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1.
Ship motions after damage are difficult to evaluate since they are affected by complex phenomena regarding fluid and structures interactions. The possibility to better understand how ship behavior in damage is influenced by these phenomena is important for improving ship safety, especially for passenger vessel.In this paper an experimental campaign is carried out on a passenger ferry hull, to show the effects of the water dynamics across damage openings on ship motions. Novel aspects of this research include the study of the effects of the damage position on the ship roll response. The study is carried out for still water and for beam regular waves at zero speed.Results from the experiments carried out underline that the roll behavior of a damaged ship is affected by the position of damage opening and not only by its size. Assuming the same final equilibrium conditions after flooding but characterized by different damage openings it is possible to observe how motions RAOs and roll decay characteristics modify according to the opening locations. 相似文献
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The dynamics of a damaged ship in waves is a complex phenomenon regarding fluid and structure interactions. Flooded water motions in the damaged compartment could be influenced by decks, obstructions and obstacles in the compartment. This becomes particularly relevant in case of flooding in the engine room that is usually characterized by the presence of large objects such as engines and machineries. In such cases the possibility to better understand the behavior of a damaged ship, influenced by the fluid and structure interactions, could provide novel outcomes and thus enhance the damaged ship safety.In this paper an experimental campaign is conducted on a passenger ferry hull. The effects of obstacles in the engine room compartment, such as decks and engines, on ship roll responses, are studied. Roll decay in still water and steady roll responses in beam regular waves at zero speed are measured for the empty compartment and for the compartment with obstructions, as defined above.The main outcomes from the conducted experiments disclose a mitigation of the resonant behavior of the coupled system, ship with damaged compartment, by having engine shapes occupying the flooded engine room. Moreover it is possible to observe how the resonant frequency of the ship modifies having a more realistic arrangement of damaged compartment and how motion RAOs and roll decay characteristics modify accordingly. 相似文献
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采用移动粒子半隐式法(moving particle semi-implicit,简称MPS)对自由漂浮二维方舱的破舱瞬时进水过程进行数值模拟。首先,采用基于GPU平台自主开发的MPS软件模拟破舱进水问题,并与其他方法得到的数值模拟结果进行对比验证。然后,对该二维方舱的各种模型进行了数值模拟,其中开孔位于不同位置以表示舷侧不同高度下的损坏。此外,还研究了不同类型的挡板对破舱进水后方舱稳定性的影响。结果表明损坏的孔洞和内部挡板会影响损坏舱段的运动特性,开孔距静水面的距离越大引起舱段的横摇等运动幅度越大,垂直挡板比水平挡板对舱内洪水的影响更大。 相似文献
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This paper outlines a procedure for the derivation of the differential equations describing the free response of a heaving and pitching ship from its stationary response to random waves. The coupled heave–pitch motion of a ship in random seas is modelled as a multi-dimensional Markov process. The partial differential equation describing the transition probability density function, known as the Fokker-Planck equation, for this process is derived. The Fokker-Planck equation is used to derive the random decrement equations for the coupled heave–pitch motion. The parameters in these equations are then identified using a neural network approach. The method is validated using numerical simulations and experimental results. The experimental data was obtained using an icebreaker ship model heaving and pitching in random waves. It is shown that the method produces good results when the system is lightly damped. An extension for using this method to identify couple heave–pitch motion in realistic seas is suggested. 相似文献
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This work aims at contributing to improve knowledge on transient asymmetric flooding through theoretical and experimental research. First, a time domain theoretical model of ship motions and flooding is described. Results from experimental work are presented evidencing that transient asymmetric flooding may cause the capsizing of a Ro-Ro shaped barge. The theoretical model is used to predict the capsize of the Ro-Ro shaped barge. Reasonable agreement between experimental and theoretical results was found. Finally, a review of the European Gateway accident is given and the theoretical model is applied to the study of this type of accident. The conclusion is that this theoretical model, together with an accurate modelling of the flooding of machinery compartments, reproduces successfully the capsizing of the European Gateway due to transient asymmetric flooding. Therefore, the internal arrangement of Ro-Ro ships should be carefully studied at the design stage in order to avoid this phenomenon. 相似文献
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The International Maritime Organization has developed the second-generation intact stability criteria. Thus, damage stability criteria can be established in the future. In order to identity the capsizing probability of damaged ship under dead ship condition, this paper investigates two methods that can be used to research the capsizing probability in time domain, which mainly focus on the nonlinear righting lever GZ curve solution. One method subjects the influence of damaged tanks on the hull shape down to the wind and wave, and the other method is consistent with the real-time calculation of the GZ curve. On the basis of one degree of freedom rolling equation, the solution is Monte Carlo method, and a damaged fishery bureau vessel is taken as a sample ship. In addition, the results of the time-domain capsizing probability under different loading conditions are compared and analyzed. The relation of GM and heeling angle with the capsizing probability is investigated, and its possible reason is analyzed. On the basis of combining the time-domain flooding process with the capsizing probability calculation, this research aims to lay the foundation for the study of capsizing probability in time domain under dead ship condition, as well as provide technical support for capsizing mechanism of dead ship stability and damage stability criteria establishment in waves. 相似文献
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This work documents a detailed series of experiments performed in a wave flume on a thin walled prismatic hull form. The model consists of a rectangular opening located on the side. The length of the model is slightly smaller than the flume breadth to achieve two-dimensional (2D) behavior in the experiments. Forced oscillatory heave tests in calm water have been carried out by varying the model-motion parameters and examining both intact and damaged conditions. Video recordings, measurements of the wave elevation inside the damaged compartment and of the force on the model were performed in all the experiments. The effect of damage opening in the model on hydrodynamic loads is examined by comparing with an intact section. A theoretical analysis is used to explain the behavior of added mass and damping coefficients in heave for a 2D damaged section. The presented results demonstrate occurrence of sloshing and piston mode resonances in the tests and their influence on the hydrodynamics loads of a damaged ship. Detailed physical investigations are presented at these resonance frequencies for the damaged section. Effect of filling level in the damage compartment, damage-opening length and air compressibility in the airtight compartment is examined. Nonlinear effects are documented and appear dominant, especially, for lowest filling level where we have shallow-water depth conditions in the damaged compartment. Resonance phenomena that can lead to significant local loads are identified for the shallow water condition. Air compressibility in the airtight compartment and floodwater act as a coupled system and influence inflow/outflow of floodwater in the compartment. It has a significant effect on local floodwater behavior in the damaged compartment. 相似文献
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The paper describes model tests of a tanker with two fixed bow-mounted foils (wavefoils), for resistance and motion reduction in waves. Measured ship resistance, wavefoil thrust and ship motions were compared with time-domain simulations. The wavefoil forces were calculated using a slightly modified Leishman–Beddoes dynamic stall model, with a two-way coupling to the ship motions. In typical sea states in head seas, employing the wavefoils reduced ship resistance by 9–17%, according to scaled model test resistance. Heave and pitch were reduced by −11% to 32% and 11% to 25%, respectively. The foils affect the flow around the hull. This should be considered when selecting the wavefoil location in the design process. 相似文献
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The use of wavelet transforms is explored to investigate the nonlinear dynamical characteristics of ship roll and coupled heave-roll motion. The harmonic character, double period character and chaotic character are observed via a time–frequency window of the wavelet transform. Typical wave parameters in different stability regions are considered. Features such as restoring rolling, divergence rolling, steady state and chaotic responses of ship roll are obtained as well. The investigation in this paper not only highlights the feasibility of using wavelet transforms in the analysis of nonlinear dynamic characteristics of ship rolling in waves, but also shows how it could enhance the analysis abilities. 相似文献
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Reliable analysis of stability and safety level in a flooding emergency onboard a damaged passenger ship is extremely important for making correct decisions on evacuation and abandonment. Thus there is demand for an automated system that detects flooding and analyzes the severity of the situation. This procedure requires estimation of the actual breach in the hull, and calculation of possible progressive flooding to undamaged compartments. A new approach to the breach assessment, based on measurement data from the flood level sensors, is presented. The developed method is complemented by time-domain flooding simulations in order to separate progressive flooding from direct inflow through the breaches in the hull of the damaged ship. The developed approach is tested and demonstrated with a large passenger ship design for various damage scenarios. The results show that the size and location of the breach can be evaluated with reasonable accuracy on the basis of the level sensor data, provided that there are enough well-placed, working level sensors. 相似文献
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3-D geometric modeler for rapid ship safety assessment 总被引：1，自引：0，他引：1
CAD systems are used broadly in the shipbuilding industry. CAD systems for naval architecture are a useful tool for hull form, internal arrangement and the structural design of ships. These systems require high precision and expertise for efficient use. Therefore, these systems are not appropriate in supporting emergency responses, which require rapid modeling even if it generates some errors.This paper describes a geometric modeler for rapid ship safety assessment. The modeler is developed based on the 3-D geometric modeling kernel ACIS. The definition of hull form, internal arrangement and major longitudinal structural members is a fundamental function of the modeler. The developed modeler is interfaced with other applications used for ship safety assessment such as hydrostatic calculation, ship motion analysis in wave condition, longitudinal strength analysis and so on. In addition, it can generate a new ship model by making variations in a previously defined ship model. 相似文献
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In this paper, the modelling of strong parametric resonance in head seas is investigated. Non-linear equations of ship motions in waves describing the couplings between heave, roll and pitch are contemplated. A third-order mathematical model is introduced, aimed at describing strong parametric excitation associated with cyclic changes of the ship restoring characteristics. A derivative model is employed to describe the coupled restoring actions up to third order. Non-linear coupling coefficients are analytically derived in terms of hull form characteristics.The main theoretical aspects of the new model are discussed. Numerical simulations obtained from the derived third-order non-linear mathematical model are compared to experimental results, corresponding to excessive motions of the model of a transom stern fishing vessel in head seas. It is shown that this enhanced model gives very realistic results and a much better comparison with the experiments than a second-order model. 相似文献
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The importance of hydroelastic analysis of large and flexible container ships of today is pointed out. A methodology for investigation of this challenging phenomenon is drawn up and a mathematical model is worked out. It includes definition of ship geometry, mass distribution, structure stiffness, and combines ship hydrostatics, hydrodynamics, wave load, ship motion and vibrations. Based on the presented theory, a computer program is developed and applied for hydroelastic analysis of a flexible segmented barge for which model test results of motion and distortion in waves have been available. A correlation analysis of numerical simulation and measured response shows quite good agreement of the transfer functions for heave, pitch, roll, vertical and horizontal bending and torsion. The tool checked in such a way can be further used for reliable hydroelastic analysis of ship-like structures. 相似文献
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Damaged ship at sea will be a direct threat to lives and property, and it has a great significance of studying ship's remaining buoyancy, stability, sinking time and other important parameters. The process of a damaged ship sinking into water is a complex motion involving ship hull, inner and outer fluid coupled with waves and many other factors. It is featured by high nonlinearity and hard to establish a precise theoretical model to study. Yet SPH (smoothed particle hydrodynamics) as a meshfree method has a great advantage in solving such problems because of the nature of self-adaptive and Lagrangian. Firstly, the experiments of two scaled ship models with different openings sinking into water are carried out, through the sinking processes of broadside opening and bottom opening models, the conclusion is drawn that although the serious loss of stability of broadside opening model, the sinking time and other parameters are more conducive to rescue after maritime distress. Secondly, the parallel program of three dimensional SPH is developed to simulate the above more complex model, broadside opening model. The coupled process of sloshing is compared with that of experiment, and the results show good agreement with each other which verify the accuracy and feasibility of three dimensional parallel program. 相似文献
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It has been argued that a major shortcoming in the International Maritime Organization (IMO) Interim Guidelines for Approval of Alternative Methods of Design and Construction of Oil Tankers in Collision and Grounding is that grounding and collision damages normalized by the main dimensions of the ship have the same probability density distributions regardless of a particular structural design and ship size.The present paper explores analytical methods for assessing the overall effect of structural design on the damage distributions in accidental grounding and collisions. The results are expressed in simple expressions involving structural dimensions and the building material of the ships. The study shows that the density distribution for collision and grounding damages normalized by the main dimensions of the ship depends on the size of the ship. A larger ship has a higher probability of a larger relative damage length than that of a smaller ship in grounding damage. On the other hand, the damages to the side structure caused by ship collisions are found to be relatively smaller for large ships.The main conclusion is that the existing IMO damage distributions will severely underestimate the grounding damages to the bottom structure of larger vessels and to a lesser extent overestimate collision damages to the side structure of the hull. 相似文献
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The present paper describes a mathematical model in which the fluid motion inside a U-tank is nonlinearly coupled to the heave, roll and pitch motions of the ship. The main purpose of the investigation is centred on the control of roll motion in the case of parametric resonance in longitudinal waves. A transom stern small vessel, known to be quite prone to parametric amplification, is employed in the study. Four tank designs are employed in order to study the influence of tank mass, tank natural frequency and tank internal damping on the control of parametric rolling at different head seas conditions. Additionally, the influence of the vertical position of the tank is also investigated. The main results are presented in the form of limits of stability, with encounter frequency and wave amplitudes as parameters. Distinct dynamical characteristics are discussed and conclusions are drawn on the relevant parameters for the efficient control of the roll amplifications in head seas. 相似文献
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《Ocean Engineering》2004,31(3-4):483-512
Six degrees of freedom motion response tests of a Ro-Ro model have been carried out in regular waves for intact and damaged conditions. The stationary model was tested in different wave heights and wave frequencies for the head, beam and stern quartering seas in order to explore the effect of damage and varying wave heights on the motion responses of the model. Analysis of the results indicates that damage has an adverse effect on the motion responses of the model depending upon the directionality of the waves and frequency range applied. 相似文献
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This paper has shown a numerical motion simulation method which can be employed to study on parametric rolling of ships in a seaway. The method takes account of the main nonlinear terms in the rolling equation which stabilize parametric rolling, including the nonlinear shape of the righting arm curve, nonlinear damping and cross coupling among all 6 degrees of freedom. For the heave, pitch, sway and yaw motions, the method uses response amplitude operators determined by means of the strip method, whereas the roll and surge motions of the ship are simulated, using nonlinear motion equations coupled with the other 4 degrees of freedom. For computing righting arms in seaways, Grim's effective wave concept is used. Using these transfer functions of effective wave together with the heave and pitch transfer functions, the mean ship immersion, its trim and the effective regular wave height are computed for every time step during the simulation. The righting arm is interpolated from tables, computed before starting the simulation, depending on these three quantities and the heel angle. The nonlinear damping moment and the effect of bilge keels are also taken into account. The numerical simulation tool has shown to be able to model the basic mechanism of parametric rolling motions. Some main characteristics of parametric rolling of ships in a seaway can be good reproduced by means of the method. Comprehensive parametric analyses on parametric rolling amplitude in regular waves have been carried out, with that the complicated parametric rolling phenomena can be understood better. 相似文献