A floating breakwater(FB)has extensive potential applications in the fields of coastal,offshore,and ocean engineering owing to its advantages such as eco-friendliness,low cost,easy and rapid construction,and quick dis...A floating breakwater(FB)has extensive potential applications in the fields of coastal,offshore,and ocean engineering owing to its advantages such as eco-friendliness,low cost,easy and rapid construction,and quick dismantling and reinstallation.An FB composed of twin pontoons and multi-porous vertical plates is proposed to improve the wave attenuation performance.The wave attenuation performance is investigated for different FB structures and vertical plate types under different incident wave heights and periods using 2D wave physical model tests in a wave flume.The results demonstrate that the proposed FB has a better performance than that of the conventional single pontoon-type FB.It reduces the wave transmission due to its enhanced wave reflection and energy loss.The wave transmission coefficient of the proposed FB decreases with an increase in the number of layers and relative draft depth of the vertical plates.However,a further decrease in the wave transmission coefficient is not observed when the number of porous vertical plates is increased from 4 to 5 layers.An equation has been derived to predict the wave transmission of the proposed FB based on the experimental results.展开更多
The dynamic responses of two pontoons while connected with each other in irregular waves are calculated by means of three-dimensional （3-D） potential flow theory. The computation is to find the optimal status for co...The dynamic responses of two pontoons while connected with each other in irregular waves are calculated by means of three-dimensional （3-D） potential flow theory. The computation is to find the optimal status for connection at a certain sea state. On the basis of the relative motion of two pontoons in irregular waves, Visual FORTRAN programming language, as well as OpenGL （Open Graphics Library）, is used to develop a set of virtual reality system of the relative motion of two pontoons, which is fully interactive with realistic effect. The transfinite interpolation scheme is applied for the mesh generation of wave surface, and the wave motion is simulated by surface elevation and calculated by 3-D potential flow theory.展开更多
Tension leg platform(TLP)is a typical compliant offshore structure for oil/gas resources exploitation.In the design process,the prediction of the free surface elevation is of great importance for the determination of ...Tension leg platform(TLP)is a typical compliant offshore structure for oil/gas resources exploitation.In the design process,the prediction of the free surface elevation is of great importance for the determination of the air gap.So far,the existing researches for predicting the air gap of the TLPs focus on the supporting columns while pay little attention to the horizontal pontoons.For the second order diffraction problem or long incident wave condition,the velocity potential decays slowly with water depth and the effect of pontoons should not be neglected.Herein the effect of pontoons on the diffracted wave field in the vicinity of a TLP platform is investigated in this study.The diffraction of regular waves by a square array of truncated cylinders and a whole TLP structure is studied in detail by using both the linear and the second-order diffraction theory.Numerical calculation is performed for the free surface elevation and wave run up.Numerical results show that the near-trapping phenomenon can occur inside the TLP and leads to significantly increased wave height.To study the effect of pontoons on the free surface elevation comparisons are carried out between the results of these two structures with and without pontoons.It is found that pontoons have an appreciable effect on the diffracted wave field for long incident regular waves and increase the largest response notably when the near-trapping phenomenon occurs at the second-order.展开更多
The sitting state of a sunken ship is usually related to the water depth, ship type, damage position, deadweight, and weight and density of the cargo. In salvage operation different means must be adopted according to ...The sitting state of a sunken ship is usually related to the water depth, ship type, damage position, deadweight, and weight and density of the cargo. In salvage operation different means must be adopted according to the sitting state of the sunken ship to make the ship refloat. Refloating a big-angle tilted sunken ship is difficult, and uprighting a ship underwater is the most complicated procedure in salvage operation. This paper, based on practical experiences, systematizes and presents the calculating methods of uprighting sunken ships underwater.展开更多
The off-bottom tow is an important method to lay pipeline for offshore oil and gas transportation in shallow water area. During the off-bottom towing operation, the actions such as sea current resistance, friction for...The off-bottom tow is an important method to lay pipeline for offshore oil and gas transportation in shallow water area. During the off-bottom towing operation, the actions such as sea current resistance, friction force of seabed, pontoon buoyancy, and tow force of tugboat can cause large deformation and fatigue damage to the pipeline. In order to keep the pipeline in safety, the lateral and vertical defomlations of pipeline must be controlled within an appropriate range. Theoretical study is carried out in the paper on the environmental forees acting on pipeline, pontoons and chaias, and the confimation of tow parameters including tow forces of tugboat, number of pontoons and length of chains. Then the pipeline in the off-bettom towing process may be simplified into a continuous beam with elastic supports under the concentrated and distributed forces. A finite element method is applied to achieve numerical solutions describing the distributions of deformation and stress along the pipeline. The results show that the lateral shape of the pipeline is like an arc with the maximal deformation appearing at the middle of the pipeline. The distributions of stress are similar between two arbitrary pontoons. Moreover, both deformation and stress have the inverse relation with the tow forces of tugboat.展开更多
A numerical study adopting the 2Dδ-SPH model is performed to compare the hydrodynamic characteristics of a single pontoon floating breakwater and a double pontoon floating breakwater.Numerical simulations are perform...A numerical study adopting the 2Dδ-SPH model is performed to compare the hydrodynamic characteristics of a single pontoon floating breakwater and a double pontoon floating breakwater.Numerical simulations are performed using theδ-SPH model and experimental tests are conducted to validate the numerical model.The numerical results of both the free surface elevations and motions of the floating breakwater are in good agreement with the experimental results.Numerical results show that when the pontoon drafts are larger,the double pontoon floating breakwater performs better in wave attenuations compared with the single pontoon floating breakwater,and for all the drafts,the amplitudes of motions including sway,heave and roll of the double pontoon floating breakwater is always smaller.In addition,increasing the spacing between the two pontoons can further reduce the amplitudes of pontoon motions and improve the wave attenuation ability of the double pontoon floating breakwater.展开更多
A numerical model is developed by use of the boundary integral equation method to investigate the responses of a two-dimensional floating structure. The structure under consideration consisting of two pontoons, is con...A numerical model is developed by use of the boundary integral equation method to investigate the responses of a two-dimensional floating structure. The structure under consideration consisting of two pontoons, is connected by a rigid framework, and linked to the sea floor by a mooring system. The theoretical conception is based on potential theory with hnear external forces, and applied to an arbitrarily shaped body and water depth. The discussion includes the influence of draft and space between pontoons on the responses of the floating structure. Finally, the validity of the method is adequately verified by experimental results.展开更多
With the rapid development of social economy, the rapid progress of science and technology, people＇s quality of life requirements are growing higher and higher, in order to further meet the growing masses of the grow...With the rapid development of social economy, the rapid progress of science and technology, people＇s quality of life requirements are growing higher and higher, in order to further meet the growing masses of the growing sports fitness needs, the State Council in June 1995 approved the ＂ Fitness program outline＂. With the sound of physical education, sports activities are increasingly rich, but also gradually from the land movement to the development of water sports, and water power center other hand, people＇s demand for the environment pontoon project and bear the brunt of the project. On the and landscape is also rising. Water pontoon in this environment, but also toward the ecological water conservancy, landscape water direction. While the pontoon is the driving force of the economic development and social needs and other aspects to be reflected展开更多
The objective of this study is to develop a procedure to analyze the motions of a floating pier comprised of several pontoons that are modeled as rigid bodies and connected to each other by flexible and rigid connecto...The objective of this study is to develop a procedure to analyze the motions of a floating pier comprised of several pontoons that are modeled as rigid bodies and connected to each other by flexible and rigid connectors.Recently,the use of floating piers has increased because of their advantages,such as faster and higher-quality construction,seismic force isolation for a full-scale mooring system,low dependence on local soil conditions and tides,ability to relocate or reconfigure the pier modules during the operation period and 75-100 years of repair-free service.A floating pier consists of a pier,access bridge,mooring system and fender system,each of which comes in many variations to suit different usages and construction considerations.The typical loads used in the design of these piers are dead loads,live loads,mooring loads,fender loads and environmental loads induced by wind,currents and waves.For numerical simulation,three types of piers are used:passenger piers,light-cargo piers and semi-heavy-cargo piers.The selected piers consist of several large pontoons joined by pivots and have a pile-based mooring system.These piers are modeled by SAP2000software as two-dimensional frames that are linked together.As the first step,each type of pier is subjected to loading,and its general behavior is assessed.According to this behavior,the major load combinations are described for the design of piers and analyzed to determine the behavior of the modules.Lastly,according to the analysis results and the safe use and stability considerations,such as the maximum draft and longitudinal gradient,the dimensions of each module in each pier type are presented.展开更多
基金This work was financially supported by the National Key R&D Program of China(Grant No.2017YFC1404200).
文摘A floating breakwater(FB)has extensive potential applications in the fields of coastal,offshore,and ocean engineering owing to its advantages such as eco-friendliness,low cost,easy and rapid construction,and quick dismantling and reinstallation.An FB composed of twin pontoons and multi-porous vertical plates is proposed to improve the wave attenuation performance.The wave attenuation performance is investigated for different FB structures and vertical plate types under different incident wave heights and periods using 2D wave physical model tests in a wave flume.The results demonstrate that the proposed FB has a better performance than that of the conventional single pontoon-type FB.It reduces the wave transmission due to its enhanced wave reflection and energy loss.The wave transmission coefficient of the proposed FB decreases with an increase in the number of layers and relative draft depth of the vertical plates.However,a further decrease in the wave transmission coefficient is not observed when the number of porous vertical plates is increased from 4 to 5 layers.An equation has been derived to predict the wave transmission of the proposed FB based on the experimental results.
基金supported by the National Natural Science Foundation of China(Grant No.50579047)
文摘The dynamic responses of two pontoons while connected with each other in irregular waves are calculated by means of three-dimensional （3-D） potential flow theory. The computation is to find the optimal status for connection at a certain sea state. On the basis of the relative motion of two pontoons in irregular waves, Visual FORTRAN programming language, as well as OpenGL （Open Graphics Library）, is used to develop a set of virtual reality system of the relative motion of two pontoons, which is fully interactive with realistic effect. The transfinite interpolation scheme is applied for the mesh generation of wave surface, and the wave motion is simulated by surface elevation and calculated by 3-D potential flow theory.
基金supported by the National Natural Science Foundation of China(Grant Nos.11072052,51221961)the National Basic Research Program of China("973"Project)(Grant No.2011CB013703)
文摘Tension leg platform(TLP)is a typical compliant offshore structure for oil/gas resources exploitation.In the design process,the prediction of the free surface elevation is of great importance for the determination of the air gap.So far,the existing researches for predicting the air gap of the TLPs focus on the supporting columns while pay little attention to the horizontal pontoons.For the second order diffraction problem or long incident wave condition,the velocity potential decays slowly with water depth and the effect of pontoons should not be neglected.Herein the effect of pontoons on the diffracted wave field in the vicinity of a TLP platform is investigated in this study.The diffraction of regular waves by a square array of truncated cylinders and a whole TLP structure is studied in detail by using both the linear and the second-order diffraction theory.Numerical calculation is performed for the free surface elevation and wave run up.Numerical results show that the near-trapping phenomenon can occur inside the TLP and leads to significantly increased wave height.To study the effect of pontoons on the free surface elevation comparisons are carried out between the results of these two structures with and without pontoons.It is found that pontoons have an appreciable effect on the diffracted wave field for long incident regular waves and increase the largest response notably when the near-trapping phenomenon occurs at the second-order.
文摘The sitting state of a sunken ship is usually related to the water depth, ship type, damage position, deadweight, and weight and density of the cargo. In salvage operation different means must be adopted according to the sitting state of the sunken ship to make the ship refloat. Refloating a big-angle tilted sunken ship is difficult, and uprighting a ship underwater is the most complicated procedure in salvage operation. This paper, based on practical experiences, systematizes and presents the calculating methods of uprighting sunken ships underwater.
基金supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA09A105)
文摘The off-bottom tow is an important method to lay pipeline for offshore oil and gas transportation in shallow water area. During the off-bottom towing operation, the actions such as sea current resistance, friction force of seabed, pontoon buoyancy, and tow force of tugboat can cause large deformation and fatigue damage to the pipeline. In order to keep the pipeline in safety, the lateral and vertical defomlations of pipeline must be controlled within an appropriate range. Theoretical study is carried out in the paper on the environmental forees acting on pipeline, pontoons and chaias, and the confimation of tow parameters including tow forces of tugboat, number of pontoons and length of chains. Then the pipeline in the off-bettom towing process may be simplified into a continuous beam with elastic supports under the concentrated and distributed forces. A finite element method is applied to achieve numerical solutions describing the distributions of deformation and stress along the pipeline. The results show that the lateral shape of the pipeline is like an arc with the maximal deformation appearing at the middle of the pipeline. The distributions of stress are similar between two arbitrary pontoons. Moreover, both deformation and stress have the inverse relation with the tow forces of tugboat.
基金supported by the National Natural Science Foundation of China(Grant Nos.51725903 and 52088102).
文摘A numerical study adopting the 2Dδ-SPH model is performed to compare the hydrodynamic characteristics of a single pontoon floating breakwater and a double pontoon floating breakwater.Numerical simulations are performed using theδ-SPH model and experimental tests are conducted to validate the numerical model.The numerical results of both the free surface elevations and motions of the floating breakwater are in good agreement with the experimental results.Numerical results show that when the pontoon drafts are larger,the double pontoon floating breakwater performs better in wave attenuations compared with the single pontoon floating breakwater,and for all the drafts,the amplitudes of motions including sway,heave and roll of the double pontoon floating breakwater is always smaller.In addition,increasing the spacing between the two pontoons can further reduce the amplitudes of pontoon motions and improve the wave attenuation ability of the double pontoon floating breakwater.
文摘A numerical model is developed by use of the boundary integral equation method to investigate the responses of a two-dimensional floating structure. The structure under consideration consisting of two pontoons, is connected by a rigid framework, and linked to the sea floor by a mooring system. The theoretical conception is based on potential theory with hnear external forces, and applied to an arbitrarily shaped body and water depth. The discussion includes the influence of draft and space between pontoons on the responses of the floating structure. Finally, the validity of the method is adequately verified by experimental results.
文摘With the rapid development of social economy, the rapid progress of science and technology, people＇s quality of life requirements are growing higher and higher, in order to further meet the growing masses of the growing sports fitness needs, the State Council in June 1995 approved the ＂ Fitness program outline＂. With the sound of physical education, sports activities are increasingly rich, but also gradually from the land movement to the development of water sports, and water power center other hand, people＇s demand for the environment pontoon project and bear the brunt of the project. On the and landscape is also rising. Water pontoon in this environment, but also toward the ecological water conservancy, landscape water direction. While the pontoon is the driving force of the economic development and social needs and other aspects to be reflected
文摘The objective of this study is to develop a procedure to analyze the motions of a floating pier comprised of several pontoons that are modeled as rigid bodies and connected to each other by flexible and rigid connectors.Recently,the use of floating piers has increased because of their advantages,such as faster and higher-quality construction,seismic force isolation for a full-scale mooring system,low dependence on local soil conditions and tides,ability to relocate or reconfigure the pier modules during the operation period and 75-100 years of repair-free service.A floating pier consists of a pier,access bridge,mooring system and fender system,each of which comes in many variations to suit different usages and construction considerations.The typical loads used in the design of these piers are dead loads,live loads,mooring loads,fender loads and environmental loads induced by wind,currents and waves.For numerical simulation,three types of piers are used:passenger piers,light-cargo piers and semi-heavy-cargo piers.The selected piers consist of several large pontoons joined by pivots and have a pile-based mooring system.These piers are modeled by SAP2000software as two-dimensional frames that are linked together.As the first step,each type of pier is subjected to loading,and its general behavior is assessed.According to this behavior,the major load combinations are described for the design of piers and analyzed to determine the behavior of the modules.Lastly,according to the analysis results and the safe use and stability considerations,such as the maximum draft and longitudinal gradient,the dimensions of each module in each pier type are presented.
