• 수산해양기술연구
• /
• 제39권4호
• /
• pp.298-304
• /
• 2003

In this paper a free-form hull design program and performance prediction program for planing boat is introduced. This program enables the designer to do complex geometric hull shape design on a personal computer and accurately to predict power requirements for a given loading and velocity. For a free form design, Bezier curve model is adopted as a basic representation tool of curves and surfaces, and this program has versatile functions to do fairing jobs with a convenient graphical user interface. After creating a hull form the geometric data is provided in a manner compatible with a variety of analysis tools including 'Motion Analysis(by Zarnick)' for prediction of motion characteristics in regular waves, 'Running Attitude (by Savitsky)' for prediction of the running attitude and required power.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
• /
• pp.128-135
• /
• 1997

The indirect boundary integral equation is formulated to analyze the behavior of a cavity in a multilayered half-plane subjected to earthquake waves. This formulation uses the fundamental solutions that are numerically calculated by the generalized transmission and reflection coefficient method. The free surface of the cavity without external excitation influences the behavior of the half-plane. Consequently this analysis adds the consideration of scattering-field into the analysis and the total motion field of the cavity is decomposed into the free-field and scattering-field motions. The free-field motion is obtained from the modification of the transmission and reflection coefficient method. The scattering-field motion is calculated is calculated by the indirect boundary value problem which has the ficticious boundaries and sources. In this study, P wave, SV wave, SH wave, and Rayleigh wave are analyzed respectively.

• 대한조선학회논문집
• /
• 제41권4호
• /
• pp.38-44
• /
• 2004

The motion response analysis of a submerged elliptic cylinder in waves is presented and the elliptic cylinder is a simplification of the section of submarine in this paper. The method is based on boundary integral method and two-dimensional 3 degree motions are calculated in regular harmonic waves. The fully nonlinear free surface boundary condition is assumed in an numerical domain and this solution is matched along an assumed boundary as a linear solution composed of transient Green function, The large amplitude motions of an elliptic cylinder are directly simulated and effects of wave frequency, wave amplitude and the distance from buoyancy center to gravity center are discussed.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 추계학술대회 논문집
• /
• pp.227-231
• /
• 2001

Analysis of two-dimensional unsteady flows with a free surface in a rectangular container subject to a linear reciprocating force is performed by numerical and experimental methods. FVM is used for the numerical computation of the two-dimensional flows. We consider the surface tension as well as the viscous/elastic properties of the free surface. One-dimensional analysis as well as experiment is used in establishing the free surface properties. The steady recirculatory flow is visualized by a laser sheet. It is shown that the one-dimensional analysis provides useful informations associated with the free surface properties.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.695-700
• /
• 2000

The dynamic stability of spinning beam with free boundary conditions for both edges subjected to a tip follower force $P_0+P_1cos{\Omega}t$ is analyzed. It is studied that the beam has a concentrated mass. and then the effects of the axial locations of the mass are studied. The beam is modelled with the Timoshenko type shear deformations. The Hamilton's principle is used to derive the equations of motion, and the critical spinning speed of a beam subjected to a follower force with various non-dimensional parameters is investigated. The finite elements are used with $C^0$ continuity to analyze the spinning beam model, and the method of multiple scales is tried to investigate the dynamic instability regions. The governing equations of motion involve periodic coefficients, which are not in the form of standard Mathieu-Hill equations. The result shows that the concentrated mass increases the dynamic stability of the spinning free-free beam subjected to a thrust.

• Journal of Mechanical Science and Technology
• /
• 제17권1호
• /
• pp.85-96
• /
• 2003

In the present investigation, the nonlinear dynamic buckling of a curved plate subjected to sinusoidal loading is examined. By the theoretical analyses, a highly nonlinear snap-through motion of a clamped-free-clamped-free plate and its effect on the overall vibration response are investigated. The problem is reduced to that of a single degree of freedom system with the Rayleigh-Ritz procedure. The resulting nonlinear governing equation is solved using Runge-Kutta (RK-4) numerical integration method. The snap-through boundaries, which vary with different damping coefficient and linear circular frequency of the flat plate are studied and given in terms of force and displacement. The relationships between static and dynamic responses at the start of a snap-through motion are also predicted. The analysis brings out various characteristic features of the phenomenon, i.e. 1) small oscillation about the buckled position-softening spring type motion, 2) chaotic motion of intermittent snap-through, and 3) large oscillation of continuous snap-through motion crossing the two buckled positions-hardening spring type. The responses of buckled plate were found to be greatly affected by the snap-through motion. Therefore, better understanding of the snap-through motion is needed to predict the full dynamic response of a curved plate.

• 대한기계학회논문집B
• /
• 제35권6호
• /
• pp.617-624
• /
• 2011

본 연구에서는 사각용기 내에서의 자유표면을 갖는 2차원 슬로싱 문제에 대하여 고찰하였다. 용기 내부의 유동은 수평방향의 조화운동을 통해 형성되며, 외부 가진 속도는 u=Asin($2{\pi}ft$)으로 정의 된다. 여기서 u, A�� 그리고 f는 외부로부터 작용하는 가진 속도, 변위 그리고 주파수를 각각 나타낸다. 큰 변위(A~O(1)) 슬로싱 문제의 해석을 위한 실험설비를 구축하였으며, 광범위한 영역에서의 PIV실험을 수행하였다. 실험을 통해 자유표면의 움직임(motion)을 각각 서로 다른 물리적 특성을 갖는 세 가지; 선형 슬로싱의 자유표면의 움직임과 유사한 standing wave motion, 사각용기의 속도가 0을 지나는 순간(the moment of turn-over) 측벽에서 발생하는 run-up motion 그리고 측벽으로부터 내부유체로 점차적으로 전파되는 bore motion으로 분류하였다.

• Wind and Structures
• /
• 제14권5호
• /
• pp.435-447
• /
• 2011

A Computational Fluid Dynamics model is presented in this study for the simulation of the complex fluid flows with free surfaces inside the Tuned Liquid Column Dampers in horizontal motion. The characteristics of the fluid model of the TLCD in horizontal motion include the free surface of the multiphase flow and the horizontal moving frame. In this study, the time depend unsteady Standard ${\kappa}-{\varepsilon}$ turbulent model based on Navier-Stokes equations is chosen. The volume of fluid (VOF) method and sliding mesh technique are adopted to track the free surface of water inside the vertical columns of TLCD and treat the moving boundary of the walls of TLCD in horizontal motion. Several model solution parameters comprising different time steps, mesh sizes, convergence criteria and discretization schemes are examined to establish model parametric independency results. The simulation results are compared with the experimental data in the dimensionless amplitude of the water column in four different configured groups of TLCDs with four different orifice areas. The predicted natural frequencies and the head loss coefficient of TLCDs from CFD model are also compared with the experimental data. The predicted numerical results agree well with the available experimental data.

• 대한조선학회논문집
• /
• 제47권3호
• /
• pp.377-387
• /
• 2010

In this study, the turbulent free surface around KVLCC1 employed in the circular motion test simulation is numerically calculated using a commercial CFD(Computational Fluid Dynamics) code, FLUENT. Also, hydrodynamic forces and yaw moments around a ship model are calculated during the steady turning. Numerical simulations of the turbulent flows with free surface around KVLCC1 have been carried out by use of RANS equation based on calculation of hydrodynamic forces and yaw moments exerted upon the ship hull. Wave elevation is simulated by using the VOF method. VOF method is known as one of the most effective numerical techniques handling two-fluid domains of different density simultaneously. Boundary layer thickness and wake field are changed various yaw velocities of ship model during the steady turning. The calculated hydrodynamic forces are compared with those obtained by model tests.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
• /
• pp.898-900
• /
• 1998

This paper describes the motion characteristics and micro-discharge of the free conducting particles between plain electrodes under alternating voltage. The particles move between both electrodes due to electrostatic force by applied AC voltage. Various types and sizes of free conducting particles were used to study the motion and micro-discharge characteristics. The micro-discharge and breakdown were observed during the particle motion.