• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.195-205
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• 1997

The propulsion marine diesel engine have been widely applied with a mechanical- hydraulic governor to control the ship speed for long time. But it was recently very difficult for the mechani¬cal - hydraulic governor to control the speed of engine under the condition of low speed and low load because of jiggling by rough fluctuation of rotating torque and hunting by dead time of Desiel engnie The performance improvement of mechanical - hydraulic governor is required to solve these problems of control system. The electro - hydraulic governor using PID algorithm is provided to compensate the faults of mechanical- hydraulic governor. In this paper, in order to analyze the ship speed control system, the transfer function was converted from the z tansformation to w transformation. The influence of dead time changing by engine speed which induces hunting phenomena was investigated by Nichols chart of w plane. As a method of performance improvement of mechanical hydraulic governor, a Eletro - hydraulic governor shows that fine control results can be obtained through optimal parameter tuning of PID

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.527-537
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• 2003

The characteristics of ship induced waves caused by navigation become widely different from both ship's speed and water depth condition. The ship induced waves specially generated in coastwise routes frequently give rise to call unforeseen danger for swimmers and small boats as well as shoreline erosion or sea wall destruction in coastal zones. The main concern of ship induced wave study until now is either how to reduce ship resistance or how to manoeuvre the ship safely under a constant water depth in the view point of shipbuilding engineers. Moreover, due to the trends for appearance of the high speed ships at the shallow coastal water, we are confronted with the danger of damages from those ship induced waves. Therefore, it is necessary to examine the development of ship induced waves and the influence of their deformation effects according to its propagation ray. In present study, in order to predict the development of the ship induced waves and their propagation under the conditions of complicate and variable shallow water depth with varying ship's speed, we constructed a computer model using Boussinesq equation with a fixed coordinate system and verified the model results by comparison with experimental results. Additionally, the model was applied under the variable water depth based on actual passage and we then confirmed the importance of the variable water depth consideration.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.17-22
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• 1993

The intersection problem of three-dimensional free form surfaces can be solved by geometrical and numerical methods. Up to now, the subdivision technique, which is classified under the former, has been largely employed to find the cross section of ship hull form. In this paper, an algorithm is presented for intersecting ship hull form in high speed. The high speed calculation algorithm is based on simple numerical methods, such as the secant method, false position method and bisection method. The algorithm is directly applicable to depicting arbitrary ship cross sections, drawing ship lines and constructing the offset table.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.106-110
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• 2002

A need fer stable and comfortable cabins in the high-speed passenger ships has increased. For active control of the motion of the ship cabin, a few control algorithms have been applied to the three dimensional real models in the vibration basin. Experimental results show that the feedforward neural network with a linear feedback controller is one of the promising control algorithms for this active control.

• Journal of Power System Engineering
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• v.14 no.5
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• pp.48-55
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• 2010

When a large ship is advancing in waves, ship undergoes the hydroelastic response, which has influences on structural stability and the fatigue destruction etc. of the ship. Therefore, to predict accurate hydroelastic response, it is necessary to analyze hydroelastic response including fluid-structure interaction. In this research, a ship is divided into many hull elements to calculate the fluid forces and wave exciting forces on each elements using three-dimensional source distribution method. The calculated fluid forces and wave exciting forces are assigned to nodes of hull elements. The neighbor nodes are connected with elastic beam elements. We analyzed hydroelastic responses, and those are formulated by using finite element method. Particularly, to estimate the influence of forward speed on the hydroelastic responses, we use two different methods : Full Hull Rotation Method(FHRM) and Sectional Hull Rotation Method(SHRM).

• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.4
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• pp.35-43
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• 1986

Recently, the SWATH concept hull form which is capable of high speed navigation with small oscillatory motions in waves, was developed from the catamaran type hull forms. This paper discribes a method to predict motion responses of a SWATH ship in regular waves using the strip theory. The 2-dimensional hydrodynamic problem was solved using the improved Green integral equation which is free from the irregular frequencies. The effects of viscous drag which is dominant in heave damping of the SWATH ship are taken into account. Further, the effects of the stationary stabilizing fins which is important in high speed performance of the SWATH ship are included in the equation of motions. It seems that the motion responses calculated by the present method show better agreement with experimental results than other existing numerical results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.5-10
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• 2003

This paper is mainly concerned with the assessment of safe navigation between ships moving each other in restricted waterways. The manoeuvring simulation was conducted parametrically to propose an appropriate sage speed and distance, which is required to avoid sea accident under the different conditions, such as ship-velocity ratios, ship-length ratios, separation and stagger between ships. The manoeuvring characteristics based on this investigation will be very useful for keeping the safety of navigation from the practical point of ships design and traffic control in confined water.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.2
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• pp.109-113
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• 1981

Most existing theories on ship waves and wave resistance are based on the perturbation of the flow field by a small pararr.eter which specifies the slenderness of the ship hull. Since however, ship hulls in practice are neither so slender nor thin enough to secure the validity of the linearized theory, the agreen:ent between the theoretical prediction and the experimental result is not generally satisfactory. The author pointed out that the contribution by the non-linear term in the free surface condition can be represented by sorr.e source distribution over the still water plane. This paper leads to a forrr.ula for the wave resistance of not slender ships at low Froude nurr.bers. and deals with the asynptotic expression. As a nurr.erical example, the wave resistance of Wigley model is calculated, and the result is compared with experimental values. It is concluded that the wave resistance coefficient varies in the rate of Fn6 at low speed limit in general. A comparison with the result derived from the linearized free surface condition shows that the non-linearity of the free surface is irr portant at low speed.

• Journal of Ship and Ocean Technology
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• v.8 no.3
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• pp.8-17
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• 2004

A numerical method is developed for computing the free surface flows around a transom stern of a ship at a high Froude number. At high speed, the flow may be detached from the flat transom stern. In the limit of the high Froude number, the problem becomes a planning problem. In the present study, we make the finite-element computations for a transom stern flows around a wedge-shaped floating ship. The numerical method is based on the Hamilton's principle. The problem is formulated as an initial value problem with nonlinear free surface conditions. In the numerical procedures, the domain was discretized into a set of finite elements and the numerical quadrature was used for the functional equation. The time integrations of the nonlinear free surface condition are made iteratively at each time step. A set of large algebraic equations is solved by GMRES(Generalized Minimal RESidual, Saad and Schultz 1986) method which is proven very efficient. The computed results are compared with previous numerical results obtained by others.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.291-305
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• 2010

A three-dimensional time-domain calculation method is of crucial importance in prediction of the motions and wave loads of a ship advancing in a severe irregular sea. The exact solution of the free surface wave-ship interaction problem is very complicated because of the essentially nonlinear boundary conditions. In this paper, an approximate body nonlinear approach based on the three-dimensional time-domain forward-speed free-surface Green function has been presented. The Froude-Krylov force and the hydrostatic restoring force are calculated over the instantaneous wetted surface of the ship while the forces due to the radiation and scattering potentials over the mean wetted surface. The time-domain radiation and scattering potentials have been obtained from a time invariant kernel of integral equations for the potentials which are discretized according to the second-order boundary element method (Hong and Hong 2008). The diffraction impulse-response functions of the Wigley seakeeping model advancing in transient head waves at various Froude numbers have been presented. A simulation of coupled heave-pitch motion of a long rectangular barge advancing in regular head waves of large amplitude has been carried out. Comparisons between the linear and the approximate body nonlinear numerical results of motions and wave loads of the barge at a nonzero Froude number have been made.