• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.309-313
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• 2000

A structural-acoustic coupling problem involving fluid in a cavity divided with flexible walls and porous materials is investigated in this paper. In many practical problems, the use of finite elements to discretize the fluid region leads to large stiffness and mass matrices. But, since the acoustic boundary element discretization requires to put elements only on the surface of structure, the size of matrices is reduced considerably. Here, we developed a numerical analysis program for the structural-acoustic coupling problems of the multi-region cavity, using boundary elements for the fluid regions and finite elements for the structure. By considering sound transmission through layered systems placed in a cavity, the accuracy of the coupled acoustical-structural finite element model has been verified by comparing its transmission loss predictions with analytical sloutions. Example problems are included to investigate the characteristics of the multi-region structural-acoustic coupling system with porous material.

• Smart Structures and Systems
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• 제15권2호
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• pp.355-373
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• 2015

An optimal sensor placement (OSP) method based on structural subsection technique (SST) and model reduction technique was proposed for modal identification of truss structures, which was conducted using genetic algorithm (GA). The constraints of GA variables were determined by SST in advance. Subsequently, according to model reduction technique, the optimal group of master degrees of freedom and the optimal objective function value were obtained using GA in a case of the given number of sensors. Correspondingly, the optimal number of sensors was determined according to optimal objective function values in cases of the different number of sensors. The proposed method was applied on a scaled jacket offshore platform to get its optimal number of sensors and the corresponding optimal sensor layout. Then modal kinetic energy and modal assurance criterion were adopted to evaluate vibration energy and mode independence property. The experiment was also conducted to verify the effectiveness of the selected optimal sensor layout. The results showed that experimental modes agreed reasonably well with numerical results. Moreover the influence of the proposed method using different optimal algorithms and model reduction technique on optimal results was also compared. The results showed that the influence was very little.

• 전산구조공학
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• 제36권2호
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• pp.24-30
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• 2023

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권3호
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• pp.652-669
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• 2014

This paper concerns the kinematic characteristics of a coupling device in a deep-seabed mining system. This coupling device connects the buffer system and the flexible pipe. The motion of the buffer system, flexible pipe and mining robot are affected by the coupling device. So the coupling device should be considered as a major factor when this device is designed. Therefore, we find a stable kinematic device, and apply it to the design coupling device through this study. The kinematic characteristics of the coupling device are analyzed by multi-body dynamics simulation method, and finite element method. The dynamic analysis model was built in the commercial software DAFUL. The Fluid Structure Interaction (FSI) method is applied to build the deep-seabed environment. Hydrodynamic force and moment are applied in the dynamic model for the FSI method. The loads and deformation of flexible pipe are estimated for analysis results of the kinematic characteristics.

• 동력기계공학회지
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• 제15권1호
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• pp.24-31
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• 2011

Rectangular box type structures are used in many fields of civil, mechanical and marine engineering. Especially, Most ship structures are often in contact with inner or outer fluid, like ballast, fuel and stem tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine and propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tanks. Many authors have studied vibration of rectangular tanks containing fluid. Few research on dynamic interaction among tank walls filled with fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass of water have to be considered. In the previous report, a numerical analysis is performed for the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region, and mode characteristics in accordance with changing breadth of the plates by using finite element method for plates and boundary element method for fluid region. In this paper, the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region, and mode characteristics in accordance with changing length, thickness, and boundary condition of the plates are investigated numerically and discussed.

• 한국소음진동공학회논문집
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• 제18권7호
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• pp.718-724
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• 2008

A flexible structure submerged in acoustic fluid is affected by its surrounding fluid. In this case, the coupling effects between structures and surrounding fluid have an effect on the submerged structure as external force and change impedance of acoustic domain. Therefore, the coupling effects by its surrounding fluid complicatedly change the characteristics of a submerged structure such as natural frequencies and damping coefficients. In this paper, using the analytic modal equation of a spherical shell surrounded by water and air, the complex changes of damping coefficients and natural frequencies of submerged structures are studied for various external acoustic fluid and structures.

• International Journal of Fluid Machinery and Systems
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• 제6권2호
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• pp.87-93
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• 2013

In order to study the effect of the fluid-structure interaction (FSI) on the simulation results, the external characteristics and internal flow features of a diffuser pump were analyzed with a two-way flow solid coupling method. And the static and dynamic structure analysis of the blade was also caculated with the FEA method. The steady flow field is based on Reynolds Averaged N-S equations with standard $k-{\varepsilon}$ turbulent model, the unsteady flow field is based on the large eddy simulation, and the structure response is based on elastic transient structural dynamic equation. The results showed that the effect of FSI on the head prediction based on CFD really exists. At the same radius, the van mises stress on the nodes closed shroud and hub was larger than other nodes. A large deformation region existed near inlet side at the middle of blades. The strength of impeller satisfied the strength requirement with static stress analysis based on the fourth strength theory. The dynamic stress varied periodically with the impeller rotating. It was also found that the fundamental frequency of the dynamic stress is the rotating frequency and its harmonic frequency. The frequency of maximum stress amplitude at node 1626 was 7 times of the rotating frequency. The frequency of maximum stress amplitude at node 2328 was 14 times of the rotating frequency. No matter strength failure or fatigue failure, the root of blades near shroud is the key region to analyse.

• 전산구조공학
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• 제25권2호
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• pp.36-40
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• 2012

• 한국해양공학회지
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• 제15권2호
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• pp.135-140
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• 2001

A simply supported pipe conveying fluid and a moving mass upon it constitute a vibrational system. The equation of motion is derived by using Lagrange's equation. The influence of the velocity and the inertia force of a moving mass and the velocities of fluid flow in the pipe have been studied on the dynamic behavior of a simply supported pipe by numerical method. The velocities of fluid low are considered within its critical values of the simply supported pipe without a moving mass upon it. Their coupling effects on the transverse vibration of a simply supported pipe are inspected too. as the velocity of a moving mass increases, the deflection of midspan of a simply supported pipe conveying fluid is increased and the frequency of transverse vibration of the pipe is not varied. Increasing of the velocity of fluid flow makes the frequency of transverse vibration of the simply supported pipe conveying fluid decrease and the deflection of midspan of the pipe increase. The deflection of the simply supported pipe conveying fluid is increased by a coupling of the moving mass and the velocities of a moving mass and fluid flow.

• International Journal of Automotive Technology
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• 제1권1호
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• pp.26-34
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• 2000

The new numerical procedure for hydroplaning has been developed by considering the following three important factors; fluid/structure interaction, tire rolling, and practical tread pattern. The tire was analyzed by FEM with Lagrangian formulation and the fluid is analyzed by FVM with Eulerian formulation. Since the tire and the fluid are modeled separately and their coupling is automatically computed by the coupling element, the fluid/structure interaction of the complex geometry such as the tire with the tread pattern can be analyzed practically. We verified the predictability of the hydroplaning simulation in the different parameters such as the water flow, the velocity dependence of hydroplaning, and the effect of the tread pattern on hydroplaning. In order to predict the streamline in the contact patch, the procedure of the global-local analysis was developed. Since the streamline could be predicted by this technology, we could develop the new pattern in a short period based on the principle; "make the stream line smooth".