Oscillating water column wave energy converter is a power generation device in which ocean waves excite the oscillation of the water surface in an air chamber, which generates fluctuations in air pressure and rotate a...Oscillating water column wave energy converter is a power generation device in which ocean waves excite the oscillation of the water surface in an air chamber, which generates fluctuations in air pressure and rotate air turbine generator(s). The oscillation of the fluid in the air chamber is a fluid oscillation phenomenon with a natural period, similar to fluid oscillation in a container such as sloshing. Previous research has shown that for an oscillating water column with a single air chamber submerged in water, the oscillation characteristics can be modeled as a one-degree-of-freedom oscillation system that takes only a single oscillation mode into account. However, a double-slit breakwater integrated oscillating water column wave energy converter using two water columns of the breakwater separated by slit walls, has been verified to have two resonance periods. In this study, the free oscillating motion of the oscillating water column wave energy converter using the double-slit breakwater is modeled by modal superposition method including the first-order and second-order modes of vertical motion of the two water surfaces. The result from the simulation is similar to the result of the free vibration experiment.展开更多
Oscillating Water Column (OWC) wave energy converting system is one of the most widely used facilities all over the world. The air chamber is utilized to convert the wave energy into the pneumatic energy. The numeri...Oscillating Water Column (OWC) wave energy converting system is one of the most widely used facilities all over the world. The air chamber is utilized to convert the wave energy into the pneumatic energy. The numerical wave tank based on the two-phase VOF model is established in the present study toinvestigate the operating performance of OWC air chamber. The RANS equations, standard k-ε turbulence model and dynamic mesh technology are employed in the numerical model. The effects of incident wave conditions and shape parameters on the wave energy converting efficiency are studied and the capability of the present numerical wave tank on the corresponding engineering application is validated.展开更多
A fixed oscillating water column(OWC)-type wave energy converter consists of an air chamber,an air turbine and a generator.The energy conversion processes are the primary conversion in an air chamber and the secondary...A fixed oscillating water column(OWC)-type wave energy converter consists of an air chamber,an air turbine and a generator.The energy conversion processes are the primary conversion in an air chamber and the secondary conversion of the turbine.For the practical use,it is necessary to develop a design method which can consider the incident wave motion,the motion of the internal free surface affected in the structure such as a partly submerged wall,the fluctuation of air pressure in an air chamber,and the rotation of the air turbine.At here,the authors carried out the wave tank tests using the model OWC equipped with the impulse turbine and a generator to obtain the experimental data needed to make this design method.As the result,the efficiencies of the three cases with different speed ratio between generator and turbine,and the effects of the curtain wall depth and the wave length on the energy conversion performance were clarified.展开更多
A structure scheme of a pile-based breakwater with integrated oscillating water column(OWC)energy conversion chamber was proposed,and four structure forms had been designed.Based on the physical test,the variations of...A structure scheme of a pile-based breakwater with integrated oscillating water column(OWC)energy conversion chamber was proposed,and four structure forms had been designed.Based on the physical test,the variations of the reflected wave height,the transmitted wave height,the air velocity at the outlet of the chamber,the air pressure and the wave height in the air chamber were studied under the conditions of different wave heights,periods,with or without elliptical front wall and the baffles on both sides of the chamber.Moreover,based on the results,the changes and relationship between the wave-eliminating effect and energy conversion effect of the scheme were analyzed.In general,it turns out,the transmission coefficients of the four structure forms are kept below 0.5.Furthermore,the transmission coefficients of the structural forms G2,G3,and G4 were all smaller than 0.4,and it is only 0.1 at its smallest.Thereinto,in general,the structure form G4 has the best wave-eliminating and energy conversion performance.At the same time,when the wave steepness is 0.066,the energy conversion and wave dissipation effect of the four structure forms is the best.The research results could be provided as the reference for the design structure selection of pile-based breakwater with integrated OWC energy conversion chamber.展开更多
Both experimental and numerical studies were presented on the flow field characteristics in the process of gaseous jet impinging on liquid–water column. The effects of the impinging process on the working performance...Both experimental and numerical studies were presented on the flow field characteristics in the process of gaseous jet impinging on liquid–water column. The effects of the impinging process on the working performance of rocket engine were also analyzed. The experimental results showed that the liquid–water had better flame and smoke dissipation effect in the process of gaseous jet impinging on liquid–water column. However, the interaction between the gaseous jet and the liquid–water column resulted in two pressure oscillations with large amplitude appearing in the combustion chamber of the rocket engine with instantaneous pressure increased by 17.73% and 17.93%, respectively. To analyze the phenomena, a new computational method was proposed by coupling the governing equations of the MIXTURE model with the phase change equations of water and the combustion equation of propellant. Numerical simulations were carried out on the generation of gas, the accelerate gas flow, and the mutual interaction between gaseous jet and liquid–water column.Numerical simulations showed that a cavity would be formed in the liquid–water column when gaseous jet impinged on the liquid–water column. The development speed of the cavity increased obviously after each pressure oscillation. In the initial stage of impingement, the gaseous jet was blocked due to the inertia effect of high-density water, and a large amount of gas gathered in the area between the nozzle throat and the gas–liquid interface. The shock wave was formed in the nozzle expansion section. Under the dual action of the reverse pressure wave and the continuously ejected high-temperature gas upstream, the shock wave moved repeatedly in the nozzle expansion section, which led to the flow of gas in the combustion chamber being blocked, released, re-blocked, and re-released. This was also the main reason for the pressure oscillations in the combustion chamber.展开更多
Freely movable wave energy converters(WECs) will greatly improve their adaptability to the marine environment.In this paper, a dual-mode oscillating water column(OWC) WEC with potential sailing capability is proposed....Freely movable wave energy converters(WECs) will greatly improve their adaptability to the marine environment.In this paper, a dual-mode oscillating water column(OWC) WEC with potential sailing capability is proposed. By opening and closing a gate on the side facing the waves, the WEC converts wave energy in the vertical duct(called VD mode) with low sailing resistance or in the backward bend duct(called BBD mode) with high sailing resistance.A small model and a medium model were designed and manufactured. The capture width ratio(CWR) of the small model in the two modes was experimentally studied. The CWR under bidirectional airflow and conversion characteristics under unidirectional airflow of the medium model in the BBD mode were obtained. Tests of the small model show that the peak CWR is 145.2% under regular waves and 90.1% under random waves in BBD mode, and in VD mode the peak CWR is about 60% of that in the BBD mode. Tests of the medium model show that the peak CWR is 228.96% under regular waves, the maximum wave-to-battery efficiency is 63.36% under regular waves and 30.17%under random waves, respectively.展开更多
Responses of the very large floating Structures(VLFS)can be mitigated by implementing oscillating water columns(OWCs).This paper explores the fundamental mechanism of present wave interactions with both structures and...Responses of the very large floating Structures(VLFS)can be mitigated by implementing oscillating water columns(OWCs).This paper explores the fundamental mechanism of present wave interactions with both structures and examines the hydrodynamic performance of VLFS equipped with OWCs(VLFS-OWCs).Under the linear potential flow theory framework,the semi-analytical model of wave interaction with VLFS-OWCs is developed using the eigenfunction matching method.The semi-analytical model is verified using the Haskind relationship and wave energy conservation law.Results show that the system with dual-chamber OWCs has a wider frequency bandwidth in wave power extraction and hydroelastic response mitigation of VLFS.It is worth noting that the presence of Bragg resonance can be trigged due to wave interaction with the chamber walls and the VLFS,which is not beneficial for the wave power extraction performance and the protection of VLFS.展开更多
振荡水柱(Oscillation Water Column,OWC)是近年来发展较快的波浪能采集技术,该装置主要由箱体、振荡水柱和压缩空气柱组成,而波浪在气室内产生的压强对能量转换效率等起到决定作用。结合三维侧向开口的振荡水柱波能转换装置,基于线性...振荡水柱(Oscillation Water Column,OWC)是近年来发展较快的波浪能采集技术,该装置主要由箱体、振荡水柱和压缩空气柱组成,而波浪在气室内产生的压强对能量转换效率等起到决定作用。结合三维侧向开口的振荡水柱波能转换装置,基于线性波理论,采用三维Green函数法建立了气室内水气动力学性能的空气压强理论计算模型,利用多维切比雪夫(Chebyshev)多项式求解,计算结果精度高,能够准确表达波浪和结构设计参数对气室内压强影响。依据理论计算模型分析了波浪周期、波长、吃水深度、入射波幅等参数对气室内压强作用。展开更多
设计一种带收缩水道的沉箱防波堤和OWC(Oscillating Water Column)波能发电装置相结合的复合结构形式,开展物理模型试验研究。通过改变水道结构形式与OWC气室参数,并分析实验数据,探讨水道形式、入射波要素和OWC气室形状参数等对该复合...设计一种带收缩水道的沉箱防波堤和OWC(Oscillating Water Column)波能发电装置相结合的复合结构形式,开展物理模型试验研究。通过改变水道结构形式与OWC气室参数,并分析实验数据,探讨水道形式、入射波要素和OWC气室形状参数等对该复合结构工作性能的影响,采用气室内波幅放大系数、气室顶部空气点压力和防波堤前波浪反射率作为考察参量。展开更多
Wave tank tests were carried out to evaluate the total efficiency of a floating OWC Pentagonal Backward Bent Duct Buoy (PBBDB). Two kinds of turbine generators were used in tests. The incident wave power, pneumatic po...Wave tank tests were carried out to evaluate the total efficiency of a floating OWC Pentagonal Backward Bent Duct Buoy (PBBDB). Two kinds of turbine generators were used in tests. The incident wave power, pneumatic power and electricity were measured. The test results show that the primary efficiency can reach up to 185.98% in regular waves and 85.86% in irregular waves. The total efficiency from wave to wire with Wells turbine-generator set is 33.43% in regular waves and 15.82% in irregular waves. The peak total efficiency of the PBBDB with check valves equipped with the impulse turbine-generator set is 41.68% in regular waves and 27.10% in irregular waves. The efficiency of the turbine-generator set is about 30% in the tests. Obviously, the total efficiency can be further improved with the increasing of turbine efficiency.展开更多
Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column(OWC) wave energy converters, which can rotate in the same direction under the bi-directional air f...Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column(OWC) wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.展开更多
Sea wave energy generators or converters(WECs)have the potential to become a viable technology for clean,renewable energy production.Among the WEC technologies,the oscillating water columns(OWCs)are the most common WE...Sea wave energy generators or converters(WECs)have the potential to become a viable technology for clean,renewable energy production.Among the WEC technologies,the oscillating water columns(OWCs)are the most common WEC devices studied.These have been studied and developed over many years.Multi-chamber oscillating water columns(MC-OWC)have the potential to have a higher energy conversion when extracting energy in mixed sea states than single-chamber devices.In the work reported in this paper,physical experiments are carried under regular wave conditions to test the wave power extraction of a fixed MC-OWC small-scale model.The Power Take-Off(PTO)of the device is simulated using orifice plates.The flow characteristics through these orifices are pre-calibrated such that the extracted power can be obtained only using the pressure measurement.Wave condition effects on the damping of the PTO of the device power extraction are addressed.The test results illustrate that the PTO system damping is critical and affects device performance.展开更多
The high investment and low return of wave energy converters(WECs)seriously hamper their large-scale commercial application.The integration of WECs and floating breakwaters is conducive to enhance the competitiveness ...The high investment and low return of wave energy converters(WECs)seriously hamper their large-scale commercial application.The integration of WECs and floating breakwaters is conducive to enhance the competitiveness of wave energy conversion.The objective of this paper is to investigate the hydrodynamic performance of a WEC-breakwater integrated system combining an upstream oscillating water column(OWC)and a downstream oscillating buoy(OB)via numerical simulations and physical experiments.A nonlinear numerical wave flume using Star-CCM+software is employed to obtain calculated results,where a tiny transverse gap is set between the flume wall and the block surface to simulate a similar two-dimensional(2D)model.The corresponding physical experiments are also carried out in a practical wave flume to verified the numerical results.The comparison of the isolated and hybrid system shows that the hybrid design leads to the decreased conversion efficiency of each WEC,but improves the transmission performance of the hybrid system.The wave resonance between two devices causes the abrupt reduction of OWC efficiency and a positive correlation exists with the OB efficiency.The total efficiency of the hybrid system is raised by an optimal opening ratio,a shallow OWC draft and a short spacing distance.Except for the OWC draft,other design parameters have weak effect on the wave attenuation of the hybrid system.This paper can help understand hydrodynamics of the hybrid WECs integrated with breakwaters and improve their performances.展开更多
Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy convert...Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy converter(OWC-WEC). This study shows a numerical analysis of the diameter determination of two types of turbines, Wells and Impulse, installed in an onshore OWC device subjected to a hypothetical sea state. Commercial software FLUENT?,which is based on RANS-VoF(Reynolds-Averaged Navier-Stokes equations and Volume of Fluid technique), is employed. A methodology that imposes air pressure on the chamber, considering the air compressibility effect, is used. The mathematical domain consists of a 10 m deep flume with a 10 m long and 10 m wide OWC chamber at its end(geometry is similar to that of the Pico's plant installed in Azores islands, Portugal). On the top of the chamber, a turbine works with air exhalation and inhalation induced by the water free surface which oscillates due to the incident wave. The hypothetical sea state, represented by a group of regular waves with periods from 6 to 12 s and heights from 1.00 to 2.00 m(each wave with an occurrence frequency), is considered to show the potential of the presented methodology. Maximum efficiency(relation between the average output and incident wave powers) of46% was obtained by using a Wells turbine with the diameter of 2.25 m, whereas the efficiency was 44% by an Impulse turbine with the diameter of 1.70 m.展开更多
文摘Oscillating water column wave energy converter is a power generation device in which ocean waves excite the oscillation of the water surface in an air chamber, which generates fluctuations in air pressure and rotate air turbine generator(s). The oscillation of the fluid in the air chamber is a fluid oscillation phenomenon with a natural period, similar to fluid oscillation in a container such as sloshing. Previous research has shown that for an oscillating water column with a single air chamber submerged in water, the oscillation characteristics can be modeled as a one-degree-of-freedom oscillation system that takes only a single oscillation mode into account. However, a double-slit breakwater integrated oscillating water column wave energy converter using two water columns of the breakwater separated by slit walls, has been verified to have two resonance periods. In this study, the free oscillating motion of the oscillating water column wave energy converter using the double-slit breakwater is modeled by modal superposition method including the first-order and second-order modes of vertical motion of the two water surfaces. The result from the simulation is similar to the result of the free vibration experiment.
基金supported by the National Natural Science Foundation of China(Grant Nos. 50909089 and 40911140281)Qingdao S&T Development Program(09-1-3-41-jch)Korean Ministry of Land,Transport & Maritime Affairs through KORDI Program
文摘Oscillating Water Column (OWC) wave energy converting system is one of the most widely used facilities all over the world. The air chamber is utilized to convert the wave energy into the pneumatic energy. The numerical wave tank based on the two-phase VOF model is established in the present study toinvestigate the operating performance of OWC air chamber. The RANS equations, standard k-ε turbulence model and dynamic mesh technology are employed in the numerical model. The effects of incident wave conditions and shape parameters on the wave energy converting efficiency are studied and the capability of the present numerical wave tank on the corresponding engineering application is validated.
基金This investigation was carried out as a continuation of the“Program for the Promotion of New Energy Infrastructure Development”,supported by the Mitsubishi Research Institute(MRI)/the Ministry of Economy,Trade and Industry(METI),Japan.
文摘A fixed oscillating water column(OWC)-type wave energy converter consists of an air chamber,an air turbine and a generator.The energy conversion processes are the primary conversion in an air chamber and the secondary conversion of the turbine.For the practical use,it is necessary to develop a design method which can consider the incident wave motion,the motion of the internal free surface affected in the structure such as a partly submerged wall,the fluctuation of air pressure in an air chamber,and the rotation of the air turbine.At here,the authors carried out the wave tank tests using the model OWC equipped with the impulse turbine and a generator to obtain the experimental data needed to make this design method.As the result,the efficiencies of the three cases with different speed ratio between generator and turbine,and the effects of the curtain wall depth and the wave length on the energy conversion performance were clarified.
基金financially supported by the National Natural Science Foundation of China(Grant No.51739010)。
文摘A structure scheme of a pile-based breakwater with integrated oscillating water column(OWC)energy conversion chamber was proposed,and four structure forms had been designed.Based on the physical test,the variations of the reflected wave height,the transmitted wave height,the air velocity at the outlet of the chamber,the air pressure and the wave height in the air chamber were studied under the conditions of different wave heights,periods,with or without elliptical front wall and the baffles on both sides of the chamber.Moreover,based on the results,the changes and relationship between the wave-eliminating effect and energy conversion effect of the scheme were analyzed.In general,it turns out,the transmission coefficients of the four structure forms are kept below 0.5.Furthermore,the transmission coefficients of the structural forms G2,G3,and G4 were all smaller than 0.4,and it is only 0.1 at its smallest.Thereinto,in general,the structure form G4 has the best wave-eliminating and energy conversion performance.At the same time,when the wave steepness is 0.066,the energy conversion and wave dissipation effect of the four structure forms is the best.The research results could be provided as the reference for the design structure selection of pile-based breakwater with integrated OWC energy conversion chamber.
基金Project supported by the National Natural Science Foundation of China(Grant No.51305204)
文摘Both experimental and numerical studies were presented on the flow field characteristics in the process of gaseous jet impinging on liquid–water column. The effects of the impinging process on the working performance of rocket engine were also analyzed. The experimental results showed that the liquid–water had better flame and smoke dissipation effect in the process of gaseous jet impinging on liquid–water column. However, the interaction between the gaseous jet and the liquid–water column resulted in two pressure oscillations with large amplitude appearing in the combustion chamber of the rocket engine with instantaneous pressure increased by 17.73% and 17.93%, respectively. To analyze the phenomena, a new computational method was proposed by coupling the governing equations of the MIXTURE model with the phase change equations of water and the combustion equation of propellant. Numerical simulations were carried out on the generation of gas, the accelerate gas flow, and the mutual interaction between gaseous jet and liquid–water column.Numerical simulations showed that a cavity would be formed in the liquid–water column when gaseous jet impinged on the liquid–water column. The development speed of the cavity increased obviously after each pressure oscillation. In the initial stage of impingement, the gaseous jet was blocked due to the inertia effect of high-density water, and a large amount of gas gathered in the area between the nozzle throat and the gas–liquid interface. The shock wave was formed in the nozzle expansion section. Under the dual action of the reverse pressure wave and the continuously ejected high-temperature gas upstream, the shock wave moved repeatedly in the nozzle expansion section, which led to the flow of gas in the combustion chamber being blocked, released, re-blocked, and re-released. This was also the main reason for the pressure oscillations in the combustion chamber.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51879253 and U20A20106)。
文摘Freely movable wave energy converters(WECs) will greatly improve their adaptability to the marine environment.In this paper, a dual-mode oscillating water column(OWC) WEC with potential sailing capability is proposed. By opening and closing a gate on the side facing the waves, the WEC converts wave energy in the vertical duct(called VD mode) with low sailing resistance or in the backward bend duct(called BBD mode) with high sailing resistance.A small model and a medium model were designed and manufactured. The capture width ratio(CWR) of the small model in the two modes was experimentally studied. The CWR under bidirectional airflow and conversion characteristics under unidirectional airflow of the medium model in the BBD mode were obtained. Tests of the small model show that the peak CWR is 145.2% under regular waves and 90.1% under random waves in BBD mode, and in VD mode the peak CWR is about 60% of that in the BBD mode. Tests of the medium model show that the peak CWR is 228.96% under regular waves, the maximum wave-to-battery efficiency is 63.36% under regular waves and 30.17%under random waves, respectively.
基金The Key Program for International Scientific and Technological Innovation Cooperation between Governments(Grant No.2019YFE0102500)National Natural Science Foundation of China(Grant No.52001086)China Postdoctoral Science Foundation Funded Project(Grant No.2019M661257).
文摘Responses of the very large floating Structures(VLFS)can be mitigated by implementing oscillating water columns(OWCs).This paper explores the fundamental mechanism of present wave interactions with both structures and examines the hydrodynamic performance of VLFS equipped with OWCs(VLFS-OWCs).Under the linear potential flow theory framework,the semi-analytical model of wave interaction with VLFS-OWCs is developed using the eigenfunction matching method.The semi-analytical model is verified using the Haskind relationship and wave energy conservation law.Results show that the system with dual-chamber OWCs has a wider frequency bandwidth in wave power extraction and hydroelastic response mitigation of VLFS.It is worth noting that the presence of Bragg resonance can be trigged due to wave interaction with the chamber walls and the VLFS,which is not beneficial for the wave power extraction performance and the protection of VLFS.
文摘振荡水柱(Oscillation Water Column,OWC)是近年来发展较快的波浪能采集技术,该装置主要由箱体、振荡水柱和压缩空气柱组成,而波浪在气室内产生的压强对能量转换效率等起到决定作用。结合三维侧向开口的振荡水柱波能转换装置,基于线性波理论,采用三维Green函数法建立了气室内水气动力学性能的空气压强理论计算模型,利用多维切比雪夫(Chebyshev)多项式求解,计算结果精度高,能够准确表达波浪和结构设计参数对气室内压强影响。依据理论计算模型分析了波浪周期、波长、吃水深度、入射波幅等参数对气室内压强作用。
文摘设计一种带收缩水道的沉箱防波堤和OWC(Oscillating Water Column)波能发电装置相结合的复合结构形式,开展物理模型试验研究。通过改变水道结构形式与OWC气室参数,并分析实验数据,探讨水道形式、入射波要素和OWC气室形状参数等对该复合结构工作性能的影响,采用气室内波幅放大系数、气室顶部空气点压力和防波堤前波浪反射率作为考察参量。
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51579231,51879253)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA13040202)
文摘Wave tank tests were carried out to evaluate the total efficiency of a floating OWC Pentagonal Backward Bent Duct Buoy (PBBDB). Two kinds of turbine generators were used in tests. The incident wave power, pneumatic power and electricity were measured. The test results show that the primary efficiency can reach up to 185.98% in regular waves and 85.86% in irregular waves. The total efficiency from wave to wire with Wells turbine-generator set is 33.43% in regular waves and 15.82% in irregular waves. The peak total efficiency of the PBBDB with check valves equipped with the impulse turbine-generator set is 41.68% in regular waves and 27.10% in irregular waves. The efficiency of the turbine-generator set is about 30% in the tests. Obviously, the total efficiency can be further improved with the increasing of turbine efficiency.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51279190 and 51311140259)the Shandong Province Natural Science Foundation for Distinguished Young Scholars(Grant No.JQ201314)
文摘Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column(OWC) wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.
文摘Sea wave energy generators or converters(WECs)have the potential to become a viable technology for clean,renewable energy production.Among the WEC technologies,the oscillating water columns(OWCs)are the most common WEC devices studied.These have been studied and developed over many years.Multi-chamber oscillating water columns(MC-OWC)have the potential to have a higher energy conversion when extracting energy in mixed sea states than single-chamber devices.In the work reported in this paper,physical experiments are carried under regular wave conditions to test the wave power extraction of a fixed MC-OWC small-scale model.The Power Take-Off(PTO)of the device is simulated using orifice plates.The flow characteristics through these orifices are pre-calibrated such that the extracted power can be obtained only using the pressure measurement.Wave condition effects on the damping of the PTO of the device power extraction are addressed.The test results illustrate that the PTO system damping is critical and affects device performance.
基金supported by the National Natural Science Foundation of China(Grant Nos.52111530137 and 52025112)the State Key Laboratory of Ocean Engineering,China(Shanghai Jiao tong University)(Grant No.1905).
文摘The high investment and low return of wave energy converters(WECs)seriously hamper their large-scale commercial application.The integration of WECs and floating breakwaters is conducive to enhance the competitiveness of wave energy conversion.The objective of this paper is to investigate the hydrodynamic performance of a WEC-breakwater integrated system combining an upstream oscillating water column(OWC)and a downstream oscillating buoy(OB)via numerical simulations and physical experiments.A nonlinear numerical wave flume using Star-CCM+software is employed to obtain calculated results,where a tiny transverse gap is set between the flume wall and the block surface to simulate a similar two-dimensional(2D)model.The corresponding physical experiments are also carried out in a practical wave flume to verified the numerical results.The comparison of the isolated and hybrid system shows that the hybrid design leads to the decreased conversion efficiency of each WEC,but improves the transmission performance of the hybrid system.The wave resonance between two devices causes the abrupt reduction of OWC efficiency and a positive correlation exists with the OB efficiency.The total efficiency of the hybrid system is raised by an optimal opening ratio,a shallow OWC draft and a short spacing distance.Except for the OWC draft,other design parameters have weak effect on the wave attenuation of the hybrid system.This paper can help understand hydrodynamics of the hybrid WECs integrated with breakwaters and improve their performances.
文摘Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy converter(OWC-WEC). This study shows a numerical analysis of the diameter determination of two types of turbines, Wells and Impulse, installed in an onshore OWC device subjected to a hypothetical sea state. Commercial software FLUENT?,which is based on RANS-VoF(Reynolds-Averaged Navier-Stokes equations and Volume of Fluid technique), is employed. A methodology that imposes air pressure on the chamber, considering the air compressibility effect, is used. The mathematical domain consists of a 10 m deep flume with a 10 m long and 10 m wide OWC chamber at its end(geometry is similar to that of the Pico's plant installed in Azores islands, Portugal). On the top of the chamber, a turbine works with air exhalation and inhalation induced by the water free surface which oscillates due to the incident wave. The hypothetical sea state, represented by a group of regular waves with periods from 6 to 12 s and heights from 1.00 to 2.00 m(each wave with an occurrence frequency), is considered to show the potential of the presented methodology. Maximum efficiency(relation between the average output and incident wave powers) of46% was obtained by using a Wells turbine with the diameter of 2.25 m, whereas the efficiency was 44% by an Impulse turbine with the diameter of 1.70 m.