• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.57-62
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• 2000

The very large flcating structure which am be used for as airport may be as large as several kilomet wide. The first order wave forces as well as wave drift forces are very important forces on such a very large floating In the present studv, the time simulation of motion responses with dolphin-moored VLFS in waves is presented The coeffcients and wave forces involved in the equations are obtained from a three-dimensionul panel method in the frequc The horizontal drift forces and mooring forces for dolphin systems are taken into account. As for numerical example, analyses are carried out for a VLFS in irregular wave condition

• Journal of Navigation and Port Research
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• v.27 no.1
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• pp.55-61
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• 2003

The maneuvering equations of motion are derived to express the motion of a ship. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The linear wave forces whose periods are equal to those of incident waves and the nonlinear wave forces that make long period drift forces are computed for the simulation. The consideration of irregular waves and nonlinear wave force effects on the slew motion are carried on the analyzing the motion of ship in the regular and irregular waves.

• Ocean Systems Engineering
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• v.9 no.1
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• pp.97-109
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• 2019

Accurate calculation of the mean drift forces and moments is necessary when studying the higher order excitations on the floater in waves. When taking the time average of the second order forces and moments, the second order potential and motion diminish with only the first order terms remained. However, in the results of the first order forces or motions, the irregular frequency effects are often observed in higher frequencies, which will affect the accuracy of the calculation of the second order forces and moments. Therefore, we need to pay close attention to the irregular frequency effects in the mean drift forces. This paper will discuss about the irregular frequency effects in the calculations of the mean drift forces and validate our in-house program MDL Multi DYN using some examples which are known to have irregular frequency effects. Finally, we prove that it is necessary to remove the effects and demonstrate that the effectiveness of the formula and methods adopted in the development of our program.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.35-44
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• 2001

A numerical procedure is described for simultaneously predicting the wave exciting forces and drift forces on a Tension Leg Platform (TLP) in multi-directional irregular waves. The numerical approach is based on a three dimensional source distribution method to the wave exciting forces, a far-field method to the steady drift forces and a spectral analysis technique of directional waves. The spectral description for the linear system of TLP in the frequency domain is sufficient to completely define the wave exciting forces and steady drift forces. This is because both the wave inputs and the outputs are stationary Gaussian random process of which the statistical properties in the amplitude domain are well known. Numerical results of steady drift forces are compared with the experimental and numerical ones, which are obtained in the literature. The results of comparison confirmed the validity of the proposed approach.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.413-420
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• 2006

The construction of a submerged breakwater has become increasing due to their multiple effects on the coastal zone. Recently, marker rocks have been installed on the submerged breakwater to indicate its position to the vessels instead of buoy systems, since a buoy is not only improper for the ocean view, but also its mooring system may be damaged by the impulsive wave force caused by wave breaking on the breakwater. The accurate estimation of wave forces on such rocks is deemed necessary for their stability design. In this study, the characteristics of irregular wave forces acting on a marker rock, which was installed on a submerged breakwater, was investigated on the basis of laboratory experiments. It was revealed that the dimensionless highest one-third wave force tends to decrease with increasing the installation distance of a marker rock from the leading crown edge of a submerged breakwater. Also, the drag and inertia coefficients for irregular wave forces, which were obtained using the Morison equation, were investigated in relation to K.C. number.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.586-595
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• 2007

The analytic solution of wave scattering of monochromatic waves on a pile breakwater by an eigenfunction expansion method is extended to the case of directional irregular waves. The scattering wave spectrum and the force spectrum can be expressed from the reflection coefficient, transmission coefficient and the wave forces obtained from changing frequencies and incident angles in monochromatic waves. By numerical integration of 2-dimensional spectrum which is function of frequencies and incident angles, the representative values for the scattered waves and wave forces are obtained and the dependence of the transmission coefficients and wave forces on the directional distribution function, the principal wave direction, the submergence depth, and porosity is analyzed.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.76-89
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• 1997

The hydrodynamic interaction characteristics between multiple floating bodies of semisubmersible type are examined to present the basic data for the design of huge offshore structures supported by a large number of the floating bodies in multi-directional irregular waves. The numerical approach is based on a combination of a three-dimensional source distribution method, the wave interaction theory and the spectral analysis method. The effects of wave directionality on the wave exciting forces acting on multiple floating bodies in multi-directional irregular waves also have been pointed out.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.10-18
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• 2001

The very large floating structure which can be used for as airport may be as large as several kilometer long and wide. The first order wave forces as well as wave drift forces are very important forces on such a very large floating structures. In the present study, the time simulation of motion responses for dolphin-moored VLFS in waves is presented. The hydrodynamic coefficients and wave forces involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The horizontal drift forces and mooring forces for dolphin systems are taken into account. As for numerical example, time domain analyses are carried out for a VLFS(Phase I) in irregular wave condition.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.1-8
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• 2000

The time simulation of motion responses of dolphin-moored BMP in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and solved in time domain by using the Newmark $\beta$ method. The hydrodynamic coefficient and first order wave exciting forces involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The second order wave drift forces and mooring for dolphin system are taken into account. As for numerical example, time domain analysis are carried out for a BMP in irregular wave condition.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.3
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• pp.43-50
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• 1984

A body form, which experiences minimum vertical wave-exciting forces in the vicinity of a prescribed wave frequency in water of finite depth, is obtained by an approximate method. Its configuration has the symmetry with respect to the vertical axis, expressed in terms of exponential functions. By distributing three-dimensional pulsating sources and dipoles on the immersed surface of the body, a velocity potential is determined and subsequently hydrodynamic forces including the 2nd-order time-mean drift forces are calculated. The dynamic behavior of the body moored in irregular waves is investigated numerically by using central difference method. Hereby irregular wave trains are simulated with examining its repeatability by comparing the resulting spectrum with original one. Numerical results indicated that the body form obtained from the present analysis possesses in general a favorable hydrodynamic characteristics in comparison with a spherical buoy and that the maximum excursion of the body can be significantly reduced by setting pre-tension of an appropriate amount in the mooring cable.