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When a vessel is damaged, seawater floods into the damaged compartments and subsequently influences the motion of the vessel. Furthermore, the vessel’s behaviour affects the floodwater motion. In this paper, a Navier-Stokes (NS) solver with a free surface capturing technique, i.e., the volume of fluid (VOF) method, was developed to numerically simulate water flooding into a damaged vessel. To verify the developed solver, a 2-D and a 3-D dam break problems were tested. The numerical results coincide well with the experimental results and with the published numerical results. Additionally, it was used to solve the problems of linear and non-linear liquid sloshing in a hexahedral tank. The numerical results are satisfactory in comparison with the experimental results and analytical solutions. Finally, the phenomenon of water flooding into a damaged compartment of a Ro-Ro ferry was simulated numerically. The computed results are in good agreement with the experimental data. 相似文献
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In an attempt to contribute to efforts for a robust and effective numerical tool addressing ship motion in astern seas, this paper presents the development of a coupled non-linear 6-DOF model with frequency dependent coefficients, incorporating memory effects and random waves. A new axes system that allows straightforward combination between seakeeping and manoeuvring, whilst accounting for extreme motions, is proposed. Validation of the numerical model with the results of benchmark tests commissioned by ITTC's Specialist Group on Stability demonstrated qualitative, yet not fully satisfactory agreement between numerical and experimental results in line with other predictive tools. The numerical results indicate that the inclusion of frequency coefficients definitely affects the accuracy of the predictions. In order to enhance further the numerical model and obtain useful information on motion coupling, extensive captive and free running model tests were carried out. Good agreement with the experimental results was achieved. These studies provide convincing evidence of the capability of the developed numerical model to predict the dangerous conditions that a ship could encounter in extreme astern seas. As a result, it could offer new insights towards establishing relationships linking ship behaviour to design, environmental and operational parameters. 相似文献
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A seakeeping analysis in the frequency domain is presented to predict the motion response of an air-lifted vessel (ALV) in waves. The ALV is supported by pressurised air in two separate cushion chambers; the pressure variation in the cushions has a significant effect on the motions of the vessel. The adiabatic gas law is used to couple cushion pressure and the free-surface elevation of water inside the chamber. Attention is focused on the waves generated by the pressure, and a method is presented to compute the corresponding free-surface elevation. New numerical schemes are proposed for calculating the three-dimensional free-surface elevation for the four wave numbers. Numerical results of the free-surface elevation, escape area, escape volume and motion responses of the ALV are provided. 相似文献
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Three-dimensional fully nonlinear waves generated by moving disturbances with steady forward speed without motions are solved using a mixed Eulerian–Lagrangian method in terms of an indirect boundary integral method and a Runge–Kutta time marching approach which integrates the fully nonlinear free surface boundary conditions with respect to time.A moving computational window is used in the computations by truncating the fluid domain (the free surface) into a computational domain. The computational window maintains the computational domain and tracks the free surface profile by a node-shifting scheme applied within it. An implicit implement of far field condition is enforced automatically at the truncation boundary of the computational window.Numerical computations are applied to free surface waves generated by Wigley and Series 60 hulls for the steady problem. The present numerical results are presented and compared with existing linear theory, experimental measurements, and other numerical nonlinear computations. The comparisons show satisfactory agreements for these hydrodynamic problems. 相似文献
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This paper elaborates on results of a recent risk analysis study for RoPax vessels, carried out as part of the activities of the SAFEDOR Integrated Project, targeting possible improvements on safety levels following large scale flooding. The study is based on a comprehensive analysis of accident statistics for the period 1994–2004, through which a high-level risk model (in the form of event trees) is established. This is then used to determine the current safety level of RoPax vessels (in various risk metrics, such as individual risk, potential loss of life and on an F–N curve), reconfirming that even though safety levels are improving, risk is still “high in the ALARP region”. In search of ways to further improve the situation possible risk control options are examined, by performing a sensitivity analysis on the effects of the Attained Index of Subdivision A onto the safety levels and by evaluating their cost-effectiveness. 相似文献
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A semi-analytic approach is presented in this paper which is capable of predicting the static performance of marine cables. The solution is derived as a function of only three parameters which can be solved numerically by implementing different kinds of boundary conditions. The efficiency and accuracy of the method permit quick parametric studies for optimal selection of the system particulars which is undoubtedly useful for preliminary design. A number of numerical examples demonstrates the validity of the approach adopted. 相似文献
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Numerical solutions for the hydroelastic problems of bodies are studied directly in the time domain using Neumann–Kelvin formulation. In the hydrodynamic part of problem, the exact initial boundary value problem is linearized using the free stream as a basis flow, replaced by the boundary integral equation applying Green theorem over the transient free surface Green function. The resultant boundary integral equation is discretized using quadrilateral elements over which the value of the potential is assumed to be constant and solved using the trapezoidal rule to integrate the memory or convolution part in time. In the structure part of the problem, the finite element method is used to solve the hydroelastic problem. The Mindlin plate as a bending element, which includes transverse shear effect and rotary inertia effect are used. The present numerical results show acceptable agreement with experimental, analytical, and other published numerical results. 相似文献
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The purpose of the present paper is to develop a potential-based panel method for determining the steady potential flow about three-dimensional hydrofoil under free surface. The method uses constant-strength doublets and source density distribution over the foil body surface and thereby Dirichlet-type boundary condition is used instead of Neumann-type condition. On the undisturbed free surface source density is used to meet the free surface condition that is linearised in terms of double-body model approach and is discretised by a one-side, upstream, four-point finite difference operator. After solving the doublets on the foil and sources on the free surface, the numerical results of pressure, lift and resistance coefficients and also wave profiles can then be calculated for different Froude number and depth of submergence to demonstrate the influence of free surface and aspect ratio effects on performance of the hydrofoil. 相似文献
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Physical modelling and similitude of marine structures 总被引：1，自引：0，他引：1
Dracos Vassalos 《Ocean Engineering》1998,26(2):111-123
This review paper is aimed at providing information on and at explaining the appropriate use of models in the design of marine structures. Emphasis is placed on the derivation of scaling laws and on limitations of accuracy. Similitude, dimensional analysis and the use of governing equations in model experiment scaling are explained before addressing the modelling of some common ocean engineering tests. 相似文献
10.
The hydrodynamic problem of 3D planing surface is studied by a finite element approach. The planing surface is represented by a number of pressure patches whose strengths are constant at each element. The unknown pressure strength is obtained by using the free surface elevation condition under the planing surface and Kutta condition at the transom stern. Previous studies indicate that, when the constant pressure distribution method is used, the number of buttocks should be less than five or six, otherwise the calculated pressure distribution will start to oscillate and even become divergent. In the present study, after careful examination of the influence coefficients, it is found that the accuracy of the influence coefficients matrix is very important to the convergence of the solution, especially when the number of elements is relatively high. The oscillation of the pressure distribution can be avoided by constant element method if the influence coefficients are sufficiently accurate. The predicted results of the present paper with more number of buttocks are in good agreement with other researchers'. It is concluded that the irregularity of the pressure distribution found in previous studies is most likely caused by the low accuracy in their calculation of the influence coefficients, not by the method itself. 相似文献
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