• 한국농공학회논문집
• /
• 제57권6호
• /
• pp.117-123
• /
• 2015

An experimental study of model truss-type vertical gate consisting of a truss and a plate was presented in this paper to examine the structural dynamics of the gates. A 1:61 scale model was constructed for the 95 m prototype gate using an acrylic truss and an acrylonitrile butadiene styrene plate. The scaled model was tested in a 1.6 m wide concrete flume for two orientations to determine the effects of gate orientation on structural vibrations. Natural frequencies of the model gate was measured and calibrated with FEM predictions. Vertical vibrations were measured under various operational conditions, including a range of bottom opening heights and different upstream and downstream water levels. The gate model with reverse direction was preferred due to its low overall vibrational response and flow level combinations. The test results also provide a basic dataset for development of operations guidelines that minimize flow-induced vibrations of the gates.

• 한국해양공학회지
• /
• 제28권3호
• /
• pp.185-192
• /
• 2014

The riser systems for floating offshore structures are known to experience tri-modal dynamic responses. These are owing to the combined loadings from the low-frequency response due to riser tension behavior, middle-range frequency response coming from winds and waves, and high-frequency response due to vortex induced-vibration. In this study, fatigue damage models were applied to predict the fatigue damages in a well-separated tri-modal spectrum, and the resultant fatigue damages of each model were compared with the most reasonable fatigue damage calculated by the inverse Fourier transform of the spectrum, rain-flow counting method, and Palmgren-Miner rule as a reference. The results show that the fatigue damage models developed for a wide-band spectrum are applicable to the tri-modal spectrum, and both the Benasciutti-Tovo and JB models could most accurately predict the fatigue damages of the tri-modal spectrum responses.

• 대한기계학회논문집A
• /
• 제31권7호
• /
• pp.784-791
• /
• 2007

Fretting, which is a special type of wear, is defined as small amplitude tangential oscillation along the contacting interface between two materials. In nuclear power plants, fretting wear caused by flow induced vibration (FIV) can make a serious problem in a U-tube bundle in steam generator. In this study, substructure method is developed and is verified the feasibility for the finite element model of fretting wear problems. This method is applied to the two-dimensional finite element analyses, which simulate the contact behavior of actual tube to support. For these examples, computing time can be reduced up to 1/5 in comparisons with conventional finite element analyses.

• Nuclear Engineering and Technology
• /
• 제12권4호
• /
• pp.286-292
• /
• 1980

원자노내부구조물의 유체흐름에 의한 진동간제실험을 위한 모델의 상의조건을 구명하였다. 레이놀드교의 영향에 관해 깊이 있는 해명을 하였다. 핵연료의 모델시험율에서는 무차원진동교 (fD/U)와 점성파라미터 ( $m_{0}$$\delta$$_{0}$$\rho$ $D^2$)가 중요한 파라미터임을 보였다.보였다.

• 한국해양공학회지
• /
• 제20권5호
• /
• pp.15-22
• /
• 2006

A finite-volume method using multi-block grid technique has been developed in order to investigate the flow field around multi-body. Here the matching grids are used at the interface between blocks and the boundary conditions are imposed there to exchange physical values across the interface. For the test problems, the laminar viscous flaw around one-and two-cylinder are simulated and the results are compared with experiments and other numerical results.

• Wind and Structures
• /
• 제19권1호
• /
• pp.35-58
• /
• 2014

A numerical simultaneous solution involving a linear elastic model was applied to study the fluid-structure interaction (FSI) of membrane structures under wind actions, i.e., formulating the fluid-structure system with a single equation system and solving it simultaneously. The linear elastic model was applied to managing the data transfer at the fluid and structure interface. The monolithic equation of the FSI system was formulated by means of variational forms of equations for the fluid, structure and linear elastic model, and was solved by the Newton-Raphson method. Computation procedures of the proposed simultaneous solution are presented. It was applied to computation of flow around an elastic cylinder and a typical FSI problem to verify the validity and accuracy of the method. Then fluid-structure interaction analyses of a saddle membrane structure under wind actions for three typical cases were performed with the method. Wind pressure, wind-induced responses, displacement power spectra, aerodynamic damping and added mass of the membrane structure were computed and analyzed.

• 대한조선학회논문집
• /
• 제30권4호
• /
• pp.46-60
• /
• 1993

캐비테이션 터널에서 변동압력의 정확한 계측은 실선에서의 진동과 소음세기 예측에 필요하다. 본문에서는 프로펠러 케비테이션에 의해 야기되는 변동압력의 실험적연구 결과를 나타내고 논의 한다. 문제시 되고 있는 프로펠러 회전수에 의한 영향을 이해하고자 변동압력을 캐비테이션 터널에서 평판을 이용하여 여러 회전수에서 계측 하였다. 균일류에서 오차를 추정하기 위하여 계측 및 계측결과에서의 불확실성 해석이 사용 되었다.

• International Journal of Fluid Machinery and Systems
• /
• 제2권4호
• /
• pp.278-285
• /
• 2009

Operational modal analysis (OMA) allows modal parameters, such as natural frequencies and damping, to be estimated solely from data collected during operation. However, a main shortcoming of these methods resides in the evaluation of the accuracy of the results. This paper will explore the uncertainty and possible variations in the estimates of modal parameters for different operating conditions. Two algorithms based on the Least Square Complex Exponential (LSCE) method will be used to estimate the modal parameters. The uncertainties will be calculated using a Monte-Carlo approach with the hypothesis of constant modal parameters at a given operating condition. In collaboration with Andritz-Hydro Ltd, data collected on two different stay vanes from an Andritz-Hydro Ltd Francis turbine will be used. This paper will present an overview of the procedure and the results obtained.

• 비파괴검사학회지
• /
• 제10권2호
• /
• pp.15-22
• /
• 1990

Since in-core flux thimble tube wear the due to flow-induced vibration could degrade the integrity of nuclear reactor, the effective detection and interpretation of the wear is important. In order to establish an inspection technique for thimble tubes, an eddy current experiment was performed to determine the optimum test frequency, defect sensitivity and evaluation accuracy. Eddy current probes were designed and fabricated with a theory. Specimens with artificial defects were fabricated using electro discharge machining method. The results from inspection technique developed and on-site inspection showed good applicability.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2001년도 제34회 추계학술대회 개최
• /
• pp.59-62
• /
• 2001

Flow induced vibration in steam generators has caused dynamic interactions between tubes and contacting materials resulting in fretting wear . Series of experiments have been performed to examine the wear properties of Inconel 690 steam generator tubes in various environmental conditions. For the present study, the test rig was designed to examine the fretting wear and rolling wear properties in high temperature(room temperature - 290。C) water. The test was performed at constant applied load and sliding distance to investigate the effect of test temperature on wear properties of the steam generator tube materials. To investigate the wear mechanism of material, the worn was observed using scanning electron microscopy. The weight loss increase at higher test temperature was caused by the decrease of water viscosity and the mechanical property change of tube material. The mechanical property changes of steam generator tube material, such as decrease of hardness or yield stress in the high temperature tests. From the SEM observation of worn surfaces, the severe wear scars were observed in specimens tested at the higher temperature.