Qibin Ou, Jin Yang, Zhenxiang Zhang, Luo Liu, Yichi Zhang, Ximo Qu
With the continuous development of the global economy and industry, and gradually expand the size of offshore oil exploration and transportation, the possibility of oil field leakage, damage of offshore tanker, oil leakage of the offshore ship and the oil spill is increasing continuously, and the harmfulness is increasing continuously. It has seriously polluted the Marine environment and destroyed the ecological balance, and seriously wasted the oil resources. Therefore, this paper developed a kind of offshore oil spill removal ship which can quickly, accurately, and effectively recover oil spill. This paper designs an offshore oil removal device with a variable Angle of attack. Through the use of Rhino and SolidWorks modeling software for the three-dimensional overall design. The variable Angle of attack offshore oil spill removal ship can be divided into seven major systems, which are the main hull of the variable angle of attack, the side hull, the oil suction, and deoiling rollers, the oil collecting groove and oil collecting chamber, the oil baffle, the steering platform, the communication equipment, the propulsion equipment, the main hull, and the external ship docking equipment. At the same time, the new type of offshore oil absorption material is installed on the double roller oil absorption mechanism, and each component system of the offshore oil removal ship is assembled. In this paper, the design of a variable Angle of attack offshore oil spill removal ship can provide a reference for the research and design of a new offshore oil spill treatment device.
{"title":"Design and Research of Offshore Oil Spill Removal Ship With Variable Angle of Attack","authors":"Qibin Ou, Jin Yang, Zhenxiang Zhang, Luo Liu, Yichi Zhang, Ximo Qu","doi":"10.1115/omae2021-63546","DOIUrl":"https://doi.org/10.1115/omae2021-63546","url":null,"abstract":"\u0000 With the continuous development of the global economy and industry, and gradually expand the size of offshore oil exploration and transportation, the possibility of oil field leakage, damage of offshore tanker, oil leakage of the offshore ship and the oil spill is increasing continuously, and the harmfulness is increasing continuously. It has seriously polluted the Marine environment and destroyed the ecological balance, and seriously wasted the oil resources. Therefore, this paper developed a kind of offshore oil spill removal ship which can quickly, accurately, and effectively recover oil spill. This paper designs an offshore oil removal device with a variable Angle of attack. Through the use of Rhino and SolidWorks modeling software for the three-dimensional overall design. The variable Angle of attack offshore oil spill removal ship can be divided into seven major systems, which are the main hull of the variable angle of attack, the side hull, the oil suction, and deoiling rollers, the oil collecting groove and oil collecting chamber, the oil baffle, the steering platform, the communication equipment, the propulsion equipment, the main hull, and the external ship docking equipment. At the same time, the new type of offshore oil absorption material is installed on the double roller oil absorption mechanism, and each component system of the offshore oil removal ship is assembled. In this paper, the design of a variable Angle of attack offshore oil spill removal ship can provide a reference for the research and design of a new offshore oil spill treatment device.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"16 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91549183","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}
Extreme waves at the sea surface can have severe impacts on marine structures. One of the theoretical mechanisms leading to extreme waves is the instability of deep-water wave trains subject to initially small perturbations, which then grow exponentially. The present study focuses on the two-dimensional Benjamin–Feir (or modulational) instability and the three-dimensional crescent (or horseshoe) waves, also known as Class I and Class II instabilities, respectively. Numerical studies on Class I and Class II wave instabilities to date have been limited to models founded on potential flow theory, thus they could only properly investigate the process from initial growth of the perturbations to the initial breaking point. The present study conducts numerical simulations to investigate the generation and development of wave instabilities involving the wave breaking process. A CFD model solving Reynolds-averaged Navier-Stokes (RANS) equations coupled with turbulence closure in terms of the anisotropic Reynolds stress model is applied. Wave form evolutions, Fourier amplitudes, and the turbulence beneath the broken waves are investigated.
{"title":"CFD Simulation of Nonlinear Deep-Water Wave Instabilities Involving Wave Breaking","authors":"Yuzhu Li, D. Fuhrman","doi":"10.1115/omae2021-62805","DOIUrl":"https://doi.org/10.1115/omae2021-62805","url":null,"abstract":"\u0000 Extreme waves at the sea surface can have severe impacts on marine structures. One of the theoretical mechanisms leading to extreme waves is the instability of deep-water wave trains subject to initially small perturbations, which then grow exponentially. The present study focuses on the two-dimensional Benjamin–Feir (or modulational) instability and the three-dimensional crescent (or horseshoe) waves, also known as Class I and Class II instabilities, respectively. Numerical studies on Class I and Class II wave instabilities to date have been limited to models founded on potential flow theory, thus they could only properly investigate the process from initial growth of the perturbations to the initial breaking point. The present study conducts numerical simulations to investigate the generation and development of wave instabilities involving the wave breaking process. A CFD model solving Reynolds-averaged Navier-Stokes (RANS) equations coupled with turbulence closure in terms of the anisotropic Reynolds stress model is applied. Wave form evolutions, Fourier amplitudes, and the turbulence beneath the broken waves are investigated.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91367062","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 testing of Gator, a hydraulic Power Take Off (PTO) being commercialised for the Aquaculture market. Gator uses a novel polymer bellows to pump pressurised water through a power take off system, while also providing a non-linear force response that reduces mooring line loads over traditional mooring lines. The Gator system is comprised of 4 distinct subsystems: The Gator pump, hydraulics, turbine, and electrical storage & control. The Gator pump is a polymer component that compresses under load, pumping water through check valves into the hydraulic system. The connected hydraulic system takes the pressurised water, regulates the pressure and flow rates with an accumulator, and provides a steady flow of water to the turbine, generating electricity. This paper will provide an overview of the technical development of the Gator system over several phases, which has focussed its adaptation for use in the aquaculture industry as an inline pump on cage mooring lines. A description of comprehensive testing undertaken on a linear test rig to simulate the variable loading that the system would experience in operation will be provided as well as some of the early characterisation results from this testing.
{"title":"Development and Testing of Bridle Line Power Generation for Aquaculture","authors":"Patrick M. Grehan, C. Casey, P. McEvoy, A. Wann","doi":"10.1115/omae2021-62888","DOIUrl":"https://doi.org/10.1115/omae2021-62888","url":null,"abstract":"\u0000 This paper presents the development and testing of Gator, a hydraulic Power Take Off (PTO) being commercialised for the Aquaculture market. Gator uses a novel polymer bellows to pump pressurised water through a power take off system, while also providing a non-linear force response that reduces mooring line loads over traditional mooring lines.\u0000 The Gator system is comprised of 4 distinct subsystems: The Gator pump, hydraulics, turbine, and electrical storage & control. The Gator pump is a polymer component that compresses under load, pumping water through check valves into the hydraulic system. The connected hydraulic system takes the pressurised water, regulates the pressure and flow rates with an accumulator, and provides a steady flow of water to the turbine, generating electricity.\u0000 This paper will provide an overview of the technical development of the Gator system over several phases, which has focussed its adaptation for use in the aquaculture industry as an inline pump on cage mooring lines.\u0000 A description of comprehensive testing undertaken on a linear test rig to simulate the variable loading that the system would experience in operation will be provided as well as some of the early characterisation results from this testing.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82098785","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}
Brendan Guillouzouic, François Pétrié, V. Lafon, Fabienne Fremont
Mooring is one of the key components of a floating offshore wind turbine since the mooring rupture may lead to the total loss of one or even several turbines in a farm. Even if a large experience in moorings of floating bodies was gained in the oil & gas industry, the renewable energies face new challenges such as reducing the cost as much as possible, reducing the footprint to limit environmental impact or avoid any interference between mooring lines and electrical cables in a farm composed of several tens of turbines. Those constraints may lead to designs suffering snap loads which shall be avoided as far as practicable or addressed with a particular attention, as this quasi-instantaneous stretching of the mooring lines may lead to very high tensions governing the design. This paper presents the results of physical model tests and numerical simulations performed on a typical floating wind turbine concept of semi-submersible type. Both qualitative and quantitative comparisons are performed. The objective is to provide guidelines for FOWT mooring designers regarding the selection of the drag coefficient to consider. A very significant influence of the line’s drag coefficient, on both the probability of occurrence and the magnitude of snap loads, was found. This subject is hereby fully documented on a given case study and general discussions on scale effects, marine growth effects and other parameters are also made. The numerical simulations were performed using the dynamic analysis software ‘OrcaFlex’. The experiments have been carried out by Océanide, in south of France.
{"title":"Experimental and Numerical Study of the Influence of Drag Coefficient on Snap Loads in Mooring Lines of a Floating Offshore Wind Turbine","authors":"Brendan Guillouzouic, François Pétrié, V. Lafon, Fabienne Fremont","doi":"10.1115/omae2021-60794","DOIUrl":"https://doi.org/10.1115/omae2021-60794","url":null,"abstract":"\u0000 Mooring is one of the key components of a floating offshore wind turbine since the mooring rupture may lead to the total loss of one or even several turbines in a farm.\u0000 Even if a large experience in moorings of floating bodies was gained in the oil & gas industry, the renewable energies face new challenges such as reducing the cost as much as possible, reducing the footprint to limit environmental impact or avoid any interference between mooring lines and electrical cables in a farm composed of several tens of turbines.\u0000 Those constraints may lead to designs suffering snap loads which shall be avoided as far as practicable or addressed with a particular attention, as this quasi-instantaneous stretching of the mooring lines may lead to very high tensions governing the design.\u0000 This paper presents the results of physical model tests and numerical simulations performed on a typical floating wind turbine concept of semi-submersible type. Both qualitative and quantitative comparisons are performed. The objective is to provide guidelines for FOWT mooring designers regarding the selection of the drag coefficient to consider.\u0000 A very significant influence of the line’s drag coefficient, on both the probability of occurrence and the magnitude of snap loads, was found. This subject is hereby fully documented on a given case study and general discussions on scale effects, marine growth effects and other parameters are also made.\u0000 The numerical simulations were performed using the dynamic analysis software ‘OrcaFlex’.\u0000 The experiments have been carried out by Océanide, in south of France.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77912061","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}
Integrity and stability of Remotely Operated Vehicle (ROV) when passing through the splash zone is one of the main concerns in the design of an ROV-umbilical system. Due to the lightweight nature of ROV in water, the umbilical experiences repetitive rapid transitions between slack and taut as the ROV travels through the splash zone. These rapid transitions induce tension spikes in the umbilical, namely snap forces, that can endanger the launch and recovery of an ROV. Therefore, it is important to ensure that the tension spikes do not exceed the safe working load of the umbilical. In this study, launch and recovery of a deep-water work class ROV are experimentally investigated using a 1:10 scaled ROV model through a series of wave flume tests. Different regular and irregular waves are generated in the flume while the ROV model is hung over the flume in four different positions. The tension time-history in the line is measured and recorded using a load cell at the top-end of the line. A simplified numerical model for launch and recovery of the ROV is developed and the numerical results are compared with the experimental ones. It is shown that the presented simplified model can be accurately used for analysis of launch and recovery of the ROV.
{"title":"Experimental Wave Flume Tests in ROV-Wave Interaction Effects on the Line Tension for a Work Class ROV in Splash Zone","authors":"Michael Binsar Lubis, M. Kimiaei","doi":"10.1115/omae2021-61098","DOIUrl":"https://doi.org/10.1115/omae2021-61098","url":null,"abstract":"\u0000 Integrity and stability of Remotely Operated Vehicle (ROV) when passing through the splash zone is one of the main concerns in the design of an ROV-umbilical system. Due to the lightweight nature of ROV in water, the umbilical experiences repetitive rapid transitions between slack and taut as the ROV travels through the splash zone. These rapid transitions induce tension spikes in the umbilical, namely snap forces, that can endanger the launch and recovery of an ROV. Therefore, it is important to ensure that the tension spikes do not exceed the safe working load of the umbilical.\u0000 In this study, launch and recovery of a deep-water work class ROV are experimentally investigated using a 1:10 scaled ROV model through a series of wave flume tests. Different regular and irregular waves are generated in the flume while the ROV model is hung over the flume in four different positions. The tension time-history in the line is measured and recorded using a load cell at the top-end of the line. A simplified numerical model for launch and recovery of the ROV is developed and the numerical results are compared with the experimental ones. It is shown that the presented simplified model can be accurately used for analysis of launch and recovery of the ROV.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"129 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79575478","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}
Three-dimensional effects on slamming loads predictions of a ship section are investigated numerically using the unsteady incompressible Reynolds-Average Navier-Stokes (RANS) equations and volume of fluid (VOF) method, which are implemented in interDyMFoam solver in open-source library OpenFoam. A convergence and uncertainty study is performed considering different resolutions and constant Courant number (CFL) following the ITTC guidelines. The numerical solutions are validated through comparisons of slamming loads and motions between the CFD simulations and the available experimental values. The total slamming force and slamming pressures on a 2D ship section and the 3D model are compared and discussed. Three-dimensional effects on the sectional force and the pressures are quantified both in transverse and longitudinal directions of the body considering various entry velocities. The non-dimensional pressure coefficient distribution on the 3D model is presented.
{"title":"Three-Dimensional Effects on Slamming Loads","authors":"Shan Wang, C. Guedes Soares","doi":"10.1115/omae2021-63741","DOIUrl":"https://doi.org/10.1115/omae2021-63741","url":null,"abstract":"\u0000 Three-dimensional effects on slamming loads predictions of a ship section are investigated numerically using the unsteady incompressible Reynolds-Average Navier-Stokes (RANS) equations and volume of fluid (VOF) method, which are implemented in interDyMFoam solver in open-source library OpenFoam. A convergence and uncertainty study is performed considering different resolutions and constant Courant number (CFL) following the ITTC guidelines. The numerical solutions are validated through comparisons of slamming loads and motions between the CFD simulations and the available experimental values. The total slamming force and slamming pressures on a 2D ship section and the 3D model are compared and discussed. Three-dimensional effects on the sectional force and the pressures are quantified both in transverse and longitudinal directions of the body considering various entry velocities. The non-dimensional pressure coefficient distribution on the 3D model is presented.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"113 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80744736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The behavior of a floating structure results from the mechanics of its, more or less, rigid body and the hydrostatic and hydrodynamic forces acting on it. Particularly for ships, as long and slender bodies, the axis of roll and its vertical position is of special importance. It is around this axis that the lowest lateral accelerations in roll motion occur, which is not only weakly damped but also easily stimulated due to the relatively low mass moment of inertia around the ship’s longitudinal axis. With the intention of clarifying some widespread misconceptions about the location of this axis and to investigate its relation to the natural roll period, full scale measurements have been carried out using a set of two mobile Inertial-Measurement-Units. The Inertial-Measurement-Units were placed on different heights, one above and one below the assumed location of the axis of rotation. Based on the measured accelerations and angular velocities, the average vertical location of the axis of the roll motion for small angles is determined.
{"title":"Determination of the Vertical Location of the Axis of Rotation of the Roll Motion From Full-Scale Measurements","authors":"L. Johnsen, S. Krüger","doi":"10.1115/omae2021-62301","DOIUrl":"https://doi.org/10.1115/omae2021-62301","url":null,"abstract":"\u0000 The behavior of a floating structure results from the mechanics of its, more or less, rigid body and the hydrostatic and hydrodynamic forces acting on it. Particularly for ships, as long and slender bodies, the axis of roll and its vertical position is of special importance. It is around this axis that the lowest lateral accelerations in roll motion occur, which is not only weakly damped but also easily stimulated due to the relatively low mass moment of inertia around the ship’s longitudinal axis. With the intention of clarifying some widespread misconceptions about the location of this axis and to investigate its relation to the natural roll period, full scale measurements have been carried out using a set of two mobile Inertial-Measurement-Units. The Inertial-Measurement-Units were placed on different heights, one above and one below the assumed location of the axis of rotation. Based on the measured accelerations and angular velocities, the average vertical location of the axis of the roll motion for small angles is determined.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81611477","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}
A wave field in a wave basin inevitably has spatial variation due to the wave’s cylindrical propagation property. Therefore, we aimed to develop an optimization method for the control of wave-makers to produce a spatially uniform wave field in a specified test zone inside a wave basin with an arbitrary arrangement of wave-makers. The optimization is based on the simulated annealing algorithm, a method for finding a globally optimal solution, which was combined with a numerical wave basin based on linear wave-maker theory. A wave generation experiment was performed in the actual sea model basin (80 m long, 40 m wide, and 4.5 m deep) at the National Maritime Research Institute to validate the proposed optimization method. A case study was conducted with a long-crested regular-wave with a wave height of 10 cm, wavelength of 4.0 m, and wave direction of 180 degrees, which corresponds to the longitudinal direction of the wave basin. A 40-m × 14-m test zone was set in the middle of the wave basin. The experimental results with and without the proposed optimization were compared, which confirmed that the spatial uniformity of the wave field was improved, and the coefficient of variation for the wave height in the test zone decreased from 0.127 to 0.029.
由于波的圆柱传播特性，波盆中的波场不可避免地存在空间变异。因此，我们的目标是开发一种控制造波器的优化方法，使造波器在任意排列的波盆内的指定测试区域内产生空间均匀的波场。该优化方法基于模拟退火算法，这是一种寻找全局最优解的方法，并结合了基于线性造波理论的数值波池。在国家海洋研究所的实际海洋模型盆地(长80 m，宽40 m，深4.5 m)中进行了波浪生成实验，验证了所提出的优化方法。以波高为10 cm、波长为4.0 m、波向为180度的长峰规则波为例进行了研究，该波方向与波盆纵向相对应。在波盆中部设置40 m × 14 m试验区。将优化前后的实验结果进行对比，证实了优化后的波场空间均匀性得到改善，试验区波高变异系数由0.127降至0.029。
{"title":"Optimization of Segmented Wave-Maker Control to Generate Spatially Uniform Regular Waves in a Rounded-Rectangular Wave Basin","authors":"Daichi Ota, H. Houtani, H. Sawada, H. Taguchi","doi":"10.1115/omae2021-62773","DOIUrl":"https://doi.org/10.1115/omae2021-62773","url":null,"abstract":"\u0000 A wave field in a wave basin inevitably has spatial variation due to the wave’s cylindrical propagation property. Therefore, we aimed to develop an optimization method for the control of wave-makers to produce a spatially uniform wave field in a specified test zone inside a wave basin with an arbitrary arrangement of wave-makers. The optimization is based on the simulated annealing algorithm, a method for finding a globally optimal solution, which was combined with a numerical wave basin based on linear wave-maker theory. A wave generation experiment was performed in the actual sea model basin (80 m long, 40 m wide, and 4.5 m deep) at the National Maritime Research Institute to validate the proposed optimization method. A case study was conducted with a long-crested regular-wave with a wave height of 10 cm, wavelength of 4.0 m, and wave direction of 180 degrees, which corresponds to the longitudinal direction of the wave basin. A 40-m × 14-m test zone was set in the middle of the wave basin. The experimental results with and without the proposed optimization were compared, which confirmed that the spatial uniformity of the wave field was improved, and the coefficient of variation for the wave height in the test zone decreased from 0.127 to 0.029.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"114 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87973820","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}
Due to the fast increase of the vessels’ size over the past few years the actual water depth is becoming more and more relevant for seakeeping problems. The highly frequented sea route TSS Terschelling – German Bight for example is a shallow water route for large vessels which are now affected by the reduced keel clearance. Many shallow water depth areas occur also in coastal areas or inland seas. If a vessel is travelling in shallow water sea states, the hydrodynamic forces will change compared to deep water sea states and they are essential for further seaway calculations. Furthermore, a rough but easy evaluation of the incoming seaway is the roll period. Shallow water effects should be taken into account for calculating roll periods and thereby predicting a manageable or risky seaway situation. This paper presents the implementation of shallow water effects into an existing 2D panel code. With this panel code the hydrodynamic forces for the vessel’s frames are calculated based on the potential theory in the frequency domain, which is a validated approach in the early design stage. The panel code is part of the ship design environment E4 which is being developed by the Institute of Ship Design and Ship Safety, among others. With the expanded method it is possible to calculate hydrodynamic forces also in shallow water in all degrees of freedom. Therefore, the frame motions are converted to global ship motions. Furthermore, for the usage in the early design stage the calculations should be fast but also accurate. The obtained calculation results are therefore validated with full scale measurement using Inertial-Measurement-Units.
近年来，由于船舶尺寸的迅速增大，船舶的实际水深与船舶的耐波性问题的关系越来越密切。例如，频繁使用的TSS Terschelling - German Bight航线是大型船只的浅水航线，现在受到龙骨间隙减少的影响。许多浅水深度区也出现在沿海地区或内陆海。如果船舶在浅水海况下航行，水动力与深水海况相比会发生变化，这对于进一步的航道计算是必不可少的。此外，一个粗略但简单的估算入海航道的方法是滚动周期。在计算滚动周期时应考虑浅水效应，从而预测可控制或危险的航道情况。本文介绍了在现有的二维面板代码中实现浅水效果。利用该面板代码，基于频域势理论计算了船体框架的水动力，这是一种在设计初期得到验证的方法。面板规范是船舶设计环境E4的一部分，该环境正在由船舶设计和船舶安全研究所等机构开发。用扩展的方法也可以计算浅水中所有自由度的水动力。因此，将帧运动转换为全局船舶运动。此外，对于早期设计阶段的使用，计算既要快速又要准确。因此，利用惯性测量单元进行了满量程测量，验证了计算结果。
{"title":"Determination of Hydrodynamic Masses and Roll Periods of Ships in Shallow Water","authors":"Larissa Jannsen, S. Krüger","doi":"10.1115/omae2021-62782","DOIUrl":"https://doi.org/10.1115/omae2021-62782","url":null,"abstract":"\u0000 Due to the fast increase of the vessels’ size over the past few years the actual water depth is becoming more and more relevant for seakeeping problems. The highly frequented sea route TSS Terschelling – German Bight for example is a shallow water route for large vessels which are now affected by the reduced keel clearance. Many shallow water depth areas occur also in coastal areas or inland seas. If a vessel is travelling in shallow water sea states, the hydrodynamic forces will change compared to deep water sea states and they are essential for further seaway calculations. Furthermore, a rough but easy evaluation of the incoming seaway is the roll period. Shallow water effects should be taken into account for calculating roll periods and thereby predicting a manageable or risky seaway situation. This paper presents the implementation of shallow water effects into an existing 2D panel code. With this panel code the hydrodynamic forces for the vessel’s frames are calculated based on the potential theory in the frequency domain, which is a validated approach in the early design stage. The panel code is part of the ship design environment E4 which is being developed by the Institute of Ship Design and Ship Safety, among others. With the expanded method it is possible to calculate hydrodynamic forces also in shallow water in all degrees of freedom. Therefore, the frame motions are converted to global ship motions. Furthermore, for the usage in the early design stage the calculations should be fast but also accurate. The obtained calculation results are therefore validated with full scale measurement using Inertial-Measurement-Units.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87320530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The forces on marine and offshore structures are often affected by spilling breakers. The spilling breaker is characterized by a roller of mixed air and water with a forward speed approximately equal to the wave celerity. This high speed in the top of the wave has the potential to induce high wave loads on upper parts of the structures. This study analyzed the effect of the air content on the forces. The analyses used the Morison equation to examine the effect of the percentage of air on the forces. An experimental set-up was developed to include the injection of air into an otherwise calm water body. The air-injection did introduce a high level a turbulence. It was possible to assess the amount of air content in the water for different amounts of air-injection. In the mixture of air and water the force on an oscillating square cylinder was measured for different levels of air-content, — also in the case without air. The measurements indicated that force coefficients for clear water could be use in the Morison equation as long as the density for water was replaced by the density for the mixture of air and water.
{"title":"Effect of Air Fraction on Force Coefficients in Oscillatory Flow","authors":"M. Vested, E. D. Christensen","doi":"10.1115/omae2021-61122","DOIUrl":"https://doi.org/10.1115/omae2021-61122","url":null,"abstract":"\u0000 The forces on marine and offshore structures are often affected by spilling breakers. The spilling breaker is characterized by a roller of mixed air and water with a forward speed approximately equal to the wave celerity. This high speed in the top of the wave has the potential to induce high wave loads on upper parts of the structures. This study analyzed the effect of the air content on the forces. The analyses used the Morison equation to examine the effect of the percentage of air on the forces. An experimental set-up was developed to include the injection of air into an otherwise calm water body. The air-injection did introduce a high level a turbulence. It was possible to assess the amount of air content in the water for different amounts of air-injection. In the mixture of air and water the force on an oscillating square cylinder was measured for different levels of air-content, — also in the case without air. The measurements indicated that force coefficients for clear water could be use in the Morison equation as long as the density for water was replaced by the density for the mixture of air and water.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"86 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85315998","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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