• International Journal of Naval Architecture and Ocean Engineering
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• 제3권3호
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• pp.201-207
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• 2011

In this paper, we focused on computing the higher-harmonic components of the transmitted wave passing over a submerged circular cylinder to show that it is causing a horizontal negative drift force. As numerical models, a circular cylinder held fixed under free surface in deep water is adopted. As the submergence of a circular cylinder decreases and the incident wavelength becomes longer, the higher-harmonic components of the transmitted wave starts to increase. An increase of the higher-harmonic components of the transmitted wave makes the horizontal drift force be negative. It is also found that the higher-harmonic amplitudes averaged over the transmitted wave region become larger with the increase of wave steepness and wavelength as well as the decrease of submergence depth.

• 대한조선학회지
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• 제21권3호
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• pp.27-34
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• 1984

When a ship is travelling in following seas, the encounter frequency is reduced to be very low. In that case broaching phenomenon is most likely to occur, and it may be due to wave exciting forces acting on ships. It is thought that the wave exciting forces acting on ships in following seas almost consist of two components. One is hydrostatic force due to Froude-Krylov hypothesis, and the other is hydrodynamic lift force due to orbital motion of water particles below the wave surface. In the present paper, the emphasis is laid upon wave exciting sway force, yaw moment and roll moment acting on ships in following seas. The authers take the case that the component of ship speed in the direction of wave propagation is equal to the wave celerity, i.e., the encounter frequency is zero. Hydrostatic force components are calculated by line integral method on Lewis form plane, and hydrodynamic lift components are calculated by lifting surface theory. Furthermore captive model tests are carried out in regular following waves generated by means of a wave making board. Through the comparison between calculated and measured values, it is confirmed that the wave exciting forces acting on ships in following seas can be predicted in terms of present method to a certain extent.

• 한국해안·해양공학회논문집
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• 제28권4호
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• pp.240-249
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• 2016

본 연구에서는 회절을 고려하여 반무한방파제 형식의 직립구조물에 작용하는 지점별 파력 분포를 검토하였다. 비쇄파 조건에서 직립구조물에 작용하는 규칙파 및 불규칙파의 파력에 대해 방파제 전, 후면의 회절을 모두 고려하여 연구하였다. 방파제의 폭이 0인 조건을 비교 대상의 기준 조건으로 채택하였다. 규칙파의 경우 방파제 두부(head of breakwater)에서는 전후면의 입사파 및 회절파가 동시에 작용하여 상대 파력이 0이 되었으며, 두부에서 멀어지면 상대 파력 1.0을 중심으로 진동하는 패턴이 나타났다. 또한 경사입사각이 증가할 경우 규칙파의 상대 파력은 감소하는 경향을 보였다. 본 연구에서는 제곱평균의 제곱근비와 파력 스펙트럼을 이용하여 불규칙파의 상대 파력을 정의하였다. 각 성분파가 갖는 임의의 위상을 고려한 경우와 고려하지 않은 경우를 비교하였으며, 그 결과는 거의 동일하게 나타났다. 불규칙파의 경우 방파제 두부 근처에서 규칙파와 마찬가지로 상대 파력이 0으로 나타났으며, 두부에서 멀어질 때에는 다양한 성분파의 합성에 의해 상대 파력 1.0을 기준으로 진동하는 패턴이 비교적 약하게 나타났다.

• Journal of applied mathematics & informatics
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• 제26권1_2호
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• pp.45-60
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• 2008

Here we consider the evaluation of the the dynamic component of the second order force due to wave diffraction by a circular cylinder analytically and numerically. The cylinder is fixed, vertical, surface piercing in water of finite uniform depth. The formulation of the wave-structure interaction is based on the assumption of a homogeneous, ideal, incompressible, and inviscid fluid. The nonlinearity in the wave-structure interaction problem arises from the free surface boundary conditions, namely, dynamic and kinematic free surface boundary conditions. We expand the velocity potential and free surface elevation functions in terms of a small parameter and then consider the second order diffraction problem. After deriving the pressure using Bernoulli's equation, we obtain the analytical expression for the dynamic component of the second order force on the cylinder by integrating the pressure over the wetted surface. The computation of the dynamic force component requires only the first order velocity potential. Numerical results for the dynamic force component are presented.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1353-1359
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• 2004

There are many massive components added on the railway overhead-line. These components cause larger fluctuations of contact forces, which are due to wave reflections and Doppler effects when a high-speed train passes those. In this paper, mathematical formula are derived for the relation between the added mass and contact force fluctuations. Using the derived formula, we calculate a added mass on the overhead-line which cause amplification factor to become 2.5. German design practice requires that amplification factor due to the wave reflection should be less than 2.5 to obtain good current collection performance. To show the validity of the formula, simulation results are compared with the calculation results. Simulation results showed that contact force fluctuations grow rapidly when an added mass is larger than the calculation result. Therefore, the simple form of formula can be used for estimating maximum added mass not to cause large fluctuations of contact forces in early design phase.

• 한국광학회지
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• 제12권6호
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• pp.437-445
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• 2001

We examine theoretically the properties of the force on Mie particles induced by evanescent fields at a system of multilayer films (including a metal film), at which the surface plasmon resonance is excited by a p-polarized plane electromagnetic wave. An expression of the surface plasmon-coupled evanescent fields produced in Kretschmann (or Sarid) geometry is expanded in terms of vector spherical wave functions, while multiple reflections between the Mie particle and the metal boundary are taken into account. The Cartesian components of the force on Mie particles by the evanescent fields are analytically formulated and numerically evaluated. The force components are increased by one or two orders of magnitude at metal boundaries over those at dielectric boundaries. As a result, we can confirm the possibility of stable manipulation or rotation of a finite-sized object by forces of surface plasmon-coupled evanescent fields.

• 한국해양공학회지
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• 제7권2호
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• pp.9-18
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• 1993

Numerical wave tank is a robust tool by which the nonlinear interactions between the body and the free-surface can be treated in time-domain. In this paper, a two-dimensional numerical wave tank based on the Spectral/Boundary-Element Method is developed, and applied successfully to the study of nonlinear wave diffraction around a submerged circular cylinder. Particularly, it is shown that the high-order wave components of significant wave height are developed in the lee-side of the cylinder and that these waves result in a negative drift force on the circular cylider.

• 대한기계학회논문집
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• 제18권2호
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• pp.292-301
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• 1994

The resultant cutting force during machining with a worn tool is viewed as a decomposition of the cutting force into a cutting force component related to chip removal from the workpiece and into a component dependent on the contact force between the tool flank's wear land and the workpiece. The shear line method, in which the cutting force is considered proportional to the length of the shear line, is used to calculate the cutting force component for the removal of the chip, while the elastic effect of the workmaterial on the tool is taken into consideration to analyze the effect of tool flank wear. The predicted resultant cutting force, expressed as the sum of both components, is compared to experimental data obtained during wave-on-wave cutting.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.457-467
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• 2004

Wave Transmission analysis is one of methods for power transmission and reflection coefficients in coupled infinite structures. This paper focuses the wave transmission analysis of point coupled structures among semi-infinite beams and infinite thin plates considering all kinds of waves. It is supposed that the junction through the beams and plates is an identical spot and no point of contact exist except the spot. The boundary conditions are applied at the spot for continuities of 6 DOF displacements and 6 DOF force equilibriums, and then wave fields are obtained in the coupled structures. Since wave components in plate field are simplified using asymptotic expressions of Henkel functions, the displacements and forces at the plate junction can be simply expressed with magnitudes of the wave components. The wave fields according to incident waves gives the power transmission coefficients in beam/plate point coupled structures. For both coupled structures with a beam vertically and obliquely joined to a plate, power transmission analysis is performed and the analysis results are compared and examined.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.7-12
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• 2000

As the offshore oil fields are moved to the deep ocean, the oil production systems of FPSO(Floating production storage and offloading system) are building these days and so it is the most important to estimate the drift motion and damping effects the drift motion importantly. The components of damping consist of viscous, wave radiation effect and wave drift damping. It is need to estimate the wave drift damping exactly among them. The wave drift damping means the change rate of mean wave drift force with respect to the ship and ocean structures speed. In order to calculate this, the 3-Dimensional panel method used to translating and pulsating Green function is adopted. The calculation is carried out for series 60(CB = 0.7) vessel and the results are compared with other theoretical ones.