In the present study, two-phase flow simulations using SedFoam (an open-source multi-dimensional Eulerian two-phase solver based on OpenFOAM) are employed to investigate the scour phenomenon around pipelines in the vicinity of the seabed. A complete transport profile from the immobile bed, to slowly moving quasi-static bed and upper transport layers can be captured by the present model. The fluid Reynolds stress is modeled using the two-phase k-ε model. The particle stresses due to binary collisions and enduring contacts are modeled by kinetic theory for granular flow and a phenomenological frictional model, respectively. The model is first validated through a two-dimensional (2D) simulation of scour around a single pipeline near the seabed. The predicted time-dependent scour profiles as well as the scour depth are compared with the simulation results of Lee et al. (2016) and the experimental data reported by Mao (1986). A numerical experiment is then carried out to investigate the scour around the piggyback near the seabed. The effects of different locations of the small pipeline on the scour depth are studied.
{"title":"Numerical Investigation of Scour Around Subsea Pipelines Near the Seabed","authors":"G. Yin, Zhen Cheng, Shengnan Liu, M. Ong","doi":"10.1115/omae2019-96069","DOIUrl":"https://doi.org/10.1115/omae2019-96069","url":null,"abstract":"\u0000 In the present study, two-phase flow simulations using SedFoam (an open-source multi-dimensional Eulerian two-phase solver based on OpenFOAM) are employed to investigate the scour phenomenon around pipelines in the vicinity of the seabed. A complete transport profile from the immobile bed, to slowly moving quasi-static bed and upper transport layers can be captured by the present model. The fluid Reynolds stress is modeled using the two-phase k-ε model. The particle stresses due to binary collisions and enduring contacts are modeled by kinetic theory for granular flow and a phenomenological frictional model, respectively. The model is first validated through a two-dimensional (2D) simulation of scour around a single pipeline near the seabed. The predicted time-dependent scour profiles as well as the scour depth are compared with the simulation results of Lee et al. (2016) and the experimental data reported by Mao (1986). A numerical experiment is then carried out to investigate the scour around the piggyback near the seabed. The effects of different locations of the small pipeline on the scour depth are studied.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81839476","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}
Pile driveability analyses play a crucial part in pile installation planning (hammer sizing, anticipated driving time) and pile design (fatigue concerns). GRLWEAP is one of the predominant pile driving analysis software tools used globally. Traditionally, the offshore community has often wished to use specific SRD prediction methods in driveability analyses. Some of the most popular of these methods (e.g. Alm & Hamre, 2001) employ a ‘friction fatigue’ approach whereby side friction reduces with increasing pile penetration. A past limitation in GRLWEAP has been that friction fatigue methods could not be used in a full driveability analysis, since only a single SRD (valid only for a particular depth of penetration) can be input. This is prohibitive when outputs such as blowcounts are desired at each intermediate penetration depth (e.g. for fatigue analysis), rather than just the final depth. With the introduction of GRLWEAP’s ‘friction fatigue’ module, a way of modelling friction fatigue is now provided, but the fatigue equations are formulated in a specific way that may not be directly applicable to various friction fatigue approaches. Using the Alm & Hamre (2001) friction fatigue method as an example, an approach is presented that shows how friction fatigue models that are not formulated in the same manner as GRLWEAP’s friction fatigue approach can be converted into a suitable form to allow full implementation in a GRLWEAP driveability analysis. This enables driveability analyses to capture the dynamic nature of the SRD as pile penetration increases, producing results that are valid for all penetrations and circumventing the need for alternative workarounds to capture friction fatigue. The general principles presented herein may be modified on similar principles for other friction fatigue models not explicitly captured within GRLWEAP.
{"title":"Application of Friction Fatigue Pile Driving Models in GRLWEAP","authors":"Henry Milewski, J. Kennedy","doi":"10.1115/omae2019-95944","DOIUrl":"https://doi.org/10.1115/omae2019-95944","url":null,"abstract":"\u0000 Pile driveability analyses play a crucial part in pile installation planning (hammer sizing, anticipated driving time) and pile design (fatigue concerns). GRLWEAP is one of the predominant pile driving analysis software tools used globally. Traditionally, the offshore community has often wished to use specific SRD prediction methods in driveability analyses. Some of the most popular of these methods (e.g. Alm & Hamre, 2001) employ a ‘friction fatigue’ approach whereby side friction reduces with increasing pile penetration. A past limitation in GRLWEAP has been that friction fatigue methods could not be used in a full driveability analysis, since only a single SRD (valid only for a particular depth of penetration) can be input. This is prohibitive when outputs such as blowcounts are desired at each intermediate penetration depth (e.g. for fatigue analysis), rather than just the final depth.\u0000 With the introduction of GRLWEAP’s ‘friction fatigue’ module, a way of modelling friction fatigue is now provided, but the fatigue equations are formulated in a specific way that may not be directly applicable to various friction fatigue approaches. Using the Alm & Hamre (2001) friction fatigue method as an example, an approach is presented that shows how friction fatigue models that are not formulated in the same manner as GRLWEAP’s friction fatigue approach can be converted into a suitable form to allow full implementation in a GRLWEAP driveability analysis. This enables driveability analyses to capture the dynamic nature of the SRD as pile penetration increases, producing results that are valid for all penetrations and circumventing the need for alternative workarounds to capture friction fatigue. The general principles presented herein may be modified on similar principles for other friction fatigue models not explicitly captured within GRLWEAP.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91412677","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}
Renewed interest in wave impact assessment has risen for various reasons: • The low airgap of some existing Mobile Units in the North Sea • The COSL Innovator incident and related to this topic the new DNV-GL guidelines (OTG 13 and OTG 14). • the installation of many large-diameter monopile foundations for wind turbines in increasingly deep water in the North Sea. • The installation of many large-diameter wind turbines in increasingly deep water in the North Sea. • Seabed subsidence (and maybe water level rises due to global warming) and their effect on the decreasing airgap of fixed platforms. Wave impact assessment has been the subject of many recent studies and research projects, and there has been a strong knowledge and tool development during the last decade, both within model testing and numerical (CFD) analysis (Huang et.al (2017), de Ridder et.al, (2017), Vestbøstad et. al. (2017), Bunnik et.al. (2018)). However, there is still a lack of efficient methods and tools to properly analyze wave impacts and derive the statistical variation of these impacts in the sea states to which these structures are exposed during their lifetime. To reduce the statistical uncertainties that are naturally arising in estimates of design loads related to extreme waves, sufficient data must be gathered. In order to estimate the design loads it is common practice not to investigate all possible sea states (i.e. long-term analysis) but to investigate a few sea states and assume that the design value occurs at a prescribed probability level in the sea states with the same probability level (i.e. contour line approach). The estimate of the design value at that probability level is then based on results from a limited number of random realizations of these sea states. For linear or weakly nonlinear response types it is possible to estimate design loads accurately with a quite limited number of realizations. For strongly nonlinear problems however this is not possible due to the large statistical variation in the maximum observations, inherent to a random nonlinear process. Estimating accurately the tail of the load distribution requires many more realizations. This approach is restricted by time and costs and eventually one may have to accept an estimated design load with a large statistical uncertainty and account for the uncertainty with a higher safety margin. In this paper an improved methodology for estimating design loads related to extreme wave impacts will be presented. The methodology is based on screening many 3-hour realizations of the design sea states with simplified, fast but sufficiently accurate methods and to focus only on the potentially critical events with a model containing a more complete description of the physics. This can be either a model test or a non-linear impact simulation (i.e. CFD analysis). By doing this many more rare/critical events can be assessed, reducing the statistical uncertainty in the estimate of the design load.
{"title":"Efficient Indicators for Screening of Random Waves for Wave Impacts on a Jacket Platform and a Fixed Offshore Wind Turbine","authors":"T. Bunnik, J. Scharnke, E. Ridder","doi":"10.1115/omae2019-95481","DOIUrl":"https://doi.org/10.1115/omae2019-95481","url":null,"abstract":"\u0000 Renewed interest in wave impact assessment has risen for various reasons:\u0000 • The low airgap of some existing Mobile Units in the North Sea\u0000 • The COSL Innovator incident and related to this topic the new DNV-GL guidelines (OTG 13 and OTG 14).\u0000 • the installation of many large-diameter monopile foundations for wind turbines in increasingly deep water in the North Sea.\u0000 • The installation of many large-diameter wind turbines in increasingly deep water in the North Sea.\u0000 • Seabed subsidence (and maybe water level rises due to global warming) and their effect on the decreasing airgap of fixed platforms.\u0000 Wave impact assessment has been the subject of many recent studies and research projects, and there has been a strong knowledge and tool development during the last decade, both within model testing and numerical (CFD) analysis (Huang et.al (2017), de Ridder et.al, (2017), Vestbøstad et. al. (2017), Bunnik et.al. (2018)). However, there is still a lack of efficient methods and tools to properly analyze wave impacts and derive the statistical variation of these impacts in the sea states to which these structures are exposed during their lifetime.\u0000 To reduce the statistical uncertainties that are naturally arising in estimates of design loads related to extreme waves, sufficient data must be gathered. In order to estimate the design loads it is common practice not to investigate all possible sea states (i.e. long-term analysis) but to investigate a few sea states and assume that the design value occurs at a prescribed probability level in the sea states with the same probability level (i.e. contour line approach). The estimate of the design value at that probability level is then based on results from a limited number of random realizations of these sea states. For linear or weakly nonlinear response types it is possible to estimate design loads accurately with a quite limited number of realizations. For strongly nonlinear problems however this is not possible due to the large statistical variation in the maximum observations, inherent to a random nonlinear process. Estimating accurately the tail of the load distribution requires many more realizations. This approach is restricted by time and costs and eventually one may have to accept an estimated design load with a large statistical uncertainty and account for the uncertainty with a higher safety margin.\u0000 In this paper an improved methodology for estimating design loads related to extreme wave impacts will be presented. The methodology is based on screening many 3-hour realizations of the design sea states with simplified, fast but sufficiently accurate methods and to focus only on the potentially critical events with a model containing a more complete description of the physics. This can be either a model test or a non-linear impact simulation (i.e. CFD analysis). By doing this many more rare/critical events can be assessed, reducing the statistical uncertainty in the estimate of the design load. ","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84120782","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}
Industries rely mostly on off-shore resources to fulfill the increase in demand for oil and gas. In general, for oil extraction and various other refinery processes, fixed or floating structures are being utilized. Floating Production Storage and Offloading (FPSO) system is one of the floating systems which have advantage of storing the crude oil and, if required, it can be easily moved to other places. Also, in deep Ocean where sub-sea pipeline infrastructures are often not possible and so the FPSOs give alternate option of storing and processing the crude oil. Being moored-systems, FPSOs are very flexible structures having high surge natural period and hence they may undergo larger surge displacement. Excessive displacement may cause damage for the riser system also it may affect the workability under extreme sea condition. Therefore, there is a need for investigating the issues of safety, efficiency and response control of FPSO systems under different sea-state conditions. Ocean wave loads on FPSO causes dynamic interaction between FPSO vessel and liquid in the oil storage containers. The liquid motion in containers disturbs the dynamics of the vessel significantly. Hence, it is essential to study the surge response control of FPSO in detail. An easy way to control the response is to use the existing cargo containers of FPSO as passive damping devices. If the natural frequency of liquid oscillation is tuned to the natural frequency of FPSO, these cargo tanks can act as Multiple Tuned Liquid Dampers (MTLDs). In case of simple linear model, Tuned liquid damper (TLD) can be idealized as a Single Degree of Freedom (SDOF) system, namely Tuned Mass Damper (TMD). The present study attempts to model a TLD using three different TMD systems to account the effects of shallow water sloshing.
{"title":"Surge Response Control of FPSO Using Multiple Tuned Liquid Dampers: A Study on Effect of Multiple Frequencies in TLD","authors":"S. Gurusamy, Deepak Kumar","doi":"10.1115/omae2019-96062","DOIUrl":"https://doi.org/10.1115/omae2019-96062","url":null,"abstract":"\u0000 Industries rely mostly on off-shore resources to fulfill the increase in demand for oil and gas. In general, for oil extraction and various other refinery processes, fixed or floating structures are being utilized. Floating Production Storage and Offloading (FPSO) system is one of the floating systems which have advantage of storing the crude oil and, if required, it can be easily moved to other places. Also, in deep Ocean where sub-sea pipeline infrastructures are often not possible and so the FPSOs give alternate option of storing and processing the crude oil. Being moored-systems, FPSOs are very flexible structures having high surge natural period and hence they may undergo larger surge displacement. Excessive displacement may cause damage for the riser system also it may affect the workability under extreme sea condition. Therefore, there is a need for investigating the issues of safety, efficiency and response control of FPSO systems under different sea-state conditions. Ocean wave loads on FPSO causes dynamic interaction between FPSO vessel and liquid in the oil storage containers. The liquid motion in containers disturbs the dynamics of the vessel significantly. Hence, it is essential to study the surge response control of FPSO in detail.\u0000 An easy way to control the response is to use the existing cargo containers of FPSO as passive damping devices. If the natural frequency of liquid oscillation is tuned to the natural frequency of FPSO, these cargo tanks can act as Multiple Tuned Liquid Dampers (MTLDs). In case of simple linear model, Tuned liquid damper (TLD) can be idealized as a Single Degree of Freedom (SDOF) system, namely Tuned Mass Damper (TMD). The present study attempts to model a TLD using three different TMD systems to account the effects of shallow water sloshing.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77076338","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}
M. Larsen, Vikas Arora, M. Lützen, R. Pedersen, E. Putnam
Several methods for modelling and finite element analysis of tubular welded joints are described in various design codes. These codes provide specific recommendations for modelling of the welded joints, using simple weld geometries. In this paper, experimental hot-spot strain range results from a full-scale automatically welded K-node test are compared to corresponding finite element models. As part of investigating the automatically welded K-joint, 3D scans of the weld surfaces have been made. These scans are included in the FE models to determine the accuracy of the FE models. The results are compared to an FE model with a simple weld geometry based on common offshore design codes and a model without any modelled weld. The results show that the FE model with 3D scanned welds is more accurate than the two simple FE models. As the weld toe location of the 3D scanned weld is difficult to locate precisely in the FE model and as misplacement of strain gauges are possible, stochastic finite element modelling is performed to analyse the resulting probabilistic hot-spot stresses. The results show large standard deviations, showing the necessity to evaluate the hot-spot stress method when using 3D scanned welds.
{"title":"Use of 3D Scan of Weld Joint in Finite Element Analysis and Stochastic Analysis of Hot-Spot Stresses in Tubular Joint for Fatigue Life Estimation","authors":"M. Larsen, Vikas Arora, M. Lützen, R. Pedersen, E. Putnam","doi":"10.1115/omae2019-95704","DOIUrl":"https://doi.org/10.1115/omae2019-95704","url":null,"abstract":"\u0000 Several methods for modelling and finite element analysis of tubular welded joints are described in various design codes. These codes provide specific recommendations for modelling of the welded joints, using simple weld geometries. In this paper, experimental hot-spot strain range results from a full-scale automatically welded K-node test are compared to corresponding finite element models. As part of investigating the automatically welded K-joint, 3D scans of the weld surfaces have been made. These scans are included in the FE models to determine the accuracy of the FE models. The results are compared to an FE model with a simple weld geometry based on common offshore design codes and a model without any modelled weld. The results show that the FE model with 3D scanned welds is more accurate than the two simple FE models. As the weld toe location of the 3D scanned weld is difficult to locate precisely in the FE model and as misplacement of strain gauges are possible, stochastic finite element modelling is performed to analyse the resulting probabilistic hot-spot stresses. The results show large standard deviations, showing the necessity to evaluate the hot-spot stress method when using 3D scanned welds.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79769750","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 achievement of low cost and fast-track construction for new-build FPSO hulls are challenging problems. In order to solve these problems, the authors developed and reported unique modular design and multi-yard construction concept, “noah-FPSO Hull” [1][2][3]. Since then, the authors continued to improve its design and expanded its flexibility for harsh environment and customer’s requests. As a result, new standardized fore/aft modules and cargo tank module have been developed to expand the flexibility. This paper presents the design of the newly developed modules and the feasibility for harsh environment.
{"title":"Improved Design of Next Generation Hull-Platform “noah-FPSO Hull”","authors":"Shigeru Tanaka, Yasuhiro Sogawa","doi":"10.1115/omae2019-95269","DOIUrl":"https://doi.org/10.1115/omae2019-95269","url":null,"abstract":"\u0000 The achievement of low cost and fast-track construction for new-build FPSO hulls are challenging problems. In order to solve these problems, the authors developed and reported unique modular design and multi-yard construction concept, “noah-FPSO Hull” [1][2][3]. Since then, the authors continued to improve its design and expanded its flexibility for harsh environment and customer’s requests. As a result, new standardized fore/aft modules and cargo tank module have been developed to expand the flexibility.\u0000 This paper presents the design of the newly developed modules and the feasibility for harsh environment.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75286614","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 way polyester ropes change their length in response to tension is often represented using a static-dynamic model with parameters for dual linear stiffness, based on testing according to defined procedures. This may not be sufficient for the mooring analysis since the stretch response to tension of fiber ropes is nonlinear. In the Syrope Joint Industry Project, a model to be used in mooring analyses was developed together with a test procedure to obtain the parameters for this model. Based on these parameters and experience from the testing, an equivalent non-linear spring-dashpot model was developed. This model can predict the response in the rope also for other test procedures than those used for establishing the parameters in the analysis model. This demonstrates the validity of this Syrope analysis model.
{"title":"Spring-Dashpot Simulations of Polyester Ropes: Validation of the Syrope Model","authors":"E. Falkenberg, Limin Yang, Vidar Åhjem","doi":"10.1115/omae2019-95469","DOIUrl":"https://doi.org/10.1115/omae2019-95469","url":null,"abstract":"\u0000 The way polyester ropes change their length in response to tension is often represented using a static-dynamic model with parameters for dual linear stiffness, based on testing according to defined procedures. This may not be sufficient for the mooring analysis since the stretch response to tension of fiber ropes is nonlinear. In the Syrope Joint Industry Project, a model to be used in mooring analyses was developed together with a test procedure to obtain the parameters for this model. Based on these parameters and experience from the testing, an equivalent non-linear spring-dashpot model was developed. This model can predict the response in the rope also for other test procedures than those used for establishing the parameters in the analysis model. This demonstrates the validity of this Syrope analysis model.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73349710","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, D. Kang, E. Kim, M. S. Kim, T. Kim, H. J. Kim, D. Lee, Y. C. Park
A deep draft semi-submersible hull has been developed by SHI (Samsung Heavy Industries) and Williams 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 pontoon and column which secure the sufficient level of GM for the stability and ballast capacity for coping with the weight change of topside structures. The hull form also has the good global motion in waves to be able to use the SCR (Steel Catenary Riser) as a deep draft semi-submersible concept. Two hull forms are designed to have 4 columns with two different cross sections and the conventional ring pontoon. The compartmentation and basic hydrodynamic analysis are performed at the hull sizing stage to achieve the sufficient stability and the motion performance as well. The mooring systems are also designed for two different water depths of 1000m and 3000m as a standard design concept of hull including mooring lines. To verify the feasibility of the proposed hull concept with regard to the hydrostatic/hydrodynamic characteristics and mooring line design, the numerical global performance analyses are carried out. Hydrostatic stability is investigated for intact and damage condition of operational loading condition and the proper tank compartments are verified under the given topside weight and the environment condition in GOM. The global motion is validated for all the possible combinations of wave, wind, current for a site in central GOM. Through the frequency-domain analysis and quasi-static time-domain analysis as well, the essential items such as the maximum offset, mooring line tension/fatigue, air-gap and the extreme acceleration at topside are examined and confirms that the certain design criteria of Semi FPU (Floating Production Unit) operation are satisfied. The possibility of SCR usage is also investigated with the fully coupled time domain analysis using the preliminary design of risers and confirms that the designed hull form has the suitable hydrodynamic characteristics to permit the minimum motion performance for SCR in the sense of extreme load and fatigue life.
三星重工(Samsung Heavy Industries)和Williams开发了一种深吃水半潜式船体，作为一种标准化概念，它可以支持上层结构达到设备重量，以满足墨西哥湾特定的日产量水平。设计的船体具有优化的浮桥和柱的尺寸，确保了足够的GM水平，以保证稳定性和压舱能力，以应对上层结构的重量变化。船体形式还具有良好的波浪全局运动，可以使用SCR(钢悬链线立管)作为深吃水半潜式概念。两种船体形式被设计成有4根不同截面的柱子和传统的环形浮筒。在船体定尺阶段进行了隔舱和基本的水动力分析，以获得足够的稳定性和运动性能。作为船体包括系泊线的标准设计概念，系泊系统还设计用于两种不同的水深(1000米和3000米)。为了验证所提出的船体概念在水静力/水动力特性和系泊线设计方面的可行性，进行了数值整体性能分析。在给定的甲板重量和环境条件下，研究了作业载荷完好和损坏情况下的静水稳定性，并验证了适当的舱室。在墨西哥湾中部的一个地点，全球运动验证了波浪、风和电流的所有可能组合。通过频域分析和准静态时域分析，对最大偏移量、系泊索张力/疲劳、气隙、上部极值加速度等关键项目进行了校核，确定了半浮式生产单元运行的一定设计标准。利用立管的初步设计，通过全耦合时域分析，研究了SCR使用的可能性，并确认了所设计的船体形式具有合适的水动力特性，可以在极端载荷和疲劳寿命的意义上允许SCR的最小运动性能。
{"title":"Global Performance Analysis of Deep Draft Semi-Submersible Designed for Standard GOM Application","authors":"R. Yuck, D. Kang, E. Kim, M. S. Kim, T. Kim, H. J. Kim, D. Lee, Y. C. Park","doi":"10.1115/omae2019-95272","DOIUrl":"https://doi.org/10.1115/omae2019-95272","url":null,"abstract":"\u0000 A deep draft semi-submersible hull has been developed by SHI (Samsung Heavy Industries) and Williams 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 pontoon and column which secure the sufficient level of GM for the stability and ballast capacity for coping with the weight change of topside structures. The hull form also has the good global motion in waves to be able to use the SCR (Steel Catenary Riser) as a deep draft semi-submersible concept.\u0000 Two hull forms are designed to have 4 columns with two different cross sections and the conventional ring pontoon. The compartmentation and basic hydrodynamic analysis are performed at the hull sizing stage to achieve the sufficient stability and the motion performance as well. The mooring systems are also designed for two different water depths of 1000m and 3000m as a standard design concept of hull including mooring lines.\u0000 To verify the feasibility of the proposed hull concept with regard to the hydrostatic/hydrodynamic characteristics and mooring line design, the numerical global performance analyses are carried out. Hydrostatic stability is investigated for intact and damage condition of operational loading condition and the proper tank compartments are verified under the given topside weight and the environment condition in GOM.\u0000 The global motion is validated for all the possible combinations of wave, wind, current for a site in central GOM. Through the frequency-domain analysis and quasi-static time-domain analysis as well, the essential items such as the maximum offset, mooring line tension/fatigue, air-gap and the extreme acceleration at topside are examined and confirms that the certain design criteria of Semi FPU (Floating Production Unit) operation are satisfied. The possibility of SCR usage is also investigated with the fully coupled time domain analysis using the preliminary design of risers and confirms that the designed hull form has the suitable hydrodynamic characteristics to permit the minimum motion performance for SCR in the sense of extreme load and fatigue life.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86112003","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}
Gurumurthy Kagita, Mahesh B. Addala, G.G.S. Achary, S. Sripada
In the mating phase of float-over operation, the topsides deck load from the vessel is transferred onto the jacket either by ballasting the vessel or by the combination of ballasting and hydraulic jacking system. During this phase of operation, the topsides and jacket experience impact loads through the contact points in a short duration of time. To evaluate the impact loads and to capture the transient effects precisely, a non-linear time domain hydrodynamic analysis is required. To obtain the design loads, generally the numerical jacking simulation is initiated at the time instant of maximum wave height when the jacking system is used. However, the conservative response may also depend on the relative velocity between the jacket and topsides legs. In this paper, a series of non-linear time domain as well as linear frequency domain hydrodynamic analyses are performed to evaluate the impact loads between 9000 tonne integrated topsides deck and a 4-legged jacket in a water depth of 50 m during float-over mating operation. The simulations are performed using MOSES software. The float-over hardware such as LMUs (leg mating unit), DSUs (deck support unit), Jacks, Fenders and Mooring lines are modelled as appropriate linear / nonlinear springs. The principle of the mating operation is considered through a combination of vessel ballasting and jacking operation. This paper discusses about random wave seed selection, effect of vessel response and wave headings on the impact loads of LMUs and Jacks/DSUs.
{"title":"Evaluation of Impact Loads on Offshore Jacket Platform During Float-Over Mating Operation","authors":"Gurumurthy Kagita, Mahesh B. Addala, G.G.S. Achary, S. Sripada","doi":"10.1115/omae2019-95467","DOIUrl":"https://doi.org/10.1115/omae2019-95467","url":null,"abstract":"\u0000 In the mating phase of float-over operation, the topsides deck load from the vessel is transferred onto the jacket either by ballasting the vessel or by the combination of ballasting and hydraulic jacking system. During this phase of operation, the topsides and jacket experience impact loads through the contact points in a short duration of time. To evaluate the impact loads and to capture the transient effects precisely, a non-linear time domain hydrodynamic analysis is required. To obtain the design loads, generally the numerical jacking simulation is initiated at the time instant of maximum wave height when the jacking system is used. However, the conservative response may also depend on the relative velocity between the jacket and topsides legs. In this paper, a series of non-linear time domain as well as linear frequency domain hydrodynamic analyses are performed to evaluate the impact loads between 9000 tonne integrated topsides deck and a 4-legged jacket in a water depth of 50 m during float-over mating operation. The simulations are performed using MOSES software. The float-over hardware such as LMUs (leg mating unit), DSUs (deck support unit), Jacks, Fenders and Mooring lines are modelled as appropriate linear / nonlinear springs. The principle of the mating operation is considered through a combination of vessel ballasting and jacking operation. This paper discusses about random wave seed selection, effect of vessel response and wave headings on the impact loads of LMUs and Jacks/DSUs.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78902053","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}
This project investigates a cantilevered cylinder projecting down into the water column moving at high velocity through still water, as is applicable to submarine masts. Surface-piercing cylinders differ from fully submerged cylinders due to the generation of surface wakes and under increasing flow speeds the formation of a ventilated pocket in the lee of the cylinder, both of which grow with increasing velocity, with concomitant effects on the hydrodynamic loading. The relative length of submergence, or immersed aspect ratio (L/D) and end conditions of the cylinder with respect to tip vortex drag effects may also impact the hydrodynamic loads and wake formation. Laboratory testing of surface-piercing cylinders to date has predominantly been confined to characterising the wakes shed from a rigid cylinder cantilevered down into the water from a towing tank carriage, which under certain test conditions will also exhibit significant Vortex-Induced-Vibration (VIV), though not adequately identified and accounted for in its magnification of drag and wake.
{"title":"Hydrodynamics of Towed Vertical Surface-Piercing Cylinders","authors":"Douglas A. Potts, J. Binns, H. Marcollo, A. Potts","doi":"10.1115/omae2019-95109","DOIUrl":"https://doi.org/10.1115/omae2019-95109","url":null,"abstract":"\u0000 This project investigates a cantilevered cylinder projecting down into the water column moving at high velocity through still water, as is applicable to submarine masts. Surface-piercing cylinders differ from fully submerged cylinders due to the generation of surface wakes and under increasing flow speeds the formation of a ventilated pocket in the lee of the cylinder, both of which grow with increasing velocity, with concomitant effects on the hydrodynamic loading. The relative length of submergence, or immersed aspect ratio (L/D) and end conditions of the cylinder with respect to tip vortex drag effects may also impact the hydrodynamic loads and wake formation. Laboratory testing of surface-piercing cylinders to date has predominantly been confined to characterising the wakes shed from a rigid cylinder cantilevered down into the water from a towing tank carriage, which under certain test conditions will also exhibit significant Vortex-Induced-Vibration (VIV), though not adequately identified and accounted for in its magnification of drag and wake.","PeriodicalId":23567,"journal":{"name":"Volume 1: Offshore Technology; Offshore Geotechnics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85933043","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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