Water current interaction with arrays of plates is studied by use of the computational fluid dynamics focusing on hydrokinetic energy production applications. Various configurations of arrays of equidistant rectangular plates are considered and the current-induced pressure and velocity distribution, and the hydrodynamic forces on the individual plates are computed and compared with empirical relations. It is found that the current-induced force on the leading plate in the array is substantially different from those on the downstream plates, which experience negative forces, due to the change of the flow field. In three parametric studies, the effect of plate spacing, the number of plates and the relative water depth on the current-induced forces is investigated. It is shown that the relative size of the plates, and the number of plates in an array play significant role on the current-induced loads. Finally, the relative direction of the plates and the incoming flow is changed and its effect on the hydrodynamic forces on the plates is studied in a three-dimensional computational tank. The current loads on an oriented set of plates is shown to be remarkably different, when compared with those perpendicular to the current direction. It is concluded that the current-induced loads on an array of plates cannot be estimated by empirical relations, and specific computations, similar to those shown here, or laboratory experiments are required to investigate the current loads.
{"title":"Water current load on arrays of rectangular plates","authors":"A. Lamei, M. Hayatdavoodi","doi":"10.1115/1.4062473","DOIUrl":"https://doi.org/10.1115/1.4062473","url":null,"abstract":"\u0000 Water current interaction with arrays of plates is studied by use of the computational fluid dynamics focusing on hydrokinetic energy production applications. Various configurations of arrays of equidistant rectangular plates are considered and the current-induced pressure and velocity distribution, and the hydrodynamic forces on the individual plates are computed and compared with empirical relations. It is found that the current-induced force on the leading plate in the array is substantially different from those on the downstream plates, which experience negative forces, due to the change of the flow field. In three parametric studies, the effect of plate spacing, the number of plates and the relative water depth on the current-induced forces is investigated. It is shown that the relative size of the plates, and the number of plates in an array play significant role on the current-induced loads. Finally, the relative direction of the plates and the incoming flow is changed and its effect on the hydrodynamic forces on the plates is studied in a three-dimensional computational tank. The current loads on an oriented set of plates is shown to be remarkably different, when compared with those perpendicular to the current direction. It is concluded that the current-induced loads on an array of plates cannot be estimated by empirical relations, and specific computations, similar to those shown here, or laboratory experiments are required to investigate the current loads.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46480798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A numerical study on the modeling and local characteristics of a predetermined freak wave has been conducted with the computational fluid dynamics (CFD) method. Following the available experimental investigations, a numerical wave tank (NWT) was accordingly set up based on OpenFOAM source packets. The experimental flap-type wave-maker motion was employed directly to reproduce a specific freak wave. The effects of the mesh scheme on freak wave modeling were investigated in depth. Reasonable agreements were achieved between the numerical and experimental results. The wavelet transform method was applied to demonstrate the energy structures of freak wave trains. Special attention was paid to the particle velocities as well as the dynamic pressure. The results showed that insufficient mesh resolutions could probably result in energy dissipations and phase errors of high-frequency wave components during wave propagations, which in turn lead to shifts in the focal positions of freak waves. The particle velocities near the wave crest are extremely large, indicating possible severe wave breaking and impact loads. The theoretical values of similar-shape regular waves could considerably underestimate the particle velocities of freak waves.
{"title":"Numerical Study on Modelling and Local Characteristics of a Predetermined Freak Wave","authors":"Yanfei Deng, Cuizhi Zhu, Zixuan Wang","doi":"10.1115/1.4062474","DOIUrl":"https://doi.org/10.1115/1.4062474","url":null,"abstract":"\u0000 A numerical study on the modeling and local characteristics of a predetermined freak wave has been conducted with the computational fluid dynamics (CFD) method. Following the available experimental investigations, a numerical wave tank (NWT) was accordingly set up based on OpenFOAM source packets. The experimental flap-type wave-maker motion was employed directly to reproduce a specific freak wave. The effects of the mesh scheme on freak wave modeling were investigated in depth. Reasonable agreements were achieved between the numerical and experimental results. The wavelet transform method was applied to demonstrate the energy structures of freak wave trains. Special attention was paid to the particle velocities as well as the dynamic pressure. The results showed that insufficient mesh resolutions could probably result in energy dissipations and phase errors of high-frequency wave components during wave propagations, which in turn lead to shifts in the focal positions of freak waves. The particle velocities near the wave crest are extremely large, indicating possible severe wave breaking and impact loads. The theoretical values of similar-shape regular waves could considerably underestimate the particle velocities of freak waves.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45224929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The stability analysis of breakwaters is very important to have a safe and economic design of these coastal protective structures and the damage level is one of the most important parameter in this context. In the recent past, machine learning techniques showed immense potential in transforming many industries and processes, for making them more efficient and accurate. In this study, five advanced machine learning algorithms; support vector regression, random forest, adaboost, gradient boosting and deep artificial neural network were employed and analysed on estimation of the damage level of rubble-mound breakwaters. A large experimental dataset, considering almost every stability variables with their whole ranges, was used in this purpose. Also, a detailed feature analysis is presented to have an insight into the relations between these variables. It was found that the present study had overcome all of the limitations of existing studies related to this field and delivered the highest level of accuracy.
{"title":"An Application of Machine Learning Algorithms on the Prediction of the Damage Level of Rubble-Mound Breakwaters","authors":"Susmita Saha, S. De, Satyasaran Changdar","doi":"10.1115/1.4062475","DOIUrl":"https://doi.org/10.1115/1.4062475","url":null,"abstract":"\u0000 The stability analysis of breakwaters is very important to have a safe and economic design of these coastal protective structures and the damage level is one of the most important parameter in this context. In the recent past, machine learning techniques showed immense potential in transforming many industries and processes, for making them more efficient and accurate. In this study, five advanced machine learning algorithms; support vector regression, random forest, adaboost, gradient boosting and deep artificial neural network were employed and analysed on estimation of the damage level of rubble-mound breakwaters. A large experimental dataset, considering almost every stability variables with their whole ranges, was used in this purpose. Also, a detailed feature analysis is presented to have an insight into the relations between these variables. It was found that the present study had overcome all of the limitations of existing studies related to this field and delivered the highest level of accuracy.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47004562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The oscillating water column (OWC) responses within forward, central, and aft located moonpools for a fixed rectangular vessel are studied numerically under regular head wave conditions using RANS-based CFD calculations. The free surface elevation of the confined water inside the moonpool for the piston mode frequencies is studied independently for the forward, central, and aft moonpools, showing a strong dependence on location, draft, and incident wave frequency. The relative response is largely magnified for wave frequencies around the resonant range. It is observed that the free surface response amplitude is significantly higher in the forward moonpool location, and the results are in well comparison with experiments performed in the towing tank. The variation of dynamic pressure and its influence on the moonpool responses is investigated. The dynamic pressure and its influence on the moonpool responses is investigated to understand the position-specific fluctuations, which showed the presence of harmonics. The phase difference between the water column oscillations within the moonpool and the propagating wave in the domain depends on the its position. Finally, the effect of the moonpool in modifying the pressure field is studied by comparison with a vessel without moonpool for a common incident wave frequency.
{"title":"Numerical investigations of water column responses at different moonpool locations within a fixed vessel","authors":"Suraj Garad, A. Bhattacharyya, R. Datta","doi":"10.1115/1.4062445","DOIUrl":"https://doi.org/10.1115/1.4062445","url":null,"abstract":"\u0000 The oscillating water column (OWC) responses within forward, central, and aft located moonpools for a fixed rectangular vessel are studied numerically under regular head wave conditions using RANS-based CFD calculations. The free surface elevation of the confined water inside the moonpool for the piston mode frequencies is studied independently for the forward, central, and aft moonpools, showing a strong dependence on location, draft, and incident wave frequency. The relative response is largely magnified for wave frequencies around the resonant range. It is observed that the free surface response amplitude is significantly higher in the forward moonpool location, and the results are in well comparison with experiments performed in the towing tank. The variation of dynamic pressure and its influence on the moonpool responses is investigated. The dynamic pressure and its influence on the moonpool responses is investigated to understand the position-specific fluctuations, which showed the presence of harmonics. The phase difference between the water column oscillations within the moonpool and the propagating wave in the domain depends on the its position. Finally, the effect of the moonpool in modifying the pressure field is studied by comparison with a vessel without moonpool for a common incident wave frequency.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47745051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A systematic study of hydrodynamic coefficients for simplified subsea modules has been performed to support the estimation of the coefficients needed for planning of subsea installation operations. The coefficients are assessed for a nearly two-dimensional test setup. The tests are performed as forced oscillations at various amplitudes and periods, representing the forces on the module lowered through the water column. The importance of each of the main components of the subsea modules – mudmat, protection roof and process equipment of different shapes inside the modules are studied at fully submerged condition. Results for the module elements, generic contents and different combinations of these elements are presented. For the tested modules, damping is generally the dominating hydrodynamic force. However, the presence of the content inside the modules will generally increase the importance of added mass. Estimation of the hydrodynamic coefficients by summation of the coefficients for the individual structure elements generally overestimates the damping, compared to the coefficients measured for the complete modules. For added mass, estimation based on summation gives generally good results.
{"title":"Hydrodynamic coefficients of generic subsea modules in forced oscillation tests – importance of structural elements","authors":"M. Prsic, F. Solaas, T. Kristiansen","doi":"10.1115/1.4062293","DOIUrl":"https://doi.org/10.1115/1.4062293","url":null,"abstract":"\u0000 A systematic study of hydrodynamic coefficients for simplified subsea modules has been performed to support the estimation of the coefficients needed for planning of subsea installation operations. The coefficients are assessed for a nearly two-dimensional test setup. The tests are performed as forced oscillations at various amplitudes and periods, representing the forces on the module lowered through the water column. The importance of each of the main components of the subsea modules – mudmat, protection roof and process equipment of different shapes inside the modules are studied at fully submerged condition. Results for the module elements, generic contents and different combinations of these elements are presented. For the tested modules, damping is generally the dominating hydrodynamic force. However, the presence of the content inside the modules will generally increase the importance of added mass. Estimation of the hydrodynamic coefficients by summation of the coefficients for the individual structure elements generally overestimates the damping, compared to the coefficients measured for the complete modules. For added mass, estimation based on summation gives generally good results.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49615614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Salman Husain, Jacob Davis, Nathan Tom, Krish Thiagarajan Sharman, Cole Burge, Nhu Nguyen
Abstract Oceans are harsh environments and can impose significant loads on deployed structures. A wave energy converter (WEC) should be designed to maximize the energy absorbed while ensuring the operating wave condition does not exceed the failure limits of the device itself. Therefore, the loads endured by the support structure are a design constraint for the system. Furthermore, the WEC should be adaptable to different sea states. This work uses a WEC-Sim model of a variable-geometry oscillating wave energy converter (VGOSWEC) mounted on a support structure simulated under different wave scenarios. A VGOSWEC resembles a paddle pitching about a fixed hinge perpendicular to the incoming wave fronts. The geometry of the VGOSWEC is varied by opening a series of controllable flaps on the pitching paddle when the structure experiences threshold loads. It is hypothesized that opening the flaps should result in load shedding at the base of the support structure by reducing the moments about the hinge axis. This work compares the hydrodynamic coefficients, natural periods, and response amplitude operators from completely closed to completely open configurations of the controllable flaps. This work shows that the completely open configuration can reduce the pitch and surge loads on the base of the support structure by as much as 80%. Increased loads at the structure’s natural period can be mitigated by an axial power take-off damping acting as an additional design parameter to control the loads at the WEC’s support structure.
{"title":"Influence on Structural Loading of a Wave Energy Converter by Controlling Variable-Geometry Components and the Power Take-Off","authors":"Salman Husain, Jacob Davis, Nathan Tom, Krish Thiagarajan Sharman, Cole Burge, Nhu Nguyen","doi":"10.1115/1.4062115","DOIUrl":"https://doi.org/10.1115/1.4062115","url":null,"abstract":"Abstract Oceans are harsh environments and can impose significant loads on deployed structures. A wave energy converter (WEC) should be designed to maximize the energy absorbed while ensuring the operating wave condition does not exceed the failure limits of the device itself. Therefore, the loads endured by the support structure are a design constraint for the system. Furthermore, the WEC should be adaptable to different sea states. This work uses a WEC-Sim model of a variable-geometry oscillating wave energy converter (VGOSWEC) mounted on a support structure simulated under different wave scenarios. A VGOSWEC resembles a paddle pitching about a fixed hinge perpendicular to the incoming wave fronts. The geometry of the VGOSWEC is varied by opening a series of controllable flaps on the pitching paddle when the structure experiences threshold loads. It is hypothesized that opening the flaps should result in load shedding at the base of the support structure by reducing the moments about the hinge axis. This work compares the hydrodynamic coefficients, natural periods, and response amplitude operators from completely closed to completely open configurations of the controllable flaps. This work shows that the completely open configuration can reduce the pitch and surge loads on the base of the support structure by as much as 80%. Increased loads at the structure’s natural period can be mitigated by an axial power take-off damping acting as an additional design parameter to control the loads at the WEC’s support structure.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135956288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Guest Editorial: Special Section on Sustainable and Innovative Use of Emerging Ocean Structural Systems","authors":"Zhiyu Jiang, L. Manuel","doi":"10.1115/1.4062260","DOIUrl":"https://doi.org/10.1115/1.4062260","url":null,"abstract":"","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42160393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sea spray icing on ships and marine structures depends on a complex correlation between metocean parameters and vessel characteristics. Sea spray icing rates have mostly been investigated and given as a function of general metocean parameters. The existing models suffer from lack of experimental data. More experimental data is required for better prediction models and understanding of the icing process. This paper presents results from a comprehensive cold laboratory study of the dependence and trends of sea spray icing rates related to 8 parameters. Experiments were performed simulating sea spray from a nozzle towards a vertical surface in freezing environment. This study presents 20 unique tests structured into 8 experiments, each of which focuses on change in icing rates due to one independent variable. Results showed that the sea spray rates dependence of the investigated parameters comply with existing knowledge, however preliminary analysis points out various unintentional covariates for most experiments which calls for further investigations. This is the greatest number of variables tested in one set of experiments to date and serve as valuable sea spray icing data experimental data – a limitation for the evaluation of previous models that pointed out to the lack of enough icing measurements in this field of research.
{"title":"Experiments with sea spray icing: Investigation of icing rates","authors":"S. Deshpande, Ane Sæterdal, P. Sundsbø","doi":"10.1115/1.4062255","DOIUrl":"https://doi.org/10.1115/1.4062255","url":null,"abstract":"\u0000 Sea spray icing on ships and marine structures depends on a complex correlation between metocean parameters and vessel characteristics. Sea spray icing rates have mostly been investigated and given as a function of general metocean parameters. The existing models suffer from lack of experimental data. More experimental data is required for better prediction models and understanding of the icing process. This paper presents results from a comprehensive cold laboratory study of the dependence and trends of sea spray icing rates related to 8 parameters. Experiments were performed simulating sea spray from a nozzle towards a vertical surface in freezing environment. This study presents 20 unique tests structured into 8 experiments, each of which focuses on change in icing rates due to one independent variable. Results showed that the sea spray rates dependence of the investigated parameters comply with existing knowledge, however preliminary analysis points out various unintentional covariates for most experiments which calls for further investigations. This is the greatest number of variables tested in one set of experiments to date and serve as valuable sea spray icing data experimental data – a limitation for the evaluation of previous models that pointed out to the lack of enough icing measurements in this field of research.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44495958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study evaluated a multi-catenary spread mooring system design of a mobile ocean test berth for wave energy converters (WECs), the Ocean Sentinel (OS) instrumentation buoy, through dynamic simulation, numerical analysis and comparison with measured field motion data of the OS off the Oregon coast. First, the accuracy of the numerical employed model based on a full coupling method of the OS and its mooring lines was validated by comparing predicted mooring tensions to the field measurements. Then, the anchor movability, fatigue damage and extreme mooring tension of the OS mooring system were analyzed to assess survivability. Field test results show that the numerical model provided accurate predictions of mooring tensions even under environmental conditions of strong wind, current and waves. Factors affecting the accuracy are discussed. One mooring anchor was shown to have moved significantly during the ocean field test. Mooring fatigue damage was calculated for different levels of sea states. Design strengths of the mooring lines were calculated and analyzed.
{"title":"Dynamic Mooring Field Experiment and Design of a WEC Platform Test System","authors":"Junhui Lou, S. Yim, A. von Jouanne","doi":"10.1115/1.4062254","DOIUrl":"https://doi.org/10.1115/1.4062254","url":null,"abstract":"\u0000 This study evaluated a multi-catenary spread mooring system design of a mobile ocean test berth for wave energy converters (WECs), the Ocean Sentinel (OS) instrumentation buoy, through dynamic simulation, numerical analysis and comparison with measured field motion data of the OS off the Oregon coast. First, the accuracy of the numerical employed model based on a full coupling method of the OS and its mooring lines was validated by comparing predicted mooring tensions to the field measurements. Then, the anchor movability, fatigue damage and extreme mooring tension of the OS mooring system were analyzed to assess survivability. Field test results show that the numerical model provided accurate predictions of mooring tensions even under environmental conditions of strong wind, current and waves. Factors affecting the accuracy are discussed. One mooring anchor was shown to have moved significantly during the ocean field test. Mooring fatigue damage was calculated for different levels of sea states. Design strengths of the mooring lines were calculated and analyzed.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46425722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work focuses on examining the dynamic behaviour of large floating offshore wind turbine (FOWT) exposed to extreme loading and accidental loading. The FOWT studied in this work is the 15 MW reference turbine recently released by the International Energy Agency. The 15 MW turbine is supported on the UMaine Volturn US-S semi-submersible platform which is stationed using catenary mooring lines. As the mooring configuration greatly affects the response of FOWT, two different mooring configurations namely non-redundant (3-line) and redundant (6-line) systems are studied and compared. The coupled multi-body dynamic system is solved using an open-source code, OpenFAST. When simulating the mooring line failure, both the operating and extreme loading conditions are considered. Failure of one mooring is considered at a time. The response of the coupled system due to breakage of the mooring indicate high displacements in surge and sway directions in comparison to the intact system especially for the nonredundant mooring system. Furthermore, failure in mooring leads to change in the platform yaw angle, which in turn results in rotor misalignment with respect to the incoming wind. Also increased tension in the other intact mooring lines is observed. The findings from this study will be helpful in accidental limit state design and preventing failure of similar large wind turbines mounted on semi-submersible platforms. In addition, insights on using non-redundant and redundant mooring configuration for such large structures with respect to extreme and accidental loading is also discussed.
{"title":"Dynamic response of 15 MW floating wind turbine with non-redundant and redundant mooring systems under extreme and accidental conditions","authors":"R. Niranjan, S. Ramisetti","doi":"10.1115/1.4062169","DOIUrl":"https://doi.org/10.1115/1.4062169","url":null,"abstract":"\u0000 This work focuses on examining the dynamic behaviour of large floating offshore wind turbine (FOWT) exposed to extreme loading and accidental loading. The FOWT studied in this work is the 15 MW reference turbine recently released by the International Energy Agency. The 15 MW turbine is supported on the UMaine Volturn US-S semi-submersible platform which is stationed using catenary mooring lines. As the mooring configuration greatly affects the response of FOWT, two different mooring configurations namely non-redundant (3-line) and redundant (6-line) systems are studied and compared. The coupled multi-body dynamic system is solved using an open-source code, OpenFAST. When simulating the mooring line failure, both the operating and extreme loading conditions are considered. Failure of one mooring is considered at a time. The response of the coupled system due to breakage of the mooring indicate high displacements in surge and sway directions in comparison to the intact system especially for the nonredundant mooring system. Furthermore, failure in mooring leads to change in the platform yaw angle, which in turn results in rotor misalignment with respect to the incoming wind. Also increased tension in the other intact mooring lines is observed. The findings from this study will be helpful in accidental limit state design and preventing failure of similar large wind turbines mounted on semi-submersible platforms. In addition, insights on using non-redundant and redundant mooring configuration for such large structures with respect to extreme and accidental loading is also discussed.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44950006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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