The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empi...The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empirical formulas for the growth of significant wave height and period. The main features of spectrum growth as specified by these parameters agree with those of the JONS-WAP experiments. For given wind speed and fetch, the high frequency parts beyond the peaks of shallow water spectra almost coincide with that of the corresponding deep water spectrum, whereas the low frequency parts differ appreciably. The method developed in this paper predicts smaller significant wave height as well as smaller wave period for shallow water spectra in contrast to the theoretical result of Kitaigorodskii ef al, in which the peak frequency, and consequently the significant wave period, remains basically unchanged for different water depths. Spectra are further reduced to a form in which only significant wave height and period are left as parameters, the peakness factor being replaced by the wave steepness through an empirical relation between them. Spectra in this form have been verified by observations.展开更多
Results of drag coefficient（CD） from field observations and laboratory wave tank experiments indicate that the operational wave model can overestimate wind energy input under high wind conditions. The wind-wave inte...Results of drag coefficient（CD） from field observations and laboratory wave tank experiments indicate that the operational wave model can overestimate wind energy input under high wind conditions. The wind-wave interaction source term in WAVEWATCH Ⅲ has been modified to examine its behavior with tropical cyclone wind forcing. Using high resolution wind input,numerical experiments under idealized wind field and tropical cyclone Bonnie（1998） were designed to evaluate performance of the modified models. Both experiments indicate that the modified models with reduced CD significantly decrease wind energy input into the wave model and then simulate lower significant wave height（SWH） than the original model. However,the effects on spatial distribution of SWH,mean wavelength,mean wave direction,and directional wave spectra are insignificant. Due to the reduced wind energy input,the idealized experiment shows that the modified models simulate lower SWH than the original model in all four quadrants. The decrease in the front quadrants is significantly larger than that in the rear quadrants;it is larger under higher winds than lower winds. The realistic experiment on tropical cyclone Bonnie shows that the modified model with the various downward trends of CD in high winds creates a simulation that agrees best with scanning radar altimeter observations.展开更多
The relationships between sea surface roughness z 0 and wind-wave parameters are analyzed,and spurious self-correlations are found in all of the parameterization schemes.Sea surface drag coefficient C D is fitted by f...The relationships between sea surface roughness z 0 and wind-wave parameters are analyzed,and spurious self-correlations are found in all of the parameterization schemes.Sea surface drag coefficient C D is fitted by four wind-wave parameters that are wave age,wave steepness,windsea Reynolds number R B and R H ,and the analyzed data are divided into laboratory,field and combined data sets respectively.Comparison and analysis of dependence of C D on wind-wave parameters show that R B can fit the C D most appropriately.Wave age and wave steepness are not suitable to fit C D with a narrow range data set.When the value of wave age has a board range,R H is not suitable to fit C D either.Three relationships between C D and R B are integrated into the bulk algorithm COARE to calculate the observational friction velocity,and the results show that the relationship between C D and R B which is fitted with field data set can describe the momentum transfer in the open ocean,under low-moderate wind speed condition,most appropriately.展开更多
A directional function for frequencies equal to and larger than the peak frequency of a wind-wave frequency spectrum is constructed by fitting the angular spreading based on the analytically derived directional spectr...A directional function for frequencies equal to and larger than the peak frequency of a wind-wave frequency spectrum is constructed by fitting the angular spreading based on the analytically derived directional spectrum of Wen et al. (1993, Journal of Oceanography, 49(2), 131～147, 149～172). For frequencies smaller than the peak frequency, the directional function is obtained by comparing and analyzing existing formulas. The nondimensional wind-wave frequency spectrum of Wen et al. (1994, Progress in Natural Seience, 4(4). 407～427;4 (5), 586～596) has been used together with the directional function just mentioned to obtain the directional spectrum for easier application.展开更多
The spectrum derived in Part 1 of the presert paper is here systematically verified with field data andcompared at some length with that obtained by multiplying the deep-water spectrum with theKitaigorodskii factor.
Wen et al.'s method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the ze...Wen et al.'s method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the zeroth moment m0 and peak frequency ω0, contains in addition to the peakness factor P= ω0S(ω0)/m0, a depth parameter ω= (2πm0)1/2/d (d being water depth), so the spectrum behavior can be studied for different wave growth stages and water depths.展开更多
Most wind turbine blades are assembled piece-by-piece onto the hub of a monopile-type offshore wind turbine using jack-up crane vessels.Despite the stable foundation of the lifting cranes,the mating process exhibits s...Most wind turbine blades are assembled piece-by-piece onto the hub of a monopile-type offshore wind turbine using jack-up crane vessels.Despite the stable foundation of the lifting cranes,the mating process exhibits substantial relative responses amidst blade root and hub.These relative motions are combined effects of wave-induced monopile motions and wind-induced blade root motions,which can cause impact loads at the blade root’s guide pin in the course of alignment procedure.Environmental parameters including the wind-wave misalignments play an important role for the safety of the installation tasks and govern the impact scenarios.The present study investigates the effects of wind-wave misalignments on the blade root mating process on a monopile-type offshore wind turbine.The dynamic responses including the impact velocities between root and hub in selected wind-wave misalignment conditions are investigated using multibody simulations.Furthermore,based on a finite element study,different impact-induced failure modes at the blade root for sideways and head-on impact scenarios,developed due to wind-wave misalignment conditions,are investigated.Finally,based on extreme value analyses of critical responses,safe domain for the mating task under different wind-wave misalignments is compared.The results show that although misaligned wind-wave conditions develop substantial relative motions between root and hub,aligned wind-wave conditions induce largest impact velocities and develop critical failure modes at a relatively low threshold velocity of impact.展开更多
An empirical formula for estimating the overtopping discharge of wind-waves on a smooth-impermeable-simple slope dyke is derived through model tests in this paper, it can be adopted by related design departments in th...An empirical formula for estimating the overtopping discharge of wind-waves on a smooth-impermeable-simple slope dyke is derived through model tests in this paper, it can be adopted by related design departments in the determination of the crest elevation of the dyke.展开更多
Spectral characteristics of wind-generated waves in labortaory are presented on the basis of a systematic measurement in a large-scale wind-wave channel and compared with those in the field. A marked characteristics o...Spectral characteristics of wind-generated waves in labortaory are presented on the basis of a systematic measurement in a large-scale wind-wave channel and compared with those in the field. A marked characteristics of the measured spetra is the existence of secondary spectrum-peak. The dependence of spectral peak-frequency, peak-value and zeroth-order moment on wind speed and fetch are presented and found roughly similar to those in the field represented by the JONSWAP spectrum, regardless of the differences in coefficient. The spectral slope beta at high-frequencies are found somewhat greater than those of field wind-waves in both cases of deep and shallow waters. Except for the low-frequency part, the spectral forms measured in different wind conditions are similar and fit for the JONSWAP spectrum with gamma = 6 and beta = 5.5. Some relevant problems are discussed.展开更多
With all the improvement in wave and hydrodynamics numerical models, the question rises in our mind that how the accuracy of the forcing functions and their input can affect the results. In this paper, a commonly used...With all the improvement in wave and hydrodynamics numerical models, the question rises in our mind that how the accuracy of the forcing functions and their input can affect the results. In this paper, a commonly used numerical third-generation wave model, SWAN is applied to predict waves in Lake Michigan. Wind data are analyzed to determine wind variation frequency over Lake Michigan. Wave predictions uncertainty due to wind local effects are compared during a period where wind has a fairly constant speed and direction over the northern and southern basins. The study shows that despite model calibration in Lake Michigan area, the model deficiency arises from ignoring wind effects in small scales. Wave prediction also emphasizes that small scale turbulence in meteorological forces can increase prediction errors by 38%. Wave frequency and coherence analysis show that both models can predict the wave variation time scale with the same accuracy. Insufficient number of meteorological stations can result in neglecting local wind effects and discrepancies in current predictions. The uncertainty of wave numerical models due to input uncertainties and model principals should be taken into account for design risk factors.展开更多
Sea spray induced by surface wave breaking plays an important role in air-sea flux.However,large differences in sea spray generation at the same wind speed were presented in previous studies.As a result,the parameteri...Sea spray induced by surface wave breaking plays an important role in air-sea flux.However,large differences in sea spray generation at the same wind speed were presented in previous studies.As a result,the parameterizations of sea spray generation functions can reach 4 orders difference.Wind speed may not be enough to explain this difference,and the surface wave state is a significant factor that causes this large difference,which then affects the estimation of the air-sea heat fluxes.In this study,synchronous observations of air-sea heat fluxes,surface waves and sea spray were conducted at a tower-based platform in a coastal region.Results showed that the sea spray generation is strongly correlated with both wind speed,and wave age as previously;more importantly,wind-wave alignment angle can cause approximately 1.3 orders(or 20 times)of sea spray generation function(SSGF)difference.A new SSGF with a dimensionless parameter RB0.7β-1cosθwas proposed.Heat fluxes caused by sea spray can be comparable to interfacial heat fluxes even at moderate wind speed.The three parameters of sea spray(α=6.4,σ=16,γ=6.3)were optimally fitted and evaluated.The air-sea heat flux evaluated in droplet evaporation layer(DEL)was improved with the new scheme,especially for sensible heat flux.The new parameters should be more suitable than other widely used parameters in numerical simulations.展开更多
Marine renewable energy,combining wave energy converters(WECs)and floating wind turbines(FWTs)into hybrid wave-wind energy converters(HWWECs),garners significant global interest.HWWECs offer potential cost reductions,...Marine renewable energy,combining wave energy converters(WECs)and floating wind turbines(FWTs)into hybrid wave-wind energy converters(HWWECs),garners significant global interest.HWWECs offer potential cost reductions,increased power generation,and enhanced system stability.The absorption power of high wind energy sites is primarily influenced by the complex hydrodynamic interactions among floating bodies,which are closely related to the location and wind-wave environment of high wind energy sites.To delve into the positive interactions among HWWECs,this paper proposes a HWWEC array optimization strategy based on the artificial ecosystem opti-mization-manta ray foraging optimization coordinated optimizer(EMCO).In EMCO,the decomposition operator of artificial ecosystem optimization(AEO)and the flipping-dipper foraging operator of manta ray foraging optimization coordinated(MRFO)cooperate dynamically to effectively balance local exploitation and global exploration.To validate the effectiveness of EMCO,experiments were conducted in scenarios with 3,5,8,and 20 HWWECs,and compared with five typical algorithms.Experimental results demonstrate the existence of multiple optimal solutions for HWWEC arrays.EMCO achieves maximum total absorp-tion power and exhibits good stability.Notably,EMCO en-hances the q-factor values of HWWECs across four scales:1.0478,1.0586,1.0612,and 0.9965,respectively.展开更多
Despite their importance in the ocean environment,the key physical processes in wind-wave interactions are poorly understood.Using a solver developed for undulatory boundaries,we perform numerical simulations of the w...Despite their importance in the ocean environment,the key physical processes in wind-wave interactions are poorly understood.Using a solver developed for undulatory boundaries,we perform numerical simulations of the wind-wave system under various sea conditions,including wind over monochromatic waves,early wind-wave generation,and wind over a broadband wave field.Our results show that the wave direction and wave age can significantly change the distribution of streamwise vorticity in the wind field.Different wave patterns are observed in the process of wind-wave generation.In a broadband wave field,the wave growth rate due to wind input is found to depend on the wave steepness.展开更多
Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines（OFWTs） draw a great deal...Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines（OFWTs） draw a great deal of attention recently as a means to exploit the steadier and stronger wind resources available in deep water seas. This paper studies the hydrodynamic characteristics of a spar-type wind turbine known as the OC3-Hywind concept and the dynamic responses of the turbine. Response characteristics of motions and mooring loads of the system under different sea states are evaluated and the effects of the loads induced by the wind and the wave on the system are discussed. The calculations are carried out with the numerical simulation code FAST in the time domain and the frequency analysis is made by using the FFT method. The results and the conclusions from this paper might help better understand the behavior characteristics of the floating wind turbine system under actual ocean environments and provide valuable data in design and engineering practice.展开更多
We present numerical computations of a new wind-wave coupling theory that is governed by a system of nonlinear advance-delay differential equations (NLADDE). NLADDE are functional differential equations for which the ...We present numerical computations of a new wind-wave coupling theory that is governed by a system of nonlinear advance-delay differential equations (NLADDE). NLADDE are functional differential equations for which the derivative of an unknown function depends nonlinearly on the past (delayed), present, and future (advanced) values of the unknown function (if time is the independent variable). A practical numerical method for solving NLADDE is implemented, based on a collocation method. The method is tested for two problems with known analytic solutions and is shown to be numerically convergent. Numerical solutions to the coupled wind and wave problem reveal estimates of the wave height spectrum, the distribution of breaking waves (both depend on wave scale), as well as the vertical air-side profiles of turbulent stress and wind speed.展开更多
为探究风波浪耦合作用下张力腿浮式平台(tension leg platform,TLP)动力学特性,提出适用于我国东海平均水深的系泊最优线径。该文以美国可再生能源实验室(national renewable energy laboratory,NREL)5 MW海上风力机和TLP浮式平台为研...为探究风波浪耦合作用下张力腿浮式平台(tension leg platform,TLP)动力学特性,提出适用于我国东海平均水深的系泊最优线径。该文以美国可再生能源实验室(national renewable energy laboratory,NREL)5 MW海上风力机和TLP浮式平台为研究对象,根据IEC 61400-3标准生成Kaimal湍流风谱和P-M不规则波浪谱,参考中国船级社海上浮式风机平台指南较系统地研究系泊线径、风浪错位角及海水深度对TLP浮式平台的影响,并通过高斯混合模型(Gaussian mixture model,GMM)和期望最大(expectation maximization,EM)迭代法优化系泊线径。研究发现,增大缆绳直径会使浮式平台在纵荡和横荡方向的初始位置与位移幅值减小,风浪失调时平台运动分量同纵荡方向一致与横荡方向相反;风浪错位角度增大致使平台横荡响应更加敏感,横摇呈现先增大后减小的趋势;海洋深度增加浮式平台纵荡位移峰值随之增加,但平台艏摇方向运动响应无明显变化;300~370 m深度海域系泊线径最优值为0.134 m。结果可为我国近海张力腿浮式平台及系泊系统的优化设计、性能评估及规模化开发提供理论指导。展开更多
文摘The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empirical formulas for the growth of significant wave height and period. The main features of spectrum growth as specified by these parameters agree with those of the JONS-WAP experiments. For given wind speed and fetch, the high frequency parts beyond the peaks of shallow water spectra almost coincide with that of the corresponding deep water spectrum, whereas the low frequency parts differ appreciably. The method developed in this paper predicts smaller significant wave height as well as smaller wave period for shallow water spectra in contrast to the theoretical result of Kitaigorodskii ef al, in which the peak frequency, and consequently the significant wave period, remains basically unchanged for different water depths. Spectra are further reduced to a form in which only significant wave height and period are left as parameters, the peakness factor being replaced by the wave steepness through an empirical relation between them. Spectra in this form have been verified by observations.
基金The National Natural Science Foundation of China under contract No. 40706008the Open Research Program of the Key Laboratory of Chinese Acadeing of Sciences for Tropical Marine Environmental Dynamics under contract No. LED0606+1 种基金the Shandong Province Natural Science Foundation of China under contract No. Z2008E02the National High Technology Research and Development Program ("863" Program) of China under contract No. 2008AA09A402
文摘Results of drag coefficient（CD） from field observations and laboratory wave tank experiments indicate that the operational wave model can overestimate wind energy input under high wind conditions. The wind-wave interaction source term in WAVEWATCH Ⅲ has been modified to examine its behavior with tropical cyclone wind forcing. Using high resolution wind input,numerical experiments under idealized wind field and tropical cyclone Bonnie（1998） were designed to evaluate performance of the modified models. Both experiments indicate that the modified models with reduced CD significantly decrease wind energy input into the wave model and then simulate lower significant wave height（SWH） than the original model. However,the effects on spatial distribution of SWH,mean wavelength,mean wave direction,and directional wave spectra are insignificant. Due to the reduced wind energy input,the idealized experiment shows that the modified models simulate lower SWH than the original model in all four quadrants. The decrease in the front quadrants is significantly larger than that in the rear quadrants;it is larger under higher winds than lower winds. The realistic experiment on tropical cyclone Bonnie shows that the modified model with the various downward trends of CD in high winds creates a simulation that agrees best with scanning radar altimeter observations.
基金The National Natural Science Foundation of China under Grant Nos 40675056 41076074National Key Basic Research Development Program under Grant No.2007CB411805the Basic Theory Foundation of Institute of Meteorology, PLA University of Science and Technology
文摘The relationships between sea surface roughness z 0 and wind-wave parameters are analyzed,and spurious self-correlations are found in all of the parameterization schemes.Sea surface drag coefficient C D is fitted by four wind-wave parameters that are wave age,wave steepness,windsea Reynolds number R B and R H ,and the analyzed data are divided into laboratory,field and combined data sets respectively.Comparison and analysis of dependence of C D on wind-wave parameters show that R B can fit the C D most appropriately.Wave age and wave steepness are not suitable to fit C D with a narrow range data set.When the value of wave age has a board range,R H is not suitable to fit C D either.Three relationships between C D and R B are integrated into the bulk algorithm COARE to calculate the observational friction velocity,and the results show that the relationship between C D and R B which is fitted with field data set can describe the momentum transfer in the open ocean,under low-moderate wind speed condition,most appropriately.
文摘A directional function for frequencies equal to and larger than the peak frequency of a wind-wave frequency spectrum is constructed by fitting the angular spreading based on the analytically derived directional spectrum of Wen et al. (1993, Journal of Oceanography, 49(2), 131～147, 149～172). For frequencies smaller than the peak frequency, the directional function is obtained by comparing and analyzing existing formulas. The nondimensional wind-wave frequency spectrum of Wen et al. (1994, Progress in Natural Seience, 4(4). 407～427;4 (5), 586～596) has been used together with the directional function just mentioned to obtain the directional spectrum for easier application.
基金Project supported by the National Natural Science Foundation of China.
文摘The spectrum derived in Part 1 of the presert paper is here systematically verified with field data andcompared at some length with that obtained by multiplying the deep-water spectrum with theKitaigorodskii factor.
基金Project supported by the National Natural Science Foundation of China.
文摘Wen et al.'s method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the zeroth moment m0 and peak frequency ω0, contains in addition to the peakness factor P= ω0S(ω0)/m0, a depth parameter ω= (2πm0)1/2/d (d being water depth), so the spectrum behavior can be studied for different wave growth stages and water depths.
基金The study is a part of SFI MOVE projects funded by the Research Council of Norway,NFR project number 237929.
文摘Most wind turbine blades are assembled piece-by-piece onto the hub of a monopile-type offshore wind turbine using jack-up crane vessels.Despite the stable foundation of the lifting cranes,the mating process exhibits substantial relative responses amidst blade root and hub.These relative motions are combined effects of wave-induced monopile motions and wind-induced blade root motions,which can cause impact loads at the blade root’s guide pin in the course of alignment procedure.Environmental parameters including the wind-wave misalignments play an important role for the safety of the installation tasks and govern the impact scenarios.The present study investigates the effects of wind-wave misalignments on the blade root mating process on a monopile-type offshore wind turbine.The dynamic responses including the impact velocities between root and hub in selected wind-wave misalignment conditions are investigated using multibody simulations.Furthermore,based on a finite element study,different impact-induced failure modes at the blade root for sideways and head-on impact scenarios,developed due to wind-wave misalignment conditions,are investigated.Finally,based on extreme value analyses of critical responses,safe domain for the mating task under different wind-wave misalignments is compared.The results show that although misaligned wind-wave conditions develop substantial relative motions between root and hub,aligned wind-wave conditions induce largest impact velocities and develop critical failure modes at a relatively low threshold velocity of impact.
文摘An empirical formula for estimating the overtopping discharge of wind-waves on a smooth-impermeable-simple slope dyke is derived through model tests in this paper, it can be adopted by related design departments in the determination of the crest elevation of the dyke.
基金This work was financially supported by the National Science Foundation of China(No.4967277)
文摘Spectral characteristics of wind-generated waves in labortaory are presented on the basis of a systematic measurement in a large-scale wind-wave channel and compared with those in the field. A marked characteristics of the measured spetra is the existence of secondary spectrum-peak. The dependence of spectral peak-frequency, peak-value and zeroth-order moment on wind speed and fetch are presented and found roughly similar to those in the field represented by the JONSWAP spectrum, regardless of the differences in coefficient. The spectral slope beta at high-frequencies are found somewhat greater than those of field wind-waves in both cases of deep and shallow waters. Except for the low-frequency part, the spectral forms measured in different wind conditions are similar and fit for the JONSWAP spectrum with gamma = 6 and beta = 5.5. Some relevant problems are discussed.
文摘With all the improvement in wave and hydrodynamics numerical models, the question rises in our mind that how the accuracy of the forcing functions and their input can affect the results. In this paper, a commonly used numerical third-generation wave model, SWAN is applied to predict waves in Lake Michigan. Wind data are analyzed to determine wind variation frequency over Lake Michigan. Wave predictions uncertainty due to wind local effects are compared during a period where wind has a fairly constant speed and direction over the northern and southern basins. The study shows that despite model calibration in Lake Michigan area, the model deficiency arises from ignoring wind effects in small scales. Wave prediction also emphasizes that small scale turbulence in meteorological forces can increase prediction errors by 38%. Wave frequency and coherence analysis show that both models can predict the wave variation time scale with the same accuracy. Insufficient number of meteorological stations can result in neglecting local wind effects and discrepancies in current predictions. The uncertainty of wave numerical models due to input uncertainties and model principals should be taken into account for design risk factors.
基金supported by the National Natural Science Foundation of China(Grant Nos.42276024,42076014)the Basic Scientific Fund for National Public Research Institutes of China(Grant No.2024S02)。
文摘Sea spray induced by surface wave breaking plays an important role in air-sea flux.However,large differences in sea spray generation at the same wind speed were presented in previous studies.As a result,the parameterizations of sea spray generation functions can reach 4 orders difference.Wind speed may not be enough to explain this difference,and the surface wave state is a significant factor that causes this large difference,which then affects the estimation of the air-sea heat fluxes.In this study,synchronous observations of air-sea heat fluxes,surface waves and sea spray were conducted at a tower-based platform in a coastal region.Results showed that the sea spray generation is strongly correlated with both wind speed,and wave age as previously;more importantly,wind-wave alignment angle can cause approximately 1.3 orders(or 20 times)of sea spray generation function(SSGF)difference.A new SSGF with a dimensionless parameter RB0.7β-1cosθwas proposed.Heat fluxes caused by sea spray can be comparable to interfacial heat fluxes even at moderate wind speed.The three parameters of sea spray(α=6.4,σ=16,γ=6.3)were optimally fitted and evaluated.The air-sea heat flux evaluated in droplet evaporation layer(DEL)was improved with the new scheme,especially for sensible heat flux.The new parameters should be more suitable than other widely used parameters in numerical simulations.
基金supported by the National Natural Science Foundation of China(No.61963020 and No.62263014)Yunnan Provincial Basic Research Project(No.202201AT070857).
文摘Marine renewable energy,combining wave energy converters(WECs)and floating wind turbines(FWTs)into hybrid wave-wind energy converters(HWWECs),garners significant global interest.HWWECs offer potential cost reductions,increased power generation,and enhanced system stability.The absorption power of high wind energy sites is primarily influenced by the complex hydrodynamic interactions among floating bodies,which are closely related to the location and wind-wave environment of high wind energy sites.To delve into the positive interactions among HWWECs,this paper proposes a HWWEC array optimization strategy based on the artificial ecosystem opti-mization-manta ray foraging optimization coordinated optimizer(EMCO).In EMCO,the decomposition operator of artificial ecosystem optimization(AEO)and the flipping-dipper foraging operator of manta ray foraging optimization coordinated(MRFO)cooperate dynamically to effectively balance local exploitation and global exploration.To validate the effectiveness of EMCO,experiments were conducted in scenarios with 3,5,8,and 20 HWWECs,and compared with five typical algorithms.Experimental results demonstrate the existence of multiple optimal solutions for HWWEC arrays.EMCO achieves maximum total absorp-tion power and exhibits good stability.Notably,EMCO en-hances the q-factor values of HWWECs across four scales:1.0478,1.0586,1.0612,and 0.9965,respectively.
文摘Despite their importance in the ocean environment,the key physical processes in wind-wave interactions are poorly understood.Using a solver developed for undulatory boundaries,we perform numerical simulations of the wind-wave system under various sea conditions,including wind over monochromatic waves,early wind-wave generation,and wind over a broadband wave field.Our results show that the wave direction and wave age can significantly change the distribution of streamwise vorticity in the wind field.Different wave patterns are observed in the process of wind-wave generation.In a broadband wave field,the wave growth rate due to wind input is found to depend on the wave steepness.
基金Project supported by the State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University(Grant No.GKZD010023)
文摘Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines（OFWTs） draw a great deal of attention recently as a means to exploit the steadier and stronger wind resources available in deep water seas. This paper studies the hydrodynamic characteristics of a spar-type wind turbine known as the OC3-Hywind concept and the dynamic responses of the turbine. Response characteristics of motions and mooring loads of the system under different sea states are evaluated and the effects of the loads induced by the wind and the wave on the system are discussed. The calculations are carried out with the numerical simulation code FAST in the time domain and the frequency analysis is made by using the FFT method. The results and the conclusions from this paper might help better understand the behavior characteristics of the floating wind turbine system under actual ocean environments and provide valuable data in design and engineering practice.
基金supported by the U.S. National Science Foundation (Grant OCE- 0526177)the U.S. Office of Naval Research (Grant N00014-06-10729)supported by a WHOI/NOAA Cooperative Institute for Climate and Ocean Research Postdoctoral Scholarship
文摘We present numerical computations of a new wind-wave coupling theory that is governed by a system of nonlinear advance-delay differential equations (NLADDE). NLADDE are functional differential equations for which the derivative of an unknown function depends nonlinearly on the past (delayed), present, and future (advanced) values of the unknown function (if time is the independent variable). A practical numerical method for solving NLADDE is implemented, based on a collocation method. The method is tested for two problems with known analytic solutions and is shown to be numerically convergent. Numerical solutions to the coupled wind and wave problem reveal estimates of the wave height spectrum, the distribution of breaking waves (both depend on wave scale), as well as the vertical air-side profiles of turbulent stress and wind speed.
