• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.84-91
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• 2003

Flow-Induced Vibration of steam generator tubes may result in fretting wear damage at the tube-to-support locations. KSNP(Korean Standard Nuclear Power plant) steam generators experienced fretting wear in the upper part of U-bend above the central cavity region of steam generators. This region has conditions susceptible to the flow-induced vibration, such as high flow velocity, high void fraction, and longer unsupported span. To improve its performance, APR1400 steam generator is designed with additional supports in this region to reduce unsupported span and to reduce peak velocity in the central cavity region. In this paper, we examined its performance improvement using ATHOS code. The thermal-hydraulic condition in the region of secondary side of APR1400 steam generator is obtained using the ATHOS3 code. The effective mass for modal analysis is calculated using the void fraction, enthalpy, and operating pressure information from ATHOS3 code result. With the effective mass distribution along the tube, natural frequency and mode shape is obtained using ANSYS code. Finally, stability ratios and real mean squared displacements for selected tubes of the APR1400 steam generator are computed. From these results, the current design of the APR1400 steam generator are examined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.739-740
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.652-653
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• 2009

In this study, flow-induced vibration (FIV) analyses have been conducted for a 3D compressor blade model. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed dynamic responses of designed compressor blades. Fluid domains are modeled using the computational grid system with local grid deforming and remeshing techniques. Reynolds-averaged Navier-Stokes equations with $\kappa-\varepsilon$ turbulence model are solved for unsteady flow problems of the rotating compressor model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D compressor blade for fluid-structure interaction (FSI) problems. Detailed dynamic responses and instantaneous pressure contours on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating compressor blade.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.6
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• pp.551-559
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• 2009

In this study, flow-induced vibration(FIV) analyses have been conducted for a 3D compressor blade model. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics(CSD) has been developed in order to investigate detailed dynamic responses of designed compressor blades. Fluid domains are modeled using the computational grid system with local grid deforming and remeshing techniques. Reynolds-averaged Navier-Stokes equations with $\kappa-\epsilon$ turbulence model are solved for unsteady flow problems of the rotating compressor model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D compressor blade for fluid-structure interaction(FSI) problems. Detailed dynamic responses and instantaneous pressure contours on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating compressor blade.

• Journal of KSNVE
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• v.9 no.4
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• pp.693-702
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• 1999

We study the characteristics of airflow and sound noise induced by disk rotation in optical disk drives. The characteristics of airflow around a rotating disk surrounded by various tray structures are numerically investigated using a commercial CFD program and then compared with experimental results. Sound pressure and intensity caused by the fluid-structure interactions in the CD/DVD-ROM drive are measured, and the effect of the ariflow on the sound noise and disk vibration is discussed. In order to reduce airflow-induced noise and vibration around the rotating disk, tray geometry is modified. Both numerical and experimental studies implemented with different tray models show that the improved tray model alters the characteristics of the disk-induced airflow, causing the reduction of the airflow-induced sound level.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.390.1-390
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• 2002

In this study, we investigate the plugging effect on the CE type steam generator tube. The natural frequency and mode shape will be changed due to decrease of the effective mass distribution along the tube. We compared the variation of stability ratio for plugged tube with that fur unplugged one. The natural frequency increased because of removing the cooling water inside the steam generator tube, but the stability ratio decreased inversely because of changing the vibrational mode shape. We also investigated the turbulent excitation effect.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.250-253
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• 2006

The in-pile Section (IPS) is subjected to flow-induced vibration(FIV) due to the flow of the primary coolant and then the structural integrity. The in-pile Section (IPS) of 3-pin Fuel Test Loop(FTL) shall be installed in the vortical hole call IR1 of HANARO reactor core. In order to verify the velocity and displacement both the inside region of IPS at the annular region of IPS, the vibration was measured by varing the flow rate on both regions. The displacements of fuel assembly in the in-pile Section (IPS) were found to be lower than the values of allowable design criteria.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.59-68
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• 2002

The cylindrical Upper Guide Structure assembly of the reactor intervals wish the Core Support Barrel and the Inner Barrel Assembly is subjected to flow induced loads horizontally which include random pressure fluctuation due to turbulent flow and pump pulsation pressures. The purpose of this papers is to perform random vibration and harmonic response analyses fort flow induced loads. The dynamic response characteristics due to random turbulence and pump pulsation loads were evaluated using the lumped mass beam model. Especially the model considered the annulus effects due to water gaps existing between cylindrical structures such as the Upper Guide Structure Barrel, the Core Support Barrel, and the Inner Barrel Assembly. The effect of the Inner Barrel Assembly inside the Upper Guide Structure assembly was studied. The peak dynamic responses lot each loading condition due to the addition of IBA were affected by the natural frequencies of the structures. Therefore the peak dynamic responses of the structures should be conservatively obtained from evaluation of dynamic analysis for various loading conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.361-365
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• 2007

우라늄을 내장한 연료봉은 핵분열이 일어나는 우라늄 펠렛(pellet)을 1차적으로 차폐하는 중요한 구조물이다. 연료봉은 원자로 내에서 유체유발진동에 의해 손상될 수 있으며, 본 연구에서는 유동유발진동 특성을 예측하기 위해 핵연료봉의 동특성 규명을 위한 모드해석을 수행하였다. 핵연료봉의 진동특성을 규명하기 위해 제작한 시험장치를 이용하여 피복관(clad tube)의 진동특성실험과 유한 요소 해석을 수행하였다. 모드시험(Modal Testing)은 현재 상용 핵연료봉(튜브)을 대상으로 수행되었으며, 유한 요소 해석 모델을 개발하여 해석 결과와 시험 결과를 비교 분석하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.377-384
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• 2022

Vortex-induced vibration (VIV) occurs owing to the vortex generated from the back side of the appendages of ships and submarines during operation. Recently, the importance of high-order modes (HOMs) vibration and fatigue failure has become increasingly emphasized by increasing the speed of ships and the size of structures. In addition, predicting the vibration of HOMs is significantly necessary as the VIV becomes stronger in the fast flow speed condition than in the low flow speed condition. This study introduces a methodology according to HOMs hybrid Fluid Structure Interaction (FSI) for predicting the HOMs VIV on the hydrofoils. The HOMs FSI system is verified by comparing the VIV results from the FSI simulation with the experimental results. Finally, the effectiveness of the HOMs FSI is determined by applying the maximum von-Mises stress obtained from the VIV on the hydrofoil to the S-N curve released from Det Norske Veritas (DNV). VIV results from the HOMs FSI include the lock-in characteristics as well as a significant increase of more than 10 times compared with that of low-order modes (LOMs) FSI. In the future works, advanced studies will be required for improving cantilever boundary conditions and the shape of hydrofoils.