• Title/Summary/Keyword: Vibration in Ship

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Hydroelastic Effects in Vibration of Plate and Ship Hull Structures Contacted with Fluid

  • Lee, Jong-Soo;Song, Chang-Yong
    • International Journal of Ocean System Engineering
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    • v.1 no.2
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    • pp.76-88
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    • 2011
  • The present study deals with the hydroelastic vibration analysis of structures in contact with fluid via coupled fluid-structure interaction (FSI) embedded with a finite element method (FEM) such that a structure displacement formulation is coupled with a fluid pressure-displacement formulation. For the preliminary study and validation of FEM based coupled FSI analysis, hydroelastic vibration characteristics of a rectangular plate in contact with fluid are first compared with the elastic vibration in terms of boundary condition and mode frequency. Numerical results from coupled FSI analysis have been shown to be rational and accurate, compared to energy method based theoretical solutions and experimental results. The effect of free surface on the vibration mode is numerically studied by changing the submerged depth of a rectangular plate. As a practical application, the hull structural vibration of 4,000 twenty-foot equivalent units (TEU) container ship is considered. Hydroelastic results of the ship hull structure are compared with those obtained from the elastic condition.

Analysis of Vibration of Ship Hull Girder (선체진동의 해석)

  • 홍봉기
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.18 no.1
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    • pp.35-38
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    • 1982
  • Ship hull Vibration is caused by troubling measure instruments installed in the ship, fatigue of the hull girder. Vibration has been studied by the View point of anti-Vibration. However, the theoretical calculation values of the Vibration analysis were not obtained accurately. Therfore, in this paper, Vibration analysis were made on the two (cylinder form, ship form) of ship hull girder by the transfer matrix method. The super-structure length was determined to be 0, 20, 40, 60, 80, 100, percentage of the ship's length from the stern. The results of analysis by the transfer matrix method are as follow. 1. Natural frequency may be determined by the order of node numbers and superstructure length. 2. Natural frequency inereased when the ship form is a finess and increasing ratio followed by high order of node numbers.

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Global Ship Vibration Analysis by Using Distributed Fluid Added Mass at Grid Points (유체부가수질량 절점분포 방법에 의한 전선진동해석)

  • Kim, Young-Bok;Choi, Moon-Gil
    • Journal of the Society of Naval Architects of Korea
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    • v.48 no.4
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    • pp.368-374
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    • 2011
  • Recently, the ship vibration analysis technique has been well set up by using FEM. The methods considering the hydrodynamic added mass and damping of the fluid surrounding a floating ship have been well developed, so that they can be calculated by using the commercial package FEM programs such as MSC/NASTRAN, ADINA and ANSYS. Especially, MSC/NASTRAN has the functions to consider the fluid in tanks(MFLUID) and to solve the Fluid-Structure Interaction(FSI) problem(DMAP). In this study, the global ship vibration with considering the added mass distributed at the grid points on the wetted shell surface is introduced to. In the new method, the velocity potentials of the fluid surrounding a floating ship are calculated by solving the Lapalce equation using the Boundary Element Method(BEM), and the point mass is obtained by integrating the potentials at the points. Then, the global vibration analyses of the ship structure with distributed added mass on the wetted surface are carried out for an oil/chemical tanker. During the future sea trial, the results will be confirmed by measurement.

A Study on the Practical Use of an Active Control System to Reduce Ship Superstructure Vibration (선박 상부구조 진동 저감을 위한 능동형 제어장치의 실용화 연구)

  • 조대승;최태묵;김진형;정성윤;백광렬;이수목;배종국;이장우
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.4
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    • pp.77-84
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    • 2004
  • Active control is regarded as one of the most efficient and economic countermeasures to reduce excessive vibration of ship superstructure. However, it is difficult to find its practical application in real ships in spite that many studies on such systems have been done. In this study, for the practical use of an active control system to reduce ship superstructure vibration, we have developed an active vibration compensator consisting of a mechanical actuator having compact size and expected lifetime over 20 years, its control panel including exclusive signal processing and computing board, sensors to detect phase and vibration, and its operation software providing various user-interface functions. From the performance verification test of the system at a 5,500 TEU container carrier, we have confirmed the system could reduce ship superstructure vibration of a harmonic component of main engine rotating frequency up to 0.1 mm/s.

Study on Vortex-Induced Vibration Predictions for Ship Rudders

  • Jang, Won-Seok;Hong, Suk-Yoon;Song, Jee-Hun;Kwon, Hyun-Wung;Choi, Woen-Sug
    • Journal of Ocean Engineering and Technology
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    • v.34 no.5
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    • pp.325-333
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    • 2020
  • As regulations concerning ship vibration and noise are becoming stricter, considerable attention is being drawn to prediction technologies for ship vibration and noise. In particular, the resonance and lock-in phenomena caused by vortex-induced vibration (VIV) have become considerably important with increases in the speed and the size of ships and ocean structures, which are known to cause structural problems. This study extends the fluid-structure interaction (FSI) analysis method to predict resonances and lock-in phenomena of high modes and VIV of ship rudders. Numerical stability is secured in underwater conditions by implementing added mass, added damping, and added stiffness by applying the potential theory to structural analysis. An expanded governing equation is developed by implementing displacements and twist angles of high modes. The lock-in velocity range and resonant frequencies of ship rudders obtained using the developed FSI method agree well with the experimental results and the analytic solution. A comparison with local vibration guidelines published by Lloyd's Register shows that predictions of resonances and lock-in phenomena of high modes are necessary in the shipbuilding industry due to the possible risks like fatigue failure.

A study on natural frequency estimation of modified ship structure by using FRF synthesis method (전달함수함성법을 이용한 선박구조변경시 고유진동수 추정에 관한 연구)

  • Kim, Kuk-Su;Choi, Su-Hyun;Jo, Sung-Je
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.176-180
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    • 2006
  • When the vibration troubles occur on the ship structure during the sea trial, the rectification work is very restricted because of in-situ limitation. Usually, the finite element method is used to improve vibration characteristics of the structure, but it takes lots of time and effort in modeling the structure and adjusting the finite element model in order to consider appropriate boundary conditions of a complex ship structure. Therefore, experimental methods have been in general suggested to obtain proper countermeasures without time-consuming in modeling. In this paper, FRE(frequency response function) synthesis method is applied to estimate natural frequency of the modified ship structure, which is obtained from experimental and numerical methods.

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PRINCIPLES OF AN ACTIVE NOISE AND VIBRATION CONTROL SYSTEM CONSTRUCTION FOR SHIP

  • Maslov, Viatcheslav L.;Soloveitchik, Leonid I.
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1994.06a
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    • pp.860-863
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    • 1994
  • Main sources of increased vibrations and air noise on ship are main and auxiliary engines and ship ducts. The various ways of transfer of vibration energy and air noise in passenger cabin of a vessel require, in general case, of various methods of attenuation. The transfer of vibration energy from engines through a support requires, alongside with shock-absorbers, availability active shock-absorbers. The transfer of vibration energy and hydrodynamic noise on ship ducts requires availability, alongside with flexible muffler, active mufflers. The availability of air noise from working equipment can require, along with absorbent covers, of space systems of active noise control. In the given article it is spoken about the unified approach to formation of the block-diagram of active noise and vibration control. The complex approach permits to receive additional efficiency in reduction of noise in passenger cabin of vessels.

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Influence of different parameters on nonlinear friction-induced vibration characteristics of water lubricated stern bearings

  • Lin, Chang-Gang;Zou, Ming-Song;Zhang, Hai-Cheng;Qi, Li-Bo;Liu, Shu-Xiao
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.13 no.1
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    • pp.746-757
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    • 2021
  • To investigate the mechanism of friction-induced vibration and noise of ship water lubricated stern bearings, a two-degree-of-freedom (2-DOF) nonlinear self-excited vibration model is established. The novelty of this work lies in the detailed analysis of influence of different parameters on the stability and nonlinear vibration characteristics of the system, which provides a theoretical basis for the various friction vibration and noise phenomenon and has a very important directive meaning for low noise design of water lubricated stern bearings. The results reveal that the change of any parameter, such as rotating speed of shaft, contact pressure, friction coefficient, system damping and stiffness, has an important influence on the stability and nonlinear response of the system. The vibration amplitudes of the system increase as (a) rotating speed of shaft, contact pressure, and the ratio of static friction coefficient to dynamic friction coefficient increase and (b) the transmission damping between motor and shaft decreases. The frequency spectrum of the system is modulated by the first mode natural frequency, which is continuous multi-harmonics of the first mode natural frequency. The response of the system presents a quasi-periodic motion.

Reduction of Fire Main Pipe System's Vibration Using Back Flow Prevent Globe Valve (역류방지 글로브 밸브를 이용한 소화 주관계의 진동개선)

  • Park, Mi-You;Han, Hyung-Suk;Lee, Seuk-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.04a
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    • pp.518-523
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    • 2009
  • Main source of URN(Underwater Radiated Noise) which is related to the ship's survivability is divided into two groups. Cavitation is main source of URN when the speed of ship is upper than CIS(Cavitation Inception Speed). But when the speed of ship is lower than CIS, main source of URN is structure-borne noise on the hull which is originated from propulsion system, pump system or transmitted vibration of pipe system. In this paper, to reduce the vibration of discharge pipe and valve system, back flow prevent globe valve and new rubber mount are applied to the ship. As the result of applying new valve and mount, the vibration is reduced drastically.

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Reduction of Fire Main Pipe System's Vibration Using Back Flow Prevent Globe Valve (역류방지 글로브 밸브를 이용한 소화 주관계의 진동개선)

  • Park, Mi-You;Han, Hyung-Suk;Lee, Seuk-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.6
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    • pp.599-606
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    • 2009
  • Main source of URN(underwater radiated noise) which is related to the ship's survivability is divided into two groups. Cavitation is the main source of URN when the speed of ship is upper than CIS(cavitation inception speed). But when the speed of ship is lower than CIS, the main source of URN is the structure-borne noise on the hull which is originated from propulsion system, pump system and trnasmitted vibration of the pipe system. In this paper, to reduce the vibration of discharge pipe and valve system, back flow prevent globe valve and new rubber mount are applied to the ship. As the result of applying new valve and mount, the vibration is reduced drastically.