• Title, Summary, Keyword: added mass

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Numerical Analysis of Hydrodynamic mass for various Tube Arrays in a circular cylindrical shell (원통 내부의 전열관 배열에 따른 유체부가질량특성 수치해석)

  • Yang, Keum-Hee;Ryu, Ki-Wahn;Park, Chi-Yong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.693-699
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    • 2011
  • The outermost SG tubes have more structural problems than inside tubes. Many studies have used a uniform added mass coefficient for all of the SG tubes during the FIV analysis. The purpose of this study is to find out the added mass coefficients for each tube in a cylindrical shell. When a number of tubes are increased, added mass coefficients are also increased. And added mass coefficients at outermost tubes are less than those of inside tubes. According to gap changes between outermost tube and cylindrical shell, added mass coefficients are decreased with increasing the gap. When the gap has very large value, it shows that the added mass coefficient is asymptotically converged to the value of the tube array in a free fluid field.

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Numerical Analysis of Added Mass Coefficient for Outer Tubes of Tube Bundle in a Circular Cylindrical Shell (원통 내부에 배열된 외곽 전열관의 유체 부가질량계수 해석)

  • Yang, Keum-Hee;Ryu, Ki-Wahn
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.2
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    • pp.203-209
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    • 2016
  • According to the wear detection history for the steam generator tubes in the nuclear power plant, the outer tubes inside the steam generator have more problems on the flow-induced vibration than inner tubes. Many researchers and engineers have used a specified added mass coefficient for a given tube array during the design stage of the steam generator even though the coefficient is not constant for entire tube in cylindrical shell. The aim of this study is to find out the distribution of added mass coefficients for each tube along the radial location. When numbers of tubes inside a cylindrical shell are increased, values of added mass coefficients are also increased. Added mass coefficients at outer tubes are less than those of inner tubes and they are decreased with increasing the gap between the outermost tube and the cylindrical shell. It also turns out when the gap between the outermost tube and the cylindrical shell approaches infinite value, the added mass coefficient converges to an asymptotic value of given tube array in a free fluid field.

Development of Simplified Formulae for Added Mass of a 2-D Floating Body with a Semi-Circle Section in a Finite Water Depth (유한 수심에서 반원형 부유체의 부가질량계수 약산식 개발)

  • Koo, Weoncheol;Kim, Jun-Dong
    • Journal of Ocean Engineering and Technology
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    • v.27 no.1
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    • pp.80-84
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    • 2013
  • This study is to develop the simplified formulae for added mass coefficient of a 2-D floating body with a semi-circle section in a finite water depth. The semi-circle floating body may represent a simplified midship section transformed by Lewis form, which can be used for the ship motion analysis by strip theory. Since the added mass coefficient varies with motion frequencies and sea bottom effect, the correction factor representing the effect of water depth and frequencies is developed for accurate prediction of added mass. Using a two-dimensional numerical wave tank (NWT) technique based on the boundary element method (BEM) including sea bottom boundary the reference values of added mass are calculated to develop the correction factor. For verification and effectiveness of the formulae, the predicted added mass coefficients for various frequencies and water depth ratios are compared with the calculated values from NWT technique.

Calculation of Added Mass and Added Moment of Inertia for Chine Hull by Strip Method (단일배골형선(單一背骨型船)의 부가질량(附加質量) 및 부가관성(附加慣性)모우멘트의 일계산(一計算))

  • J.H.,Hwang;K.J.,Cho
    • Bulletin of the Society of Naval Architects of Korea
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    • v.5 no.2
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    • pp.45-50
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    • 1968
  • The added mass and the added moment of inertia of a hard chine hull for heave and pitch were calculated by strip method. For the $k_2$ coefficients, Hwang's values for the straight-framed sections were used and for $k_2$ coefficients Porter's values for ellipses were used in the calculation. Comparisons on added mass and added moment of inertia of hard chine hull with those of ordinary hull form were briefly discussed. The results of the calculation for hard Chine hull give greater valves than ordinary ships at zero Froude Number. Beam draft ratio seems to be much influenced on the added mass and added moment of inertia.

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The Study on the Added Moment of Inertia of Two Dimensional Cylinder induced by the Torsional Vibration coupled with the Flexural Vibration (자유수면(自由水面)에서의 비틀림 수평(水平)굽힘의 연성진동(連成振動)을 하는 선체단면형(船體斷面形)의 이차원적(二次元的) 부가관성(附加慣性) Moment에 관(關)한 연구(硏究))

  • S.S.,Kim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.7 no.2
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    • pp.3-18
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    • 1970
  • An investigation was made for the added mass moment of inertia induced by the rotational motion of the cylinder with hull section on water in order to obtain the information to estimate the natural frequency of the torsional vibration of ships. The special consideration to the effect of the draught upon the added mass moment of inertia is taken into account in the study. In this paper, the general expression for the added mass coefficients of moment of inertia of arbitary two dimensional forms induced by the torsional vibration, was derived by the author. Hence, the coefficients for these forms are represented as functions of parameters, the section area coefficient and draft beam ratio, from which the added mass coefficients for arbitrary forms can be obtained. The result was shown in a chart for estimation of the added mass moment of inertia induced by the torsional vibration, as first trial, for the convenience of practical use.

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Simplified formulas of heave added mass coefficients at high frequency for various two-dimensional bodies in a finite water depth

  • Koo, Weoncheol;Kim, Jun-Dong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.7 no.1
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    • pp.115-127
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    • 2015
  • The aim of this study is to develop a simplified formula for added mass coefficients of a two-dimensional floating body moving vertically in a finite water depth. Floating bodies with various sectional areas may represent simplified structure sections transformed by Lewis form, and can be used for floating body motion analysis using strip theory or another relevant method. Since the added mass of a floating body varies with wave frequency and water depth, a correction factor is developed to take these effects into account. Using a developed two-dimensional numerical wave tank technique, the reference added masses are calculated for various water depths at high frequency, and used them as basis values to formulate the correction factors. To verify the effectiveness of the developed formulas, the predicted heave added mass coefficients for various wetted body sections and wave frequencies are compared with numerical results from the Numerical Wave Tank (NWT) technique.

3-D Vibration Analysis of Floating Structures Like Ships Using FEM-BEM

  • Kim, Byung-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.107-112
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    • 1990
  • In the vibration analysis of structure in fluid such as ships and offshore structures, the hydrodynamic added mass considerably affects the result of analysis. Therefore correct evaluation of the hydrodynamic added mass effect is required for an accurate analysis. But the correct evaluation of the effect is not simple because the added mass varies with the mode shape of vibration as well as the configuration of the structure. The universal method employed to evaluate added mass in ship hull vibration is Lewis's method via the introduction of 3 dimensional correction factor. But this conventional method is valid only for beam-like vibration.

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Development of FAMD Code to Calculate the Fluid Added Mass and Damping of Arbitrary Structures Submerged in Confined Viscous Fluid

  • Koo, Gyeong-Hoi;Lee, Jae-Han
    • Journal of Mechanical Science and Technology
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    • v.17 no.3
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    • pp.457-466
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    • 2003
  • In this paper, the numerical finite element formulations were derived for the linearized Navier-Stokes' equations with assumptions of two-dimensional incompressible, homogeneous viscous fluid field, and small oscillation and the FAMD (Fluid Added Mass and Damping) code was developed for practical applications calculating the fluid added mass and damping. In formulations, a fluid domain is discretized with C$\^$0/-type quadratic quadrilateral elements containing eight nodes using a mixed interpolation method, i.e., the interpolation function for the velocity variable is approximated by a quadratic function based on all eight nodal points and the interpolation function for the pressure variable is approximated by a linear function based on the four nodal points at vertices. Using the developed code, the various characteristics of the fluid added mass and damping are investigated for the concentric cylindrical shell and the actual hexagon arrays of the liquid metal reactor cores.

Added Mass Estimation of Square Sections Coupled with a Liquid Using Finite Element Method

  • Jeong, Kyeong Hoon;Jhung, Myung Jo
    • Nuclear Engineering and Technology
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    • v.49 no.1
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    • pp.234-244
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    • 2017
  • Natural frequencies of immersed square sections decrease due to a contribution of added mass to the movement of square sections. In this study, natural frequencies of square sections are obtained as a function of gap size between the square section and a rigid square wall using the finite element method. Additionally, they are used to extract the added mass effect on translational and rotation motions. Published information and studies on the translational and torsional vibration of square beams are also examined for practical use. D coupling of a square section is also investigated for multiple square sections. The suggested added mass estimation can be applicable to the spent fuel storage design of a pressurized light water modulated nuclear power plant.

Hydrodynamic Forces Characteristics of a Circular Cylinder with a Damping Plate (감쇠판이 부착된 원기둥의 동유체력 특성)

  • Cho, Il-Hyoung
    • Journal of Ocean Engineering and Technology
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    • v.25 no.1
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    • pp.1-7
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    • 2011
  • The radiation of water waves by a heaving truncated circular cylinder with damping plate is solved in the frame of the three-dimensional linear potential theory. The damping plate has a distinct advantage in reducing the motion response of a floating circular cylinder by increasing the added mass and the damping coefficient. Using the matched eigenfunction expansion method, the characteristics of hydrodynamic added mass and the damping coefficient are investigated with various system parameters, such as the radius and submergence depth of the damping plate. It is found that both added mass and the damping coefficient are significantly increased due to the arranged features of the larger damping plate with shallow submergence, which are positive factors as a motion reduction device of the floating offshore platform. Also the numerical results for an oscillating submerged disk show that the added mass is negative and that the damping coefficient has a peak value at resonant frequency when submergence depth is sufficiently small.