| As a new energy source,wave energy has huge reserves worldwide.Due to its advantages of easy availability,high load,and low pollution,it has great development value and has attracted widespread attention all over the world.Among various wave energy devices,the oscillating water column type wave energy convertor device can be widely used worldwide due to its high durability,and can be used in combination with breakwaters.In this paper,a dual cylindrical caisson embodying a U-shaped oscillating water column(OWC)wave energy convertor with a circular cross-section was designed.The physical model test was performed on the wave energy conversion efficiency of multiple sets of models,such as different outer cylinder water-retaining heights and opening ratios.Under the action of regular waves of different water depths and periods,experimental data such as wave height,air pressure in the chamber,and air pressure and flow velocity in the pipeline of the device were obtained simultaneously.The effects of incident wave elements,outer cylinder water-retaining heights and opening ratios of the air chamber on the performance of the air chamber were discussed.The factors affecting the damping coefficient of the device were analyzed,and the relationship between the damping coefficient and the wave energy conversion efficiency was studied.Three indexes for evaluating the average wave energy conversion efficiency of the OWC device were proposed.Based on the subjective and objective weight integration method,an evaluation system for the wave energy conversion efficiency of an OWC device is established.The analytic hierarchy process and the entropy method were used to calculate the subjective and objective weights of each index.The single-objective optimization model method and the differential-maximum combination weighting method were used to combine the subjective and objective weights to obtain comprehensive weights.Weighted calculation of the average wave energy conversion efficiency score of each OWC device,which provides a reference for engineering selection.The physical model test results suggested that dual cylindrical caisson embodying a U-OWC wave energy convertor with a circular cross-section,compared with traditional OWC,the wave energy conversion efficiency in long-period waves was significantly improved.Within the test range,the maximum wave energy conversion efficiency had reached 50% the above.Under different water depths,the device had different resonance periods and maximum wave energy conversion efficiency.The change in the water-retaining height of the outer cylinder cannot affect the wave energy conversion efficiency of the device.The opening ratio can significantly effect the wave energy conversion efficiency of the devices,The best opening ratio in this test was 2.11%.The damping coefficient is a characteristic of the dual-cylindrical U-OWC device itself,and is not affected by the incident wave elements.The opening rate of the air chamber is a factor that affects the damping coefficient which can significantly affect the wave energy conversion efficiency of the device.According to the scoring results of the four selected OWC devices,the average wave energy conversion efficiency of the dual-cylinder U-OWC device and the rectangular U-OWC device was higher.Compared with the traditional OWC device,the U-OWC devices had better performance,which was a better choice in actual engineering. |
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