The Experts below are selected from a list of 5244 Experts worldwide ranked by ideXlab platform
Michael H. Meylan - One of the best experts on this subject based on the ideXlab platform.
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Resonances and the Approximation of Wave Forcing for Elastic Floating Bodies
2015Co-Authors: Michael H. Meylan, Marko TomicAbstract:The central problem in Hydroelasticity is to cal-culating the response of an elastic body subject to wave forcing. The majority of the research in Hydroelasticity has been aimed at predictin
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Spectral solution of time-dependent shallow water Hydroelasticity
2015Co-Authors: Michael H. MeylanAbstract:If a hydroelastic problem is linear the time-dependent motion can be found using spectral theory, at least theoretically. However the spectral theory for linear Hydroelasticity has not been developed, even for the simplest cases. For example, the work of [1] which presented a method to determine the scattering frequencies for hydroelastic problems did not develop any spectral theory. This has meant that spectral methods to solve the time-dependent motion, such as [4], hav
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Spectral solution of time-dependent shallow water Hydroelasticity
Journal of Fluid Mechanics, 2002Co-Authors: Michael H. MeylanAbstract:The spectral theory of a thin plate floating on shallow water is derived and used to solve the time-dependent motion. This theory is based on an energy inner product in which the evolution operator becomes unitary. Two solution methods are presented. In the first, the solution is expanded in the eigenfunctions of a self-adjoint operator, which are the incoming wave solutions for a single frequency. In the second, the scattering theory of Lax–Phillips is used. The Lax–Phillips scattering solution is suitable for calculating only the free motion of the plate. However, it determines the modes of vibration of the plate–water system. These modes, which both oscillate and decay, are found by a complex search algorithm based contour integration. As well as an application to modelling floating runways, the spectral theory for a floating thin plate on shallow water is a solvable model for more complicated hydroelastic systems.
P Temarel - One of the best experts on this subject based on the ideXlab platform.
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two dimensional numerical modelling of slamming impact loads on high speed craft
2015Co-Authors: Josef Camilleri, D J Taunton, P TemarelAbstract:The constant velocity impact of a flexible panel with water is simulated by using the computational fluid dynamics code Star CCM+ coupled with the finite element code ABAQUS. A detailed description of the numerical model is given, and issues with numerical stability are discussed. The influence of different structural boundary conditions in the two-dimensional model is examined. The effects of Hydroelasticity on the fluid loading are discussed by comparing the results from hydroelastic and rigid body simulations. Comparisons with published experimental data show favourable agreement for the test case investigated.
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service factor assessment of a great lakes bulk carrier incorporating the effects of Hydroelasticity
Marine Technology and Sname News, 2009Co-Authors: S E Hirdaris, Norbert Bakkers, Nigel White, P TemarelAbstract:This paper presents a summary of an investigation into the effects of hull flexibility when deriving an equiva- lentservicefactorforasinglepassageofaGreatLakesBulkCarrierfromtheCanadianGreatLakestoChina. The long term wave induced bending moment predicted using traditional three-dimensional rigid body hydrodynamic methods is augmented due to the effects of springing and whipping by including allowances based on two-dimensional Hydroelasticity predictions across a range of headings and sea states. The analysis results are correlated with full scale measurements that are available for this ship. By combining the long term "rigid body" wave-bending moment with the effects of Hydroelasticity, a suitable service factor is derived for a Great Lakes Bulk Carrier traveling from the Canadian Great Lakes to China via the Suez Canal. THE number of published investigations on springing and whipping of Great Lakes bulk carriers is limited. Springing was first noticed by Matthews (1967), who highlighted that long ships of shallow draft and depth are comparatively flex- ible in longitudinal bending and become prone to two-node vertical hull vibration of periods of 2 s (or longer). The first theoretical study, presented by Goodman (1970), was based on linear strip theory. This approach did not predict success- fully the level of resonant frequencies possibly because of uncertainty in the hull internal damping and inaccuracy of the measured excitation wave spectrum. Cleary et al. (1971) carried out extensive measurements on a Great Lakes ore carrier. They recorded maximum bending stresses of 80 MPa, of which 30% were shown to entail significant springing. This phenomenon was observed in low sea states and was considered to be the main cause of fatigue cracking. The data confirmed a substantial increase in springing with increasing speed. Stiansen (1984) presented a comparison between numeri- cal predictions and full-scale measurements for three Great Lakes bulk carriers with approximate overall lengths of 305 m, 246 m, and 192 m. Although the springing contribu- tion increased with wave height for the first two ships, for the smaller vessel it was reduced in larger waves. The damp- ing ratio of the larger ship was estimated as 1.6% with a standard deviation of 0.6%. This paper presents a summary of an investigation into the effects of hull flexibility when deriving an equivalent service factor for a single passage of a Great Lakes bulk carrier from the Canadian Great Lakes to China. The long- term wave-induced bending moment predicted using tradi- tional three-dimensional rigid body hydrodynamic methods is increased due to the effects of springing and whipping by including allowances based on two-dimensional hydroelasti- city predictions. Including the effects of springing and whipping generates at least a double-peak response spec- trum that invalidates the standard long-term approach, as this is only valid for narrow-band Rayleigh random processes. The two-dimensional Hydroelasticity analysis was used to investigate the sensitivity to whipping and springing responses across a range of headings and sea states. The analysis results were correlated with full-scale measure- ments that are available for this ship. By combining the long-term "rigid body" wave-bending moment with the effects of Hydroelasticity, a suitable service factor was derived for a Great Lakes bulk carrier traveling from the Canadian Great Lakes to China via the Suez Canal.
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dynamic behaviour of a container ship using two and three dimensional Hydroelasticity analyses
Volume 6: Nick Newman Symposium on Marine Hydrodynamics; Yoshida and Maeda Special Symposium on Ocean Space Utilization; Special Symposium on Offshore, 2008Co-Authors: Ismail Basaran, Omer Belik, P TemarelAbstract:The symmetric (vertical bending) and antisymmetric (coupled horizontal bending and twisting) dynamic behaviours of a feeder container ship travelling in regular oblique waves are investigated using two- and three-dimensional Hydroelasticity theories. Different three-dimensional FE structural models are generated in order to investigate the influence of hatch coamings and on-deck container cargo. Corresponding beam structural idealizations are obtained from these models. Comparisons are carried out between the dynamic characteristics and wave-induced loads predicted by both methods.
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Feasibility study for the estimation of service factors of a Great Lakes bulk carrier incorporating the effects of springing and whipping
2007Co-Authors: S E Hirdaris, Norbert Bakkers, Nigel White, P TemarelAbstract:This paper presents a summary of an investigation into the effects of hull flexibility when deriving an equivalent service factor for a GLBC. The long term wave induced bending moment predicted using traditional 3D rigid body hydrodynamic methods is increased for the effects of springing and whipping, based on 2D Hydroelasticity predictions. The analysis results were correlated with full scale measurements that are available for this ship.
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LOAD AND STRESS DISTRIBUTION ON BULK CARRIERS AND TANKERS IN VARIOUS LOADING CONDITIONS
1992Co-Authors: S Aksu, W.g. Price, P TemarelAbstract:The unacceptably high rate in bulk carrier casualties in recent years has lead to the expression of concern by many in the shipping industry. Furthermore, VLCCs and other tankers are not immune to structural problems. It is, therefore, reasonable to expect more large scale failures, losses and disappearances of bulk carriers, tankers and other large beamlike ships designed and built according to existing practices. The way ahead lies in a reappraisal of the fundamental concepts and assumptions enshrined in these practices followed by a radical overhaul of rules and regulations. Ships are flexible structures. The environment in which they operate induces, steady state and transient loads, distortions and stresses in them. The proper evaluation and including of these dynamic effects is a prerequisite for any safe design. Hydroelasticity theory was developed with this aim in mind. This paper discusses the loads and stresses predicted using a Hydroelasticity analysis, applied to symmetric bending (and shear) only, for ships in still water and travelling in simulated random seaways. A bulk carrier and a tanker in fully loaded and ballast conditions are used to illustrate the effect of loading, forward speed and seaway parameters on the loads and stresses induced and their variation along the hulls.
Odd M. Faltinsen - One of the best experts on this subject based on the ideXlab platform.
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Resonant Liquid Motion in Marine Hydrodynamics
Procedia Engineering, 2015Co-Authors: Odd M. FaltinsenAbstract:Sloshing in ship tanks and piston-mode resonance in moonpools are discussed. A nonlinear analytically based multimodal method is used to explain how sloshing depends on the liquid depth in 2D flow. The importance of 3D flow with possible swirling and chaos for nearly square base tanks as well as vertical cylindrical and spherical tanks is emphasized. The many physical phenomena involving fluid mechanic and thermodynamic parameters as well as Hydroelasticity effecting slamming load effects and associated scaling from model to full scale for LNG are discussed.
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Water entry of a wedge by hydroelastic orthotropic plate theory
Journal of Ship Research, 1999Co-Authors: Odd M. FaltinsenAbstract:Water entry of a hull with wedge-shaped cross sections is analyzed. The stiffened platings between two transverse girders on each side of the keel are separately modeled. Orthotropic plate theory is used. The effect of structural vibrations on the fluid flow is incorporated by solving the two-dimensional Laplace equation in the cross-sectional fluid domain by a generalized Wagner's theory. The coupling with the plate theory provides three-dimensional flow effects. The theory is validated by comparison with full-scale experiments and drop tests. The importance of global ship accelerations is pointed out. Hydrodynamic and structural error sources are discussed. Systematic studies on the importance of Hydroelasticity as a function of deadrise angle and impact velocity are presented. This can be related to the ratio between the wetting time of the structure and the greatest wet natural period of the stiffened plating. This ratio is proportional to the deadrise angle and inversely proportional to the Impact velocity. A small ratio means that Hydroelasticity is important and a large ratio means that Hydroelasticity is not important.
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The effect of Hydroelasticity on ship slamming
Philosophical Transactions of the Royal Society A: Mathematical Physical and Engineering Sciences, 1997Co-Authors: Odd M. FaltinsenAbstract:Wetdeck slamming is studied theoretically by a hydroelastic beam model.\nThe problem is simplified by introducing an initial structural inertia\nphase and a subsequent free vibration phase. Forward speed effects\nare included. The theoretical model is validated by comparing with\ndrop tests of elastic plates on waves. The stresses in the plates\nhave a linear dependence on the impact speed and are neither sensitive\nto the radius of curvature of the waves nor where the waves initially\nhit. Hydroelasticity is important. The maximum impact pressures can\nbe extremely high and have a stochastic nature even under deterministic\nenvironmental conditions, but they are not important for maximum\nbending stresses.
Yonghwan Kim - One of the best experts on this subject based on the ideXlab platform.
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Prediction of extreme loads on ultra-large containerships with structural Hydroelasticity
Journal of Marine Science and Technology, 2018Co-Authors: Junghyun Kim, Yonghwan KimAbstract:Design rules for very large seagoing vessels are undergoing changes owing to the Hydroelasticity of the ship. The Hydroelasticity of the ship is in the form of wave-induced vibrations such as springing and whipping, which are known to aggravate fatigue and extreme loads. The present study deals with a method for the estimation of extreme loads. The method consists of a preliminary analysis of linear responses of motions and loads, and a sequential analysis of the nonlinear extreme load. First, a full-time series of the linear response is obtained using response amplitude operators and wave spectra. Next, the candidate waves of extreme event are extracted from the full-time series based on the linear response. The linear response may be a motion or a load depending on the target value of the sequential analysis. Finally, the sequential analysis is conducted using a fully coupled model of the three-dimensional Rankine panel method, three-dimensional finite-element method, and two-dimensional generalized Wagner model with the candidate waves. The method is validated for a nonlinear hogging moment in a short-term sea state and applied for a long-term prediction of an extreme hogging moment on an ultra-large containership. The extreme values of linear and nonlinear loads are compared in terms of the most probable value and probabilistic distribution.
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Linear and Nonlinear Springing Analyses in Time Domain using a Fully Coupled BEM-FEM
2015Co-Authors: Yooil Kim, Kyonghwan Kim, Yonghwan KimAbstract:Global Hydroelasticity of modern merchant ship is gathering a lot of attention due to the rising concerns about its negative impact on design of sound structure especially in terms of unexpected increase of design load as well as fatigue loading. Recent experiences from a real ship in operation tell that cracks are observed at bracket toe in deck longitudinal in way of transverse bulkhead after one year of operation i
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Study on Slamming and Whipping Response of Ship Structure
2015Co-Authors: Junghyun Kim, Yonghwan Kim, Er A. Korobkin, Dong-yeon LeeAbstract:Ship structural Hydroelasticity is observed in the presence of slamming loads and whipping responses. GWM shows a fair performance in the wedge drop test with similar results in peak pressure, pressure descent, and forces to those of the experiment. Peak pressure is mainly proportional to a square of velocity, while pressure descent is proportional to acceleration. Fully-coupled hydroelastic analysis of whipping response via GWM shows a good correspondance with measurements of the segmented ship model test. 1
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fully coupled bem fem analysis for ship Hydroelasticity in waves
Marine Structures, 2013Co-Authors: Kyonghwan Kim, Jesung Bang, Yonghwan Kim, Seungjo Kim, Junghyun Kim, Yooil KimAbstract:This paper considers the problem of ship Hydroelasticity, which is an important technical issue in the design of ultra-large vessels. For the analysis of fluid-structure interaction problems, a partitioned method is applied. The fluid domain surrounding a flexible body is solved using a B-spline Rankine panel method, and the structural domain is handled with a three-dimensional finite element method. The two distinct methods are fully coupled in the time domain by using an implicit iterative scheme. The numerical results of natural frequency and the motion responses of simple and segmented barges are computed to validate the present method through comparisons with experimental and numerical results. This study extends to the application to two real ships, 6500 TEU and 10,000 TEU containerships, for more validation and also observation on the practicality of the present method. Based on this study, it is found that the present method provides reliable solutions to linear ship Hydroelasticity problems.
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analysis on the Hydroelasticity of whole ship structure by coupling three dimensional bem and fem
Journal of The Society of Naval Architects of Korea, 2012Co-Authors: Kyonghwan Kim, Jesung Bang, Yonghwan Kim, Seungjo KimAbstract:This paper considers a fully coupled 3D BEM-FEM analysis for the ship structural Hydroelasticity problem in waves. Fluid flows and structural responses are analyzed by using a 3D Rankine panel method and a 3D finite element method, respectively. The two methods are fully coupled in the time domain using a fixed-point iteration scheme, and a relaxation scheme is applied for improve convergence. In order to validate the developed method, numerical tests are carried out for a barge model. The computed natural frequency, motion responses, and time histories of stress are compared with the results of the beam-based Hydroelasticity program, WISH-FLEX, which was thoroughly validated in previous studies. This study extends to a real-ship application, particularly the springing analysis for a 6500 TEU containership. Based on this study, it is found that the present method provides reliable solutions to the ship Hydroelasticity problems.
Junghyun Kim - One of the best experts on this subject based on the ideXlab platform.
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Prediction of extreme loads on ultra-large containerships with structural Hydroelasticity
Journal of Marine Science and Technology, 2018Co-Authors: Junghyun Kim, Yonghwan KimAbstract:Design rules for very large seagoing vessels are undergoing changes owing to the Hydroelasticity of the ship. The Hydroelasticity of the ship is in the form of wave-induced vibrations such as springing and whipping, which are known to aggravate fatigue and extreme loads. The present study deals with a method for the estimation of extreme loads. The method consists of a preliminary analysis of linear responses of motions and loads, and a sequential analysis of the nonlinear extreme load. First, a full-time series of the linear response is obtained using response amplitude operators and wave spectra. Next, the candidate waves of extreme event are extracted from the full-time series based on the linear response. The linear response may be a motion or a load depending on the target value of the sequential analysis. Finally, the sequential analysis is conducted using a fully coupled model of the three-dimensional Rankine panel method, three-dimensional finite-element method, and two-dimensional generalized Wagner model with the candidate waves. The method is validated for a nonlinear hogging moment in a short-term sea state and applied for a long-term prediction of an extreme hogging moment on an ultra-large containership. The extreme values of linear and nonlinear loads are compared in terms of the most probable value and probabilistic distribution.
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Study on Slamming and Whipping Response of Ship Structure
2015Co-Authors: Junghyun Kim, Yonghwan Kim, Er A. Korobkin, Dong-yeon LeeAbstract:Ship structural Hydroelasticity is observed in the presence of slamming loads and whipping responses. GWM shows a fair performance in the wedge drop test with similar results in peak pressure, pressure descent, and forces to those of the experiment. Peak pressure is mainly proportional to a square of velocity, while pressure descent is proportional to acceleration. Fully-coupled hydroelastic analysis of whipping response via GWM shows a good correspondance with measurements of the segmented ship model test. 1
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fully coupled bem fem analysis for ship Hydroelasticity in waves
Marine Structures, 2013Co-Authors: Kyonghwan Kim, Jesung Bang, Yonghwan Kim, Seungjo Kim, Junghyun Kim, Yooil KimAbstract:This paper considers the problem of ship Hydroelasticity, which is an important technical issue in the design of ultra-large vessels. For the analysis of fluid-structure interaction problems, a partitioned method is applied. The fluid domain surrounding a flexible body is solved using a B-spline Rankine panel method, and the structural domain is handled with a three-dimensional finite element method. The two distinct methods are fully coupled in the time domain by using an implicit iterative scheme. The numerical results of natural frequency and the motion responses of simple and segmented barges are computed to validate the present method through comparisons with experimental and numerical results. This study extends to the application to two real ships, 6500 TEU and 10,000 TEU containerships, for more validation and also observation on the practicality of the present method. Based on this study, it is found that the present method provides reliable solutions to linear ship Hydroelasticity problems.
