• 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.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.80-87
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• 2003

Tank structures in ships are in contact with various fluid. The vibration characteristics of those structures are strongly affected by the added mass due to containing fluid. It is important to predict vibration characteristics of tank structures, but it is difficult to do. That's because the interaction problem concerned with the free surface, the variation of water depth and stiffener is to be considered between the fluid and the structure. Many authors have studied vibration of rectangular tank structures containing water. Kito studied added mass effect of water in contact with thin elastic flat plates. Kim et al. studied flexural vibration of stiffened plates in contact with water. However, few researches on dynamic interaction tank walls with water are reported in the vibration of rectangular tanks recently. in the present report, the coupling effect of added mass of fluid and structural constraint between panels on each vibration mode changing breadth of elastic plate, and dynamic pressure distribution have investigated numerically and discussed.

• Bulletin of the Society of Naval Architects of Korea
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• v.15 no.2
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• pp.1-11
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• 1978

Using the elliptical cylindrical function, the added masses of thin rectangular plates vibrating elastically in an infinite ideal fluid are calculated. For the boundary conditions of the plates, two models are adopted. The plate which is simply-supported on two opposite edges while the other edges are clamped is one and the other is the plate which is simply-supported on two opposite edges while the other edges are free. Same examples are calculated numerically for the fundamental mode in each cases. And the effect of the boundary condition on the added mass are investigated by comparing these data with those of Kim's[4] which were calculated for the simply-supported plates by the same method. It is concluded that it is possible to predict the added mass of a rectangular plate, whose boundary condition is not treated in this report, by using the result of this investigation.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1353-1359
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• 2004

There are many massive components added on the railway overhead-line. These components cause larger fluctuations of contact forces, which are due to wave reflections and Doppler effects when a high-speed train passes those. In this paper, mathematical formula are derived for the relation between the added mass and contact force fluctuations. Using the derived formula, we calculate a added mass on the overhead-line which cause amplification factor to become 2.5. German design practice requires that amplification factor due to the wave reflection should be less than 2.5 to obtain good current collection performance. To show the validity of the formula, simulation results are compared with the calculation results. Simulation results showed that contact force fluctuations grow rapidly when an added mass is larger than the calculation result. Therefore, the simple form of formula can be used for estimating maximum added mass not to cause large fluctuations of contact forces in early design phase.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.683-688
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• 2003

Vibration characteristics of a fuel rod to be used in KALIMER(Korean Advanced LIquid MEtal Reactor) have been estimated through 3-dimensional finite element analysis and verified by experiment. The fundamental natural frequencies are found to be 6㎐ in air and 2.5㎐ in water. respectively. It has been found that in-water natural frequencies of the fuel rod are lower than in-air ones due to the added mass effect of the fluid filled inside the outer cylinder and they further decreases as the gap between the fuel rod and the outer cylinder increases, namely the added mass effect increases as the gap increases(maximum 54%). It has been also shown that the mass of the wire wrap axially coiled around the fuel rod do not affect the natural frequencies.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.21-27
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• 2003

In general, simple fluid added mass method is used for the seismic and vibration analysis of the immersed structure to consider the fluid-structure interaction effect. Actually, the structural response of the immersed structure can be affected by both the fluid added mass and damping caused by the fluid viscosity. These variables appeared as a consistent matrix form with the coupling terms. In this paper, finite element formula for the inviscid fluid case and viscous fluid case are derived from the linearized Navier Stoke's equations. Using the finite element program developed in this paper, the analyses of fluid added mass and damping for the hexagon core structure of the liquid metal reactor are carried out to investigate the effect of fluid viscosity with variation of the fluid gap and Reynolds number. From the analysis results, it is verified that the viscosity significantly affects the fluid added mass and damping as the fluid gap size decrease. From the analysis results of eccentricity effect on the fluid added mass and damping of the concentric cylinders, the fluid added mass increase as the eccentricity increases, however the fluid damping increases only when the eccentricity is very severe.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.361-364
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• 2018

Binary Ti-Al alloys below 51.0 mass%Al content exhibit a breakaway, transferring from parabolic to linear rate law. The second $Al_2O_3$ layer might have some protectiveness before breakaway. Ti-63.1 mass%Al oxidized at 1173 K under parabolic law. Breakaway oxidation is observed in every alloy, except for Ti-63.1 mass%Al. After breakaway, oxidation rates of the binary TiAl alloys below 34.5 mass%Al obey almost linear kinetics. The corrosion rate of Ti-63.1 mass%Al appears to be almost parabolic. As content greater than 63.0 mass% is found to be necessary to form a protective alumina film. Addition of Mo improves the oxidation resistance dramatically. No breakaway is observed at 1123 K, and breakaway is delayed by Mo addition at 1173 K. At 1123 K, no breakaway, but a parabolic increase in mass gain, are observed in the Mo-added TiAl alloys. The binary Ti-34.5 mass%Al exhibits a transfer from parabolic to linear kinetics. At 1173 K, the binary alloys show vary fast linear oxidation and even the Mo-added alloys exhibit breakaway oxidation. The 2.0 mass%Mo-added TiAl exhibits a slope between linear and parabolic. At values of 4.0 and 6.0 mass% added TiAl alloys, slightly larger rates are observed than those for the parabolic rate law, even after breakaway. On those alloys, the second $Al_2O_3$ layer appears to be persistently continuous. Oxidation resistance is considerably degraded by the addition of Mn. Mn appears to have the effect of breaking the continuity of the second $Al_2O_3$ layer.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.46-52
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• 2003

In ship structures, many parts are in contact with inner or outer fluid as stern, ballast and oil tanks. Fatigue damages can be sometimes observed in these tanks which seem to be caused by resonance. Tank structures in ships are in contact with water and the vibration characteristics are strongly affected by the added mass of containing water. Therefore it is important to predict vibration characteristics of tank structures. In order to estimate the vibration characteristics, the fluid-structure interaction problem has to be solved precisely. In the present paper, we have developed a numerical tool of vibration analysis of 3-dimensional tank structures using finite elements for plates and boundary elements for water region. To verify the present analysis, we have made an experiment for vibration characteristics of a tank with elastic opposite panels. And the added mass effect of containing water and the effect of structural constraint between panels are investigated numerically and discussed.

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.1-8
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• 2015

An analytical model of liquid sloshing is developed to consider the energy-loss effect through a partially submerged porous baffle in a horizontally oscillating rectangular tank. The nonlinear boundary condition at the porous baffle is derived to accurately capture both the added inertia effects and the energy-loss effects from an equivalent non-linear drag law. Using the eigenfunction expansion method, the horizontal hydrodynamic force (added mass, damping coefficient) on both the wall and baffle induced by the fluid motion is assessed for various combinations of porosity, submergence depth, and the tank's motion amplitude. It is found that a negative value for the added mass and a sharp peak in the damping curve occur near the resonant frequencies. In particular, the hydrodynamic force and free surface amplitude can be largely reduced by installing the proper porous baffle in a tank. The optimal porosity of a porous baffle is near P=0.1.

• International Journal of Ocean System Engineering
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• v.4 no.1
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• pp.1-18
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• 2014

Heave plates have been widely used to enhance viscous damping and thus reduces the heave response of Spar platforms. Single heave plate attached to the keel of the Spar has been reported in literature (Tao and Cai 2004). The effect of double heave plates on hydrodynamic response in random waves has been investigated in this study. The influence of relative spacing $L_d/D_d$ ($D_d$-the diameter of the heave plate) on the hydrodynamic response in random waves has been simulated in wave basin experiments and numerical model. The experimental investigation has been carried out using 1:100 scale model of Spar with double heave plates in random waves for different relative spacing and varying wave period. The influence of relative spacing between the heave plates on the motion responses of Spar are evaluated and presented. Numerical investigation has been carried out to investigate effect of relative spacing on hydrodynamic characteristics such as heave added mass and hydrodynamic responses. The measured results were compared with those obtained from numerical simulation and found to be in good agreement. Experimental and numerical simulation shows that the damping coefficient and added mass does not increase for relative spacing of 0.4 and the effect greater than relative spacing on significant heave response is insignificant.