Csaba Pákozdi, A. Kamath, Weizhi Wang, T. Martin, H. Bihs
Estimation of the hydrodynamic loads based on strip theory with the Morrison equation provides a fast and inexpensive method for load estimation for the offshore industry. The advantage of this approach is that it requires only the undisturbed wave kinematics along with inertia and viscous force coefficients. Over the recent years, the development in numerical wave tank simulations makes it possible to simulate nonlinear three-hour sea states, with computational times in the order of real time. This provides an opportunity to calculate loads using wave spectrum input in numerical simulations at reasonable computational time and effort. In the current paper, the open-source fully nonlinear potential flow model REEF3D::FNPF is employed for the wave propagation calculations. Here, the Laplace equation for the velocity potential is solved on a sigma-coordinate mesh with the nonlinear free surface boundary conditions to close the system. A technique to calculate the total acceleration on the sigma-coordinate grid is introduced which makes it possible to apply strip theory in a moving grid framework. With the combination of strip theory and three-hour wave simulations, a unique possibility to estimate the hydrodynamic loads in real time for all discrete positions in space within the domain of the numerical wave tank is presented in this paper. The numerical results for inline forces on an offshore wind mono-pile substructure are compared with measurements, and the new approach shows good agreement.
{"title":"Efficient Calculation of Spatial and Temporal Evolution of Hydrodynamic Loads on Offshore Wind Substructures","authors":"Csaba Pákozdi, A. Kamath, Weizhi Wang, T. Martin, H. Bihs","doi":"10.1115/omae2021-62256","DOIUrl":"https://doi.org/10.1115/omae2021-62256","url":null,"abstract":"\u0000 Estimation of the hydrodynamic loads based on strip theory with the Morrison equation provides a fast and inexpensive method for load estimation for the offshore industry. The advantage of this approach is that it requires only the undisturbed wave kinematics along with inertia and viscous force coefficients. Over the recent years, the development in numerical wave tank simulations makes it possible to simulate nonlinear three-hour sea states, with computational times in the order of real time. This provides an opportunity to calculate loads using wave spectrum input in numerical simulations at reasonable computational time and effort. In the current paper, the open-source fully nonlinear potential flow model REEF3D::FNPF is employed for the wave propagation calculations. Here, the Laplace equation for the velocity potential is solved on a sigma-coordinate mesh with the nonlinear free surface boundary conditions to close the system. A technique to calculate the total acceleration on the sigma-coordinate grid is introduced which makes it possible to apply strip theory in a moving grid framework. With the combination of strip theory and three-hour wave simulations, a unique possibility to estimate the hydrodynamic loads in real time for all discrete positions in space within the domain of the numerical wave tank is presented in this paper. The numerical results for inline forces on an offshore wind mono-pile substructure are compared with measurements, and the new approach shows good agreement.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91345554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
José Lucas De Melo Costa, Asdrubal N. Queiroz Filho, Ismael H. F. Santos, Rodrigo A. Barreira, A. H. R. Costa, E. Gomi, E. Tannuri
Offshore production facilities play a central role in the oil industry given the growing demand for energy resources. The mooring system of these floating structures is a critical component for safety maintenance. The timely identification of mooring lines failures can prevent environmental pollution, property losses and further system failures. In this paper we propose a system to detect and classify failures of the mooring lines based on the natural period in the longitudinal axis and in the lateral axis of the long drift oscillatory motion of the platform. The proposal starts from the hypothesis that when a line break occurs, the natural period of oscillation of the platform is increased, and this difference may indicate the malfunction of the mooring system. The proof of concept developed for the proposed system demonstrates the potential of using the natural period to detect failures in mooring lines for floating vessels, validating the initial hypothesis that the difference in a natural period appears when a line breaks and that this difference may detect line break.
{"title":"FPSO Mooring Line Integrity Supervising System Based on Motion Data and Natural Frequency Estimation","authors":"José Lucas De Melo Costa, Asdrubal N. Queiroz Filho, Ismael H. F. Santos, Rodrigo A. Barreira, A. H. R. Costa, E. Gomi, E. Tannuri","doi":"10.1115/omae2021-62991","DOIUrl":"https://doi.org/10.1115/omae2021-62991","url":null,"abstract":"\u0000 Offshore production facilities play a central role in the oil industry given the growing demand for energy resources. The mooring system of these floating structures is a critical component for safety maintenance. The timely identification of mooring lines failures can prevent environmental pollution, property losses and further system failures. In this paper we propose a system to detect and classify failures of the mooring lines based on the natural period in the longitudinal axis and in the lateral axis of the long drift oscillatory motion of the platform. The proposal starts from the hypothesis that when a line break occurs, the natural period of oscillation of the platform is increased, and this difference may indicate the malfunction of the mooring system. The proof of concept developed for the proposed system demonstrates the potential of using the natural period to detect failures in mooring lines for floating vessels, validating the initial hypothesis that the difference in a natural period appears when a line breaks and that this difference may detect line break.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90496364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Henry Bandringa, Frédérick Jaouën, J. Helder, T. Bunnik
The Catenary Anchor-Leg Mooring (CALM) is the most popular and widely-used type of offshore loading terminal. A CALM buoy consists of a floating buoy anchored to the seabed by catenary chain legs which are secured to anchors or piles. Due to the small inertia of CALM buoys, the mooring line responses are very sensitive to waves and considerable fatigue risk is introduced to the mooring lines. Extreme waves may even lead to mooring line failure. Therefore it is highly relevant to study the motions of the CALM buoy in (extreme) wave conditions. This paper presents a validation study of a coupled CFD – dynamic mooring model for simulating the response of a shallow water CALM buoy in extreme waves (Figure 1). Simulations of an interactively moving CALM buoy in a horizontal mooring system were performed by coupling a Navier-Stokes based finite-volume, VoF CFD solver with a dynamic mooring model. The CFD results are validated against model tests performed in MARIN’s shallow-water basin during the ComFLOW-2 joint industry project. The validation study concentrates on the correct prediction of the coupled responses of the CALM buoy in extreme, regular shallow-water waves. As an alternative to simulations with a fully coupled dynamic mooring set-up, also CFD simulations are presented in which the mooring system is represented by a linearly equivalent spring matrix, including cross terms. The importance of correctly modelling these cross terms is presented in the paper, and the results obtained with- and without these off-diagonal spring terms are compared.
{"title":"On the Validity of CFD for Simulating a Shallow Water CALM Buoy in Extreme Waves","authors":"Henry Bandringa, Frédérick Jaouën, J. Helder, T. Bunnik","doi":"10.1115/omae2021-62738","DOIUrl":"https://doi.org/10.1115/omae2021-62738","url":null,"abstract":"\u0000 The Catenary Anchor-Leg Mooring (CALM) is the most popular and widely-used type of offshore loading terminal. A CALM buoy consists of a floating buoy anchored to the seabed by catenary chain legs which are secured to anchors or piles. Due to the small inertia of CALM buoys, the mooring line responses are very sensitive to waves and considerable fatigue risk is introduced to the mooring lines. Extreme waves may even lead to mooring line failure. Therefore it is highly relevant to study the motions of the CALM buoy in (extreme) wave conditions.\u0000 This paper presents a validation study of a coupled CFD – dynamic mooring model for simulating the response of a shallow water CALM buoy in extreme waves (Figure 1). Simulations of an interactively moving CALM buoy in a horizontal mooring system were performed by coupling a Navier-Stokes based finite-volume, VoF CFD solver with a dynamic mooring model. The CFD results are validated against model tests performed in MARIN’s shallow-water basin during the ComFLOW-2 joint industry project. The validation study concentrates on the correct prediction of the coupled responses of the CALM buoy in extreme, regular shallow-water waves.\u0000 As an alternative to simulations with a fully coupled dynamic mooring set-up, also CFD simulations are presented in which the mooring system is represented by a linearly equivalent spring matrix, including cross terms. The importance of correctly modelling these cross terms is presented in the paper, and the results obtained with- and without these off-diagonal spring terms are compared.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82734309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xi-Ying Zhang, Charles Loader, Spencer Schilling, V. Hernández, K. Mcsweeney, H. Gu
3D scanning technology uses lasers to scan and capture object surfaces without physical surface contact. Laser scanning is gaining acceptance by many, including owners of marine or offshore assets as a viable inspection and validation method. Laser technology reduces operational times compared to traditional pit gauging techniques, particularly for large areas of widespread wastage or pitting. This paper studies the use of 3D scanning technology for inspection, thickness gauging, and steel wastage measurements of hull structures. Pilot tests were conducted on coated and uncorroded plates in Houston, USA, and uncoated and corroded plates and uncoated and deformed plates in Perth, Australia. Manual Ultrasonic Testing (UT) was conducted, which is the method currently accepted by International Association of Classification Societies (IACS) for thickness measurements of hull structures. For the coated plate, the coating thickness was measured on both sides of the plate. The coating thickness was deducted from the total thickness from 3D scanning before the plate thickness was compared with the UT results. Acceptance criteria are proposed to compare the Manual UT measurements with the 3D scanning measurements to determine if 3D laser scanning is a possible alternative thickness measurement method. The difference of thickness measurements from 3D scanning on coated and uncorroded plates is within 13% when compared with those from UT. The discrepancy is attributed to equipment accuracy tolerances, errors from data post-processing, and measurement errors due to coating surface roughness. For uncoated and corroded plates, the difference reduces to 3%, making the results of 3D scanning acceptable based on acceptance criteria. In addition, the higher accuracy of using 3D scanning to measure plate deformation is demonstrated over traditional methods which use stringlines or laser levels to create a reference surface. Comparisons of the coefficient of variation (CV) on all plates demonstrate the higher precision of 3D scanning technology than that of manual UT. The main limitation of 3D laser scanners is their inability to directly obtain steel thickness for structures that have been coated or painted, especially in watertight/oil-tight structures. The study identifies capabilities, accuracy, and limitations of using 3D scanning technology for thickness measurements of hull structures in the marine or offshore industries. Scanning technology can support inspections providing fast and precise means of thickness measurements of corroded plates without coating. It provides the potential for producing 3D models and analysis for follow-up inspections. Plausible use cases in the maritime industry include defect analysis, fitness for service assessment, damage assessment, and corrosion monitoring.
{"title":"3D Laser Scanning for Thickness Measurements of Hull Structures","authors":"Xi-Ying Zhang, Charles Loader, Spencer Schilling, V. Hernández, K. Mcsweeney, H. Gu","doi":"10.1115/omae2021-63178","DOIUrl":"https://doi.org/10.1115/omae2021-63178","url":null,"abstract":"\u0000 3D scanning technology uses lasers to scan and capture object surfaces without physical surface contact. Laser scanning is gaining acceptance by many, including owners of marine or offshore assets as a viable inspection and validation method. Laser technology reduces operational times compared to traditional pit gauging techniques, particularly for large areas of widespread wastage or pitting. This paper studies the use of 3D scanning technology for inspection, thickness gauging, and steel wastage measurements of hull structures.\u0000 Pilot tests were conducted on coated and uncorroded plates in Houston, USA, and uncoated and corroded plates and uncoated and deformed plates in Perth, Australia. Manual Ultrasonic Testing (UT) was conducted, which is the method currently accepted by International Association of Classification Societies (IACS) for thickness measurements of hull structures. For the coated plate, the coating thickness was measured on both sides of the plate. The coating thickness was deducted from the total thickness from 3D scanning before the plate thickness was compared with the UT results.\u0000 Acceptance criteria are proposed to compare the Manual UT measurements with the 3D scanning measurements to determine if 3D laser scanning is a possible alternative thickness measurement method. The difference of thickness measurements from 3D scanning on coated and uncorroded plates is within 13% when compared with those from UT. The discrepancy is attributed to equipment accuracy tolerances, errors from data post-processing, and measurement errors due to coating surface roughness. For uncoated and corroded plates, the difference reduces to 3%, making the results of 3D scanning acceptable based on acceptance criteria. In addition, the higher accuracy of using 3D scanning to measure plate deformation is demonstrated over traditional methods which use stringlines or laser levels to create a reference surface. Comparisons of the coefficient of variation (CV) on all plates demonstrate the higher precision of 3D scanning technology than that of manual UT. The main limitation of 3D laser scanners is their inability to directly obtain steel thickness for structures that have been coated or painted, especially in watertight/oil-tight structures.\u0000 The study identifies capabilities, accuracy, and limitations of using 3D scanning technology for thickness measurements of hull structures in the marine or offshore industries. Scanning technology can support inspections providing fast and precise means of thickness measurements of corroded plates without coating. It provides the potential for producing 3D models and analysis for follow-up inspections. Plausible use cases in the maritime industry include defect analysis, fitness for service assessment, damage assessment, and corrosion monitoring.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84907280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Sidarta, N. Tcherniguin, H. Lim, P. Bouchard, Mengchen Kang, Aurelien Leridon
The use of an Artificial Neural Network (ANN) for detection of mooring line failure has been a growing subject of discussion over the past several years. Sidarta et al. [6, 8, 12] have presented papers on the detection of mooring line failure of a moored vessel by monitoring shifts in the low frequency periods, mean yaw angles as a function of vessel positions, mass and added mass. An ANN model has been trained using MLTSIM hydrodynamic simulations based on information from the early stages of the project. The restoring forces and moments from mooring lines, risers and umbilicals have been solved using catenary equations to significantly reduce the computational time to generate the ANN training data. This paper presents the evaluation of this ANN model using fully coupled OrcaFlex hydrodynamic simulations, based on the latest information of the project. The results of this evaluation demonstrate the tolerance of the trained ANN model as it can properly function when tested using time series of vessel motions from the fully coupled OrcaFlex hydrodynamic simulations. Furthermore, although the ANN model has been trained using simulations with a completely removed line, the trained model can still function when tested with simulations of a line broken at the bottom. These give affirmation that the ANN model can tolerate the differences that exist between the test and training data. Sensitivity of the polyester line stiffness has also been performed using fully coupled OrcaFlex hydrodynamic simulations, and the computed time series of vessel motions have been used to test the ANN model. The ANN model can deal with some level of differences between the sensitivity tests and training data. However, sensitivity tests of the polyester line stiffness to model aging lines has posed a real challenge to the ANN model as its prediction accuracy has decreased significantly. This paper presents an adaptive method that can be implemented such that the ANN model can adapt to relatively new conditions that are quite different from the training data and maintain the accuracy of its prediction. With this approach, an existing ANN model that has been trained under certain assumptions of the system can still function although the behavior of the system has drifted away from those assumptions. This phenomenon may have similarity with a possible reality that measured behavior in the field can be somewhat different from numerical simulations. This adaptive method has a potential for addressing this issue such that a simulation trained ANN model can maintain its expected accuracy although dealing with different conditions from the training data. If successful, this is a good cost saving scenario that an ANN model adapts to some degree to relatively new and different conditions before the differences become too much to handle and the only solution is to retrain the model.
{"title":"An Adaptive Method to Further Improve the Tolerance of an ANN-Based Detection System for Mooring Line Failure","authors":"D. Sidarta, N. Tcherniguin, H. Lim, P. Bouchard, Mengchen Kang, Aurelien Leridon","doi":"10.1115/omae2021-63326","DOIUrl":"https://doi.org/10.1115/omae2021-63326","url":null,"abstract":"\u0000 The use of an Artificial Neural Network (ANN) for detection of mooring line failure has been a growing subject of discussion over the past several years. Sidarta et al. [6, 8, 12] have presented papers on the detection of mooring line failure of a moored vessel by monitoring shifts in the low frequency periods, mean yaw angles as a function of vessel positions, mass and added mass.\u0000 An ANN model has been trained using MLTSIM hydrodynamic simulations based on information from the early stages of the project. The restoring forces and moments from mooring lines, risers and umbilicals have been solved using catenary equations to significantly reduce the computational time to generate the ANN training data. This paper presents the evaluation of this ANN model using fully coupled OrcaFlex hydrodynamic simulations, based on the latest information of the project. The results of this evaluation demonstrate the tolerance of the trained ANN model as it can properly function when tested using time series of vessel motions from the fully coupled OrcaFlex hydrodynamic simulations. Furthermore, although the ANN model has been trained using simulations with a completely removed line, the trained model can still function when tested with simulations of a line broken at the bottom. These give affirmation that the ANN model can tolerate the differences that exist between the test and training data.\u0000 Sensitivity of the polyester line stiffness has also been performed using fully coupled OrcaFlex hydrodynamic simulations, and the computed time series of vessel motions have been used to test the ANN model. The ANN model can deal with some level of differences between the sensitivity tests and training data. However, sensitivity tests of the polyester line stiffness to model aging lines has posed a real challenge to the ANN model as its prediction accuracy has decreased significantly. This paper presents an adaptive method that can be implemented such that the ANN model can adapt to relatively new conditions that are quite different from the training data and maintain the accuracy of its prediction. With this approach, an existing ANN model that has been trained under certain assumptions of the system can still function although the behavior of the system has drifted away from those assumptions.\u0000 This phenomenon may have similarity with a possible reality that measured behavior in the field can be somewhat different from numerical simulations. This adaptive method has a potential for addressing this issue such that a simulation trained ANN model can maintain its expected accuracy although dealing with different conditions from the training data. If successful, this is a good cost saving scenario that an ANN model adapts to some degree to relatively new and different conditions before the differences become too much to handle and the only solution is to retrain the model.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74605059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The JCSM concept (short for Jackup Combined Semisubmersible Multifunction Platform) is a new type of semisubmersible platform presented by the first author, which overcomes the shortcomings of the available semisubmersible platforms, and combines the advantages of the traditional semisubmersible platform, the Jackup platform and the new FPSO concept - IQFP. Due to the complicated interaction between stability and hydrodynamic performance, it is necessary to explore the effect of geometrical parameters of the main body on the stability and hydrodynamic performance in order to obtain the optimal design plan of a JCSM platform. Firstly, the structure components and innovations of the JCSM were briefly reviewed in order to facilitate readers to understand its full picture. Then, six independent geometric parameters were selected by carefully studying the shape characteristics of the initial design plan of a JCSM study case. Furthermore, the stability heights and motion responses of various floating bodies of the JCSM case with different geometric parameters in wave were calculated using boundary element method based on potential flow theory. Lastly, effect of the shape parameters on stability and hydrodynamic performance of the JCSM was qualitatively evaluated. The research would shed lights on the shape design of the JCSM main body.
{"title":"Effect of Geometric Parameters of New Semisubmersible Platform on Stability and Hydrodynamic Performance","authors":"Tianying Wang, Yanjun Zhou, Honglin Tang, Shihua Zhang, Haiqing Tian","doi":"10.1115/omae2021-63218","DOIUrl":"https://doi.org/10.1115/omae2021-63218","url":null,"abstract":"\u0000 The JCSM concept (short for Jackup Combined Semisubmersible Multifunction Platform) is a new type of semisubmersible platform presented by the first author, which overcomes the shortcomings of the available semisubmersible platforms, and combines the advantages of the traditional semisubmersible platform, the Jackup platform and the new FPSO concept - IQFP. Due to the complicated interaction between stability and hydrodynamic performance, it is necessary to explore the effect of geometrical parameters of the main body on the stability and hydrodynamic performance in order to obtain the optimal design plan of a JCSM platform. Firstly, the structure components and innovations of the JCSM were briefly reviewed in order to facilitate readers to understand its full picture. Then, six independent geometric parameters were selected by carefully studying the shape characteristics of the initial design plan of a JCSM study case. Furthermore, the stability heights and motion responses of various floating bodies of the JCSM case with different geometric parameters in wave were calculated using boundary element method based on potential flow theory. Lastly, effect of the shape parameters on stability and hydrodynamic performance of the JCSM was qualitatively evaluated. The research would shed lights on the shape design of the JCSM main body.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"84 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72812558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
LNG carriers are vessels used to store and transport liquefied natural gas. LNG, in its liquid form has the temperature of minus 163 degrees Celsius. Therefore, the types of steel used to build the hull structure must withstand the impact of low temperatures. Cargo Containment System (CCS) is used to reduce the transfer of heat from the outside environment into the cargo tank and to keep the LNG in liquid state. Presently, the most popular types of CCS are designed by GTT (Gaztransport & Technigaz). However, Korean shipyards, KOGAS (Korea Gas Corporation) and many other companies around the world are developing their own CCS systems. The thermal analysis of LNG carrier hull is generally performed by the CCS developer and therefore, in order to assist the new CCS developers and LNG carrier designers, KR has developed a guideline for temperature calculation of Membrane type LNG carrier’s hull. This study is a part of the guidelines and focuses on numerical and analytical solution procedures for accurate hull temperature calculation. For verification and accuracy of these methods, temperature calculation of a Membrane type LNG carrier hull is carried out and the results are compared with each other. Both methods, thoroughly analyzed in this study, could be applied in the design of membrane type LNG carrier hulls.
{"title":"Development of Methods for Temperature Calculation of LNG Carrier Hull","authors":"M. Islam, Taewoo Choi, T. An, K. Song","doi":"10.1115/omae2021-66564","DOIUrl":"https://doi.org/10.1115/omae2021-66564","url":null,"abstract":"\u0000 LNG carriers are vessels used to store and transport liquefied natural gas. LNG, in its liquid form has the temperature of minus 163 degrees Celsius. Therefore, the types of steel used to build the hull structure must withstand the impact of low temperatures. Cargo Containment System (CCS) is used to reduce the transfer of heat from the outside environment into the cargo tank and to keep the LNG in liquid state. Presently, the most popular types of CCS are designed by GTT (Gaztransport & Technigaz). However, Korean shipyards, KOGAS (Korea Gas Corporation) and many other companies around the world are developing their own CCS systems. The thermal analysis of LNG carrier hull is generally performed by the CCS developer and therefore, in order to assist the new CCS developers and LNG carrier designers, KR has developed a guideline for temperature calculation of Membrane type LNG carrier’s hull. This study is a part of the guidelines and focuses on numerical and analytical solution procedures for accurate hull temperature calculation. For verification and accuracy of these methods, temperature calculation of a Membrane type LNG carrier hull is carried out and the results are compared with each other. Both methods, thoroughly analyzed in this study, could be applied in the design of membrane type LNG carrier hulls.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85022737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. P. Cotrim, H. B. Oliveira, Asdrubal N. Queiroz Filho, Ismael H. F. Santos, Rodrigo A. Barreira, E. Tannuri, A. H. R. Costa, E. Gomi
The current design process of mooring systems for FPSOs is highly dependent on the availability of the platform’s mathematical model and accuracy of dynamic simulations, through which resulting time series motion is evaluated according to design constraints. This process can be time-consuming and present inaccurate results due to the mathematical model’s limitations and overall complexity of the vessel’s dynamics. We propose a Neural Simulator, a set of data-based surrogate models with environmental data as input, each specialized in the prediction of different motion statistics relevant to mooring system design: Maximum Roll, Platform Offset and Fairlead Displacements. The meta-models are trained by real current, wind and wave data measured in 3h periods at the Campos Basin (Brazil) from 2003 to 2010 and the associated dynamic response of a spread-moored FPSO obtained through time-domain simulations using the Dynasim software. A comparative analysis of different model architectures is conducted and the proposed models are shown to correctly capture platform dynamics, providing good results when compared to the statistical analysis of time series motion obtained from Dynasim.
{"title":"Neural Network Meta-Models for FPSO Motion Prediction From Environmental Data","authors":"L. P. Cotrim, H. B. Oliveira, Asdrubal N. Queiroz Filho, Ismael H. F. Santos, Rodrigo A. Barreira, E. Tannuri, A. H. R. Costa, E. Gomi","doi":"10.1115/omae2021-62674","DOIUrl":"https://doi.org/10.1115/omae2021-62674","url":null,"abstract":"\u0000 The current design process of mooring systems for FPSOs is highly dependent on the availability of the platform’s mathematical model and accuracy of dynamic simulations, through which resulting time series motion is evaluated according to design constraints. This process can be time-consuming and present inaccurate results due to the mathematical model’s limitations and overall complexity of the vessel’s dynamics. We propose a Neural Simulator, a set of data-based surrogate models with environmental data as input, each specialized in the prediction of different motion statistics relevant to mooring system design: Maximum Roll, Platform Offset and Fairlead Displacements. The meta-models are trained by real current, wind and wave data measured in 3h periods at the Campos Basin (Brazil) from 2003 to 2010 and the associated dynamic response of a spread-moored FPSO obtained through time-domain simulations using the Dynasim software. A comparative analysis of different model architectures is conducted and the proposed models are shown to correctly capture platform dynamics, providing good results when compared to the statistical analysis of time series motion obtained from Dynasim.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"252 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75822043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Serret, B. Kahn, Bruce Cavanagh, Patricia Lorente, R. Pascal, Clementine Girandier, Carlos Cortes, Rubén Duran, P. McEvoy, A. Castro
This paper presents the first iteration design of the Flotant concept developed within the framework of a Cooperation Research Project funded by the European Union’s Horizon 2020 research and innovation programme. The Flotant concept is a hybrid concrete-plastic barge-type floating offshore substructure holding a 12MW wind turbine with the singularity of getting floatability by using plastic foam material fitted within the floater substructure. The INS12MW generic wind turbine, an upscaling exercise based on the DTU10MW reference wind turbine, is presented and simulated using open-source certified aeroelastic code. The floating platform and the mooring system are designed for two different sites, West of Barra and South East of Gran Canaria island. The principal dimensions are presented along with the hydrostatic and hydrodynamic properties of the floating system. A relevant subset of design load cases derived from International Electrotechnical Commission and Det Norske Veritas standards was simulated using an open-source aeroelastic code (NREL FAST) to check the coupled aero-hydro-elastic behaviour of the floating system and to generate the required load-matrix for the structural assessment of the different components. The evaluation of the design includes the seakeeping performance, the stability of the floating platform and the global performance analysis for the abovementioned sites. It demonstrates the technology developed within the Flotant project is feasible even in rough conditions like the ones in the West of Barra site.
本文介绍了在欧盟“地平线2020”研究和创新计划资助的合作研究项目框架内开发的Flotant概念的第一次迭代设计。Flotant概念是一种混合混凝土-塑料驳船式浮动海上基础结构，可容纳12MW风力涡轮机，其独特性是通过在浮子结构内安装塑料泡沫材料来获得可浮性。INS12MW通用风力涡轮机是基于DTU10MW参考风力涡轮机的升级演习，并使用开源认证的气动弹性代码进行了模拟。浮动平台和系泊系统是为两个不同的地点设计的，巴拉岛西部和大加那利岛东南部。给出了浮体的主要尺寸以及浮体的静、动力特性。根据国际电工委员会(International Electrotechnical Commission)和挪威船东公司(Det Norske Veritas)的标准，采用开源气动弹性代码(NREL FAST)模拟了相关的设计载荷案例子集，以检查浮动系统的气动-水-弹性耦合行为，并生成所需的载荷矩阵，用于不同组件的结构评估。对设计的评价包括耐浪性能、浮式平台的稳定性以及对上述地点的整体性能分析。它证明了Flotant项目中开发的技术即使在恶劣的条件下也是可行的，比如在Barra西部的现场。
{"title":"First Iteration Design of the Flotant Concept","authors":"J. Serret, B. Kahn, Bruce Cavanagh, Patricia Lorente, R. Pascal, Clementine Girandier, Carlos Cortes, Rubén Duran, P. McEvoy, A. Castro","doi":"10.1115/omae2021-62281","DOIUrl":"https://doi.org/10.1115/omae2021-62281","url":null,"abstract":"\u0000 This paper presents the first iteration design of the Flotant concept developed within the framework of a Cooperation Research Project funded by the European Union’s Horizon 2020 research and innovation programme. The Flotant concept is a hybrid concrete-plastic barge-type floating offshore substructure holding a 12MW wind turbine with the singularity of getting floatability by using plastic foam material fitted within the floater substructure.\u0000 The INS12MW generic wind turbine, an upscaling exercise based on the DTU10MW reference wind turbine, is presented and simulated using open-source certified aeroelastic code.\u0000 The floating platform and the mooring system are designed for two different sites, West of Barra and South East of Gran Canaria island. The principal dimensions are presented along with the hydrostatic and hydrodynamic properties of the floating system.\u0000 A relevant subset of design load cases derived from International Electrotechnical Commission and Det Norske Veritas standards was simulated using an open-source aeroelastic code (NREL FAST) to check the coupled aero-hydro-elastic behaviour of the floating system and to generate the required load-matrix for the structural assessment of the different components.\u0000 The evaluation of the design includes the seakeeping performance, the stability of the floating platform and the global performance analysis for the abovementioned sites. It demonstrates the technology developed within the Flotant project is feasible even in rough conditions like the ones in the West of Barra site.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84573992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Yuck, Daeho Kang, I. Han, Eungsu Kim, Munsung Kim, Ki-young Shin, Jong-woo Park, Tae-min Kim, Sang-gu Kang
A deep draft semi-submersible hull has been developed as a standardization concept which can support the topside structures up to the facility weight for the specific level of daily oil production in GOM (Gulf of Mexico). The designed hull has the optimized dimensions of ring pontoon and four columns for coping with the weight change of topside and the innovated hull shape to eliminate the casting which is normally used at the corner node area where high stress concentrated on. The hull form also has the good global motion in waves, winds and currents to be able to use the SCR (Steel Catenary Riser). The mooring systems are designed for water depths of 1,500m as a standard design concept of hull including mooring lines (3 × 4). The global performance is validated for the maximum offset, the mooring line tension and the acceleration. The possibility of SCR usage is also investigated with the fully coupled time-domain analysis to confirm that the designed hull form has the suitable hydrodynamic characteristics to permit the minimum vertical motion performance for SCR. Throughout the global performance and mooring analysis, the designed Semi-FPU fulfills all stability requirements of rules and codes specified in design of basis for both intact and damaged conditions, and has good motion characteristics such as inclination, acceleration, sectional loads and air gap and mooring system compliance with design criteria in the view point of mooring tension, offset and fatigue damage. Also, the global structural strength analysis has been performed to extract stresses and displacements where local points which are pontoon-column connection areas from the global model. The local points need to reinforce during detail design stage from buckling, yielding and fatigue analysis for normal operating and extreme storm conditions.
{"title":"Development of Deep Draft Semi-Submersible FPU Hull (Casting-Free) Targets for Oil Field in Gulf of Mexico","authors":"R. Yuck, Daeho Kang, I. Han, Eungsu Kim, Munsung Kim, Ki-young Shin, Jong-woo Park, Tae-min Kim, Sang-gu Kang","doi":"10.1115/omae2021-62655","DOIUrl":"https://doi.org/10.1115/omae2021-62655","url":null,"abstract":"\u0000 A deep draft semi-submersible hull has been developed as a standardization concept which can support the topside structures up to the facility weight for the specific level of daily oil production in GOM (Gulf of Mexico).\u0000 The designed hull has the optimized dimensions of ring pontoon and four columns for coping with the weight change of topside and the innovated hull shape to eliminate the casting which is normally used at the corner node area where high stress concentrated on. The hull form also has the good global motion in waves, winds and currents to be able to use the SCR (Steel Catenary Riser).\u0000 The mooring systems are designed for water depths of 1,500m as a standard design concept of hull including mooring lines (3 × 4). The global performance is validated for the maximum offset, the mooring line tension and the acceleration. The possibility of SCR usage is also investigated with the fully coupled time-domain analysis to confirm that the designed hull form has the suitable hydrodynamic characteristics to permit the minimum vertical motion performance for SCR.\u0000 Throughout the global performance and mooring analysis, the designed Semi-FPU fulfills all stability requirements of rules and codes specified in design of basis for both intact and damaged conditions, and has good motion characteristics such as inclination, acceleration, sectional loads and air gap and mooring system compliance with design criteria in the view point of mooring tension, offset and fatigue damage.\u0000 Also, the global structural strength analysis has been performed to extract stresses and displacements where local points which are pontoon-column connection areas from the global model. The local points need to reinforce during detail design stage from buckling, yielding and fatigue analysis for normal operating and extreme storm conditions.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85331156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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