Volume 5A: Ocean Engineering最新文献

{"title":"Identification and Investigation of Extreme Events on Marine Structures Using ALE Approach and Hydrodynamic Coupling of Navier Stokes- and Laplace Equation-Based Models","authors":"A. Kamath, T. Martin, Weizhi Wang, Csaba Pákozdi, H. Bihs","doi":"10.1115/omae2022-79036","DOIUrl":"https://doi.org/10.1115/omae2022-79036","url":null,"abstract":"\u0000 Increased deployment of offshore wind turbines is seen as an important pathway to increase green renewable energy production. Improved and rapid identification of extreme events and evaluation of hydrodynamic loads due to such events is essential to reduce the cost of energy production. Numerical modelling to pre-screen sea states and identify the crucial events to prioritise model tests will make a major contribution to reduce design times and costs for such structures. In this effort, a highly efficient and nonlinear numerical model based on the Laplace equations is used to generate undisturbed wave kinematics. Such a simulation is used to identify extreme wave events in a sea state realisation and further, the wave loading due to such events are evaluated using Morison Formula. Events screened in this manner can then be transferred to a high-resolution model such as a Navier-Stokes equations-based solver to investigate the hydrodynamics in details. The implementation of such a method in the open-source hydrodynamic model REEF3D is presented in this work.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126629428","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}

{"title":"An Experimental Study on the Wave Force on the Slope of Smoothed Mound Breakwater With and Without Crown Wall Under Medium-Long Period Waves","authors":"Xinyu Han, Sheng Dong","doi":"10.1115/omae2022-79286","DOIUrl":"https://doi.org/10.1115/omae2022-79286","url":null,"abstract":"A Mound breakwater is a common coastal defence against waves. The wave force has greatly related to the stability of the armour blocks. Medium-long period waves have greatly impact on coastal structures and are attracting more and more attention. In this work, the wave force and pressure distribution on the slope of smoothed mound breakwater were studied by experiments. Total of 140 tests were carried out, in which 70 sets are breakwaters with crown wall, and the other 70 sets are breakwaters without crown wall. In the scope of medium-long period waves, the wave force on slope of the breakwater with crown wall is similar to that without crown wall. Neelamani method is more suitable for the breakwater without crown wall and its top submerged. Under short period waves, the maximum pressure on the slope is different. The pressure on the slope with and without crown wall is similar. Pressure at berm with crown wall is greater than that without crown wall. The maximum ratio of the horizontal velocity in front of breakwater with and without crown wall is about 2. A formula was proposed to predict the difference of pressure at the berm with and without crown wall through the difference of reflection coefficient Cr.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126648077","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}

{"title":"Modelling Green Water Impact Load on a Single Circular Cylinder","authors":"Min Gao, S. Draper, G. McCauley, Lifen Chen, Xiantao Zhang, H. Wolgamot, P. Taylor","doi":"10.1115/omae2022-81242","DOIUrl":"https://doi.org/10.1115/omae2022-81242","url":null,"abstract":"\u0000 This paper investigates the ability of physical and numerical models to simulate green water impact loads on a circular cylinder located on top of a fixed box. A focused wave group was used to overtop the box and generate the green water event, which resembled a plunging wave with air entrainment. The plunger collapsed and ran across the deck before impacting the cylinder and scattering. With respect to the physical modelling, identical experiments were conducted in two different laboratories, in different countries. The numerical modelling comprised computational fluid dynamics (CFD) simulations performed using OpenFOAM. The flow features, the force on the cylinder and the surface elevation on top of the box are compared in detail across the two physical models and the CFD. Good agreement in the load measurements from the two physical model tests implies very repeatable results despite the complex flow-structure interaction observed. Comparison of the physical and numerical models indicate the flow measured on top of the box and the green water load are sensitive to experimental precision, but agreement is generally satisfactory. This agreement between experiment and CFD serves as an example of the reliability of CFD for modelling green water impact loads.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131026027","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}

{"title":"Wave Loads and Ship Motions Evaluated by Linear Strip and Panel Methods","authors":"Aaro Karola, S. Hirdaris, J. Matusiak, T. Mikkola","doi":"10.1115/omae2022-79702","DOIUrl":"https://doi.org/10.1115/omae2022-79702","url":null,"abstract":"\u0000 Despite the rapid development of Computational Fluid Dynamics (CFD) the demand for potential flow hydrodynamics in ship design remains relevant. This is because 2D and 3D Boundary Element Methods (BEM) can be applied for rapid prediction of motions and wave loads. This paper compares results from linear 2D strip-theory and 3D Green function methods with empirical forward speed correction factors in terms of ship motions, radiation forces and wave loads. The former approach applies a “Frank Close-fit” method to solve the radiation problem in 2D. The latter utilizes a pulsating “Green function” source distribution method to solve the radiation problem in 3D. Results are validated against experimental data available for a container ship. It is shown that the motion RAOs obtained by both methods are similar and agree with the experimental values. However, responses in terms of longitudinal distribution of wave loads show discrepancies which increase with wave length shortening and closer to the bow region. An increasing role of diffraction and disregarding forward speed wave making affect the results in short waves. Moreover, it is concluded that solving the linear seakeeping problem is not very sensitive to hull form details and to the modelling of forward speed effects on radiation.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117210993","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}

{"title":"Multiple Hinged Floaters – An Experimental Study on Hydrodynamic Responses in Waves","authors":"Gerrit Assbrock, J. Lucas, Jens Ley","doi":"10.1115/omae2022-78435","DOIUrl":"https://doi.org/10.1115/omae2022-78435","url":null,"abstract":"\u0000 Exploiting space at sea is a conceivable solution in case of land scarcity in coastal areas. A modular floating platform can meet this growing need. The modularity allows platform expansions by linking multiple floaters with dedicated connectors. A durable structural design of connectors requires a reliable prediction of loads in waves. Multi-body hydrodynamics and effects of wave shielding are decisive factors that need to be considered. This experimental study comprised the measurement of motions and loads in long-crested waves with different configurations of floaters. Three component force gauges captured the loads acting on the connectors. An optical tracking system measured the motions of the connected floaters in regular waves and irregular sea states of different steepness’. The experimental results revealed higher order structural responses, relative motions, and impact loads subject to the wave’s steepness. Tensioning and compressing loads showed to be asymmetric and occurred at different return periods.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114250951","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}

{"title":"Two-Dimensional Numerical Analysis of Mean Wave Drift Loads on Two Fixed Boxes","authors":"L. Tan, T. Ikoma, Changhong Hu","doi":"10.1115/omae2022-79910","DOIUrl":"https://doi.org/10.1115/omae2022-79910","url":null,"abstract":"\u0000 Wave drift forces on two barges in side-by-side arrangement are of engineering significance for control of the distance between the vessels. Hence the influence of resonant behaviors between the two barges on drift forces is worthy to investigating. In this paper, a two-dimensional numerical model is developed to evaluate the time-averaged drift forces on two floating bodies. The near-field and far-field methods have been implemented in an in-house program code for computations. First, numerical validations were conducted against published data in literatures. Then, the influence of the gap width and edge shapes of two fixed floating boxes were investigated numerically. It is found that the total mean surge drift force in wave direction was substantially reduced by the piston mode resonance in the gap, whereas considerable drift forces were observed on two respective boxes in opposite directions. Further examinations indicate that the effect of resonant wave behaviors on drift force is dependent on viscous damping of gap resonance.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125044247","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}

{"title":"Spray Icing on ONEGA Vessel- A Comparison of Liquid Water Content Expressions","authors":"S. Dhar, E. Samuelsen, M. Naseri, K. G. Aarsæther, K. Edvardsen","doi":"10.1115/omae2022-79919","DOIUrl":"https://doi.org/10.1115/omae2022-79919","url":null,"abstract":"\u0000 The hazards associated with ice accretion primarily due to impinging freezing sea spray on ship structures are considered among serious safety concerns for ships operating in the colder regions. An accurate sea-spray icing-estimation model to evaluate the ice accumulation during operations in these regions can make marine operations safer. The accuracy of the present icing models for estimating icing on ships is substantially dependent on the incoming spray flux generated by the wave-ship interaction. In order to illustrate this, the vessel icing incident of the fishing vessel ONEGA is considered, which capsized after encountering heavy icing. In this study, the ONEGA vessel is modeled using a stability-calculation program. Then assuming the vessel to maintain minimum stability criteria prior to icing, the minimum likely amount of ice accumulation in the exposed locations that destabilized the vessel is estimated. This estimation is compared against another method used to evaluate ice thickness over the period ONEGA was accreting ice. The latter method utilizes the operational weather forecasting model used by MET Norway — “Marine-Icing model for the Norwegian COast Guard (MINCOG)”. The MINCOG model uses spray-flux estimations based on past empirical observations mainly obtained from fishing trawlers. The spray-flux consists of important elements like the liquid-water content (lwc) and the spray-generation frequency. An analysis is carried out applying different formulations for these two elements proposed by different researchers to see the variation in evaluating the total ice accumulation. After noticing the difference in results in total ice thickness from the stability and the icing-model methods used in this study, it is concluded that more investigation and field measurements are needed concerning the neglecting of the contribution of wind-generated spray in the spray flux formula used in MINCOG. Accordingly, multiple real-time spray measurements to develop a more suitable spray-flux formulation may improve the ice accumulation estimation over a longer time period.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126414031","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}

{"title":"A Physical-Based Damping Model of Gap and Moonpool Resonance in WAMIT","authors":"Senthuran Ravinthrakumar, Babak Ommani, T. Kristiansen, Idunn Olimb, Bernt Karsten Lyngvær","doi":"10.1115/omae2022-79673","DOIUrl":"https://doi.org/10.1115/omae2022-79673","url":null,"abstract":"\u0000 An engineering model to estimate and incorporate quadratic damping of the piston-mode moonpool responses in the proximity of the piston mode period is proposed. The model provides a physical-based equivalent linearized damping coefficient. The method is not limited to forced motion, but applicable to freely floating moonpool vessels. Further, it is not limited to moonopools, but can be generalized to gap resonance problems, such as side-by-side operations. The soundness of the proposed physical-based method is demonstrated using the panel code WAMIT with a linear damping term in the free-surface boundary condition inside the moonpool using two existing moonpool experiments as case studies; (1) a two-dimensional rectangular box with a moonpool subject to forced heave, and (2) a freely floating offshore vessel in incident waves. The WAMIT computations using the proposed method reconstructs the experimentally obtained piston-mode and vessel responses well. We suggest that the proposed method can be used with fair degree of confidence in an early design or operational analysis phase, in the (often) case that the quadratic damping is not known from either experiments or CFD. To our knowledge, this is the first general, physical-based piston-mode damping model that does not require any tuning from experiments.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"37 20","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131806291","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}

{"title":"An Implicit Time-Domain Rankine Panel Method for Ship Motions in a Non-Inertial Body-Fixed Frame of Reference","authors":"H. Liang, Yanlin Shao, Kie Hian Chua, A. Magee","doi":"10.1115/omae2022-79054","DOIUrl":"https://doi.org/10.1115/omae2022-79054","url":null,"abstract":"\u0000 Evaluation of wave loads on a ship translating in water waves is of practical importance in ship hydrodynamics, because it is paramount to the design of ship hull structures and provides essential inputs for ship maneuvering analysis. The linear radiation and diffraction of water waves by a translating ship is studied in this paper. A time-domain Rankine panel method is developed in a non-inertial body-fixed coordinate system, which is able to consider large-amplitude horizontal motions consistently. The double-body flow is used as the basic steady flow model. To ensure numerical stability, an implicit Euler scheme is adopted for time marching, and horizontal derivatives on the free surface are calculated using an upwind-biased finite difference scheme. Numerical examples in comparison with experimental measurements are exhibited to demonstrate the validity of the developed solver.","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134002643","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}

{"title":"A Single Cavitation Bubble Induced Damage","authors":"H. Sagar, O. el Moctar","doi":"10.1115/omae2022-78536","DOIUrl":"https://doi.org/10.1115/omae2022-78536","url":null,"abstract":"\u0000 In the present work, we experimentally and numerically investigated the dynamics of a millimeter-sized cavitation bubble generated nearby a solid surface. In experiments, bubbles are induced by a focused Nd-YAG laser generating plasma. A specimen of the commercially pure aluminum surface was placed nearby a bubble at varying relative wall distances. Here, the relative wall distance is a ratio of the distance between the bubble center and specimen surface, and the maximum radius of the bubble. In experiments, we captured the bubble’s dynamics by back illumination method using a highspeed camera. Damage obtained was characterized by an optical microscope and profilometer. The surface profiles and damage patterns quantified the damage characteristics. The three-dimensional flow was captured numerically by solving the Navier-Stokes equations in an Euler-Euler approach with barotropic equations of state. The computations were performed assuming both water and vapor as compressible phases. The dynamics of a single bubble obtained in computations were compared with the experiments for shapes and collapsing times. The computed characteristics of flow around a bubble near the solid surface, e.g. impact velocities and pressures were also discussed. Additionally, the dynamics of a microscopic bubble collapse near the surface was also investigated to compute collapse-induced wall shear rate and flow around the collapsing bubble. The results of numerical simulations were compared with the existing experimental data. The comparisons showed, a good qualitative and quantitative agreement. Overall, the numerical method well reflected the dynamics bubble up to three collapses and resolved flow around the bubble. The statistical data of pits obtained are also useful in deriving loads induced by a single bubble collapse. Overall, this work extensively comprises the single cavitation bubble dynamics and induced damage. This article summarizes the investigations of Sagar (2018) and Sagar & el Moctar (2020).","PeriodicalId":408227,"journal":{"name":"Volume 5A: Ocean Engineering","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114729112","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}