S. Yeon, Hyunchul Jang, Jang-Whan Kim, Joo-Sung Kim, B. Nam, Z. Huang, J. O'Sullivan, Hyun Joe Kim, S. Hong
This paper summarizes a joint effort, TESK JDP, initiated by TechnipFMC, ExxonMobil Upstream Research Company (EMURC), Samsung Heavy Industries (SHI) and Korea Research Institute of Ships & Ocean Engineering (KRISO) in order to develop reliable modeling practices for the application of Computational Fluid Dynamics (CFD) to the design of the offshore floating structures. The modeling practice for the wind load on offshore floating structures, which was one of the topics in this JDP, was studied and verified against model test results. The wind load on the offshore floating structures mostly depends on the shape of the wind profile rather than the design wind speed. Much weight is put on the generation and retainment of the wind profile within the computational domain. The modeling practice for generating the wind profile referred to as sustainable atmospheric boundary layer (ABL) or horizontally homogeneous turbulent boundary layer (HHTBL) as well as domain size, mesh strategy, turbulence model are used to perform wind load simulations for a semi-submersible and FPSO respectively as a blind test between JDP members. In order to minimize uncertainties from geometric similarity, special care was taken during the simulation and model test for the FPSO due to the complicated top side modules. Given the modeling practice, the results are compared between JDP members and show consistent tendency. Also, a good agreement was observed for the hydrodynamic coefficients of the wind load for both the FPSO and semi-submersible.
{"title":"Numerical Modeling Practice and Verification of the Wind Load Estimation for FPSO and Semi-Submersible","authors":"S. Yeon, Hyunchul Jang, Jang-Whan Kim, Joo-Sung Kim, B. Nam, Z. Huang, J. O'Sullivan, Hyun Joe Kim, S. Hong","doi":"10.1115/omae2019-96429","DOIUrl":"https://doi.org/10.1115/omae2019-96429","url":null,"abstract":"This paper summarizes a joint effort, TESK JDP, initiated by TechnipFMC, ExxonMobil Upstream Research Company (EMURC), Samsung Heavy Industries (SHI) and Korea Research Institute of Ships & Ocean Engineering (KRISO) in order to develop reliable modeling practices for the application of Computational Fluid Dynamics (CFD) to the design of the offshore floating structures. The modeling practice for the wind load on offshore floating structures, which was one of the topics in this JDP, was studied and verified against model test results.\u0000 The wind load on the offshore floating structures mostly depends on the shape of the wind profile rather than the design wind speed. Much weight is put on the generation and retainment of the wind profile within the computational domain. The modeling practice for generating the wind profile referred to as sustainable atmospheric boundary layer (ABL) or horizontally homogeneous turbulent boundary layer (HHTBL) as well as domain size, mesh strategy, turbulence model are used to perform wind load simulations for a semi-submersible and FPSO respectively as a blind test between JDP members. In order to minimize uncertainties from geometric similarity, special care was taken during the simulation and model test for the FPSO due to the complicated top side modules. Given the modeling practice, the results are compared between JDP members and show consistent tendency. Also, a good agreement was observed for the hydrodynamic coefficients of the wind load for both the FPSO and semi-submersible.","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":"74135573","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}
Model tests under 1g condition and numerical simulations of spudcan penetration in the silty fine sand were conducted to study effects of spudcan penetration on the p-delta effect of adjacent free-head and elastic-head piles subjected to lateral and vertical head loads. The p-delta factors were defined and determined based on the maximum pile shaft bending moments and pile head deflections before and after spudcan penetration, which were used to analyze the variations of the p-delta effect with the spudcan penetration depth. The conclusions were obtained as follows. The p-delta effect depends on the pile head constraint condition, the direction of the lateral pile head load and the spudcan penetration depth. For a free-head pile, the p-delta factors decrease with increasing the spudcan penetration depth. For an elastic-head pile, the p-delta factors also decrease during spudcan penetration and the decreases depend on the spudcan penetration depth and the lateral pile head load direction. The decrease associated with the lateral load direction facing back to the spudcan is larger than that associated with the lateral load direction facing to the spudcan. Therefore, the spudcan penetration does not increase the p-delta effect of adjacent piles subjected to lateral and vertical head loads. But the maximum bending moment and its occurring position change during spudcan penetration.
{"title":"Model Tests and Numerical Simulation on Effect of Spudcan Penetration on P-Delta of an Adjacent Pile","authors":"Jianhua Wang, Fan Yifei, Dong Guo","doi":"10.1115/omae2019-95752","DOIUrl":"https://doi.org/10.1115/omae2019-95752","url":null,"abstract":"\u0000 Model tests under 1g condition and numerical simulations of spudcan penetration in the silty fine sand were conducted to study effects of spudcan penetration on the p-delta effect of adjacent free-head and elastic-head piles subjected to lateral and vertical head loads. The p-delta factors were defined and determined based on the maximum pile shaft bending moments and pile head deflections before and after spudcan penetration, which were used to analyze the variations of the p-delta effect with the spudcan penetration depth. The conclusions were obtained as follows. The p-delta effect depends on the pile head constraint condition, the direction of the lateral pile head load and the spudcan penetration depth. For a free-head pile, the p-delta factors decrease with increasing the spudcan penetration depth. For an elastic-head pile, the p-delta factors also decrease during spudcan penetration and the decreases depend on the spudcan penetration depth and the lateral pile head load direction. The decrease associated with the lateral load direction facing back to the spudcan is larger than that associated with the lateral load direction facing to the spudcan. Therefore, the spudcan penetration does not increase the p-delta effect of adjacent piles subjected to lateral and vertical head loads. But the maximum bending moment and its occurring position change during spudcan penetration.","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":"75718135","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}
Anurag Yenduri, A. Magee, J. Liu, W. Xu, A. Choudhary, A. Hussain
Side-by-side operation of multiple floaters in the ocean environment is very challenging and the operators always prefer a maximum operable weather window, in order to minimise the cost incurred from the downtime. The safety of the gangway connecting the floaters is very crucial and its dynamic response in the ocean environment raises concerns during operations. Therefore, an efficient dynamic positioning system is essential to maintain the floater and ultimately, the gangway response within the desired limits. In this work, a novel dynamic positioning system for floater operating aside another vessel is presented. The system includes an adaptive controller combined an optimised thruster allocation law and with a sea state detector. The adaptive control is achieved by using the barrier Lyapunov function and a predictor-based method in combination with the neural network scheme. The limitations include the saturation of inputs and the forbidden zones due to thruster-thruster or thruster-hull interaction. An optimised allocation for lower fuel consumption, wear and tear of the thruster equipment and to ensure the resultant command in the respective direction of the azimuth thrusters is designed. The optimisation here is a non-convex problem and a locally convex reformulation of second order is implemented. The presence of unknown shielding effect due to nearby vessel in a side-by-side configuration and input time delay is also considered in the development of this thruster allocation law. In order to overcome these effects, a novel sea state detector is designed. The sea state detector can effectively monitor the variation of drift wave-induced force on the vessel and activate the neural network compensator in the controller when a large wave drift force is identified. Simulation studies are conducted to verify the efficiency of this dynamic position system and a demonstration of flotel in side-by-side configuration with a turret moored FPSO is presented for the non-collinear ocean environment.
{"title":"Realistic Adaptive DP Controller for Flotel Operating in Side-by-Side Configuration With FPSO","authors":"Anurag Yenduri, A. Magee, J. Liu, W. Xu, A. Choudhary, A. Hussain","doi":"10.1115/omae2019-96577","DOIUrl":"https://doi.org/10.1115/omae2019-96577","url":null,"abstract":"\u0000 Side-by-side operation of multiple floaters in the ocean environment is very challenging and the operators always prefer a maximum operable weather window, in order to minimise the cost incurred from the downtime. The safety of the gangway connecting the floaters is very crucial and its dynamic response in the ocean environment raises concerns during operations. Therefore, an efficient dynamic positioning system is essential to maintain the floater and ultimately, the gangway response within the desired limits. In this work, a novel dynamic positioning system for floater operating aside another vessel is presented. The system includes an adaptive controller combined an optimised thruster allocation law and with a sea state detector. The adaptive control is achieved by using the barrier Lyapunov function and a predictor-based method in combination with the neural network scheme. The limitations include the saturation of inputs and the forbidden zones due to thruster-thruster or thruster-hull interaction. An optimised allocation for lower fuel consumption, wear and tear of the thruster equipment and to ensure the resultant command in the respective direction of the azimuth thrusters is designed. The optimisation here is a non-convex problem and a locally convex reformulation of second order is implemented. The presence of unknown shielding effect due to nearby vessel in a side-by-side configuration and input time delay is also considered in the development of this thruster allocation law. In order to overcome these effects, a novel sea state detector is designed. The sea state detector can effectively monitor the variation of drift wave-induced force on the vessel and activate the neural network compensator in the controller when a large wave drift force is identified. Simulation studies are conducted to verify the efficiency of this dynamic position system and a demonstration of flotel in side-by-side configuration with a turret moored FPSO is presented for the non-collinear ocean 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":"84428137","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}
In this study, direct time domain offloading simulations are conducted without condensing the metocean data using High Performance Computing (HPC). With rapidly growing computing power, from increased CPU speeds and parallel processing capability, the direct time domain simulation for offloading analyses has become a practical option. For instance, 3-hour time domain simulations, covering the entire service life (e.g. 100,000 simulations for 35 years) of a floating platform, can now be conducted within a day. The simulation results provide realistic offloading operational time windows which consider both offloading operation sequence (i.e. berthing, connection, offloading duration and disconnection) and required criteria (i.e. relative responses, loads on hawser and flow line, etc.). The direct time domain offloading analyses improve the prediction of offloading operability, the sizing of the FPSO tank capacity, and the shuttle tanker selection. In addition, this method enables accurate evaluations of the economic feasibility for field development using FPSOs.
{"title":"Direct Time Domain Simulations for a FPSO Tandem Offloading Operation","authors":"Bonjun Koo, Manoj Jegannathan, J. Kyoung, H. Lim","doi":"10.1115/omae2019-96638","DOIUrl":"https://doi.org/10.1115/omae2019-96638","url":null,"abstract":"\u0000 In this study, direct time domain offloading simulations are conducted without condensing the metocean data using High Performance Computing (HPC). With rapidly growing computing power, from increased CPU speeds and parallel processing capability, the direct time domain simulation for offloading analyses has become a practical option. For instance, 3-hour time domain simulations, covering the entire service life (e.g. 100,000 simulations for 35 years) of a floating platform, can now be conducted within a day. The simulation results provide realistic offloading operational time windows which consider both offloading operation sequence (i.e. berthing, connection, offloading duration and disconnection) and required criteria (i.e. relative responses, loads on hawser and flow line, etc.). The direct time domain offloading analyses improve the prediction of offloading operability, the sizing of the FPSO tank capacity, and the shuttle tanker selection. In addition, this method enables accurate evaluations of the economic feasibility for field development using FPSOs.","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":"85382637","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}
Yunfei Teng, Liang Cheng, H. An, F. Tong, T. Griffiths, Wei Sun, Jiawei Chi, Zhijian Xiong
Experimental investigations on the hydrodynamic forces on an intermittently spanning pipeline exposed to steady currents were carried out. The effect of intermittent local spanning sections on the global hydrodynamic behavior was studied by changing the ratio between the non-spanning length (B) and the total length (L), namely the blocking ratio B / L. A range of gap height (G) to diameter (D) ratios, i.e. gap ratio G / D, and 4 different Reynolds numbers (Re) in the subcritical region were tested in the experiments. The results show: i) for a certain gap ratio, the mean drag increases gently with the decreasing blocking ratio at Re = 5.5 × 104, whereas the mean lift decreases significantly with the decreasing blocking ratio at all values of Re tested; and ii) for a certain blocking ratio, increasing the gap ratio leads to an increase in mean drag and decrease in mean lift. Further, simple approaches are proposed based on the present dataset for estimating the global effects on hydrodynamic drag and lift forces due to local spanning geometry.
{"title":"Hydrodynamic Forces on Intermittently Spanning Pipelines in Steady Currents","authors":"Yunfei Teng, Liang Cheng, H. An, F. Tong, T. Griffiths, Wei Sun, Jiawei Chi, Zhijian Xiong","doi":"10.1115/omae2019-95585","DOIUrl":"https://doi.org/10.1115/omae2019-95585","url":null,"abstract":"\u0000 Experimental investigations on the hydrodynamic forces on an intermittently spanning pipeline exposed to steady currents were carried out. The effect of intermittent local spanning sections on the global hydrodynamic behavior was studied by changing the ratio between the non-spanning length (B) and the total length (L), namely the blocking ratio B / L. A range of gap height (G) to diameter (D) ratios, i.e. gap ratio G / D, and 4 different Reynolds numbers (Re) in the subcritical region were tested in the experiments. The results show: i) for a certain gap ratio, the mean drag increases gently with the decreasing blocking ratio at Re = 5.5 × 104, whereas the mean lift decreases significantly with the decreasing blocking ratio at all values of Re tested; and ii) for a certain blocking ratio, increasing the gap ratio leads to an increase in mean drag and decrease in mean lift. Further, simple approaches are proposed based on the present dataset for estimating the global effects on hydrodynamic drag and lift forces due to local spanning geometry.","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":"85697679","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 paper addresses the selection of an appropriate consolidation coefficient for the analysis of drainage beneath foundations and pipelines in offshore geotechnical design. An emerging trend in the design of subsea infrastructure is the consideration of ‘whole life’ effects — namely the changes in soil properties and geotechnical capacity over the operating life. Seabed pipelines that undergo repeated thermal expansion and contraction cause shearing and consolidation in the underlying soil, leading to significant changes in the available seabed friction. Also, foundations that are either fixed or designed to slide on the seabed, are subjected to intermittent loads interspersed with periods of consolidation. These also cause a change in seabed strength and geotechnical capacity. To assess the time over which these effects occur, and therefore their influence on the response and the reliability of the system, it is necessary to perform consolidation calculations, using an appropriate consolidation coefficient. This paper presents observed operative consolidation coefficients drawn from recent model testing measurements and numerical analyses. It is shown that the consolidation rate can vary by more than an order of magnitude for the same soil profile under different loading conditions, due to the differences in stiffness and permeability. Meanwhile, design parameters are commonly drawn from one-dimensional oedometer compression tests. This compendium of data highlights the potential variation in consolidation coefficient for different loading types and through the ‘whole life’ of infrastructure. A key conclusion is that consolidation effects generally occur faster than is commonly assumed, meaning that changes in strength and stiffness — that are commonly beneficial in design — may be more readily relied on than is done so in current practice.
{"title":"On the Selection of an Appropriate Consolidation Coefficient for Offshore Geotechnical Design","authors":"D. White, Jinbo Chen, S. Gourvenec, C. O’Loughlin","doi":"10.1115/OMAE2019-95800","DOIUrl":"https://doi.org/10.1115/OMAE2019-95800","url":null,"abstract":"\u0000 This paper addresses the selection of an appropriate consolidation coefficient for the analysis of drainage beneath foundations and pipelines in offshore geotechnical design. An emerging trend in the design of subsea infrastructure is the consideration of ‘whole life’ effects — namely the changes in soil properties and geotechnical capacity over the operating life.\u0000 Seabed pipelines that undergo repeated thermal expansion and contraction cause shearing and consolidation in the underlying soil, leading to significant changes in the available seabed friction. Also, foundations that are either fixed or designed to slide on the seabed, are subjected to intermittent loads interspersed with periods of consolidation. These also cause a change in seabed strength and geotechnical capacity.\u0000 To assess the time over which these effects occur, and therefore their influence on the response and the reliability of the system, it is necessary to perform consolidation calculations, using an appropriate consolidation coefficient. This paper presents observed operative consolidation coefficients drawn from recent model testing measurements and numerical analyses. It is shown that the consolidation rate can vary by more than an order of magnitude for the same soil profile under different loading conditions, due to the differences in stiffness and permeability. Meanwhile, design parameters are commonly drawn from one-dimensional oedometer compression tests.\u0000 This compendium of data highlights the potential variation in consolidation coefficient for different loading types and through the ‘whole life’ of infrastructure. A key conclusion is that consolidation effects generally occur faster than is commonly assumed, meaning that changes in strength and stiffness — that are commonly beneficial in design — may be more readily relied on than is done so in current practice.","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":"88444466","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}
Subsea 7 is supporting its offshore fleet by incorporating emulation. Virtualising the actual control system software used offshore and integrating a high resolution functional 3D “digital twin” model of its vessels and equipment. Subsea 7 can effectively test control systems under as near to live conditions as possible by also incorporating historical dynamic positioning archives of vessel sea states and other external influences such as temperatures, loads and faults into the system. Using the Subsea 7 emulation techniques means operatives can be trained on exact virtualised control system software in advance of actual construction and as a result, software faults can be highlighted, de-bugged and rectified using the emulator system. The digital twin models can also be used to facilitate efficient planning of deck operations. This paper demonstrates how technology helps improve Subsea 7’s offshore operations. Methods, Procedures, Process: A vessel emulation room is in use for control system testing and familiarisation of construction equipment, including for instance, lay, crane or diving systems and is currently developing its library of vessel functional 3D models with full integration to the control system software. By use of physics engine feedback into the functional 3D model and control systems, projects operations can be verified. Results, Observations, and Conclusions: It is proven using emulation from an office base, for vessels operating anywhere in the world, that Subsea 7 are able to save significant costs and time. The emulations can be re-used and expanded for the full life cycle of the equipment. Over 90% of software bugs can be ironed out prior to installation, a significant advantage for Operations. Novel/Additive Information: This paper describes a significant step towards the digitalisation of the Subsea 7 fleet and equipment incorporating the actual control system software used to operate the equipment.
{"title":"How Emulation Improves Offshore Operations","authors":"L. McGuire","doi":"10.1115/omae2019-95178","DOIUrl":"https://doi.org/10.1115/omae2019-95178","url":null,"abstract":"\u0000 Subsea 7 is supporting its offshore fleet by incorporating emulation. Virtualising the actual control system software used offshore and integrating a high resolution functional 3D “digital twin” model of its vessels and equipment. Subsea 7 can effectively test control systems under as near to live conditions as possible by also incorporating historical dynamic positioning archives of vessel sea states and other external influences such as temperatures, loads and faults into the system. Using the Subsea 7 emulation techniques means operatives can be trained on exact virtualised control system software in advance of actual construction and as a result, software faults can be highlighted, de-bugged and rectified using the emulator system. The digital twin models can also be used to facilitate efficient planning of deck operations. This paper demonstrates how technology helps improve Subsea 7’s offshore operations.\u0000 Methods, Procedures, Process: A vessel emulation room is in use for control system testing and familiarisation of construction equipment, including for instance, lay, crane or diving systems and is currently developing its library of vessel functional 3D models with full integration to the control system software. By use of physics engine feedback into the functional 3D model and control systems, projects operations can be verified.\u0000 Results, Observations, and Conclusions: It is proven using emulation from an office base, for vessels operating anywhere in the world, that Subsea 7 are able to save significant costs and time. The emulations can be re-used and expanded for the full life cycle of the equipment. Over 90% of software bugs can be ironed out prior to installation, a significant advantage for Operations.\u0000 Novel/Additive Information: This paper describes a significant step towards the digitalisation of the Subsea 7 fleet and equipment incorporating the actual control system software used to operate the equipment.","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":"89527546","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 paper presents the development and application of an in-house manoeuvring method for the prediction of the track of a moored vessel in the case of a temporary or total loss of station keeping capability as a result of exceeded permissible anchor loads. The described method is implemented in the in-house ship design environment E4, which already contains a method for manoeuvring simulations. The equations of motion are solved for three degrees of freedom: surge, sway and yaw. Any effects due to dynamic heel are considered quasi-statically. The method is based on a force model with components for environmental and body forces as well as propeller, rudder and steering forces for dynamic positioning applications. For the purpose of mooring system analysis an additional force component for the mooring line loads is introduced by using load-deflection curves. These curves can be calculated within E4 or imported from other sources. The resulting method allows detailed response calculations in the time-domain and can be used in various applications due to its great computational efficiency. In the presented paper the method is used for the analysis of a marine casualty due to harsh weather conditions.
{"title":"Trajectory Prediction of Moored Vessels With Reduced Station Keeping Capability due to Exceeded Anchor Load Limits","authors":"M. Josten","doi":"10.1115/omae2019-96145","DOIUrl":"https://doi.org/10.1115/omae2019-96145","url":null,"abstract":"\u0000 This paper presents the development and application of an in-house manoeuvring method for the prediction of the track of a moored vessel in the case of a temporary or total loss of station keeping capability as a result of exceeded permissible anchor loads. The described method is implemented in the in-house ship design environment E4, which already contains a method for manoeuvring simulations. The equations of motion are solved for three degrees of freedom: surge, sway and yaw. Any effects due to dynamic heel are considered quasi-statically. The method is based on a force model with components for environmental and body forces as well as propeller, rudder and steering forces for dynamic positioning applications. For the purpose of mooring system analysis an additional force component for the mooring line loads is introduced by using load-deflection curves. These curves can be calculated within E4 or imported from other sources. The resulting method allows detailed response calculations in the time-domain and can be used in various applications due to its great computational efficiency. In the presented paper the method is used for the analysis of a marine casualty due to harsh weather conditions.","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":"76806030","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}
Jiaguo Feng, Yi Yu, Yan-cheng Qu, Wenhui Xie, Min Wu, Jingrui Zhao
The stability of platform is important to ensure the platforms are safe, especially during the mooring line breaking process in typhoon condition. The paper presents a stability analysis method for floating platforms of the mooring line breaking process based on the time-domain analysis. The time-domain simulation during the mooring line breaking is provided. The time of the mooring line break, the max tilt angle of platform and the amended equivalent overturning moment are calculated for the stability analysis. The results show that the platform would have a serious tilt when the mooring line breaks, this increases the overturning moments and may cause the platform not meets the stability requirements during this process. It is necessary to pay attention to the stability problem during the mooring line breaking process in typhoon condition. And properly locating the down-flooding points is recommended to avoide the stability problem.
{"title":"A Conjoint Analysis of the Stability and Time-Domain Analysis on Floating Platform During Mooring Line Breaking","authors":"Jiaguo Feng, Yi Yu, Yan-cheng Qu, Wenhui Xie, Min Wu, Jingrui Zhao","doi":"10.1115/omae2019-96661","DOIUrl":"https://doi.org/10.1115/omae2019-96661","url":null,"abstract":"\u0000 The stability of platform is important to ensure the platforms are safe, especially during the mooring line breaking process in typhoon condition. The paper presents a stability analysis method for floating platforms of the mooring line breaking process based on the time-domain analysis. The time-domain simulation during the mooring line breaking is provided. The time of the mooring line break, the max tilt angle of platform and the amended equivalent overturning moment are calculated for the stability analysis. The results show that the platform would have a serious tilt when the mooring line breaks, this increases the overturning moments and may cause the platform not meets the stability requirements during this process. It is necessary to pay attention to the stability problem during the mooring line breaking process in typhoon condition. And properly locating the down-flooding points is recommended to avoide the stability problem.","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":"72871270","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}
Compared with other types of anchors, gravity-installed anchors (GIAs) have several main advantages such as simple structure, convenient installation way and cost reduction. The torpedo anchor is one type of GIAs. The geometric configurations have a direct influence on the hydrodynamic characteristics of the anchor, and thus affect its installation performance in water. The present work aimed to put forward some new aspects for optimizing the existing geometries of torpedo anchors by comprehensively improving the hydrodynamic characteristics of the anchor during installation in water. A computational fluid dynamics (CFD) model was established and numerical simulations were carried out using the software of ANSYS FLUENT. The hydrodynamic characteristics concerned involved the drag coefficient, the terminal velocity and the directional stability. The present study paid more attention to the fin’s design. By changing the fin parameters, including the aspect ratio and the area of the fin, the optimum design method of the fin was proposed, which would make sure of a higher terminal velocity as well as good directional stability. Besides, effects of the mass distribution on the hydrodynamic characteristics were investigated. The present work provides a design reference for torpedo anchors and is also beneficial to the research and development of new types of GIAs.
{"title":"CFD Analysis on Hydrodynamic Characteristics for Optimizing Torpedo Anchors","authors":"Jing Sun, Haixiao Liu","doi":"10.1115/omae2019-95778","DOIUrl":"https://doi.org/10.1115/omae2019-95778","url":null,"abstract":"\u0000 Compared with other types of anchors, gravity-installed anchors (GIAs) have several main advantages such as simple structure, convenient installation way and cost reduction. The torpedo anchor is one type of GIAs. The geometric configurations have a direct influence on the hydrodynamic characteristics of the anchor, and thus affect its installation performance in water. The present work aimed to put forward some new aspects for optimizing the existing geometries of torpedo anchors by comprehensively improving the hydrodynamic characteristics of the anchor during installation in water. A computational fluid dynamics (CFD) model was established and numerical simulations were carried out using the software of ANSYS FLUENT. The hydrodynamic characteristics concerned involved the drag coefficient, the terminal velocity and the directional stability. The present study paid more attention to the fin’s design. By changing the fin parameters, including the aspect ratio and the area of the fin, the optimum design method of the fin was proposed, which would make sure of a higher terminal velocity as well as good directional stability. Besides, effects of the mass distribution on the hydrodynamic characteristics were investigated. The present work provides a design reference for torpedo anchors and is also beneficial to the research and development of new types of GIAs.","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":"73160922","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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