• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2885-2889
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• 2007

In this study, the effect of particle aggregation on dynamic response time of Electrorheological (ER) fluid is investigated. The particle aggregation time is defined as the time interval between the application of the field and the formation of the first chain bridging the two electrodes. The dynamic response times of an ER fluid sheared between two concentric cylinders have been obtained under two different experimental conditions: the one is that the electric field is induced before shearing, and the other is that the electric field is induced after shearing. From the difference between two response times, the particle aggregation times are determined under various electric fields and shear rates. The experimental results show that the aggregation rate is decreased with an increase of shear rate, while electric field has little effect on it. Therefore, it is verified that the hydrodynamic force hinders the formation of chain-like structures.

• Earthquakes and Structures
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• 제22권4호
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• pp.431-437
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• 2022

One of the best choice for transportation of oil and gas at the end of rivers or seas is concrete pipelines. In this article, a concrete pipe at the end of river is assumed under the earthquake load. The Classic shell theory is applied for the modelling and the corresponding motion equations are derived by energy method. An external force induced by fluid around the pipe is asssumed in the final motion equations. For the solution of motion equations, the differential quadrature method (DQM) and Newmark method are applied for deriving the dynamic deflection of the pipe. The effects of various parameters including boundary conditions, fluid and length to thickness ratio are presented on the seismic response of the concrete pipe. The outcomes show that the clamped pipe has lower dynamic deflection with respect to simply pipe. In addition, with the effect of fluid, the dynamic defelction is increased significantly.

• Earthquakes and Structures
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• 제22권5호
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• pp.439-445
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• 2022

One of the best choice for transportation of oil and gas at the end of rivers or seas is concrete pipelines. In this article, a concrete pipe at the end of river is assumed under the earthquake load. The Classic shell theory is applied for the modelling and the corresponding motion equations are derived by energy method. An external force induced by fluid around the pipe is asssumed in the final motion equations. For the solution of motion equations, the differential quadrature method (DQM) and Newmark method are applied for deriving the dynamic deflection of the pipe. The effects of various parameters including boundary conditions, fluid and length to thickness ratio are presented on the seismic response of the concrete pipe. The outcomes show that the clamped pipe has lower dynamic deflection with respect to simply pipe. In addition, with the effect of fluid, the dynamic defelction is increased significantly.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1333-1346
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• 2009

To assure the reliability of cylinders or shells with fluid-filled annulus, it is necessary to investigate the modal characteristics considering fluid-structure interaction effect. In this study, theoretical background and several finite element models are developed for cylindrical shells with fluid-filled annulus considering fluid-structure interaction. The effect of the inclusion of the fluid-filled annulus on the natural frequencies is investigated, which frequencies are used for typical dynamic analyses such as responses spectrum, power spectral density and unit load excitation. Their response characteristics are addressed with respect to the various representations of the fluid-structure interaction effect.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.689-694
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• 2003

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported pipe conveying fluid subject to the moving mass. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass and the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The presence of crack results in higher deflections of pipe. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow and the crack severity are increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The time which produce the maximum dynamic deflection of the simply supported pipe is delayed according to the increment of the crack severity.

• 한국소음진동공학회논문집
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• 제12권7호
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• pp.550-556
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• 2002

The vibrational system of this study is consisted of a cantilever pipe conveying fluid. the moving mass upon it and an attacked tip mass. The equation of motion is derived by using Lagrange equation. The influences of the velocity and the inertia force of the moving mass and the velocities of fluid flow in the pipe haute been studied on the dynamic behavior of a cantilever pipe by numerical method. As the velocity of the moving mass increases, the deflection of cantilever pipe conveying fluid is decreased. Increasing of the velocity of fluid flow make the amplitude of cantilever pipe conveying fluid decrease. The deflection of the cantilever pipe conveying fluid is increased by moving masses. After the moving mass passed upon the cantilever pipe, the amplitude of pipe is influenced due to the deflection of pipe tilth the effect of moving mass and gravity.

• 전산구조공학
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• 제6권4호
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• pp.73-82
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• 1993

원자로내부구조물은 유체속에 잠겨있기 때문에 동적해석시 이의 영향을 고려해야한다. 본 논문에서는 지진 및 배관파단에 대한 원자로내부구조물의 동적해석을 위한 비선형해석모델을 제시하였고 유체-구조물 상호작용의 효과를 고려하는 방법에 대하여 설명하였다. 실제 해석을 통하여 유체-구조물 상호작용이 원자로내부구조물의 응답에 미치는 영향을 조사한 결과 지진해석시에는 유체-구조물 상호작용을 나타내는 hydrodynamic coupling항이 첨가됨으로써 높은 응답이 나왔으나, 배관파단시에는 이와 반대의 결과가 나왔다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.275-282
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• 2007

In this study, a fluid-structure interaction (FSI) analysis system has been developed in order to evaluate the turbine cascade performance with blade structural deformation effect. Relative movement of the rotor with respect to stator is reflected by modeling independent two computational domains. To consider the deformed position of rotor airfoil, dynamic moving grid method is applied. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation SST $k-{\varepsilon}$ turbulence models are solved to predict unsteady fluid dynamic loads. A fully implicit time marching scheme based on the Newmark direct integration method with high artificial damping is used to compute the fluid-structure interaction problem. Cascade performance evaluations for different elastic axis positions are presented and compared each other. It is importantly shown that the predicted aerodynamic performance considering structural deformation effect of blade can show some deviations compared to the data generally computed from rigid blade configurations and the position of elastic axis also tend to give sensitive effect.

• Structural Engineering and Mechanics
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• 제82권3호
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• pp.355-367
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• 2022

The effect of hydrodynamic damping on intake tower is twofold: one is fluid damping and another is structural damping. Fluid damping can be derived analytically from the governing equation of the fluid-structure-interaction (FSI) problem which yields a very complicated solution. To avoid the complexity of the FSI problem water-tower system can be simplified by considering water as added mass. However, in such a system a reconsideration of structural damping is required. This study investigates the effects of this damping on the dynamic response of the intake tower, where, apart from the "no water (NW)" condition, six other cases have been adopted depending on water height. Two different cross-sections of the tower are considered and also two different damping properties have been used for each case as well. Dynamic analysis has been carried out using horizontal ground motion as input. Finally, the result shows how hydrodynamic damping affects the dynamic behavior of an intake tower with the change of water height and cross-section. This research will help a designer to consider more conservative damping properties of intake tower which might vary depending on the shape of the tower and height of water.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1073-1078
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• 2003

This paper presents the vibration characteristics of a cantilever beam in contact with a fluid using a PZT actuator and PVDF film. dynamic behaviors of a flexible beam-water interaction system are examined. The effect of the liquid level on free vibration of the composite beam in a partially liquid-filled circular cylinder is investigated. The coupled system is subject to an undisturbed boundary condition un the fluid domain. In the vibration analysis of a wetted beam. the decoupled analyses between beam and fluid have been conventionally employed by considering first the composite beam vibration in the all and secondly Performing the correction taking account for surrounding fluid effects. That is, this investigation was to look at how natural frequencies, mode shapes. and damping are affected by liquid level variations. The signals from the sensor according to the applied input voltage are digitalized and filtered in order to obtain the dynamic characteristics of the composite beam in contact with fluid. It was found that the coupled natural frequencies decreased with the fluid level for the identical composite beam due to added mass effect. In case of the free-free boundary condition, the natural frequency gently decreased at fluid water level between 20% and 80% in the first tending mode and we found out the bends of stair shape for added mass effect of the fluid.