Rachael E. Smith, A. Pillai, G. Tabor, P. Thies, L. Johanning
The rotor of a horizontal-axis floating offshore wind turbine is more frequently misaligned with the oncoming wind than that of a fixed offshore or onshore wind turbine due to the pitch and yaw motions of the floating support structure. This can lead to increased unsteady loading and fatigue on the components beyond those considered in the standard load cases. In this work, the Simulator fOr Wind Farm Applications (SOWFA) tool within the CFD toolbox OpenFOAM is used to perform simulations of a wind turbine at different stationary angles to the oncoming wind flow that a floating wind turbine may experience, so that the impact of misaligned flow on power production and blade loading can be studied. The turbine is modelled using an actuator line method which is coupled with NREL’s aeroelastic code FAST to compute the structural response. The results of this study will be used in future work to optimise the rotor geometry of a floating offshore wind turbine.
由于浮动支承结构的俯仰和偏航运动，水平轴浮动式海上风电机组的转子与迎面风的错位比固定式海上或陆上风电机组的转子更频繁。这可能导致非定常载荷和疲劳的增加，超出了标准载荷情况下的考虑范围。在这项工作中，使用CFD工具箱OpenFOAM中的Simulator fOr Wind Farm Applications (soffa)工具对浮动式风力涡轮机可能遇到的迎面风流进行不同静止角度的风力涡轮机模拟，从而研究失调气流对发电和叶片负荷的影响。采用执行器线法对涡轮进行建模，并结合NREL气动弹性代码FAST进行结构响应计算。这项研究的结果将用于未来的工作，以优化浮式海上风力涡轮机的转子几何形状。
{"title":"Impact of Rotor Misalignment due to Platform Motions on Floating Offshore Wind Turbine Blade Loads","authors":"Rachael E. Smith, A. Pillai, G. Tabor, P. Thies, L. Johanning","doi":"10.1115/OMAE2019-95759","DOIUrl":"https://doi.org/10.1115/OMAE2019-95759","url":null,"abstract":"\u0000 The rotor of a horizontal-axis floating offshore wind turbine is more frequently misaligned with the oncoming wind than that of a fixed offshore or onshore wind turbine due to the pitch and yaw motions of the floating support structure. This can lead to increased unsteady loading and fatigue on the components beyond those considered in the standard load cases. In this work, the Simulator fOr Wind Farm Applications (SOWFA) tool within the CFD toolbox OpenFOAM is used to perform simulations of a wind turbine at different stationary angles to the oncoming wind flow that a floating wind turbine may experience, so that the impact of misaligned flow on power production and blade loading can be studied. The turbine is modelled using an actuator line method which is coupled with NREL’s aeroelastic code FAST to compute the structural response. The results of this study will be used in future work to optimise the rotor geometry of a floating offshore wind turbine.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124858287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohammad Mahdi Abaei, N. Arini, P. Thies, Johanning Lars
Improving the reliability of marine renewable energy devices such as wave and tidal energy convertors is an important task, primarily to minimize the perceived risks and reduce the associated cost for operation and maintenance. Marine systems involve a wide range of uncertainties, due to the complexity of failure mechanism of the marine components, scarcity of data, human interactions and randomness of the sea environment. The fundamental element of a probabilistic risk analysis necessarily needs to rely on operational information and observation data to quantify the performance of the system. However, in reality it is difficult to ascertain observation of the precursor data according to the number of component failures that have occurred, mainly as a result of imprecision in the failure criterion, record keeping, or experimental and physical modelling of the process. Traditional reliability estimation approaches such as Fault Tree, Event Tree and Reliability Block Diagram analysis offer simplified, rarely realistic models of this complex reliability problem. The main reason is that they all rely on accurate prior information as a perquisite for performing reliability assessment. In this paper, a hierarchical Bayesian framework is developed for modelling marine renewable component failures encountered the uncertainty. The proposed approach is capable to incorporate the conditions, which lack reliable observation data (e.g. unknown/uncertain failure rate of a component). The hierarchical Bayesian framework provides a platform for the propagation of uncertainties through the reliability assessment of the system, via Markov Chain Monte Carlo (MCMC) sampling. The advantages of using MCMC sampling has proliferated Bayesian inference for conducting risk and reliability assessment of engineering system. It is able to use hyper-priors to represent prior parameters as a subjective observations for probability estimation of the failure events and enable an updating process for quantitative reasoning of interdependence between parameters. The developed framework will be an assistive tool for a better monitoring of the operation in terms of evaluating performance of marine renewable system under the risk of failure. The paper illustrates the approach using a tidal energy convertor as a case study for estimating components failure rates and representing the uncertainties of system reliability. The paper will be of interest to reliability practitioners and researchers, as well as tidal energy technology and project developers, seeking a more accurate reliability estimation framework.
{"title":"Failure Estimation of Offshore Renewable Energy Devices Based on Hierarchical Bayesian Approach","authors":"Mohammad Mahdi Abaei, N. Arini, P. Thies, Johanning Lars","doi":"10.1115/omae2019-95099","DOIUrl":"https://doi.org/10.1115/omae2019-95099","url":null,"abstract":"\u0000 Improving the reliability of marine renewable energy devices such as wave and tidal energy convertors is an important task, primarily to minimize the perceived risks and reduce the associated cost for operation and maintenance. Marine systems involve a wide range of uncertainties, due to the complexity of failure mechanism of the marine components, scarcity of data, human interactions and randomness of the sea environment. The fundamental element of a probabilistic risk analysis necessarily needs to rely on operational information and observation data to quantify the performance of the system. However, in reality it is difficult to ascertain observation of the precursor data according to the number of component failures that have occurred, mainly as a result of imprecision in the failure criterion, record keeping, or experimental and physical modelling of the process. Traditional reliability estimation approaches such as Fault Tree, Event Tree and Reliability Block Diagram analysis offer simplified, rarely realistic models of this complex reliability problem. The main reason is that they all rely on accurate prior information as a perquisite for performing reliability assessment. In this paper, a hierarchical Bayesian framework is developed for modelling marine renewable component failures encountered the uncertainty. The proposed approach is capable to incorporate the conditions, which lack reliable observation data (e.g. unknown/uncertain failure rate of a component). The hierarchical Bayesian framework provides a platform for the propagation of uncertainties through the reliability assessment of the system, via Markov Chain Monte Carlo (MCMC) sampling. The advantages of using MCMC sampling has proliferated Bayesian inference for conducting risk and reliability assessment of engineering system. It is able to use hyper-priors to represent prior parameters as a subjective observations for probability estimation of the failure events and enable an updating process for quantitative reasoning of interdependence between parameters. The developed framework will be an assistive tool for a better monitoring of the operation in terms of evaluating performance of marine renewable system under the risk of failure. The paper illustrates the approach using a tidal energy convertor as a case study for estimating components failure rates and representing the uncertainties of system reliability. The paper will be of interest to reliability practitioners and researchers, as well as tidal energy technology and project developers, seeking a more accurate reliability estimation framework.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124873390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wave energy is sustainable and clean energy, so it has great potential to be an eco-friendly and lasting renewable energy resource in the future. Recently, a number of researchers have investigated different types of wave energy converters (WECs) using numerical models such as potential theory and Computational Fluid Dynamics (CFD) to enhance the efficiency of such devices. In this paper, a validation of a point absorber type WECs is investigated to capture the movement of the WEC system and to measure the moment on the WEC system. The WEC consists of a lever and a buoy. The geometry is the same as the existing experimental geometry of the reference in order to validate the present numerical simulation. The buoy is connected to the lever and has a hinge on the connection point. Besides, another hinge is installed in the middle of the lever, and the WEC system rotates in the pitch direction. The commercial CFD package Star-CCM+, which solves Reynolds-Averaged Navier-Stokes equations, is employed in this study. In the initial stages of this research, a validation study against published experimental results was conducted. The rotational displacement and the moment on the buoy were compared with the existing experimental data of the reference. The result shows good agreement. In the near future, a study on a new pivoted point absorber WEC device regarding the buoy shape of the WEC device and an operation principle will be performed based on this numerical study.
波浪能是一种可持续、清洁的能源，在未来成为一种环保、持久的可再生能源具有很大的潜力。最近，许多研究人员利用势理论和计算流体动力学(CFD)等数值模型研究了不同类型的波浪能转换器(WECs)，以提高此类设备的效率。本文研究了一种点吸收体型微气泡阱的验证方法，用于捕捉微气泡阱系统的运动并测量微气泡阱系统上的力矩。WEC由杠杆和浮标组成。为了验证本文的数值模拟，几何形状与参考文献已有的实验几何形状相同。所述浮筒与杠杆连接，并在连接点上设有铰链。在杠杆中间安装另一个铰链，WEC系统沿俯仰方向旋转。本研究采用求解reynolds - average Navier-Stokes方程的商用CFD软件包Star-CCM+。在本研究的初始阶段，对已发表的实验结果进行了验证研究。将浮标上的旋转位移和力矩与已有的参考实验数据进行了比较。结果吻合较好。在不久的将来，我们将在此数值研究的基础上，对一种新型的轴心点吸波WEC装置的浮筒形状和工作原理进行研究。
{"title":"A Validation of a Pivoted Point Absorber Type Wave Energy Converter Using CFD","authors":"Injun Yang, T. Tezdogan, A. Incecik","doi":"10.1115/OMAE2019-96030","DOIUrl":"https://doi.org/10.1115/OMAE2019-96030","url":null,"abstract":"\u0000 Wave energy is sustainable and clean energy, so it has great potential to be an eco-friendly and lasting renewable energy resource in the future. Recently, a number of researchers have investigated different types of wave energy converters (WECs) using numerical models such as potential theory and Computational Fluid Dynamics (CFD) to enhance the efficiency of such devices. In this paper, a validation of a point absorber type WECs is investigated to capture the movement of the WEC system and to measure the moment on the WEC system. The WEC consists of a lever and a buoy. The geometry is the same as the existing experimental geometry of the reference in order to validate the present numerical simulation. The buoy is connected to the lever and has a hinge on the connection point. Besides, another hinge is installed in the middle of the lever, and the WEC system rotates in the pitch direction. The commercial CFD package Star-CCM+, which solves Reynolds-Averaged Navier-Stokes equations, is employed in this study. In the initial stages of this research, a validation study against published experimental results was conducted. The rotational displacement and the moment on the buoy were compared with the existing experimental data of the reference. The result shows good agreement. In the near future, a study on a new pivoted point absorber WEC device regarding the buoy shape of the WEC device and an operation principle will be performed based on this numerical study.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126496383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mitchell G. Borg, Q. Xiao, A. Incecik, Steven Allsop, C. Peyrard
This work elaborates a computational fluid dynamic model utilised in the investigation of the hydrodynamic performance concerning a ducted high-solidity tidal turbine in yawed inlet flows. Analysing the performance at distinct bearing angles with the axis of the turbine, increases in torque and mechanical rotational power were acknowledged to be induced within a limited angular range at distinct tip-speed ratio values. Through multiple yaw iterations, the peak attainment was found to fall between bearing angles of 15° and 30°, resulting in a maximum power increase of 3.22%, together with an extension of power development to higher tip-speed ratios. In confirmation, these outcomes were subsequently analysed by means of actuator disc theory, attaining a distinguishable relationship with blade-integrated outcomes.
{"title":"An Actuator Disc Analysis of a Ducted High-Solidity Tidal Turbine in Yawed Flow","authors":"Mitchell G. Borg, Q. Xiao, A. Incecik, Steven Allsop, C. Peyrard","doi":"10.1115/omae2019-96014","DOIUrl":"https://doi.org/10.1115/omae2019-96014","url":null,"abstract":"\u0000 This work elaborates a computational fluid dynamic model utilised in the investigation of the hydrodynamic performance concerning a ducted high-solidity tidal turbine in yawed inlet flows. Analysing the performance at distinct bearing angles with the axis of the turbine, increases in torque and mechanical rotational power were acknowledged to be induced within a limited angular range at distinct tip-speed ratio values. Through multiple yaw iterations, the peak attainment was found to fall between bearing angles of 15° and 30°, resulting in a maximum power increase of 3.22%, together with an extension of power development to higher tip-speed ratios. In confirmation, these outcomes were subsequently analysed by means of actuator disc theory, attaining a distinguishable relationship with blade-integrated outcomes.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116575438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jian Wang, G. He, W. Mo, Shijun Zhang, Jiangtao Man
The hydrodynamic performance of a novel current energy generator is studied with consideration of the effect of Wing in Ground (WIG) by Star CCM+. The pitch and heave motions of a turbine with a 2D single oscillating wing and two parallelized oscillating wings in uniform flow are simulated, and the numerical results including the lift force, drag force and moment coefficients of the hydrofoil are calculated to analyze the hydrodynamic performance of the generator. First, the convergence studies with respect to the mesh and time step are firstly carried out by compared with the published data. Secondly, the hydrodynamic performance of the WIG-based current energy extraction is investigated, and a good performance of the current energy extraction is confirmed. Finally, the effect of boundary conditions of wing and wall on the performance of the current energy generator is investigated.
采用Star CCM+软件对一种新型电流发电机的水动力性能进行了研究，并考虑了地中翼(Wing in Ground, WIG)的影响。对具有二维单振翼和双平行振翼的水轮机在均匀流动条件下的俯仰和升沉运动进行了数值模拟，计算了水翼的升力、阻力和力矩系数等数值结果，分析了发电机的水动力性能。首先，通过与已发表数据的对比，进行了网格和时间步长的收敛性研究。其次，研究了基于wigg的电流能量提取的水动力性能，证实了其良好的电流能量提取性能。最后，研究了机翼和壁面边界条件对电流发生器性能的影响。
{"title":"Hydrodynamic Performance of a Current Energy Generator Based on WIG","authors":"Jian Wang, G. He, W. Mo, Shijun Zhang, Jiangtao Man","doi":"10.1115/omae2019-96378","DOIUrl":"https://doi.org/10.1115/omae2019-96378","url":null,"abstract":"\u0000 The hydrodynamic performance of a novel current energy generator is studied with consideration of the effect of Wing in Ground (WIG) by Star CCM+. The pitch and heave motions of a turbine with a 2D single oscillating wing and two parallelized oscillating wings in uniform flow are simulated, and the numerical results including the lift force, drag force and moment coefficients of the hydrofoil are calculated to analyze the hydrodynamic performance of the generator. First, the convergence studies with respect to the mesh and time step are firstly carried out by compared with the published data. Secondly, the hydrodynamic performance of the WIG-based current energy extraction is investigated, and a good performance of the current energy extraction is confirmed. Finally, the effect of boundary conditions of wing and wall on the performance of the current energy generator is investigated.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"216 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121726909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Tamimi, M. Armin, S. Shahvaghar-Asl, S. Naeeni, M. Zeinoddini
The relative incompetency of rectangular galloping excavators against conventional circular VIV harvesters is already known. In this experimental study, the hydroelastic energy performances of new right-angle isosceles triangular cylinder against circular, square and diamond cross-sections are investigated. The triangular cylinder displays VIV or galloping type of response in four different symmetrical and unsymmetrical configurations tested. The results show the distinct higher overall galloping energy performance of the triangular cylinder in Config. 2 among other VIV and galloping harvesters. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is employed to order the remaining tested cross-sections using the averaged and maximum values of the mechanical power and efficiency as criteria. The TOPSIS algorithm shows that the VIV diamond and circular harvesters stay at the second and third places of the energy performance, respectively. The preference value of the diamond and circular cross-sections are almost comparable but are less than half of that in Config. 2. In general, the sharp-edge cylinders display superior energy performance over circular cross-section. However, the axisymmetric circular cylinders, because of their omnidirectional performances, are more efficient in places with the varying flow direction.
{"title":"FIV Energy Harvesting From Sharp-Edge Oscillators","authors":"V. Tamimi, M. Armin, S. Shahvaghar-Asl, S. Naeeni, M. Zeinoddini","doi":"10.1115/omae2019-95227","DOIUrl":"https://doi.org/10.1115/omae2019-95227","url":null,"abstract":"\u0000 The relative incompetency of rectangular galloping excavators against conventional circular VIV harvesters is already known. In this experimental study, the hydroelastic energy performances of new right-angle isosceles triangular cylinder against circular, square and diamond cross-sections are investigated. The triangular cylinder displays VIV or galloping type of response in four different symmetrical and unsymmetrical configurations tested. The results show the distinct higher overall galloping energy performance of the triangular cylinder in Config. 2 among other VIV and galloping harvesters. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is employed to order the remaining tested cross-sections using the averaged and maximum values of the mechanical power and efficiency as criteria. The TOPSIS algorithm shows that the VIV diamond and circular harvesters stay at the second and third places of the energy performance, respectively. The preference value of the diamond and circular cross-sections are almost comparable but are less than half of that in Config. 2. In general, the sharp-edge cylinders display superior energy performance over circular cross-section. However, the axisymmetric circular cylinders, because of their omnidirectional performances, are more efficient in places with the varying flow direction.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114267849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mao Baijin, Jili Sun, Zecheng Tang, Bo Feng, Zhang Weijie, Dahai Zhang, Yulin Si
Floating offshore wind turbine (FOWT) has been a hot research topic in recent years due to its great potential in deep sea wind energy harvesting. However, the floating platforms will introduce additional degrees of freedom to the system, which results in much more ultimate and fatigue loads onto the wind turbine structure compared with fixed bottom types. The load issue has been the major design challenge in developing FOWTs. In this paper, we report a novel semi-submersible supporting platform design, named MUsupport, aiming to improve the dynamic responses and reduce loads for FOWTs. The proposed semi-submersible MUsupport is mainly composed of one main column attached to the tower and four offset columns. Particularly, instead of simply filled with ballast water, the four columns act as four tuned liquid column dampers (TLCDs), and the oscillating liquid inside the TLCDs is supposed to help improve the dynamic responses of the semi-submersible platform, thus reducing the loads. The sizing of these TLCDs are determined by frequency analysis, and the detailed structural properties for MUsupport are described in this paper. Additionally, in order to better study the damping effects of the TLCDs, the dynamic model of MUsupport FOWT in the pitch-surge-heave plane is derived based on the Lagrangian approach, and free decay simulation test is performed. It can be observed from the results that the introduction of TLCDs will bring more damping to the system dynamics, which is helpful for FOWT load reduction. Note that this is only preliminary study, and future works will comprehensively investigate its hydrodynamic and mooring behaviors of MUsupport, and aero-hydro-servo-elastic numerical simulations or experimental tests should be performed to further verify its effectiveness.
{"title":"A Novel Semi-Submersible Floating Wind Turbine Platform Design Based on Tuned Liquid Column Dampers","authors":"Mao Baijin, Jili Sun, Zecheng Tang, Bo Feng, Zhang Weijie, Dahai Zhang, Yulin Si","doi":"10.1115/omae2019-95945","DOIUrl":"https://doi.org/10.1115/omae2019-95945","url":null,"abstract":"\u0000 Floating offshore wind turbine (FOWT) has been a hot research topic in recent years due to its great potential in deep sea wind energy harvesting. However, the floating platforms will introduce additional degrees of freedom to the system, which results in much more ultimate and fatigue loads onto the wind turbine structure compared with fixed bottom types. The load issue has been the major design challenge in developing FOWTs.\u0000 In this paper, we report a novel semi-submersible supporting platform design, named MUsupport, aiming to improve the dynamic responses and reduce loads for FOWTs. The proposed semi-submersible MUsupport is mainly composed of one main column attached to the tower and four offset columns. Particularly, instead of simply filled with ballast water, the four columns act as four tuned liquid column dampers (TLCDs), and the oscillating liquid inside the TLCDs is supposed to help improve the dynamic responses of the semi-submersible platform, thus reducing the loads. The sizing of these TLCDs are determined by frequency analysis, and the detailed structural properties for MUsupport are described in this paper. Additionally, in order to better study the damping effects of the TLCDs, the dynamic model of MUsupport FOWT in the pitch-surge-heave plane is derived based on the Lagrangian approach, and free decay simulation test is performed. It can be observed from the results that the introduction of TLCDs will bring more damping to the system dynamics, which is helpful for FOWT load reduction. Note that this is only preliminary study, and future works will comprehensively investigate its hydrodynamic and mooring behaviors of MUsupport, and aero-hydro-servo-elastic numerical simulations or experimental tests should be performed to further verify its effectiveness.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134197994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Yim, N. Adami, B. Bosma, T. Brekken, M. Chen, L. G. Zadeh, D. Glennon, Y-S. Lian, P. Lomónaco, A. Mohtat, T. Ozkan-Haller, J. Thomson
This article describes the model development and preliminary progress of an on-going research study on the effects of nonlinearities in ocean wave input and power-take-off (PTO) control on wave energy conversion system dynamics and efficiency. The model system employed and progress on recent developments are: (1) nonlinear wave modeling in the ocean, generation and propagation in a wave basin, and (2) nonlinear PTO control algorithm. An overview of the holistic analytical, numerical and experimental research approach/work plan is presented. To provide a simple means for analysis, comparison and performance evaluation, the WEC-Sim numerical platform is used for model implementation and system dynamic simulation. Analytical and numerical predictions of the nonlinear wave fields in a wave basin using the nonlinear Fourier analysis (NLFA) technique and corresponding nonlinear wavemaker theory and a plan for future validation using a comprehensive series of experimental test data as well as ocean wave measurements are described. Efficiency of the nonlinear PTO control and a future evaluation work plan by comparing numerical simulations with results of WEC model test data under corresponding wave conditions of the experimental studies without the presence of the WEC system are also presented.
{"title":"A Preliminary Study on the Modeling and Analysis of Nonlinear Effects of Ocean Waves and Power-Take-Off Control on Wave Energy Conversion System Dynamics","authors":"S. Yim, N. Adami, B. Bosma, T. Brekken, M. Chen, L. G. Zadeh, D. Glennon, Y-S. Lian, P. Lomónaco, A. Mohtat, T. Ozkan-Haller, J. Thomson","doi":"10.1115/omae2019-96802","DOIUrl":"https://doi.org/10.1115/omae2019-96802","url":null,"abstract":"\u0000 This article describes the model development and preliminary progress of an on-going research study on the effects of nonlinearities in ocean wave input and power-take-off (PTO) control on wave energy conversion system dynamics and efficiency. The model system employed and progress on recent developments are: (1) nonlinear wave modeling in the ocean, generation and propagation in a wave basin, and (2) nonlinear PTO control algorithm. An overview of the holistic analytical, numerical and experimental research approach/work plan is presented. To provide a simple means for analysis, comparison and performance evaluation, the WEC-Sim numerical platform is used for model implementation and system dynamic simulation. Analytical and numerical predictions of the nonlinear wave fields in a wave basin using the nonlinear Fourier analysis (NLFA) technique and corresponding nonlinear wavemaker theory and a plan for future validation using a comprehensive series of experimental test data as well as ocean wave measurements are described. Efficiency of the nonlinear PTO control and a future evaluation work plan by comparing numerical simulations with results of WEC model test data under corresponding wave conditions of the experimental studies without the presence of the WEC system are also presented.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115550336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The main drivers for the continued decarbonisation of the global energy market are renewable energy sources. Moreover, the leading technological solutions to achieve this are offshore wind turbines. As installed capacity has been increasing rapidly and shallow water near shore sites are exhausted, projects will need to be developed further from shore and often in deeper waters, which will pose greater technical challenges and constrain efforts to reduce costs. Current floating platform solutions such as the spar and semi-submersible rely on large amounts of ballast and complex structural designs with active stabilisation systems for stability of the floating offshore wind turbine platform (FOWT). The primary focus of this study is to present a design concept and mooring arrangement for an alternative floating platform solution that places emphasis on the mooring system to achieve stability for a FOWT. The tension leg buoy (TLB) is designed to support future 10MW offshore wind turbine generators. This paper presents the numerical methodology used for a coupled hydro-elastic analysis of the floater and mooring system under combined wind, wave and current effects. A concept TLB design is presented and its platform motion and mooring line tension characteristics are analysed for a three-hour time domain simulation representing operating and survival conditions in the northern North Sea with water depths of 110 metres. The importance of wave drift forces and the other non-linear excitation forces in the concept design stage are evaluated by comparing the motion and tension responses of three different numerical simulation cases with increasing numerical complexity. The preliminary TLB system design demonstrated satisfactory motion response for the operation of a FOWT and survival in a 100-year storm condition. The results show that accounting for second-order effect is vital in terms of having a clear understanding of the full behaviour of the system and the detailed response characteristics in operational and survival conditions. Extreme loads are significantly reduced when accounting for the second-order effects. This can be a key aspect to not overdesign the system and consequently achieve significant cost savings.
{"title":"Coupled Numerical Analysis of a Concept TLB Type Floating Offshore Wind Turbine","authors":"Iman Ramzanpoor, M. Nuernberg, L. Tao","doi":"10.1115/OMAE2019-95244","DOIUrl":"https://doi.org/10.1115/OMAE2019-95244","url":null,"abstract":"\u0000 The main drivers for the continued decarbonisation of the global energy market are renewable energy sources. Moreover, the leading technological solutions to achieve this are offshore wind turbines. As installed capacity has been increasing rapidly and shallow water near shore sites are exhausted, projects will need to be developed further from shore and often in deeper waters, which will pose greater technical challenges and constrain efforts to reduce costs.\u0000 Current floating platform solutions such as the spar and semi-submersible rely on large amounts of ballast and complex structural designs with active stabilisation systems for stability of the floating offshore wind turbine platform (FOWT).\u0000 The primary focus of this study is to present a design concept and mooring arrangement for an alternative floating platform solution that places emphasis on the mooring system to achieve stability for a FOWT. The tension leg buoy (TLB) is designed to support future 10MW offshore wind turbine generators.\u0000 This paper presents the numerical methodology used for a coupled hydro-elastic analysis of the floater and mooring system under combined wind, wave and current effects.\u0000 A concept TLB design is presented and its platform motion and mooring line tension characteristics are analysed for a three-hour time domain simulation representing operating and survival conditions in the northern North Sea with water depths of 110 metres. The importance of wave drift forces and the other non-linear excitation forces in the concept design stage are evaluated by comparing the motion and tension responses of three different numerical simulation cases with increasing numerical complexity.\u0000 The preliminary TLB system design demonstrated satisfactory motion response for the operation of a FOWT and survival in a 100-year storm condition. The results show that accounting for second-order effect is vital in terms of having a clear understanding of the full behaviour of the system and the detailed response characteristics in operational and survival conditions. Extreme loads are significantly reduced when accounting for the second-order effects. This can be a key aspect to not overdesign the system and consequently achieve significant cost savings.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"50 199 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125949961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent times, drag-based vertical-axis wind turbine rotors have gained increasing interests in offshore applications because of their performance potential and reliability. Their advantages like simplicity, easier manufacture and lower maintenance cost have attracted the researcher’s attention toward improving their design further. However, this type of rotor is still suffering from lower efficiency than the lift-based Darrius and the horizontal-axis wind turbine rotors. A recently developed elliptical-bladed Savonius rotor has shown its potential to harvest wind energy more efficiently. However, the geometric parameters of this rotor such as aspect ratio, overlap ratio, number of blades, shaft and end plates, the aerodynamic parameters such as Reynolds number, lift and drag coefficients are needed to be optimized for further improvement of its performance. In the present investigation, the wind tunnel tests have been conducted to analyze the effect of shaft and end-plates of a newly developed elliptical-bladed vertical-axis Savonius wind turbine rotor. Experiments have been conducted over a range of tip speed ratios to find the torque and power coefficients of a two-bladed rotor system for two individual cases viz., the rotor with a shaft and the rotor with end-plates. In order to have a direct comparison, the experimental data are also obtained for the same rotor without the shaft and without the end-plates. The wind tunnel tests have demonstrated an improvement of power coefficient by 26.31% for the rotor with the end plates.
{"title":"Analyzing the Effect of Shaft and End-Plates of a Newly Developed Elliptical-Bladed Savonius Rotor From Wind Tunnel Tests","authors":"N. Alom, Nitish Kumar, U. Saha","doi":"10.1115/omae2019-95570","DOIUrl":"https://doi.org/10.1115/omae2019-95570","url":null,"abstract":"\u0000 In recent times, drag-based vertical-axis wind turbine rotors have gained increasing interests in offshore applications because of their performance potential and reliability. Their advantages like simplicity, easier manufacture and lower maintenance cost have attracted the researcher’s attention toward improving their design further. However, this type of rotor is still suffering from lower efficiency than the lift-based Darrius and the horizontal-axis wind turbine rotors. A recently developed elliptical-bladed Savonius rotor has shown its potential to harvest wind energy more efficiently. However, the geometric parameters of this rotor such as aspect ratio, overlap ratio, number of blades, shaft and end plates, the aerodynamic parameters such as Reynolds number, lift and drag coefficients are needed to be optimized for further improvement of its performance. In the present investigation, the wind tunnel tests have been conducted to analyze the effect of shaft and end-plates of a newly developed elliptical-bladed vertical-axis Savonius wind turbine rotor. Experiments have been conducted over a range of tip speed ratios to find the torque and power coefficients of a two-bladed rotor system for two individual cases viz., the rotor with a shaft and the rotor with end-plates. In order to have a direct comparison, the experimental data are also obtained for the same rotor without the shaft and without the end-plates. The wind tunnel tests have demonstrated an improvement of power coefficient by 26.31% for the rotor with the end plates.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129322734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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