Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data...Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data that mooring system designers aim to acquire.To address the need for long-term continuous monitoring of mooring tension in deep-sea marine environments,this paper presents a mooring cable tension monitoring method based on the principle of direct mechanical measurement.The developed tension monitoring sensors were installed and applied in the mooring system of the"Yongle"scientific experimental platform.Over the course of one year,a substantial amount of in-situ tension monitoring data was obtained.Under wave heights of up to 1.24 m,the mooring tension on the floating platform reached 16.5 tons.Through frequency domain and time domain analysis,the spectral characteristics of mooring tension,including waveinduced force,slow drift force,and mooring cable elastic restoring force,were determined.The mooring cable elastic restoring force frequency was approximately half of that of the wave signal.Due to the characteristics of the hinge connection structure of the dual module floating platform,under some specific working conditions the wave-induced force was the maximum of the three different frequency forces,and restoring force was the smallest.展开更多
In the process of developing oil and gas resources in the Arctic,the impact of icebergs can pose a considerable threat to the structural safety of semi-submersible mooring platforms in ice regions.On the basis of the ...In the process of developing oil and gas resources in the Arctic,the impact of icebergs can pose a considerable threat to the structural safety of semi-submersible mooring platforms in ice regions.On the basis of the arbitrary Lagrangian Eulerian(ALE)algorithm,a numerical model for the interaction between an iceberg and a semi-submersible mooring platform is built in this work.First,a mooring system with a link element is designed and validated.An ice material model for the target iceberg is built and validated.A numerical model for the interaction between an iceberg and a semi-submersible mooring platform is then built.A parametric study(cable angle,tension angle and number of cables)is carried out to study the performance of the mooring system.The collision process between the semi-submersible mooring platform and the iceberg in the polar marine environment can be predicted by the present numerical model,and then the optimal mooring arrangement scheme can be obtained.The research results in this work can provide a reference for the design of mooring systems.展开更多
This study employs the Smoothed Particle Hydrodynamics(SPH)method to develop a computational fluid dynamics(CFD)model for analyzing the interaction between rogue waves and mooring systems.Four floating body configurat...This study employs the Smoothed Particle Hydrodynamics(SPH)method to develop a computational fluid dynamics(CFD)model for analyzing the interaction between rogue waves and mooring systems.Four floating body configurations are investigated:(1)dual rectangular prisms,(2)rectangular prism–sphere composites,(3)sphere–rectangular prism composites,and(4)dual spheres.These configurations are systematically evaluated under varying mooring conditions to assess their hydrodynamic performance and wave attenuation capabilities.The model accurately captures the complex fluid–structure interaction dynamics between moored floating breakwaters and incident wave fields.Among the configurations,the dual rectangular prism system demonstrates superior performance in both wave dissipation and mooring force reduction.Under conditions involving dual wave makers,the influence of floating body shape and number on wave height is found to be minimal.However,dual-body arrangements consistently outperform single-body setups in terms of both energy dissipation and structural stability.From a cost-efficiency perspective,the configuration comprising two rectangular prisms connected via a single mooring system offers significant advantages in material usage and deployment feasibility.展开更多
To address the mooring issues of floating photovoltaic systems in areas with large tidal variations,three mooring schemes were designed and compared in this paper:anchor chain,anchor chain with added weights,and ancho...To address the mooring issues of floating photovoltaic systems in areas with large tidal variations,three mooring schemes were designed and compared in this paper:anchor chain,anchor chain with added weights,and anchor chain with Superflex.The model was established via the numerical simulation tool Orcaflex,which considers the combined effects of wind,waves,and currents.A time-domain coupled dynamic analysis was conducted on the performance of the three mooring schemes under various tidal conditions to determine the mooring cable tension and platform motion response.Furthermore,the mooring system with an anchor chain and Superflex was optimized,with a focus on analyzing the effects of the Superflex length,the diameter of the anchor chains,and the mooring radius.The mooring system with the anchor chain and Superflex exhibits more controllable and stable mooring performance in areas with large tidal variations,so that it more effectively maintains the required mooring tension level.These findings not only provide a reference for the feasibility and optimization design of photovoltaic systems in areas with large tidal variations but also offer valuable experience for the sustainable application of clean energy under specific environmental conditions.展开更多
Inductively coupled mooring chain transmission technology plays a crucial role in the long-distance online monitoring of marine hydrographic information.However,the impedance characteristics of the seawater medium pos...Inductively coupled mooring chain transmission technology plays a crucial role in the long-distance online monitoring of marine hydrographic information.However,the impedance characteristics of the seawater medium pose a limitation on its capability to achieve high-speed real-time transmission of underwater images.In this paper,based on the principle of inductively coupled transmission for marine applications,the selected 1920×1080 pixel images are segmented,packaged,and then transmitted to the sending node using the user datagram protocol(UDP),and the modulation and demodulation of the transmitted images are realized using the orthogonal frequency division multiplexing(OFDM)algorithm of least squares(LS)estimation,and eight combinations with different mapping modes and coding rates are tested in the bandwidth of 200-800 k Hz and the quality of the transmitted images is evaluated using three criteria:mean squared error(MSE),peak signal to noise ratio(PSNR),and structural similarity index(SSIM).The results indicate that the image transmission quality is optimal when the mapping method is 16-quadrature amplitude modulation(16QAM),the coding rate is 1/2,and the center frequency is 800 k Hz.Under these conditions,the maximum transmission rate is 0.84 Mbit s^(-1),the SSIM criterion exceeds 0.91690 d B,and the learned perceptual image patch similarity(LPIPS)is less than 0.06000.This paper provides a solution for the underwater image transmission of inductively coupled mooring chains for marine applications.展开更多
Insufficient observations near the origin of the Kuroshio have led to incomplete understanding of the intraseasonal variability(ISV)of the Kuroshio.Direct measurements of the Kuroshio velocity were performed with an a...Insufficient observations near the origin of the Kuroshio have led to incomplete understanding of the intraseasonal variability(ISV)of the Kuroshio.Direct measurements of the Kuroshio velocity were performed with an array of three profiler moorings(122.7°E,123°E,and 123.3°E)along 18°N from January 2018 to February 2020.The ISV of the Kuroshio at 18°N was investigated based on a combination of mooring observations and global high-resolution HYbrid Coordinate Ocean Model reanalysis data.The estimated time-averaged transport in the upper 350 m across the observation transect was 6.5±2.6 Sv(1.0 Sv=10^(6)m^(3)/s).Two significant ISV peaks at 50-60 and~100 d were recognized in the power spectra of the meridional velocity and transport.Further analysis indicated that the ISV at 50-60 d was caused by westward-propagating eddies at average propagation speed of~13 cm/s and wavelength of~635 km.Another ISV peak at~100 d was mainly caused by northward-propagating eddies generated in the North Equatorial Current region.Further investigation indicated that the ISV of the Kuroshio at 18°N is dominated by meridional transport,rather than by the zonal migration of the Kuroshio main axis.Our findings provide a better understanding of the ISV of the Kuroshio east of Luzon Island.展开更多
The basic structure and intraseasonal evolution of currents in the southeastern Andaman Sea was analyzed based on data collected in 2017 from two subsurface moorings(C1 and C5).Periodic variation in the upper ocean cu...The basic structure and intraseasonal evolution of currents in the southeastern Andaman Sea was analyzed based on data collected in 2017 from two subsurface moorings(C1 and C5).Periodic variation in the upper ocean currents of the Andaman Sea was investigated by combining observational and satellite data.Mooring observations show that rapid changes of current speed and direction occurred in May and June,with a significant increase in current velocity at the C1 mooring.In the second half of the year,southward flow dominated at the C1 mooring,and alternating northward and southward flows were evident at the C5 mooring during the same period but the northward flow prevailed in boreal winter.In addition,analysis of the power spectra of the upper currents revealed that the tidal period at both moorings is primarily semidiurnal with weaker energy than that of the low-frequency currents.The upper ocean currents at the C1 and C5 moorings exhibited intraseasonal variation of 30-60 d and 120 d,while the zonal current at the C1 mooring exhibited a notable period of approximately 180 d.Further analysis indicated that the variability of currents in the Andaman Sea is influenced primarily by equatorial Kelvin waves and Rossby wave packets.Moreover,our results suggest that equatorial Kelvin waves from the eastern Indian Ocean entered the Andaman Sea in the form of Wyrtki Jets and propagated primarily along two distinct pathways during the observation period.In addition to coastal boundary Kelvin waves,it was found that a branch of the Wyrtki Jet that directly enters the Andaman Sea and flows northward along the slope of the continental shelf,and reflected Rossby wave packets by topography.展开更多
The offshore renewable energy industry has been developing farms of floating offshore wind turbines in water depths up to 100 m.In Vietnam,floating offshore wind turbines have been developed to increase the production...The offshore renewable energy industry has been developing farms of floating offshore wind turbines in water depths up to 100 m.In Vietnam,floating offshore wind turbines have been developed to increase the production of clean and sustainable energy.The mooring system,which is used to keep the turbine stable and ensure the safety and economic efficiency of wind power production,is an important part of a floating offshore wind turbine.Appropriate selection of the mooring type and mooring line material can reduce the risks arising from the motion of wind turbines.Different types of mooring line material have been simulated and compared in order to determine the optimal type with the minimum motion risk for a floating wind turbine.This study focused on numerical modeling of semi-taut mooring systems using nonlinear materials for a semi-submersible wind turbine.Several modeling approaches common to current practice were applied.Hydrodynamic analysis was performed to investigate the motion of the response amplitude operators of the floating wind turbine.Dynamic analysis of mooring systems was performed using a time domain to obtain the tension responses of mooring lines under the ultimate limit states and fatigue limit states in Vietnamese sea conditions.The results showed that the use of nonlinear materials(polyester and/or nylon)for mooring systems can minimize the movement of the turbine and save costs.The use of synthetic fibers can reduce the maximum tension in mooring lines and the length of mooring lines.However,synthetic fiber ropes showed highly nonlinear load elongation properties,which were difficult to simulate using numerical software.The comparison of the characteristics of polyester and nylon mooring lines showed that the maximum and mean tensions of the nylon line were less than those of the polyester line.In addition,the un-stretched length of the polyester line was greater than that of the nylon line under the same mean tension load.Therefore,nylon material is recommended for the mooring lines of a floating offshore wind turbine.展开更多
With the increasing demand of energy and the limitation of bottom-fixed wind turbines in moderate and deep waters,floating offshore wind turbines are doomed to be the right technical choice and they are bound to enter...With the increasing demand of energy and the limitation of bottom-fixed wind turbines in moderate and deep waters,floating offshore wind turbines are doomed to be the right technical choice and they are bound to enter a new era of rapid development.The mooring system is a vital system of a floating wind turbine for station-keeping under harsh environmental conditions.In terms of existing floating wind turbine projects,this paper is devoted to discussing the current status of mooring systems and mooring equipment.This paper also presents the mooring analysis methods and points out the technical difficulties and challenges in mooring design,installation,operation and maintenance stages.Finally,the developing trends of the mooring system are summarized,aiming to provide a reference for future mooring research.展开更多
This paper quantitatively studies the transient dynamic response of a semi-submersible production platform with the loss of one or several positioning mooring lines.A semi-submersible platform,production risers,and po...This paper quantitatively studies the transient dynamic response of a semi-submersible production platform with the loss of one or several positioning mooring lines.A semi-submersible platform,production risers,and positioning mooring lines are all included in the numerical simulation.Increased motion of the semi-submersible platform,tension variation of the remaining mooring lines/risers and the risk of mooring line or riser clashing are all investigated through fully coupled time-domain analysis.Combined environmental loads are selected from irregular waves and the steady current varying from very rough to extreme sea conditions.Three dimension radiation/diffraction theories and Morison’s equation are applied to calculate first-order wave force and second-order mean drift force of floating semi-submersible platform.Nonlinear time-domain finite element methods are employed to analyze the behavior of mooring lines and risers.Results show that the failure of mooring lines seriously reduce the platform’s stability performance.The tension of the rest lines is also increased accordingly.Remaining lines which are closer to the failed lines will have larger tension increase to compensate.Line-Line distance provides practical information for the risk of clashing investigation.展开更多
The development of offshore wind farms was originally carried out in shallow water areas with fixed （seabed mounted） structures. However, countries with limited shallow water areas require innovative floating platfo...The development of offshore wind farms was originally carried out in shallow water areas with fixed （seabed mounted） structures. However, countries with limited shallow water areas require innovative floating platforms to deploy wind turbines offshore in order to harness wind energy to generate electricity in deep seas. The performances of motion and mooring system dynamics are vital to designing a cost effective and durable floating platform. This paper describes a numerical model to simulate dynamic behavior of a new semi-submersible type floating offshore wind turbine （FOWT） system. The wind turbine was modeled as a wind block with a certain thrust coefficient, and the hydrodynamics and mooting system dynamics of the platform were calculated by SESAM soRware. The effect of change in environmental conditions on the dynamic response of the system under wave and wind loading was examined. The results indicate that the semi-submersible concept has excellent performance and SESAM could be an effective tool for floating wind turbine design and analysis.展开更多
The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester ro...The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester rope has attracted much attention among numerous synthetic fiber rope materials due to its lightweight,low price,corrosion resistance,and high strength.Thus,the mooring characteristics of it are worth studying.Polyester mooring lines are flexible in deep water,when a marine structure is moored by them,the geometric nonlinearity such as large displacement,large stretch,and large bending deformation,and the material nonlinearity like viscoelastic of the polyester ropes become complex integrated problems to be studied.Considering the nonlinear phenomenon,the simulation and calculation of a polyester line were carried out by the absolute nodal coordinate formulation(ANCF)in this paper since the ANCF method has advantages in dealing with the significant deformation problems of the flexible structures.In addition,a chain mooring line was also simulated for comparison,and the results show that the polyester ropes reduce the self-weight of the mooring lines and provide sufficient mooring strength at the same time,and the nonlinear phenomenon of the polyester ropes is different from that of the chain mooring lines.展开更多
The dynamic responses of any floating platform arc dependent on the mass, stiffness and damping characteristics of the body as well as mooring system. Therefore, it is very essential to study the effect of individual ...The dynamic responses of any floating platform arc dependent on the mass, stiffness and damping characteristics of the body as well as mooring system. Therefore, it is very essential to study the effect of individual contributions to the system that can finally help to economise their cost. This paper focuses on the effect of mooring stiffness on the responses of a truss spar platform, obtained by different grouping of lines. The study is part of our present researches on mooring systems which include the effect of line pretension, diameter and azimuth angles. The platform is modelled as a rigid body with three degrees-of-freedom and its motions are analyzed in time-domain using the implicit Newmark Beta technique. The mooring lines restoring force-excursion relationship is evaluated using a quasi-static approach. It is observed that the mooring system with lines arranged in less number of groups exhibits better performance in terms of the restoring forces as well as mean position of platform. However, the dynamic motions of platform remain unaffected for different line groups.展开更多
Moored structures are suitable for operations in ice-covered regions owing to their security and efficiency.This paper aims to present a new method for simulating the ice load and mooring force on the moored structure...Moored structures are suitable for operations in ice-covered regions owing to their security and efficiency.This paper aims to present a new method for simulating the ice load and mooring force on the moored structure during ice-structure interaction with a spherical Discrete Element Method(DEM).In this method,the level ice and mooring lines consist of bonded sphere elements arranged in different patterns.The level ice model has been widely validated in simulation of the ice load of fixed structures.In the mooring line simulation,a string of spherical elements was jointed with the parallel bond model to simulate the chains or cable structure.The accuracy of the mooring line model was proved by comparing the numerical results with the nonlinear FEM results and model towing experiment results.The motion of the structure was calculated in the quaternion method,considering the ice load,mooring force,and hydrodynamic force.The hydrodynamic force comprised wave-making damping,current drag,and buoyancy force.Based on the proposed model,the interaction of a semi-submersible structure with level ice was simulated,and the effect of ice thickness on the ice load was analyzed.The numerical results show that the DEM method is suitable to simulate the ice load and mooring force on moored floating structures.展开更多
With the floating structures pushing their activities to the ultra-deep water, model tests have presented a challenge due to the limitation of the existing wave basins. Therefore, the concept of truncated mooring syst...With the floating structures pushing their activities to the ultra-deep water, model tests have presented a challenge due to the limitation of the existing wave basins. Therefore, the concept of truncated mooring system is implemented to replace the full depth mooring system in the model tests, which aims to have the same dynamic responses as the full depth system. The truncated mooring system plays such a significant role that extra attention should be paid to the mooring systems with large truncation factor. Three different types of large truncation factor mooring system are being employed in the simulations, including the homogenously truncated mooring system, non-homogenously truncated mooring system and simplified truncated mooring system. A catenary moored semi-submersible operating at 1000 m water depth is presented. In addition, truncated mooring systems are proposed at the truncated water depth of 200 m. In order to explore the applicability of these truncated mooring systems, numerical simulations of the platform’s surge free decay interacting with three different styles of truncated mooring systems are studied in calm water. Furthermore, the mooring-induced damping of the truncated mooring systems is simulated in the regular wave. Finally, the platform motion responses and mooring line dynamics are simulated in irregular wave. All these simulations are implemented by employing full time domain coupled dynamic analysis, and the results are compared with those of the full depth simulations in the same cases. The results show that the mooring-induced damping plays a significant role in platform motion responses, and all truncated mooring systems are suitable for model tests with appropriate truncated mooring line diameters. However, a large diameter is needed for simplified truncated mooring lines. The suggestions are given to the selection of truncated mooring system for different situations as well as to the truncated mooring design criteria.展开更多
This paper presents a series of design curves to aid in the selection of turret mooring systems for tankers based Floating Production Storage and Offloading (FPSO) systems. These curves are appropriate to water depths...This paper presents a series of design curves to aid in the selection of turret mooring systems for tankers based Floating Production Storage and Offloading (FPSO) systems. These curves are appropriate to water depths ranging from 100 m to 600 m. The curves can be used as a preliminary design tool, allowing the designer to quickly evaluate alternative mooring system configurations, including the number of mooring lines, the characteristics of chain and wire rope to be deployed and the. initial tension. With a knowledge of the total environmental force and vessel motion characteristics, the designer can determine the appropriate system for closer evaluation.展开更多
Polyester mooring has become increasing popular to serve as permanent station-keeping system for deepwater floating system during recent years. Comparing to the traditional steel wire mooring,polyester mooring provide...Polyester mooring has become increasing popular to serve as permanent station-keeping system for deepwater floating system during recent years. Comparing to the traditional steel wire mooring,polyester mooring provides significant benefits in deepwater,such as reduced installed capital expenditure (CAPEX) and smaller vertical loads on host platform. Polyester rope is a visco-elastic material,and its stiffness is nonlinear and affected by mean load,load range,loading period and loading history. There is a perception that the polyester stiffness model has significant impact on the floating system's performance. This paper presents a detailed description and comparison of two stiffness models and three analytic approaches,and provides a systematic study of the impact of polyester mooring stiffness modeling on the deepwater floating system performance.展开更多
In order to solve the performance limitations of traditional ship-type and cylindrical FDPSO(floating drilling production, storage and offloading unit), we present a new FDPSO with a sandglass-type floating body.Based...In order to solve the performance limitations of traditional ship-type and cylindrical FDPSO(floating drilling production, storage and offloading unit), we present a new FDPSO with a sandglass-type floating body.Based on the hydrodynamic performance of the newly developed floating model, a suitable analysis method for its deepwater mooring system has been proposed. Furthermore, by studying the effects of different mooring parameters on the motion performance of FDPSO, we achieve some useful conclusions and principles to design the mooring scheme in deep sea which has been validated to satisfy the Det Norshke Veritas(DNV) requirements.The study of this paper is expected to provide a reasonable and feasible reference and design solution for the deep sea positions of the new sandglass-type FDPSO.展开更多
20-day in-situ ADCP current and CTD data are used to investigate the characteristics and energy of the internal tides in the northern South China Sea （NSCS）. The results show that the O1, K1, M2 and S2 constituents ...20-day in-situ ADCP current and CTD data are used to investigate the characteristics and energy of the internal tides in the northern South China Sea （NSCS）. The results show that the O1, K1, M2 and S2 constituents of internal tides are energetic and diurnal constituents （O1 and K1） are dominating. In the observational period, the current vectors of these four constituents all rotate clockwise and the maximum semi-major axe of internal tidal ellipses is more than 14 cm/s. The variation of ocean temperature shows that the internal tides present obvious quasi-diurnal oscillation and the average amplitude reaches 50 m. Furthermore, these internal tides carry high energy and appear to be intermittent. The maximum values of KE （PE） during the observational period are up to 2 （3.5） k J/m^2 for diurnal internal tides, and up to 1 （1.5） k J/m^2 for semidiurnal internal tides.展开更多
Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to det...Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response,mooring force,incident coefficient,reflection coefficient and energy dissipation coefficient.Eight mooring cables are symmetrically arranged on both sides of the model.The floating body model satisfies the similarity of stiffness and gravity,while the cable satisfies the similarity of elasticity and gravity.The results show that the effect of mooring type on mooring force is greater than that on hydroelastic response.Increasing the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS model.The mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force occurs.The transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring types.These results may provide a reference to facilitate the mooring design of VLFS.展开更多
文摘Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data that mooring system designers aim to acquire.To address the need for long-term continuous monitoring of mooring tension in deep-sea marine environments,this paper presents a mooring cable tension monitoring method based on the principle of direct mechanical measurement.The developed tension monitoring sensors were installed and applied in the mooring system of the"Yongle"scientific experimental platform.Over the course of one year,a substantial amount of in-situ tension monitoring data was obtained.Under wave heights of up to 1.24 m,the mooring tension on the floating platform reached 16.5 tons.Through frequency domain and time domain analysis,the spectral characteristics of mooring tension,including waveinduced force,slow drift force,and mooring cable elastic restoring force,were determined.The mooring cable elastic restoring force frequency was approximately half of that of the wave signal.Due to the characteristics of the hinge connection structure of the dual module floating platform,under some specific working conditions the wave-induced force was the maximum of the three different frequency forces,and restoring force was the smallest.
基金financially supported by the Open Project Program of Shandong Marine Aerospace Equipment Technological Innovation Center,Ludong University(Grant Nos.MAETIC202209 and MAETIC202201)Shandong Provincial Natural Science Foundation(Grant No.ZR2022QE092)+2 种基金China Postdoctoral Science Foundation(Grant No.2023M730829)Open Fund of the State Key Laboratory of Industrial Equipment Structural Analysis(Grant No.GZ23109)the National Natural Science Foundation of China(Grant Nos.52001284 and 52192694).
文摘In the process of developing oil and gas resources in the Arctic,the impact of icebergs can pose a considerable threat to the structural safety of semi-submersible mooring platforms in ice regions.On the basis of the arbitrary Lagrangian Eulerian(ALE)algorithm,a numerical model for the interaction between an iceberg and a semi-submersible mooring platform is built in this work.First,a mooring system with a link element is designed and validated.An ice material model for the target iceberg is built and validated.A numerical model for the interaction between an iceberg and a semi-submersible mooring platform is then built.A parametric study(cable angle,tension angle and number of cables)is carried out to study the performance of the mooring system.The collision process between the semi-submersible mooring platform and the iceberg in the polar marine environment can be predicted by the present numerical model,and then the optimal mooring arrangement scheme can be obtained.The research results in this work can provide a reference for the design of mooring systems.
基金funding from the National Natural Science Foundation of China(No.12462028).
文摘This study employs the Smoothed Particle Hydrodynamics(SPH)method to develop a computational fluid dynamics(CFD)model for analyzing the interaction between rogue waves and mooring systems.Four floating body configurations are investigated:(1)dual rectangular prisms,(2)rectangular prism–sphere composites,(3)sphere–rectangular prism composites,and(4)dual spheres.These configurations are systematically evaluated under varying mooring conditions to assess their hydrodynamic performance and wave attenuation capabilities.The model accurately captures the complex fluid–structure interaction dynamics between moored floating breakwaters and incident wave fields.Among the configurations,the dual rectangular prism system demonstrates superior performance in both wave dissipation and mooring force reduction.Under conditions involving dual wave makers,the influence of floating body shape and number on wave height is found to be minimal.However,dual-body arrangements consistently outperform single-body setups in terms of both energy dissipation and structural stability.From a cost-efficiency perspective,the configuration comprising two rectangular prisms connected via a single mooring system offers significant advantages in material usage and deployment feasibility.
基金financially supported by the National Key R&D Program of China(Grant No.2022YFB4200700).
文摘To address the mooring issues of floating photovoltaic systems in areas with large tidal variations,three mooring schemes were designed and compared in this paper:anchor chain,anchor chain with added weights,and anchor chain with Superflex.The model was established via the numerical simulation tool Orcaflex,which considers the combined effects of wind,waves,and currents.A time-domain coupled dynamic analysis was conducted on the performance of the three mooring schemes under various tidal conditions to determine the mooring cable tension and platform motion response.Furthermore,the mooring system with an anchor chain and Superflex was optimized,with a focus on analyzing the effects of the Superflex length,the diameter of the anchor chains,and the mooring radius.The mooring system with the anchor chain and Superflex exhibits more controllable and stable mooring performance in areas with large tidal variations,so that it more effectively maintains the required mooring tension level.These findings not only provide a reference for the feasibility and optimization design of photovoltaic systems in areas with large tidal variations but also offer valuable experience for the sustainable application of clean energy under specific environmental conditions.
基金supported by grants from the National Natural Science Foundation of China(No.62071329)the National Science Foundation of Tianjin(No.23JCZD JC00440)。
文摘Inductively coupled mooring chain transmission technology plays a crucial role in the long-distance online monitoring of marine hydrographic information.However,the impedance characteristics of the seawater medium pose a limitation on its capability to achieve high-speed real-time transmission of underwater images.In this paper,based on the principle of inductively coupled transmission for marine applications,the selected 1920×1080 pixel images are segmented,packaged,and then transmitted to the sending node using the user datagram protocol(UDP),and the modulation and demodulation of the transmitted images are realized using the orthogonal frequency division multiplexing(OFDM)algorithm of least squares(LS)estimation,and eight combinations with different mapping modes and coding rates are tested in the bandwidth of 200-800 k Hz and the quality of the transmitted images is evaluated using three criteria:mean squared error(MSE),peak signal to noise ratio(PSNR),and structural similarity index(SSIM).The results indicate that the image transmission quality is optimal when the mapping method is 16-quadrature amplitude modulation(16QAM),the coding rate is 1/2,and the center frequency is 800 k Hz.Under these conditions,the maximum transmission rate is 0.84 Mbit s^(-1),the SSIM criterion exceeds 0.91690 d B,and the learned perceptual image patch similarity(LPIPS)is less than 0.06000.This paper provides a solution for the underwater image transmission of inductively coupled mooring chains for marine applications.
基金Supported by the National Natural Science Foundation of China(Nos.41976011,42022040)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42010102)+1 种基金the Shandong Provincial Natural Science Foundation(No.ZR2020JQ18)Shijian HU is a member of the CAS Interdisciplinary Innovation Team(No.JCTD2020-12)。
文摘Insufficient observations near the origin of the Kuroshio have led to incomplete understanding of the intraseasonal variability(ISV)of the Kuroshio.Direct measurements of the Kuroshio velocity were performed with an array of three profiler moorings(122.7°E,123°E,and 123.3°E)along 18°N from January 2018 to February 2020.The ISV of the Kuroshio at 18°N was investigated based on a combination of mooring observations and global high-resolution HYbrid Coordinate Ocean Model reanalysis data.The estimated time-averaged transport in the upper 350 m across the observation transect was 6.5±2.6 Sv(1.0 Sv=10^(6)m^(3)/s).Two significant ISV peaks at 50-60 and~100 d were recognized in the power spectra of the meridional velocity and transport.Further analysis indicated that the ISV at 50-60 d was caused by westward-propagating eddies at average propagation speed of~13 cm/s and wavelength of~635 km.Another ISV peak at~100 d was mainly caused by northward-propagating eddies generated in the North Equatorial Current region.Further investigation indicated that the ISV of the Kuroshio at 18°N is dominated by meridional transport,rather than by the zonal migration of the Kuroshio main axis.Our findings provide a better understanding of the ISV of the Kuroshio east of Luzon Island.
基金Supported by the Laoshan Laboratory(No.LSK 202203003)the National Key R&D Program of China(No.2022YFC3104100)。
文摘The basic structure and intraseasonal evolution of currents in the southeastern Andaman Sea was analyzed based on data collected in 2017 from two subsurface moorings(C1 and C5).Periodic variation in the upper ocean currents of the Andaman Sea was investigated by combining observational and satellite data.Mooring observations show that rapid changes of current speed and direction occurred in May and June,with a significant increase in current velocity at the C1 mooring.In the second half of the year,southward flow dominated at the C1 mooring,and alternating northward and southward flows were evident at the C5 mooring during the same period but the northward flow prevailed in boreal winter.In addition,analysis of the power spectra of the upper currents revealed that the tidal period at both moorings is primarily semidiurnal with weaker energy than that of the low-frequency currents.The upper ocean currents at the C1 and C5 moorings exhibited intraseasonal variation of 30-60 d and 120 d,while the zonal current at the C1 mooring exhibited a notable period of approximately 180 d.Further analysis indicated that the variability of currents in the Andaman Sea is influenced primarily by equatorial Kelvin waves and Rossby wave packets.Moreover,our results suggest that equatorial Kelvin waves from the eastern Indian Ocean entered the Andaman Sea in the form of Wyrtki Jets and propagated primarily along two distinct pathways during the observation period.In addition to coastal boundary Kelvin waves,it was found that a branch of the Wyrtki Jet that directly enters the Andaman Sea and flows northward along the slope of the continental shelf,and reflected Rossby wave packets by topography.
文摘The offshore renewable energy industry has been developing farms of floating offshore wind turbines in water depths up to 100 m.In Vietnam,floating offshore wind turbines have been developed to increase the production of clean and sustainable energy.The mooring system,which is used to keep the turbine stable and ensure the safety and economic efficiency of wind power production,is an important part of a floating offshore wind turbine.Appropriate selection of the mooring type and mooring line material can reduce the risks arising from the motion of wind turbines.Different types of mooring line material have been simulated and compared in order to determine the optimal type with the minimum motion risk for a floating wind turbine.This study focused on numerical modeling of semi-taut mooring systems using nonlinear materials for a semi-submersible wind turbine.Several modeling approaches common to current practice were applied.Hydrodynamic analysis was performed to investigate the motion of the response amplitude operators of the floating wind turbine.Dynamic analysis of mooring systems was performed using a time domain to obtain the tension responses of mooring lines under the ultimate limit states and fatigue limit states in Vietnamese sea conditions.The results showed that the use of nonlinear materials(polyester and/or nylon)for mooring systems can minimize the movement of the turbine and save costs.The use of synthetic fibers can reduce the maximum tension in mooring lines and the length of mooring lines.However,synthetic fiber ropes showed highly nonlinear load elongation properties,which were difficult to simulate using numerical software.The comparison of the characteristics of polyester and nylon mooring lines showed that the maximum and mean tensions of the nylon line were less than those of the polyester line.In addition,the un-stretched length of the polyester line was greater than that of the nylon line under the same mean tension load.Therefore,nylon material is recommended for the mooring lines of a floating offshore wind turbine.
基金The financial supports received from China National Science Foundation Program(52071186)Shenzhen Science and Technology Program(Grant No.KQTD20200820113004005)+1 种基金the Key Promotion Program of High Quality Marine Economy Development by Guangdong Province of China(GDNRC[2022]33)The Major Program of Stable Sponsorship for Higher Institutions(Shenzhen Science&Technology Commission,WDZC20200819174646001)are greatly acknowledged.
文摘With the increasing demand of energy and the limitation of bottom-fixed wind turbines in moderate and deep waters,floating offshore wind turbines are doomed to be the right technical choice and they are bound to enter a new era of rapid development.The mooring system is a vital system of a floating wind turbine for station-keeping under harsh environmental conditions.In terms of existing floating wind turbine projects,this paper is devoted to discussing the current status of mooring systems and mooring equipment.This paper also presents the mooring analysis methods and points out the technical difficulties and challenges in mooring design,installation,operation and maintenance stages.Finally,the developing trends of the mooring system are summarized,aiming to provide a reference for future mooring research.
基金supported by the Fundamental Research Funds for the Central Universities,Dalian Maritime University,China(Grant Nos.3132019306 and 3132020116).
文摘This paper quantitatively studies the transient dynamic response of a semi-submersible production platform with the loss of one or several positioning mooring lines.A semi-submersible platform,production risers,and positioning mooring lines are all included in the numerical simulation.Increased motion of the semi-submersible platform,tension variation of the remaining mooring lines/risers and the risk of mooring line or riser clashing are all investigated through fully coupled time-domain analysis.Combined environmental loads are selected from irregular waves and the steady current varying from very rough to extreme sea conditions.Three dimension radiation/diffraction theories and Morison’s equation are applied to calculate first-order wave force and second-order mean drift force of floating semi-submersible platform.Nonlinear time-domain finite element methods are employed to analyze the behavior of mooring lines and risers.Results show that the failure of mooring lines seriously reduce the platform’s stability performance.The tension of the rest lines is also increased accordingly.Remaining lines which are closer to the failed lines will have larger tension increase to compensate.Line-Line distance provides practical information for the risk of clashing investigation.
基金Foundation item： Supported by the 111 Project under Grant No.B07019, and the National Natural Science Foundation of China under Grant No.50979020.
文摘The development of offshore wind farms was originally carried out in shallow water areas with fixed （seabed mounted） structures. However, countries with limited shallow water areas require innovative floating platforms to deploy wind turbines offshore in order to harness wind energy to generate electricity in deep seas. The performances of motion and mooring system dynamics are vital to designing a cost effective and durable floating platform. This paper describes a numerical model to simulate dynamic behavior of a new semi-submersible type floating offshore wind turbine （FOWT） system. The wind turbine was modeled as a wind block with a certain thrust coefficient, and the hydrodynamics and mooting system dynamics of the platform were calculated by SESAM soRware. The effect of change in environmental conditions on the dynamic response of the system under wave and wind loading was examined. The results indicate that the semi-submersible concept has excellent performance and SESAM could be an effective tool for floating wind turbine design and analysis.
基金Supported by the Specialized Research Project for LS17-2 Semi-submersible Production Platform(LSZX-2020-HN-05-0405).
文摘The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester rope has attracted much attention among numerous synthetic fiber rope materials due to its lightweight,low price,corrosion resistance,and high strength.Thus,the mooring characteristics of it are worth studying.Polyester mooring lines are flexible in deep water,when a marine structure is moored by them,the geometric nonlinearity such as large displacement,large stretch,and large bending deformation,and the material nonlinearity like viscoelastic of the polyester ropes become complex integrated problems to be studied.Considering the nonlinear phenomenon,the simulation and calculation of a polyester line were carried out by the absolute nodal coordinate formulation(ANCF)in this paper since the ANCF method has advantages in dealing with the significant deformation problems of the flexible structures.In addition,a chain mooring line was also simulated for comparison,and the results show that the polyester ropes reduce the self-weight of the mooring lines and provide sufficient mooring strength at the same time,and the nonlinear phenomenon of the polyester ropes is different from that of the chain mooring lines.
文摘The dynamic responses of any floating platform arc dependent on the mass, stiffness and damping characteristics of the body as well as mooring system. Therefore, it is very essential to study the effect of individual contributions to the system that can finally help to economise their cost. This paper focuses on the effect of mooring stiffness on the responses of a truss spar platform, obtained by different grouping of lines. The study is part of our present researches on mooring systems which include the effect of line pretension, diameter and azimuth angles. The platform is modelled as a rigid body with three degrees-of-freedom and its motions are analyzed in time-domain using the implicit Newmark Beta technique. The mooring lines restoring force-excursion relationship is evaluated using a quasi-static approach. It is observed that the mooring system with lines arranged in less number of groups exhibits better performance in terms of the restoring forces as well as mean position of platform. However, the dynamic motions of platform remain unaffected for different line groups.
基金This study is financially supported by the National Natural Science Foundation of China(Grant Nos.11872136,U20A20327 and 42176241).
文摘Moored structures are suitable for operations in ice-covered regions owing to their security and efficiency.This paper aims to present a new method for simulating the ice load and mooring force on the moored structure during ice-structure interaction with a spherical Discrete Element Method(DEM).In this method,the level ice and mooring lines consist of bonded sphere elements arranged in different patterns.The level ice model has been widely validated in simulation of the ice load of fixed structures.In the mooring line simulation,a string of spherical elements was jointed with the parallel bond model to simulate the chains or cable structure.The accuracy of the mooring line model was proved by comparing the numerical results with the nonlinear FEM results and model towing experiment results.The motion of the structure was calculated in the quaternion method,considering the ice load,mooring force,and hydrodynamic force.The hydrodynamic force comprised wave-making damping,current drag,and buoyancy force.Based on the proposed model,the interaction of a semi-submersible structure with level ice was simulated,and the effect of ice thickness on the ice load was analyzed.The numerical results show that the DEM method is suitable to simulate the ice load and mooring force on moored floating structures.
基金financially supported by the National Natural Science Foundation of China(Grant No.51379095)
文摘With the floating structures pushing their activities to the ultra-deep water, model tests have presented a challenge due to the limitation of the existing wave basins. Therefore, the concept of truncated mooring system is implemented to replace the full depth mooring system in the model tests, which aims to have the same dynamic responses as the full depth system. The truncated mooring system plays such a significant role that extra attention should be paid to the mooring systems with large truncation factor. Three different types of large truncation factor mooring system are being employed in the simulations, including the homogenously truncated mooring system, non-homogenously truncated mooring system and simplified truncated mooring system. A catenary moored semi-submersible operating at 1000 m water depth is presented. In addition, truncated mooring systems are proposed at the truncated water depth of 200 m. In order to explore the applicability of these truncated mooring systems, numerical simulations of the platform’s surge free decay interacting with three different styles of truncated mooring systems are studied in calm water. Furthermore, the mooring-induced damping of the truncated mooring systems is simulated in the regular wave. Finally, the platform motion responses and mooring line dynamics are simulated in irregular wave. All these simulations are implemented by employing full time domain coupled dynamic analysis, and the results are compared with those of the full depth simulations in the same cases. The results show that the mooring-induced damping plays a significant role in platform motion responses, and all truncated mooring systems are suitable for model tests with appropriate truncated mooring line diameters. However, a large diameter is needed for simplified truncated mooring lines. The suggestions are given to the selection of truncated mooring system for different situations as well as to the truncated mooring design criteria.
文摘This paper presents a series of design curves to aid in the selection of turret mooring systems for tankers based Floating Production Storage and Offloading (FPSO) systems. These curves are appropriate to water depths ranging from 100 m to 600 m. The curves can be used as a preliminary design tool, allowing the designer to quickly evaluate alternative mooring system configurations, including the number of mooring lines, the characteristics of chain and wire rope to be deployed and the. initial tension. With a knowledge of the total environmental force and vessel motion characteristics, the designer can determine the appropriate system for closer evaluation.
文摘Polyester mooring has become increasing popular to serve as permanent station-keeping system for deepwater floating system during recent years. Comparing to the traditional steel wire mooring,polyester mooring provides significant benefits in deepwater,such as reduced installed capital expenditure (CAPEX) and smaller vertical loads on host platform. Polyester rope is a visco-elastic material,and its stiffness is nonlinear and affected by mean load,load range,loading period and loading history. There is a perception that the polyester stiffness model has significant impact on the floating system's performance. This paper presents a detailed description and comparison of two stiffness models and three analytic approaches,and provides a systematic study of the impact of polyester mooring stiffness modeling on the deepwater floating system performance.
基金the National Innovation Team Foundation of China(No.50921001)the Scientific Research Foundation for Introduction of Talent of Dalian University of Technology(No.DUT13RC(3)46)
文摘In order to solve the performance limitations of traditional ship-type and cylindrical FDPSO(floating drilling production, storage and offloading unit), we present a new FDPSO with a sandglass-type floating body.Based on the hydrodynamic performance of the newly developed floating model, a suitable analysis method for its deepwater mooring system has been proposed. Furthermore, by studying the effects of different mooring parameters on the motion performance of FDPSO, we achieve some useful conclusions and principles to design the mooring scheme in deep sea which has been validated to satisfy the Det Norshke Veritas(DNV) requirements.The study of this paper is expected to provide a reasonable and feasible reference and design solution for the deep sea positions of the new sandglass-type FDPSO.
基金supported by the National Natural Science Foundation of China (No.41176025, 40876008)the SCSMEX project
文摘20-day in-situ ADCP current and CTD data are used to investigate the characteristics and energy of the internal tides in the northern South China Sea （NSCS）. The results show that the O1, K1, M2 and S2 constituents of internal tides are energetic and diurnal constituents （O1 and K1） are dominating. In the observational period, the current vectors of these four constituents all rotate clockwise and the maximum semi-major axe of internal tidal ellipses is more than 14 cm/s. The variation of ocean temperature shows that the internal tides present obvious quasi-diurnal oscillation and the average amplitude reaches 50 m. Furthermore, these internal tides carry high energy and appear to be intermittent. The maximum values of KE （PE） during the observational period are up to 2 （3.5） k J/m^2 for diurnal internal tides, and up to 1 （1.5） k J/m^2 for semidiurnal internal tides.
基金financially supported by the National Key R&D Program of China (Grant Nos. 2019YFC1407702 and 2019YFC1407705)
文摘Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response,mooring force,incident coefficient,reflection coefficient and energy dissipation coefficient.Eight mooring cables are symmetrically arranged on both sides of the model.The floating body model satisfies the similarity of stiffness and gravity,while the cable satisfies the similarity of elasticity and gravity.The results show that the effect of mooring type on mooring force is greater than that on hydroelastic response.Increasing the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS model.The mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force occurs.The transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring types.These results may provide a reference to facilitate the mooring design of VLFS.
