Pipelines tend to buckle laterally under thermal expansion. In existing analytical solutions by Kerr and Hobbs, it is assumed that the seabed resistance q0 to lateral pipe movements is constant in magnitude, and opposite in direction to the total displacement. Here it is opposite to the velocity instead, i.e. the seabed is taken to be frictional rather than nonlinear elastic with a V-shaped potential function. A 3-lobe (“Mode 3f”) analytical solution is provided for the frictional case, using the same approximate end-of-buckle condition v=v'=v''=0 used by Hobbs in his “Mode 3” solution for the nonlinear elastic case. For both Mode 3 and 3f solutions, the shape of the buckle does not change as it grows with increasing thermal expansion, though the scaling factors in the axial and lateral directions are different, i.e. the solutions are self-similar. A single finite element solution for the frictional case with an initial imperfection imposed by a bumper can be scaled to cover all such cases. It shows that the shape of the buckle depends on the amplitude of the initial triggering imperfection, and is close to the Mode 3f solution for very small initial imperfections. The difference between Mode 3 and 3f is significant in regard to buckle shape and the relative size of the buckle lobes, but small in regard to the maximum bending moment for a given amount of thermal expansion accommodated by the buckle.
{"title":"Lateral Buckling of an Elastic Pipe on a Frictional Seabed","authors":"R. Peek","doi":"10.1115/1.4056648","DOIUrl":"https://doi.org/10.1115/1.4056648","url":null,"abstract":"\u0000 Pipelines tend to buckle laterally under thermal expansion. In existing analytical solutions by Kerr and Hobbs, it is assumed that the seabed resistance q0 to lateral pipe movements is constant in magnitude, and opposite in direction to the total displacement. Here it is opposite to the velocity instead, i.e. the seabed is taken to be frictional rather than nonlinear elastic with a V-shaped potential function. A 3-lobe (“Mode 3f”) analytical solution is provided for the frictional case, using the same approximate end-of-buckle condition v=v'=v''=0 used by Hobbs in his “Mode 3” solution for the nonlinear elastic case. For both Mode 3 and 3f solutions, the shape of the buckle does not change as it grows with increasing thermal expansion, though the scaling factors in the axial and lateral directions are different, i.e. the solutions are self-similar. A single finite element solution for the frictional case with an initial imperfection imposed by a bumper can be scaled to cover all such cases. It shows that the shape of the buckle depends on the amplitude of the initial triggering imperfection, and is close to the Mode 3f solution for very small initial imperfections. The difference between Mode 3 and 3f is significant in regard to buckle shape and the relative size of the buckle lobes, but small in regard to the maximum bending moment for a given amount of thermal expansion accommodated by the buckle.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42334165","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 this work, an Oscillating Water Column (OWC) device is considered placed in front of a V-shaped vertical breakwater. The idea conceived, is based on the amplified wave power absorption due to the wave interactions originated from the presence of the breakwater. A theoretical analysis is presented in the realm of linear potential theory, based on the solution of proper diffraction, and radiation problems in the frequency domain, using the eigenfunction expansion method, the method of images and the multiple scattering approach. Optimum absorption efficiency is examined taking into consideration the characteristics of the Power Take Off (PTO) system and the air compressibility. Numerical results are presented and discussed in terms of the expected power absorption. The effect of the distance between the OWC and the vertical walls, the breakwater's forming angle, and the wave heading angle, is examined to demonstrate the enhanced absorption ability of the device. It is concluded that the device's efficiency is strongly dependent on the position of the OWC in front of the walls, as well as the angle of the wave impact, and should be taken into account when determining the optimum device parameters for maximization of its performance.
{"title":"Assessment of the hydrodynamic performance of an Oscillating Water Column device in front of a V-shaped vertical wall","authors":"D. Konispoliatis","doi":"10.1115/1.4056643","DOIUrl":"https://doi.org/10.1115/1.4056643","url":null,"abstract":"\u0000 In this work, an Oscillating Water Column (OWC) device is considered placed in front of a V-shaped vertical breakwater. The idea conceived, is based on the amplified wave power absorption due to the wave interactions originated from the presence of the breakwater. A theoretical analysis is presented in the realm of linear potential theory, based on the solution of proper diffraction, and radiation problems in the frequency domain, using the eigenfunction expansion method, the method of images and the multiple scattering approach. Optimum absorption efficiency is examined taking into consideration the characteristics of the Power Take Off (PTO) system and the air compressibility. Numerical results are presented and discussed in terms of the expected power absorption. The effect of the distance between the OWC and the vertical walls, the breakwater's forming angle, and the wave heading angle, is examined to demonstrate the enhanced absorption ability of the device. It is concluded that the device's efficiency is strongly dependent on the position of the OWC in front of the walls, as well as the angle of the wave impact, and should be taken into account when determining the optimum device parameters for maximization of its performance.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44862291","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 paper introduces a pipeline that assembles a dataset of metocean conditions consisting of wind, wave and surface currents, and then clusters this data to find the characteristic environmental conditions of each region in the Brazilian coast and the associated Exclusive Economic Zone. Clustering uses the Partitioning Around Medoids algorithm with the silhouette coefficient. As examples, we first present an analysis for the whole Exclusive Economic Zone and then a focused analysis around the Santos port in Southeastern Brazil.
{"title":"AUTOMATIC CLUSTERING OF METOCEAN CONDITIONS IN THE BRAZILIAN COAST","authors":"Felipe Marino Moreno, E. Tannuri, F. G. Cozman","doi":"10.1115/1.4056618","DOIUrl":"https://doi.org/10.1115/1.4056618","url":null,"abstract":"\u0000 This paper introduces a pipeline that assembles a dataset of metocean conditions consisting of wind, wave and surface currents, and then clusters this data to find the characteristic environmental conditions of each region in the Brazilian coast and the associated Exclusive Economic Zone. Clustering uses the Partitioning Around Medoids algorithm with the silhouette coefficient. As examples, we first present an analysis for the whole Exclusive Economic Zone and then a focused analysis around the Santos port in Southeastern Brazil.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42165163","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}
Saravanan Bhaskaran, A. Verma, Shuai Yuan, Zhiyu Jiang, K. Halse
Offshore wind turbine blade installation using jack up crane vessel is a challenging task. Wave and wind induced loads on the installation system can cause large relative motion between the blade root and the hub during the mating process. Currently, several numerical tools are used to analyse such critical global motion responses; however, the industry suffers from lack of experiments and full-scale measurements to validate the accuracy of these results. Consequently, a code-to-code comparison exercise becomes critical as it allows comparing different numerical tools for reliable prediction and verification of results. In the present paper, a numerical model of the offshore wind turbine blade mating process using a jack-up crane vessel is developed in OrcaFlex, and a code-to-code comparison is performed against SIMA; both these tools are immensely used in the industry for modelling marine operations. Different comparisons are made between both the tools such as: (1) modal analyses of the jack-up vessel and the blade lifting gear, (2) time-domain analysis of the fully coupled installation vessel-crane-blade system, and (3) a comprehensive sensitivity study based on different seed numbers and simulation periods. The results of the study show a good agreement between both the tools with a deviation of less than 3% in terms of modal analysis and less than 5% variation in time domain results. Further, the paper provides modelling guidelines for the industry practitioners that heavily rely on both the tools for modelling marine operations.
{"title":"A code-to-code comparison for dynamic modelling and response analysis of offshore wind turbine blade mating process","authors":"Saravanan Bhaskaran, A. Verma, Shuai Yuan, Zhiyu Jiang, K. Halse","doi":"10.1115/1.4056617","DOIUrl":"https://doi.org/10.1115/1.4056617","url":null,"abstract":"\u0000 Offshore wind turbine blade installation using jack up crane vessel is a challenging task. Wave and wind induced loads on the installation system can cause large relative motion between the blade root and the hub during the mating process. Currently, several numerical tools are used to analyse such critical global motion responses; however, the industry suffers from lack of experiments and full-scale measurements to validate the accuracy of these results. Consequently, a code-to-code comparison exercise becomes critical as it allows comparing different numerical tools for reliable prediction and verification of results. In the present paper, a numerical model of the offshore wind turbine blade mating process using a jack-up crane vessel is developed in OrcaFlex, and a code-to-code comparison is performed against SIMA; both these tools are immensely used in the industry for modelling marine operations. Different comparisons are made between both the tools such as: (1) modal analyses of the jack-up vessel and the blade lifting gear, (2) time-domain analysis of the fully coupled installation vessel-crane-blade system, and (3) a comprehensive sensitivity study based on different seed numbers and simulation periods. The results of the study show a good agreement between both the tools with a deviation of less than 3% in terms of modal analysis and less than 5% variation in time domain results. Further, the paper provides modelling guidelines for the industry practitioners that heavily rely on both the tools for modelling marine operations.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42352818","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}
Decao Yin, Jie Wu, H. Lie, E. Passano, Svein Savik, G. Grytøyr, M. Tognarelli, T. Andersen, R. Igland, D. Karunakaran, Collin Gaskill
Offshore drilling risers, top-tensioned risers and many production risers are top tensioned, connecting the vessel and seabed via joints. External loads such as currents, waves and vessel motions introduce cyclic loads and motions on riser sections, which may shorten the service life due to accumulated fatigue damage. Dynamic responses under combined currents and waves are more complicated than vortex-induced vibrations (VIV) due to pure currents, and it is not fully understood. Several model test campaigns on top-tensioned riser (TTR) have been carried out at SINTEF Ocean (former MARINTEK) during the past decades. Currents, waves and vessel motions were modeled, and the riser model responses were measured. In this study, selected cases from such model tests are analysed, and used to validate a semi-empirical time domain VIV prediction tool – VIVANA-TD. A better understanding of the dynamic responses of TTR under combined currents and waves has been achieved. By comparing the results from numerical simulation using VIVANA-TD and model test measurements, validity and limitation of the time domain tool have been investigated. Important features that need to be considered are discussed. The experience gained from the present study establishes a good basis for VIV and wave load prediction of full-scale TTRs under combined currents and waves where the uncertainty of VIV prediction is further reduced.
{"title":"Wave effects on vortex-induced vibrations of a top-tensioned riser","authors":"Decao Yin, Jie Wu, H. Lie, E. Passano, Svein Savik, G. Grytøyr, M. Tognarelli, T. Andersen, R. Igland, D. Karunakaran, Collin Gaskill","doi":"10.1115/1.4056521","DOIUrl":"https://doi.org/10.1115/1.4056521","url":null,"abstract":"\u0000 Offshore drilling risers, top-tensioned risers and many production risers are top tensioned, connecting the vessel and seabed via joints. External loads such as currents, waves and vessel motions introduce cyclic loads and motions on riser sections, which may shorten the service life due to accumulated fatigue damage. Dynamic responses under combined currents and waves are more complicated than vortex-induced vibrations (VIV) due to pure currents, and it is not fully understood. Several model test campaigns on top-tensioned riser (TTR) have been carried out at SINTEF Ocean (former MARINTEK) during the past decades. Currents, waves and vessel motions were modeled, and the riser model responses were measured. In this study, selected cases from such model tests are analysed, and used to validate a semi-empirical time domain VIV prediction tool – VIVANA-TD. A better understanding of the dynamic responses of TTR under combined currents and waves has been achieved. By comparing the results from numerical simulation using VIVANA-TD and model test measurements, validity and limitation of the time domain tool have been investigated. Important features that need to be considered are discussed. The experience gained from the present study establishes a good basis for VIV and wave load prediction of full-scale TTRs under combined currents and waves where the uncertainty of VIV prediction is further reduced.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44892688","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}
Changqing Jiang, Peng Xu, O. el Moctar, Guiyong Zhang
Wave-induced motions of and loads on a moored and articulated multibody offshore structure are numerically analyzed, where a coupled mooring-joint-viscous flow solver was used to account for mooring dynamics, joint restrictions, nonlinear rigid body motions, and viscous flow effects. The considered concepts consisted of two MFSs connected by two types of connections, namely a rigid joint and a flexible joint, and positioned by four symmetrical catenary mooring lines. The analyzed responses comprised multibody motions as well as associated forces acting in the hinged joints and the mooring lines. Results indicated that surge motions of the articulated bodies were almost identical to each other, whereas the effects of the joint on heave motions were not pronounced. However, highly dynamic pitch motions between two hinged MFSs were observed. Apart from motion responses, forces acting on the hinged joint and the mooring lines were estimated. The coupled mooring-joint-viscous flow solver demonstrated its capability to predict wave-induced motions of and loads on a moored multibody offshore structure articulated by various types of joints.
{"title":"Analysis of a Moored and Articulated Multibody Offshore System in Steep Waves","authors":"Changqing Jiang, Peng Xu, O. el Moctar, Guiyong Zhang","doi":"10.1115/1.4056522","DOIUrl":"https://doi.org/10.1115/1.4056522","url":null,"abstract":"\u0000 Wave-induced motions of and loads on a moored and articulated multibody offshore structure are numerically analyzed, where a coupled mooring-joint-viscous flow solver was used to account for mooring dynamics, joint restrictions, nonlinear rigid body motions, and viscous flow effects. The considered concepts consisted of two MFSs connected by two types of connections, namely a rigid joint and a flexible joint, and positioned by four symmetrical catenary mooring lines. The analyzed responses comprised multibody motions as well as associated forces acting in the hinged joints and the mooring lines. Results indicated that surge motions of the articulated bodies were almost identical to each other, whereas the effects of the joint on heave motions were not pronounced. However, highly dynamic pitch motions between two hinged MFSs were observed. Apart from motion responses, forces acting on the hinged joint and the mooring lines were estimated. The coupled mooring-joint-viscous flow solver demonstrated its capability to predict wave-induced motions of and loads on a moored multibody offshore structure articulated by various types of joints.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49450020","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 the present work an extensive verification and validation study is performed to evaluate the accuracy and credibility for CFD simulations of the hydrodynamic responses of a semi-submersible Floating Offshore Wind Turbine (FOWT) platform under bichromatic waves and random waves. A dynamic mooring model is coupled with the CFD code to accurately simulate the mooring system. For the bichromatic wave case, the surge, heave and pitch RAOs at wave frequencies, mean surge offset and mean surge force of the semi-submersible platform are investigated. The numerical uncertainties of the above metrics are quantified, which are primarily sourced from the discretization uncertainty. For the random wave case, the surge, heave and pitch PSD sums in wave frequency range and low frequency range are validated against the experimental results. The numerical uncertainty derived from the bichromatic wave case is applied in the validation of the random wave case. The PSD sums in wave frequency range have achieved the validation within the validation uncertainty. Though the PSD sums in low frequency range are under-predicted, the results with the utilization of the CFD code agree more with the experimental value than the mid-fidelity tools.
{"title":"Verification and Validation of CFD Simulations of a FOWT Semi-submersible under Bichromatic and Random Waves","authors":"Yu Wang, Hamn-Ching Chen","doi":"10.1115/1.4056421","DOIUrl":"https://doi.org/10.1115/1.4056421","url":null,"abstract":"\u0000 In the present work an extensive verification and validation study is performed to evaluate the accuracy and credibility for CFD simulations of the hydrodynamic responses of a semi-submersible Floating Offshore Wind Turbine (FOWT) platform under bichromatic waves and random waves. A dynamic mooring model is coupled with the CFD code to accurately simulate the mooring system. For the bichromatic wave case, the surge, heave and pitch RAOs at wave frequencies, mean surge offset and mean surge force of the semi-submersible platform are investigated. The numerical uncertainties of the above metrics are quantified, which are primarily sourced from the discretization uncertainty. For the random wave case, the surge, heave and pitch PSD sums in wave frequency range and low frequency range are validated against the experimental results. The numerical uncertainty derived from the bichromatic wave case is applied in the validation of the random wave case. The PSD sums in wave frequency range have achieved the validation within the validation uncertainty. Though the PSD sums in low frequency range are under-predicted, the results with the utilization of the CFD code agree more with the experimental value than the mid-fidelity tools.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49413129","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 novel subsea shuttle tanker (SST) concept was proposed as a cost-effective alternative to subsea pipelines and tanker ships for liquid CO2 transportation between a source facility and a subsea well. The SST will be deployed to transport CO2 to marginal subsea fields with an annual CO2 storage capacity around 1 million tonnes. A baseline design was recently developed by the authors to support research work aimed at assessing large and ultra-efficient subsea cargo drone technology. One crucial aspect is the development of SST's operation envelope, i.e., the safe depth versus speed regions. The development of this envelope entails comprehensive and detailed studies of SST's dynamic load-effects under all expected operating scenarios which in the early concept development phase can be performed using suitable computational models. In this technical brief, the initial development of such a model is unveiled. This fully coupled 2D planar model considers the most relevant load-effects which are from hydrodynamics, hydrostatics, and control surface induced loads. The most important features of the model such as the derivation of hydrodynamic derivatives and model verification are also discussed. As an example, this model is then used to study the depth control problem which is a key aspect in the determination of the safety operational envelope. The results show that unsuitable control schemes that do not look ahead in the trajectory lead to undesirable results. In contrast, a feed-forward heading control method achieves a good and fast control response.
{"title":"2D Planar Modelling of the Depth Control of a Subsea Shuttle Tanker","authors":"Yucong Ma, Y. Xing, D. Sui, M. Ong, T. Hemmingsen","doi":"10.1115/1.4056418","DOIUrl":"https://doi.org/10.1115/1.4056418","url":null,"abstract":"\u0000 A novel subsea shuttle tanker (SST) concept was proposed as a cost-effective alternative to subsea pipelines and tanker ships for liquid CO2 transportation between a source facility and a subsea well. The SST will be deployed to transport CO2 to marginal subsea fields with an annual CO2 storage capacity around 1 million tonnes. A baseline design was recently developed by the authors to support research work aimed at assessing large and ultra-efficient subsea cargo drone technology. One crucial aspect is the development of SST's operation envelope, i.e., the safe depth versus speed regions. The development of this envelope entails comprehensive and detailed studies of SST's dynamic load-effects under all expected operating scenarios which in the early concept development phase can be performed using suitable computational models. In this technical brief, the initial development of such a model is unveiled. This fully coupled 2D planar model considers the most relevant load-effects which are from hydrodynamics, hydrostatics, and control surface induced loads. The most important features of the model such as the derivation of hydrodynamic derivatives and model verification are also discussed. As an example, this model is then used to study the depth control problem which is a key aspect in the determination of the safety operational envelope. The results show that unsuitable control schemes that do not look ahead in the trajectory lead to undesirable results. In contrast, a feed-forward heading control method achieves a good and fast control response.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48020793","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 presents the baseline design for the autonomous subsea vehicle capable of traveling at a lower speed of 1 m/s with an operating range of 400 km. Owing to UiS subsea-freight glider's (USFG) exceedingly economical and unique propulsion system, it can transport various types of cargo over variable distances. The primary use-case scenario for the USFG is to serve as an autonomous transport vessel to carry CO2 from land-based facilities to subsea injection sites. This allows the USFG to serve as a substitute for weather-dependent cargo tankers and underwater pipelines. The length of the USFG is 50.25 m along with a beam of 5.50 m, which allows the vessel to carry 518 m3 of CO2 while serving the storage needs of the carbon capture and storage (CCS) ventures on the Norwegian continental shelf. The USFG is powered by battery cells, and it only consumes a little less than 8 kW of electrical power. Along with the mechanical design of the USFG, the control design is also presented in the final part of the paper. The manoeuvring model of the USFG is presented along with two operational case studies. For this purpose, an LQR and PID-based control system is designed, and a detailed comparison study is also shown in terms of tuning and response characteristics for both controllers.
{"title":"UiS Subsea-Freight Glider: A Large Buoyancy-Driven Autonomous Cargo Glider","authors":"Usman Ahmad, Y. Xing, Yucong Ma","doi":"10.1115/1.4056419","DOIUrl":"https://doi.org/10.1115/1.4056419","url":null,"abstract":"\u0000 This work presents the baseline design for the autonomous subsea vehicle capable of traveling at a lower speed of 1 m/s with an operating range of 400 km. Owing to UiS subsea-freight glider's (USFG) exceedingly economical and unique propulsion system, it can transport various types of cargo over variable distances. The primary use-case scenario for the USFG is to serve as an autonomous transport vessel to carry CO2 from land-based facilities to subsea injection sites. This allows the USFG to serve as a substitute for weather-dependent cargo tankers and underwater pipelines. The length of the USFG is 50.25 m along with a beam of 5.50 m, which allows the vessel to carry 518 m3 of CO2 while serving the storage needs of the carbon capture and storage (CCS) ventures on the Norwegian continental shelf. The USFG is powered by battery cells, and it only consumes a little less than 8 kW of electrical power. Along with the mechanical design of the USFG, the control design is also presented in the final part of the paper. The manoeuvring model of the USFG is presented along with two operational case studies. For this purpose, an LQR and PID-based control system is designed, and a detailed comparison study is also shown in terms of tuning and response characteristics for both controllers.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47989017","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 an emerging “blue economy,” the use of large multipurpose floating platforms in the open ocean is being considered. Such platforms could possibly support a diversified range of commercial activities including energy generation, aquaculture, seabed mining, transport, tourism, and sea-based laboratories. A Markov Decision Process (MDP) framework is proposed to deal with operations and maintenance issues that are inevitable; challenges arise from the complex stochastic weather conditions that need to be accounted for. Using data as well as contrasting synthetic simulations of relevant weather variables, we demonstrate the robustness/versatility of the MDP model. Two case studies-one involving constant and another involving time-dependent downtime costs-are conducted to demonstrate how the proposed MDP framework incorporates weather patterns from available data and can offer optimal policies for distinct metocean conditions (i.e., temporal variations in the weather). A realistic example that illustrates the implementation of the proposed framework for multiple O&M issues involving salmon net pens and wave energy converters demonstrates how our optimal policies can minimize O&M costs and maximize crew safety almost as if the true future were known for scheduling.
{"title":"Weather Window Analysis in Operations and Maintenance Policies for Offshore Floating Multi-Purpose Platforms","authors":"Taemin Heo, Ding-Peng Liu, L. Manuel","doi":"10.1115/1.4056344","DOIUrl":"https://doi.org/10.1115/1.4056344","url":null,"abstract":"\u0000 In an emerging “blue economy,” the use of large multipurpose floating platforms in the open ocean is being considered. Such platforms could possibly support a diversified range of commercial activities including energy generation, aquaculture, seabed mining, transport, tourism, and sea-based laboratories. A Markov Decision Process (MDP) framework is proposed to deal with operations and maintenance issues that are inevitable; challenges arise from the complex stochastic weather conditions that need to be accounted for. Using data as well as contrasting synthetic simulations of relevant weather variables, we demonstrate the robustness/versatility of the MDP model. Two case studies-one involving constant and another involving time-dependent downtime costs-are conducted to demonstrate how the proposed MDP framework incorporates weather patterns from available data and can offer optimal policies for distinct metocean conditions (i.e., temporal variations in the weather). A realistic example that illustrates the implementation of the proposed framework for multiple O&M issues involving salmon net pens and wave energy converters demonstrates how our optimal policies can minimize O&M costs and maximize crew safety almost as if the true future were known for scheduling.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42170129","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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