• Title/Summary/Keyword: 모리슨 방정식

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Development of a Program for Analyzing the Stability of Artificial Reefs - Application of a Computer Coding System - (인공어초 안정성 해석 프로그램 개발 - 컴퓨터 코딩시스템 적용)

  • Jeon, Yong-Ho;Park, Jae-Hyung;Yoon, Han-Sam
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.5
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    • pp.537-544
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    • 2018
  • In this study, a simple, efficient, user-based program called SCAR was developed for evaluating the sliding and collapse of artificial reefs due to hydrodynamic forces in ocean environments. SCAR was developed by applying Delphi code and a Graphical User Interface (GUI) based on the Morison formula for evaluating and analyzing the stability of artificial reefs. SCAR can be applied widely for design and stability evaluation of fishery structures (such as artificial reefs or other underwater structures) in undergraduate and graduate courses and by experts in the field.

A Reliability Study of Coastal Structures Under the Influence of Waves and Currents -Random Analysis of Fixed Structures- (파랑과 흐름을 받는 여안 구조물의 안정성에 관한 연구 -고정식 해양 구조물의 랜덤 해석-)

  • Choe, Yong-Ho;Gwon, Sun-Hong;Kim, Dae-Ung;Park, Sang-Gil
    • Journal of Ocean Engineering and Technology
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    • v.9 no.2
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    • pp.186-192
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    • 1995
  • This paper investigates the problem of random analysis of fixed structures which are influenced by waves and current. Morison eqution was employed to deal with the wave and current load. The wave kinematics are randomly generated from the wave spectrum. The necessary statistics are calculated from the resulting response time history. The simulation results are turned out to be very sensitive to the simulation technique.

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Numerical Analysis of Hydrodynamic Characteristics for Various Types of Jack-up Legs (다양한 형상의 Jack-up Leg에 대한 해양 동역학적 수치해석)

  • Kim, Ji-Seok;Park, Min-Su;Koo, Weoncheol
    • Journal of Ocean Engineering and Technology
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    • v.28 no.5
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    • pp.371-377
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    • 2014
  • In this study, the hydrodynamic characteristics of various types of jack-up legs for a wind turbine installation vessel were analyzed. Using the modified Morison equation, the wave and current excitation forces on the jack-up legs were calculated. A modal analysis was performed to predict the dynamic responses for various types of jack-up legs. The Newmark-beta time integration scheme was used to solve the equation of motion in waves in the time domain. The maximum displacement and maximum bending stress were computed for four different types of legs, and their results were compared to select an optimum leg type. Finally, a six-leg jack-up rig with the selected optimal legs was modeled, and its natural period and hydrodynamic behaviors were evaluated.

A Study of Wave and Current Forces on Cylinders (실린더에 작용하는 파력 및 조류력에 관한 연구)

  • 박광동;조효제;구자삼
    • Journal of Ocean Engineering and Technology
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    • v.15 no.4
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    • pp.14-19
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    • 2001
  • In this paper, the wave and current forces acting on cylinders are investigated by theoretical and experimental methods. The models used are one-cylinder, four-cylinder and semi-submersible types. The theoretical investigations are carried out by the Morison equation and three dimensional source distribution method to calculate exciting forces in waves with and without currents. The experimental investigations are carried out in the wave tank which can generate currents in both directions. In these tests, the models have been exposed to the regular waves with and without currents. It is shown that the exciting forces acting on the one-cylinder or four-cylinders can be approximately estimated by the Morison equation and also by the diffraction theory. However, the Morison equation seems to be not appropriate to estimate the exciting forces on the present type of semi-submersible.

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Evaluation of Fluid Forces Acting on Offshore Structures Placed in the Vicinity of Underwater Shoal (수중 천퇴 인근에 설치된 해양구조물에 작용하는 유체력 결정에 대한 고찰)

  • Chun, In-Sik;Min, In-Ki;Sim, Jae-Seol
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.19 no.2
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    • pp.136-145
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    • 2007
  • When waves propagating over an underwater shoal break at the top of the shoal, wave heights are drastically decreased in the downstream breaking zone, but a secondary current shooting downstream with strong velocity can be induced by the breaking waves themselves. In the case that an offshore structure is placed in the breaking zone, the estimation of wave farce purely based on the visible wave height may cause an under-design of the structure. Thus, for the safe design of the structure, the breaking wave induced current should be necessarily considered in the comprehensive estimation of design load. In the present study, Boussinesq equation model to calculate the wave height distribution and breaking wave induced current was set up and applied to the scheme of a hydraulic model test previously undertaken. Based on the results of the Boussinesq model, fluid forces acting on the model structure were calculated and compared with the experimental results. The importance of the breaking wave induced current was quantitatively assessed by comparing fluid forces with or without current.

Dynamic Analysis of Wave Energy Generation System by Using Multibody Dynamics (다물체 동역학을 이용한 파력발전기의 동적거동 분석)

  • Jang, Jin-Seok;Sohn, Jeong-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.12
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    • pp.1579-1584
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    • 2011
  • This paper discusses an energy system that can convert wave energy into electrical energy. This wave energy generation system is movable and has 12 arms and one generator. A multibody dynamic model for this system is established by using kinematic constraints. A gear mechanism, several kinematic constraints, and force elements are included in the model. Wave forces are obtained numerically from the time domain formulation based on the Morison equation. The MSC/ADAMS program is employed to carry out dynamic analysis of the wave energy generation system. The dynamic behavior responses of this system are analyzed for design verification. According to the results of the dynamic analysis, the yaw motion is relatively stable and kinetic energy sufficient to generate electrical energy is obtained when the wave height exceeds 1m.

Structural Analysis of a Breakwater in Wave and Seismic Loads (파랑하중과 지진하중하의 방파제 구조해석)

  • Cho, Kyu-Nam
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.1
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    • pp.45-52
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    • 2009
  • In this paper, a guideline for designing breakwater in wave loads and in seismic loads is proposed. A simple model structure in breaking wave zone is examined using Morison equation in consideration with the effect of an impact load, for evaluation of the wave loads. As the impact load effect is not significant, pressure distributions according to Goda are applied for evaluation of wave loads on breakwater. Structural behavior of breakwater in wave loads can be obtained using the Goda method, as well. For seismic analysis, Ofunato and Hachinohe models, as well as an artificial seismic acceleration loads model, are adopted. Soil-structure interaction analysis is carried out to find the seismic load effect. It is found that, in certain cases, structural deformation in wave loads is in the same level as deformation that in seismic loads. Thus, it is our recommendation that these two loads are considered at the same level in breakwater design.

Vibration Control of Offshore Platform using Tuned Mass Damper (동조질량감쇠기를 이용한 해양구조물의 진동제어)

  • Kim, Ju Myung;Lee, Gyu Won
    • Journal of Korean Society of Steel Construction
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    • v.16 no.1 s.68
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    • pp.73-79
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    • 2004
  • Tuned Mass Damper (TMD) was applied to control the vibration of an offshore structure due to ocean waves. The errors caused by the linearization of the fluid-structure interaction effect and the phenomena when using the linearized equation of motion in TMD design were analyzed. To determine the performance of TMD in controlling vibration, both regular waves with varying periods and irregular waves with different significant wave heights were used. When the offshore structure received regular waves with a period similar to the first natural period of structure. TMD performed well in terms of response reduction. Such was not the case for the other periods. however, In the case of irregular waves, TMD triggered the reduction of structural response for waves with relatively small significant wave height. For irregular waves with relatively big significant wave height, however, TMD did not show any control effect. Therefore, TMD is useful in reducing offshore structural vibration due to ambient waves, thereby helping secure fatigue life.

Seismic control of offshore platform using artificial neural network (인공신경망을 이용한 해양구조물의 지진시 진동제어)

  • Kim, Dong Hyawn;Kim, Ju Myung;Shim, Jae Seol
    • Journal of Korean Society of Steel Construction
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    • v.21 no.2
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    • pp.175-181
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    • 2009
  • An intelligent control technique using a neural network is proposed for offshore structures exposed to sea-bed earthquakes. Fluid-structure interaction effect was considered in developing controller and a training algorithm for the neural network is presented. In the numerical example, the performance of the proposed neural network controller was compared with that of a passive controller and uncontrolled structures. Based on the example, it can be concluded that the proposed neuro-control scheme can be used for offshore structures with nonlinear characteristics due to its interaction with fluid.

Analysis of Dynamic Behavior of Floating Offshore Wind Turbine System (해상 부유식 풍력 타워의 동적거동해석)

  • Jang, Jin-Seok;Sohn, Jeong-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.1
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    • pp.77-83
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    • 2011
  • In this study, the dynamic modeling of floating offshore wind turbine system is reported and the dynamic behavior of the platform for the offshore wind turbine system is analyzed. The modeling of the wind load for a floating offshore wind turbine tower is based on the vertical profile of wind speed. The relative Morison equation is employed to obtain the wave load. ADAMS is used to carry out the dynamic analysis of the floating system that should withstand waves and the wind load. Computer simulations for four types of tension leg platforms are performed, and the simulation results for the platforms are compared with each other.