• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.422-429
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• 2011

The critical fluid velocity of cantilevered cylindrical shells subjected to internal fluid flow is investigated in this study. The fluid-structure interaction is considered in the analysis. The cantilevered cylindrical shell is supported intermediately at an arbitrary axial position. The intermediate support is simulated by two types of artificial springs: translational and rotational spring. It is assumed that the artificial springs are placed continuously and uniformly on the middle surface of an intermediate support along the circumferential direction. The steady flow of fluid is described by the classical potential flow theory. The motion of shell is represented by the first order shear deformation theory (FSDT) to account for rotary inertia and transverse shear strains. The effect of internal fluid can be considered by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. Numerical examples are presented and compared with existing results.

• Selected Papers of The Society of Naval Architects of Korea
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• v.2 no.1
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• pp.18-28
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• 1994

In the vibration analysis of submerged or floating bodies such as ships and offshore structures, the coupled system between fluid and structure should be considered using the compatibility conditions on the wetted surface. It is well known that the hydroelastic vibration analysis of structures in contact with fluid can be done by applying the finite element method(FEM) to structures and the boundary element method(BEM) to the fluid domain. However, such an approach is impractical due to the characteristics of the fully coupled added mass matrix of fluid on the entire wetted surface. To overcome this difficulty, an efficient approach based on a reanalysis scheme is proposed in this paper. The proposed method can be applied for cases of higher local modes and beam-like modes for which three-dimensional reduction factors are not known. The three dimensional reduction factors are not needled and thus the restrictions can be removed in the analyses of non-beam like modes or local vibration modes by considering fluid-structure interaction. The validity and calculation efficiency of the proposed method are proved through numerical examples.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1298-1302
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• 2011

The present study deals with the results of a thermo-fluid analysis applied to the cooling plate of the water cooling system developed for IGBT stacks, which was designed to keep the power semi-conductors from over heating problems. The cooling plate is to absorb a maximum quantity of 10kW from 4 IGBTs which are to be placed on both sides of the cooling plate, 2 IGBTs of them on each surface. For the analysis, Adina of CFD Program was used and an analysis was conducted to obtain the knowledges on heat and mass flow at both the plate and fluid flow inside. For the simulation, the operational conditions of a temperature difference of $15^{\circ}C$ for the working fluid and a uniform heat flux of about 92000 $W/m^2$ on the surface in contact with an IGBTs.

• Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.330-336
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• 2016

The present work is concerned with heat and mass transfer of an electrically conducting second grade MHD fluid past a semi-infinite stretching sheet with convective surface heat flux. The analysis accounts for thermophoresis and thermal radiation. A similarity transformations is used to reduce the governing equations into a dimensionless form. The local similarity equations are derived and solved using Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. Results for various flow characteristics are presented through graphs and tables delineating the effect of various parameters characterizing the flow. Our analysis explores that the rate of heat transfer enhances with increasing the values of the surface convection parameter. Also the fluid velocity and temperature in the boundary layer region rise significantly for increasing the values of thermal radiation parameter.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.143-149
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• 2016

In this study, a method for the multi-objective optimization of an impeller for a centrifugal compressor using fluid-structure interaction (FSI) and response surface method (RSM) was proposed. Numerical simulation was conducted using ANSYS CFX and Mechanical with various configurations of impeller geometry. Each design parameter was divided into 3 levels. A total of 15 design points were planned using Box-Behnken design, which is one of the design of experiment (DOE) techniques. Response surfaces based on the results of the DOE were used to find the optimal shape of the impeller. Two objective functions, isentropic efficiency and equivalent stress were selected. Each objective function is an important factor of aerodynamic performance and structural safety. The entire process of optimization was conducted using the ANSYS Design Xplorer (DX). The trade-off between the two objectives was analyzed in the light of Pareto-optimal solutions. Through the optimization, the structural safety and aerodynamic performance of the centrifugal compressor were increased.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.81-86
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• 2001

Interfacial pressure jump terms based on the physics of phasic interface and bubble dynamics are introduced into the momentum equations of the two-fluid model for bubbly flow. The pressure discontinuity across the phasic interface due to the surface tension force is expressed as the function of fluid bulk moduli and bubble radius. The consequence is that we obtain from the system of equations the real eigenvalues representing the void-fraction propagation speed and the pressure wave speed in terms of the bubble diameter. Inversely, we obtain an analytic closure relation for the radius of bubbles in the bubbly flow by using the kinematic wave speed given empirically in the literature. It is remarkable to see that the present mechanistic model using this practical bubble radius can indeed represent both the mathematical well-posedness and the physical wave speeds in the bubbly flow.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.49-56
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• 1991

Seismic analysis of liquid storage structures is carried out by utilizing 2-dimensional fluid elements of a general purpose structural analysis computer program(ADINA), The present analysis focuses on the effects of the wall flexibility and the sloshing of the free water surface. Due considerations are given to the facts that the fluid has no shear resistance and the free surface motion is subjected to the gravity effect. To validate the present method using 2-dimensional fluid elements, the results of several example cases are compared with those by the Housner's approach for rigid wall case, and with those by the Eulerian formulation for flexible wall case.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.27-33
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• 2004

Electro-theological fluid is recently used for the micro polishing of 3-dimensional micro-aspherical lens. It's also used for polishing small area defects on the wide flat wafer. Since ER fluid shows a behavior of viscosity changing under certain electric fields. micro polishing efficiency may be enhanced for certain cases. In this paper, a perfluorinated carbonyl fluoride oil based ER fluids was used to improve surface polishing rate and submicron-scale accuracy. As the polishing electrodes, micro size cylindrical tools had been used for maximizing the electric field. An experimental device, which was applied for micro polishing a number of wafers of 4inches in size and other workpiece. was made on a precision polishing system. It consisted of a steel electrode. a wafer fixture. l0㎃ current and DC 5㎸ power supply unit, and a controller unit. From the Experiments. the ER fluid is applicable for micro polishing of small parts.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.3
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• pp.9-16
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• 1987

In this paper, the fluid flow in the two-dimensional tank is analyzed by the Finite Difference Method. The Navier-Stokes equation is modified for the tank fixed coordinate system. For the treatment of the free surface, the Volume of Fluid Method by Hirt and Nichols is adopted. The continuity equation and the Poisson equation which is derived from the Navier-Stokes equation to find the pressure are solved by the Successive-Line-Overrelaxation Method. The comparison of the calculated results with experimental data show a favorable agreement. The fluid flow in the two-dimensional tank can be predicted reasonably before the free surface reaches breaking by this numerical method.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1147-1150
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• 2003

When a braun tube becomes wider, one of the major problems to be experienced is the non-uniform coating along the four diagonal directions on its surface. This non-uniformity in the coating thickness has a deep relation with the fluid flow on the surface of a braun tube. In order to control the fluid flow properly, we install the plate to block fluid flow at the corner of a braun tube. In the present study, we investigate the effects of the geometry of plate to control the fluid flow and coating uniformity and determine the optimal shape of plate to improve the quality of coating uniformity.