and breakwater combination can provide clean energy for port development and coastal urban development.In this paper,an integrated system of comb-type breakwaters and oscillating water column wave energy converter(CTB-OWC integrated system)is proposed.Focusing on CTB-OWC integrated system research,the physical model test method is used to explore the factors of aerodynamic performance,wave reduction performance,wave energy capture efficiency and force characteristics.The impact of opening ratios of the capture chamber,the nonlinearity of the incident wave,and the length of comb structure are studied.Aiming at optimizing the form of CTB-OWC integrated system structure,improving the wave attenuation performance of the converter,the efficiency of wave conversion and the survivability of extreme waves,and providing a theoretical basis for the design of CTB-OWC integrated system,a series of study is carried out as follows:Firstly,the influence factors,i.e.aerodynamic performance,wave reduction performance,wave energy capture characteristics and force characteristics of CTB-OWC integrated system,are discussed based on the physical model test.Under the action of regular waves,the influence law of different factors on the integrated system is expounded from the aspect of opening ratios,wave nonlinearity and comb length of the valve.It is found that with the increase of opening ratios of the capture chamber,the wave load on the inside of the CTB-OWC integrated system static surface shows the increasing trend in the low frequency region,and the reverse trend in the high frequency region is shown;the reflection coefficient of the integrated system increases in the low frequency region as the nonlinear wave component increases,and decreases in the high frequency zone;the comb structure can reduce the wave height and air pressure in the air chamber in the low frequency region,and shows the opposite trend in the high frequency area;the reflection coefficient and wave energy capture efficiency of CTB-OWC integrated system are significant when the comb length is greater than that of 1/3 tank.Secondly,under the action of regular wave,OWC wave energy capture efficiency test and comb-type breakwater wave reduction test are carried out to explore the influence law of OWC wave energy converter on the wave loss performance of comb-type breakwater and the influence law of comb-type breakwater on the energy capture efficiency of OWC wave energy converter.It is found that the OWC wave energy converter can reduce the transmission coefficient of comb-type breakwater and improve the performance of the wave;the comb-type breakwater can increase the air pressure of the OWC catch-up air chamber,which is beneficial to extracting small amplitude wave energy.Finally,the effect of the opening ratios and wave nonlinearity on the force characteristics of the front wall of the OWC wave energy converter is considered under the action of the focused waves to carry out the model test.It is found that the maximum wave load appears near the static water surface;the grain load effect of the valley value load at the front wall of the chamber is greater than the peak load effect;the wave load reaches the maximum under the opening ratios corresponding to the optimal wave energy capture efficiency;the wave load is increased as the nonlinear component increases of the wave;the wave load above the static water surface increases,and the wave load is decreases in the position of the static water surface and the position below the static water surface.