There is an ever-increasing interest to analyze problems related to the dynamics of fluids and their interactions with fixed or floating offshore structures. Continued technological advances in computer power have enabled the development of novel numerical methods and its application to analysis and engineering design; this has improved our understanding of many complex problems that were unsolved before. The increasing demands for harnessing marine renewable energy, and the challenges from more extreme weather due to climate change add difficulties and opportunities to this field. This Special Issue aims to highlight recent efforts in the development of advanced numerical methods as well as their applications to marine hydrodynamics for a wide range of applications.
{"title":"Guest Editorial: Special Section on Advanced Numerical Methods and Applications in Marine Hydrodynamics","authors":"J. Zang, Qing Xiao, L. Manuel","doi":"10.1115/1.4056343","DOIUrl":"https://doi.org/10.1115/1.4056343","url":null,"abstract":"\u0000 There is an ever-increasing interest to analyze problems related to the dynamics of fluids and their interactions with fixed or floating offshore structures. Continued technological advances in computer power have enabled the development of novel numerical methods and its application to analysis and engineering design; this has improved our understanding of many complex problems that were unsolved before. The increasing demands for harnessing marine renewable energy, and the challenges from more extreme weather due to climate change add difficulties and opportunities to this field. This Special Issue aims to highlight recent efforts in the development of advanced numerical methods as well as their applications to marine hydrodynamics for a wide range of applications.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41844053","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 ship waves and related hydrodynamics over a sloping bed are investigated numerically in this paper, and we aim to clarify the characteristics of ship wave deformation and its hydrodynamic effects. Laboratory experiments are performed with a self-propelled ship model to produce various wave conditions over a sloping bed in the water flume, providing the datasets for validation works of numerical simulations. With the implementation of model sensitivity analysis, numerical calculations of ship-induced waves and flow velocities are completed using the non-hydrostatic model in XBeach, and compared against experimental measurements. The results show that the model is not only able to calculate primary and secondary waves well, but also the ship-induced near-bed velocity, when ship waves are prominent in the water flume. Further numerical investigations of ship wave transformation and associated hydrodynamic effects are conducted over a sloping bed under different ship speed conditions. The ship wave height and run-up variations along the cross-shore transect clearly indicate the wave energy dissipation due to breaking and bottom friction. The ship-induced flow velocities are found to be mainly contributed by the low-frequency primary waves in our numerical experiments.
{"title":"Numerical Investigation of Ship Waves and associated Hydrodynamics over a Sloping Bed with a Non-hydrostatic Model","authors":"Lilei Mao, Xin Li, Yi-mei Chen","doi":"10.1115/1.4056314","DOIUrl":"https://doi.org/10.1115/1.4056314","url":null,"abstract":"\u0000 The ship waves and related hydrodynamics over a sloping bed are investigated numerically in this paper, and we aim to clarify the characteristics of ship wave deformation and its hydrodynamic effects. Laboratory experiments are performed with a self-propelled ship model to produce various wave conditions over a sloping bed in the water flume, providing the datasets for validation works of numerical simulations. With the implementation of model sensitivity analysis, numerical calculations of ship-induced waves and flow velocities are completed using the non-hydrostatic model in XBeach, and compared against experimental measurements. The results show that the model is not only able to calculate primary and secondary waves well, but also the ship-induced near-bed velocity, when ship waves are prominent in the water flume. Further numerical investigations of ship wave transformation and associated hydrodynamic effects are conducted over a sloping bed under different ship speed conditions. The ship wave height and run-up variations along the cross-shore transect clearly indicate the wave energy dissipation due to breaking and bottom friction. The ship-induced flow velocities are found to be mainly contributed by the low-frequency primary waves in our numerical experiments.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45317473","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}
T. Sakimoto, Hisakazu Tajika, T. Handa, S. Igi, J. Kondo
This study discusses the collapse criteria for thermally-treated line pipe and their bending interaction against collapse based on a full-scale test under external pressure with and without bending loading. The critical collapse strain in the pressure bending test was much higher than that estimated by the DNV-ST-F101 standard because it was calculated based on estimating collapse pressures without bending interaction based on SMYS of design pipe in the standard. However, the collapse pressures without bending interaction in fullscale test was significantly higher than that of the estimation according to DNV-ST-F101 standard. The effect of the thermal heat cycle simulated anti-corrosion coating heating on line pipe collapse criteria is also discussed based on the change of yield stress of pre-strained and thermally-treated material. As the maximum heat cycle temperature increases, the reduction of the compressive yield stress along circumferential direction by the Baushinger effect due to UOE process becomes small. It is thought that a DNV equation for estimating the critical bending strain to collapse will provide a more accurate estimation of the critical collapse pressure and strain for thermally-treated line pipe when the collapse pressure is calculated considering the change of strength parameters due to the tensile pre-strain level and heat cycle temperature.
{"title":"Collapse Limit of Thermally Treated Line Pipe under Combined External Pressure and Bending Deformation","authors":"T. Sakimoto, Hisakazu Tajika, T. Handa, S. Igi, J. Kondo","doi":"10.1115/1.4056186","DOIUrl":"https://doi.org/10.1115/1.4056186","url":null,"abstract":"\u0000 This study discusses the collapse criteria for thermally-treated line pipe and their bending interaction against collapse based on a full-scale test under external pressure with and without bending loading. The critical collapse strain in the pressure bending test was much higher than that estimated by the DNV-ST-F101 standard because it was calculated based on estimating collapse pressures without bending interaction based on SMYS of design pipe in the standard. However, the collapse pressures without bending interaction in fullscale test was significantly higher than that of the estimation according to DNV-ST-F101 standard. The effect of the thermal heat cycle simulated anti-corrosion coating heating on line pipe collapse criteria is also discussed based on the change of yield stress of pre-strained and thermally-treated material. As the maximum heat cycle temperature increases, the reduction of the compressive yield stress along circumferential direction by the Baushinger effect due to UOE process becomes small. It is thought that a DNV equation for estimating the critical bending strain to collapse will provide a more accurate estimation of the critical collapse pressure and strain for thermally-treated line pipe when the collapse pressure is calculated considering the change of strength parameters due to the tensile pre-strain level and heat cycle temperature.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44175371","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}
Wing-in Ground Effect (WIG) vehicles and planing hulls are exposed to unsteady, high magnitude hydrodynamic forces as their bow enters water. The resulting forces can lead to structural damages and uncomfortable conditions for passengers onboard. This article aims to provide deeper understanding on the influence of structural flexibility throughout the water entry process of a hard chine section. A Finite Volume Method (FVM) based flexible fluid-structure interaction (FFSI) model is used to solve multi-physics. Quantitative comparisons are made between experimental and computational data. Simulations demonstrate that structural responses can attenuate the pressure acting on the body of hard-chine sections impinging water with deadrise angles of 10°, 20° and 30°.However, they cannot affect that of a section with deadrise angle of 45° since its pressure distribution pattern is different. It is shown that the impact speed has an important role in hydroelastic response while the sectional Young’s modulus affects impact pressures and resulting equivalent stresses. The former increases under the increase of Young’s modulus. The latter may increase when the impact speed is low and decreases when the impact speed is high. It is concluded that the results presented may be useful for preliminary design.
{"title":"Hydroelastic analysis of hard-chine sections entering water – observations for use in preliminary design stage","authors":"S. Tavakoli, A. Babanin, S. Hirdaris","doi":"10.1115/1.4056162","DOIUrl":"https://doi.org/10.1115/1.4056162","url":null,"abstract":"\u0000 Wing-in Ground Effect (WIG) vehicles and planing hulls are exposed to unsteady, high magnitude hydrodynamic forces as their bow enters water. The resulting forces can lead to structural damages and uncomfortable conditions for passengers onboard. This article aims to provide deeper understanding on the influence of structural flexibility throughout the water entry process of a hard chine section. A Finite Volume Method (FVM) based flexible fluid-structure interaction (FFSI) model is used to solve multi-physics. Quantitative comparisons are made between experimental and computational data. Simulations demonstrate that structural responses can attenuate the pressure acting on the body of hard-chine sections impinging water with deadrise angles of 10°, 20° and 30°.However, they cannot affect that of a section with deadrise angle of 45° since its pressure distribution pattern is different. It is shown that the impact speed has an important role in hydroelastic response while the sectional Young’s modulus affects impact pressures and resulting equivalent stresses. The former increases under the increase of Young’s modulus. The latter may increase when the impact speed is low and decreases when the impact speed is high. It is concluded that the results presented may be useful for preliminary design.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47754738","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}
In order to comprehensively utilize ocean resources and renewable energy, a novel modular floating structure (MFS) system with multi-direction expansibility has been proposed, which includes inner hexagonal tension leg platform (TLP) modules and outermost floating artificial reef modules coupled with the function of the wave energy converter (WEC). Considering both the hydrodynamic interaction effect and the mechanical coupling effect, main dynamic responses of the MFS system has been analyzed under different incident wave directions, and the corresponding physical mechanism has been clarified. Results indicate that connector loads slightly increase, but motion responses of the MFS system are more stable when the outermost floating artificial reefs serve as the up-wave modules. Outermost floating artificial reef modules have shown good wave-attenuation capacity for inner TLP modules, as well as producing considerable output wave power. The effect of key power take-off (PTO) parameters on the WECs’ performance has been investigated, and the optimal PTO damping coefficient has been suggested. In addition, extreme responses of the proposed MFS system have been further studied, and its safety has been well verified under typical extreme sea conditions. Main results in this work can serve as a helpful reference for the construction of future offshore floating cities.
{"title":"Hydrodynamic responses of a novel modular floating structure system with multi-direction expansion","authors":"Yanwei Li, Xiang Li, Nianixn Ren, J. Ou","doi":"10.1115/1.4056163","DOIUrl":"https://doi.org/10.1115/1.4056163","url":null,"abstract":"\u0000 In order to comprehensively utilize ocean resources and renewable energy, a novel modular floating structure (MFS) system with multi-direction expansibility has been proposed, which includes inner hexagonal tension leg platform (TLP) modules and outermost floating artificial reef modules coupled with the function of the wave energy converter (WEC). Considering both the hydrodynamic interaction effect and the mechanical coupling effect, main dynamic responses of the MFS system has been analyzed under different incident wave directions, and the corresponding physical mechanism has been clarified. Results indicate that connector loads slightly increase, but motion responses of the MFS system are more stable when the outermost floating artificial reefs serve as the up-wave modules. Outermost floating artificial reef modules have shown good wave-attenuation capacity for inner TLP modules, as well as producing considerable output wave power. The effect of key power take-off (PTO) parameters on the WECs’ performance has been investigated, and the optimal PTO damping coefficient has been suggested. In addition, extreme responses of the proposed MFS system have been further studied, and its safety has been well verified under typical extreme sea conditions. Main results in this work can serve as a helpful reference for the construction of future offshore floating cities.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46690799","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}
L. Dempwolff, C. Windt, N. Goseberg, T. Martin, H. Bihs, G. Melling
In recent years, increasing ship-sizes and associated increasing wave loads have led to a demand for prediction tools quantifying the ship-induced loads on waterways. Depth-averaged numerical models, using a free surface pressure term, are a prominent method to obtain the relevant design parameters. These models incorporate the wave deformation processes due to attributes of complex bathymetries, while allowing for an efficient simulation of large computational domains. The non-hydrostatic shallow water equations model REEF3D::SFLOW uses a quadratic pressure approximation and high-order discretisation schemes. This paper presents the implementation of a pressure term to account for the displacement of the free surface by solid moving objects. Two test cases verifying the implementation are shown based upon the analytical one-dimensional solution of the wave propagation due to surface pressure and the estimation of Havelock angles. These verification tests are the first step towards a holistic model, combining a large scale model with CFD simulations near waterway banks.
{"title":"Verification of a free-surface pressure term extension to represent ships in a non-hydrostatic shallow-water-equations solver","authors":"L. Dempwolff, C. Windt, N. Goseberg, T. Martin, H. Bihs, G. Melling","doi":"10.1115/1.4056121","DOIUrl":"https://doi.org/10.1115/1.4056121","url":null,"abstract":"\u0000 In recent years, increasing ship-sizes and associated increasing wave loads have led to a demand for prediction tools quantifying the ship-induced loads on waterways. Depth-averaged numerical models, using a free surface pressure term, are a prominent method to obtain the relevant design parameters. These models incorporate the wave deformation processes due to attributes of complex bathymetries, while allowing for an efficient simulation of large computational domains. The non-hydrostatic shallow water equations model REEF3D::SFLOW uses a quadratic pressure approximation and high-order discretisation schemes. This paper presents the implementation of a pressure term to account for the displacement of the free surface by solid moving objects. Two test cases verifying the implementation are shown based upon the analytical one-dimensional solution of the wave propagation due to surface pressure and the estimation of Havelock angles. These verification tests are the first step towards a holistic model, combining a large scale model with CFD simulations near waterway banks.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43523880","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}
Typhoon is a disastrous weather system, which usually induces strong waves, currents, and surges along the coastal area, and causes severe hydrodynamic loads on the elevated pile cap foundation, which is widely used to support the sea-crossing bridge. Estimating the hydrodynamic loads under typhoons is essential to ensure the bridge's safety. This paper develops an environmental contour-based framework that can estimate the extreme hydrodynamic loads induced by typhoons while considering the correlation among environmental conditions. The elevated pile cap foundation of the Xihoumen Rail-cum-road Bridge was used to illustrate the framework. The SWAN+ADCIRC model was employed to simulate the environmental conditions under typhoons. The pair-copulas were adopted to construct joint probability distributions, and the environmental contours with a given return period were then established by the inverse first-order reliability method. Given the hydrodynamic model and short-term peak value of structural response, the AK-LHS method was then used to find the maximum hydrodynamic loads based on the environmental contours. The environmental contour constructing methods, and selection methods of short-term peak values were compared and discussed. The main findings include: 1) ignoring correlations of the environmental conditions overestimates the extreme hydrodynamic loads and results in a conservative design; 2) the estimation of extreme hydrodynamic loads is affected by the selection and fitting of short-term peak values significantly; and 3) the extreme hydrodynamic loads estimated by either Rosenblatt or Nataf transformation shows similar results.
{"title":"Integrated Approach for Estimating Extreme Hydrodynamic Loads on Elevated Pile Cap Foundation using Environmental Contour of Simulated Typhoon Wave, Current and Surge Conditions","authors":"Kai Wei, Daimeng Shang, Xi Zhong","doi":"10.1115/1.4056037","DOIUrl":"https://doi.org/10.1115/1.4056037","url":null,"abstract":"\u0000 Typhoon is a disastrous weather system, which usually induces strong waves, currents, and surges along the coastal area, and causes severe hydrodynamic loads on the elevated pile cap foundation, which is widely used to support the sea-crossing bridge. Estimating the hydrodynamic loads under typhoons is essential to ensure the bridge's safety. This paper develops an environmental contour-based framework that can estimate the extreme hydrodynamic loads induced by typhoons while considering the correlation among environmental conditions. The elevated pile cap foundation of the Xihoumen Rail-cum-road Bridge was used to illustrate the framework. The SWAN+ADCIRC model was employed to simulate the environmental conditions under typhoons. The pair-copulas were adopted to construct joint probability distributions, and the environmental contours with a given return period were then established by the inverse first-order reliability method. Given the hydrodynamic model and short-term peak value of structural response, the AK-LHS method was then used to find the maximum hydrodynamic loads based on the environmental contours. The environmental contour constructing methods, and selection methods of short-term peak values were compared and discussed. The main findings include: 1) ignoring correlations of the environmental conditions overestimates the extreme hydrodynamic loads and results in a conservative design; 2) the estimation of extreme hydrodynamic loads is affected by the selection and fitting of short-term peak values significantly; and 3) the extreme hydrodynamic loads estimated by either Rosenblatt or Nataf transformation shows similar results.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41980158","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 special issue focuses on the topic of Data-Driven Mechanics and Digital Twins for Ocean Engineering. Two categories of papers are included in this issue; they deal with: (i) reduced-order modeling and data analytics; and (ii) data-driven computing and digital twins. In the first category, Yin et al. present the modal analysis of hydrodynamic forces in flow-induced vibrations using dynamic mode decomposition (DMD). Using snapshots of the flow field, spatio-temporal evolution characteristics of the wake patterns are analyzed. The dominant DMD modes with their corresponding frequencies are identified and used to reconstruct the flow fields. In another paper in this category, Janocha et al. presented a 3D large-eddy simulation and data-driven analysis of the flow around a flexibly mounted cylinder via proper orthogonal decomposition (POD) analysis. The POD-based modal extractions are performed on slices in the wake to identify the coherent structure in the flow. Vortex shedding modes are analyzed and classified by examining three-dimensional wake flow structures. Such a body of work is useful for building reduced-order (surrogate) models that can be considered for multi-query analysis, design optimization, and feedback control. However, these POD/DMD studies are restricted to linear physics as well as to idealized canonical geometries. There is a need for further extension to large-scale marine and offshore structures (e.g., offshore wind turbines, marine risers and pipelines). Moreover, projection-based POD/DMD techniques generally face difficulties to scale for highly nonlinear turbulent flow. Nonlinear model reduction and deep neural networks (e.g., convolutional autoencoders) are possible alternatives to be explored for advanced reduced-order modeling.
{"title":"Guest Editorial: Data-Driven Mechanics and Digital Twins for Ocean Engineering","authors":"R. Jaiman, L. Manuel","doi":"10.1115/1.4056012","DOIUrl":"https://doi.org/10.1115/1.4056012","url":null,"abstract":"\u0000 This special issue focuses on the topic of Data-Driven Mechanics and Digital Twins for Ocean Engineering. Two categories of papers are included in this issue; they deal with: (i) reduced-order modeling and data analytics; and (ii) data-driven computing and digital twins. In the first category, Yin et al. present the modal analysis of hydrodynamic forces in flow-induced vibrations using dynamic mode decomposition (DMD). Using snapshots of the flow field, spatio-temporal evolution characteristics of the wake patterns are analyzed. The dominant DMD modes with their corresponding frequencies are identified and used to reconstruct the flow fields. In another paper in this category, Janocha et al. presented a 3D large-eddy simulation and data-driven analysis of the flow around a flexibly mounted cylinder via proper orthogonal decomposition (POD) analysis. The POD-based modal extractions are performed on slices in the wake to identify the coherent structure in the flow. Vortex shedding modes are analyzed and classified by examining three-dimensional wake flow structures. Such a body of work is useful for building reduced-order (surrogate) models that can be considered for multi-query analysis, design optimization, and feedback control. However, these POD/DMD studies are restricted to linear physics as well as to idealized canonical geometries. There is a need for further extension to large-scale marine and offshore structures (e.g., offshore wind turbines, marine risers and pipelines). Moreover, projection-based POD/DMD techniques generally face difficulties to scale for highly nonlinear turbulent flow. Nonlinear model reduction and deep neural networks (e.g., convolutional autoencoders) are possible alternatives to be explored for advanced reduced-order modeling.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41649273","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 dynamic performance prediction of Floating offshore wind turbines (FOWTs) is a challenging task, as the existing theories might not be fully reliable for FOWTs due to the high nonlinearities and coupling effects. The artificial intelligent method gives a promising solution for this issue, and Chen and Hu (2021) proposed a novel AI-based method, named SADA to overcome these challenges. This paper addresses a further and in-depth investigation on the key technologies of the Key Disciplinary Parameters (KDPs) in the SADA method, to obtain a novel and accurate analysis method for dynamic responses prediction of FOWTs. Firstly, the categorization of KDPs is introduced, which can be divided into three categories: Environmental KDPs, Disciplinary KDPs, and Specific KDPs. Secondly, two factors, the number of KDPs and boundary adjustment of KDPs are investigated through the reinforcement learning algorithm within the SADA method. Basin experimental data of a Spar-type FOWT is used for AI training. The results show that more proper KDPs set in the SADA method can lead to higher accuracy for the prediction of FOWTs. Besides, reasonable boundary conditions will also contribute to the convergence of the algorithms efficiently. Finally, the instruction on how to better choose KDPs and how to set and adjust their boundary conditions is given in the conclusion. The application of KDPs in the SADA method not only provides a deeper understanding of the dynamic response of the entire FOWTs system but also provides a promising solution to overcome the challenges of validation.
{"title":"A study on Key Disciplinary Parameters of AI-based Analysis Method for Dynamic Response Prediction of Floating Offshore Wind Turbines","authors":"Peng Chen, Zhiqiang Hu","doi":"10.1115/1.4055993","DOIUrl":"https://doi.org/10.1115/1.4055993","url":null,"abstract":"\u0000 The dynamic performance prediction of Floating offshore wind turbines (FOWTs) is a challenging task, as the existing theories might not be fully reliable for FOWTs due to the high nonlinearities and coupling effects. The artificial intelligent method gives a promising solution for this issue, and Chen and Hu (2021) proposed a novel AI-based method, named SADA to overcome these challenges. This paper addresses a further and in-depth investigation on the key technologies of the Key Disciplinary Parameters (KDPs) in the SADA method, to obtain a novel and accurate analysis method for dynamic responses prediction of FOWTs. Firstly, the categorization of KDPs is introduced, which can be divided into three categories: Environmental KDPs, Disciplinary KDPs, and Specific KDPs. Secondly, two factors, the number of KDPs and boundary adjustment of KDPs are investigated through the reinforcement learning algorithm within the SADA method. Basin experimental data of a Spar-type FOWT is used for AI training. The results show that more proper KDPs set in the SADA method can lead to higher accuracy for the prediction of FOWTs. Besides, reasonable boundary conditions will also contribute to the convergence of the algorithms efficiently. Finally, the instruction on how to better choose KDPs and how to set and adjust their boundary conditions is given in the conclusion. The application of KDPs in the SADA method not only provides a deeper understanding of the dynamic response of the entire FOWTs system but also provides a promising solution to overcome the challenges of validation.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42771538","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}
On the basis of linearised theory of water waves, the present study has demonstrated a semi-analytical method to assess the hydrodynamic performance of a pair of partially immersed barriers just above a thick bottom-standing barrier. By means of eigenfunction expansion method, a system of first kind Fredholm-type integral equation involving horizontal component of velocity as unknown functions is developed for interaction of water waves with both types of barriers. The multi-term Galerkin approximation is adopted to determine these unknown functions having square root singularities at the submerged edge of the thin barriers and one-third singularities at the corners of the thick barrier. In order to overcome such types of singularities, Chebychev polynomials for half-singularities and ultra-spherical Gegenbauer polynomials for one-third singularities with suitable weight functions have been taken into consideration. The numerical examples of both reflection and transmission coefficients are presented to examine the hydrodynamic performance of breakwater. Some fascinating results like resonant frequencies are obtained for practical engineering. At the same time, reflection coefficients for the present breakwater agree reasonable for the limiting cases with previous available result.
{"title":"Oblique wave diffraction by a bottom-standing thick barrier and a pair of partially immersed barriers","authors":"Biman Sarkar, S. De","doi":"10.1115/1.4055912","DOIUrl":"https://doi.org/10.1115/1.4055912","url":null,"abstract":"\u0000 On the basis of linearised theory of water waves, the present study has demonstrated a semi-analytical method to assess the hydrodynamic performance of a pair of partially immersed barriers just above a thick bottom-standing barrier. By means of eigenfunction expansion method, a system of first kind Fredholm-type integral equation involving horizontal component of velocity as unknown functions is developed for interaction of water waves with both types of barriers. The multi-term Galerkin approximation is adopted to determine these unknown functions having square root singularities at the submerged edge of the thin barriers and one-third singularities at the corners of the thick barrier. In order to overcome such types of singularities, Chebychev polynomials for half-singularities and ultra-spherical Gegenbauer polynomials for one-third singularities with suitable weight functions have been taken into consideration. The numerical examples of both reflection and transmission coefficients are presented to examine the hydrodynamic performance of breakwater. Some fascinating results like resonant frequencies are obtained for practical engineering. At the same time, reflection coefficients for the present breakwater agree reasonable for the limiting cases with previous available result.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41641878","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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