• Journal of computational fluids engineering
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• v.13 no.1
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• pp.28-34
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• 2008

A particle method recognized as one of the gridless methods has been developed to investigate the nonlinear free-surface motions interacting to the structures. The method is more feasible and effective than convectional grid methods for solving the non-linear free-surface motion with complicated boundary shapes. The right-handed side of the governing equations for incompressible fluid, which includes gradient, viscous and external force terms, can be replaced by the particle interaction models. In the present study, the developed method is applied to the dam-broken problem on dried- and wet-floor and its adequacy will be discussed by the comparison with the experimental results.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.258-263
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• 2007

A particle method recognized as one of the gridless methods has been developed to investigate the nonlinear free-surface motions interacting to the structures. The method is more feasible and effective than convectional grid methods for solving the non-linear free-surface motion with complicated boundary shapes. The right-handed side of the governing equations for incompressible fluid, which includes gradient, viscous and external force terms, can be replaced by the particle interaction models. In the present study, the developed method is applied to the dam-broken problem on dried- and wet-floor and its adequacy will be discussed by the comparison with the experimental results.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.25-31
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• 1989

Two-dimensional large-amplitude motions in regular harmonic wave are treated in time domain, by satisfying the exact body boundary condition and the linear free surface condition. For the present numerical calculation, the method of free-surface spectral representation with simple source distribution on the instantaneous body surface has been extended to include the effect of the incident wave. Calculations of the wave exciting force are performed for a submerged circular cylinder fixed or oscillating with large amplitude. Especially, nonlinear effects on the time-mean forces are studied in detail. It is shown that relative motion between the body and the fluid particle gives a significant effect on the lift and drift forces. Also, large-amplitude motion of a submerged circular cylinder and that of a floating Lewis-form cylinder are directly simulated in time domain. In the calculation results, some nonlinear effects are shown.

• Journal of Ocean Engineering and Technology
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• v.17 no.6
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• pp.7-15
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• 2003

A Digital Wave Tank simulation technique, based on a finite-difference method and a modified marker-and-cell (MAC) algorithm, is applied in order to investigate the characteristics of nonlinear Tsunami propagations and their interactions with a 2D sloping beach, Ohkushiri Island, and to predict maximum wove run-up around the island. The Navier-Stokes (NS) and continuity equation are governed in the computational domain, and the boundary values are updated at each time step, by a finite-difference time-marching scheme in the frame of the rectangular coordinate system. The fully nonlinear, kinematic, free-surface condition is satisfied by the modified marker-density function technique. The near shore Tsunami is assumed to be a solitary wave, and is generated from the numerical wave-maker in the developed Digital Wave Tank. The simulation results are compared with the experiments and other numerical methods, based on the shallow-water wave theory.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.231-239
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• 2003

A Digital Wave Tank simulation technique based on a finite-difference method and a modified marker-and-cell (MAC) algorithm is applied to investigate the characteristics of nonlinear Tsunami propagations and their interactions with a 2D sloping beach and Ohkushiri island, and to predict maximum wave run-up around the island. The Navier-Stokes (NS) and continuity equation are governed in the computational domain and the boundary values updated at each time step by a finite-difference time-marching scheme in the frame of rectangular coordinate system. The fully nonlinear kinematic free-surface condition is satisfied by the modified marker-density function technique. The Nearshore Tsunami is assumed to be a solitary wave and generated from the numerical wavemaker in the developed Digital Wave Tank. The simulation results are compared with the experiments and other numerical methods based on the shallow-water wave theory.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.617-624
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• 2011

The two-dimensional sloshing problem in a rigid rectangular tank with a free surface is considered. The flow is generated by a container in harmonic motion in time along the horizontal axis, i.e., a container excited by u=Asin($2{\pi}ft$) where u denotes the container velocity imposed externally, A is the amplitude of the oscillation velocity, and f is the frequency of oscillation. Experimental apparatus is arranged to investigate the large-amplitude sloshing flows in off-resonant conditions, where the large amplitude means that A~O(1), and the distance, S, is comparable to the breadth, L, of the container, i.e., L/S~O(1). Comprehensive particle image velocimetry (PIV) data are obtained, which show that the flow physics of the nonlinear off-resonant sloshing problem can be characterized into three peculiar free surface motions: standing-wave motions similar to those of linear sloshing, a run-up phenomenon along the vertical sidewall at the moment of turn-over of the container, and gradually propagating bore motion from the sidewall to the interior fluid region, like a hydraulic jump.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.4
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• pp.81-87
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• 2002

In this paper, the transonic aeroelastic behavior of the generic fighter model is investigated in the time domain. The simulation of flutter flight test using forced harmonic motion of control surfaces including inertial coupling effects is conducted at the various conditions. The nonlinear aerodynamic effects are considered using a transonic small disturbance equation. A modal model obtained by a free vibration analysis is used for the structural model. The relations between the computed flutter boundary and the simulation results of the responses using the harmonic motions of control surfaces at various conditions are investigated.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.1
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• pp.105-110
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• 2011

Some research work on CFD computation of ship motions and added resistance in waves for a high speed trimaran is carried out in this paper. The governing equations, Reynolds Averaged Navier-Stokes and continuity equations are discretized by finite volume method. Volume of fluid method is adopted to deal with the nonlinear free surface. The incident waves are generated from the inflow boundary by prescribing a velocity profile resembling flexible flap wavemaker motions, and the outgoing waves are dissipated inside an artificial damping zone located at the rear part of the wave tank. In this paper, the computed results of ship motion and added resistance for a high speed trimaran are presented. The results of seakeeping experiment for the high speed trimaran carried out in CSSRC towing tank are also presented in this paper. Rather good agreements are shown between the computational and experimental results. The work in this paper provides a numerical tool for the study of seakeeping performance of high speed trimarans.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.403-406
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• 2006

A particle method recognized as one of gridless methods has been developed to investigate the nonlinear free-surface motions interacting to the structures. The method is more feasible and effective than convectional grid methods in order to solve the flow field with complicated boundary shapes. In the present study, breaking waves with a floating body are simulated to investigate fluid-structure interactions in the coastal zone.

• Korean Journal of Computational Design and Engineering
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• v.8 no.4
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• pp.278-288
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• 2003

Presented in this paper is a numerical method for calculating the intersection points between Z-map vectors and the tool swept surface for circularly moving filleted-end mills. In numerically controlled(NC) machining simulation for large moulds and dies, a workpiece is frequently approximated as a set of z-axis aligned vectors, called Z-map vectors, and then the machining processes can be simulated through updating the Z-map with the intersection points. Circular motions are typically used for machining the free-form surfaces. For fast computation, we express each of intersection points with a single-variable non-linear equation and calculate the candidate interval in which the unique solution exists. Then, we prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the nonlinear equation within a given precision. Experimental results are given for the case of a TV monitor and the hood of a car.