• Ocean Systems Engineering
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• v.13 no.1
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• pp.57-77
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• 2023

In the present study, the total hydrodynamic pressure exerted by the fluid on walls of rectangular tanks due to horizontal excitations of different frequencies, is investigated by pressure based finite element method. Fluid within the tanks is invisid, compressible and its motion is considered to be irrotational and it is simulated by two dimensional eight-node isoparametric. The walls of the tanks are assumed to be rigid. The total hydrodynamic pressure increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency. However, the hydrodynamic pressure has decreasing trend for the frequency greater than the fundamental frequency. Hydrodynamic pressure at the free surface is independent to the height of fluid. However, the pressure at base and mid height of vertical wall depends on height of fluid. At these two locations, the hydrodynamic pressure decreases with the increase of fluid depth. The depth of undisturbed fluid near the base increases with the increase of depth of fluid when it is excited with fundamental frequency of fluid. The sloshing of fluid with in the tank increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency of liquid. However, this vertical displacement is quite less when the exciting frequency is greater than the fundamental frequency.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1033-1042
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• 1994

Dynamic behavior of flexible rectangular liquid containers is analyzed by a two-dimensional coupled boundary element-finite element method. The irrotational motion of inviscid and incompressible ideal fluid is modeled by boundary elements and the motion of structure by finite elements. A singularity free integral formulation is employed for the implementation of boundary element method. Coupling is performed by using compatibility and equilibrium conditions along the interface between the fluid and structure. The fluid-structure interaction effects are reflected into the coupled equation of motion as added fluid mass matrix and sloshing stiffness matrix. By solving the eigen-problem for the coupled equation of motion, natural frequencies and mode shapes of coupled system are obtained. The free surface sloshing motion and hydrodynamic pressure developed in a flexible rectangular container due to horizontal and vertical ground motions are computed in time domain.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.211-216
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• 2008

In this study, we have developed a program which can calculate phase and group velocities, attenuation and wave structures of each mode in multi-layered plates. The wave structures of each mode are obtained, varying material properties and number of layers. The key in the success of guided wave NDE is how to optimize the mode selection scheme by minimizing energy loss when a structure is in contact with liquid. In this study, the normalized out-of-plane displacements at the surface of a free plate are used to predict the variation of modal attenuation and verily the correlation between attenuation and wave structure. It turns out that the guided wave attenuation can be efficiently obtain from the out-of-plane displacement variation of a free wave guide alleviating such mathematical difficulties in extracting complex roots for the eigenvalue problem of a liquid loaded wave guide. Through this study, the concert to optimize guided wave mode selection is accomplished to enhance sensitivity and efficiency in nondestructive evaluation for multi-layered structures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1869-1872
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• 2003

As SLA(Sterealithography), SLS(Selective Laser Sintering), LOM(Laminated Object Manufacturing), FDM(Fused Deposition Modeling) etc. The FDM system the heart of a study and is developed by Stratasys co. ltd, in US., is small and cheap R.P. The material filament is heated until the material reaches a near-liquid state, it is pumped through a nozzle and become hand with a shape required, and this nozzle move pumping on the previously deposited material. Such FDM system that choice deposition type with X-Y plouter obtain in the thin continue layer by decreasing amount of extrusion or to central the injection amount when the head slow down at the corner, but in the process that fusion wax or resin become hand, deformation occur and it will affect the shape accuracy and the surface roughness. Such effect will depreciate quality and reliability of the product. Therefore, when the product made in actuality, the fundamental study on the basis geometry(surface, volume, line, angle) must be preceded and it have been research by many Free Form Fabrication. So, this basic object study purpose to obtain the fundamental geometry data and to enhance the surface roughness of the shape. And an operant can use the data for the progress of the surface roughness. This study research the estimation and application of the prototype surface roughness by adjustment the injection amount. And basie of this research, describe the pattern of prototype surface roughness and also used the result to estimate the surface of prototype.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.24-29
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• 2003

Deep sea water has cold temperature, abundant nutrients and minerals, and good water quality that is pathogen-free and stable. Compared with surface water, deep sea water contains more nutrition salt, such as nitrogen and phosphor. Moreover, if has the good balance of minerals. Because of the ability of the spray drying process to produce a free-flowing power considering of spherical particles with a well-defined size distribution and the rapid drying times for heat-sensitive material, spray drying is attractive for a wide range of applications spray drying is a unique unit operation in which powders are produced from a liquid feed in a single processing step. Key component of the process are atomizer, spray chamber. Design of spray chamber should be based on the atomizer type, the production rate, and the particle size required. Because of the complex processes taking place during spray drying, traditional design method are based on pilot-plant tests and empirical scale-up rules. Modern technique such as CFD have a role to play in design and troubleshooting.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.723-733
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• 2011

A numerical method of the CSF(Continuum Surface Force) model is presented for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The application of the present method to a 2-D liquid drop problem is illustrated by an equilibrium and nonequilibrium oscillating drop calculation. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.430-430
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• 2007

In general, polyimides (PIs) are used in liquid crystal displays (LCDs) as alignment layer of liquid crystals (LCs). Up to date, the rubbing alignment technique has been widely used to align liquid crystals on the PI surface, which is suitable for mass-production of LCDs because of its simple process and high productivity. However, this method has some disadvantages. Rubbed PI surfaces include the debris left by the cloth and the generation of electrostatic charges during rubbing process. Therefore, rubbing-free techniques for LC alignment are strongly required in LCD technology. In this experiment, PI was uniformly coated on indium-tin-oxide electrode substrates to form LC alignment layers using a spin-coating method and the PI layers were subsequently imidized at 433 K for 1 h. The thickness of the PI layer was set at 50 nm. The LC alignment layer surfaces were exposed to an $Ar^+$ ion-beam under various ion-beam energies. The antiparallel cells and twisted-nematic (TN) cells for the measurement of pretile angle and electro-optical characteristics were fabricated with the cell gap of 60 and $5\;{\mu}m$, respectively. The LC cells were filled with nematic LC (NLC, MJ001929, Merck) and were assembled. The NLC alignment capability on ion-beam-treated PI was observed using photomicroscope and the pretilt angle of the NLC was measured by the crystal-rotation method at room temperature. Voltage-transmittance (V-T) and response time characteristics of the ion-beam irradiated TN cell were measured by a LCD evaluation system.

• Korean Journal of Optics and Photonics
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• v.16 no.2
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• pp.113-120
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• 2005

Luminous efficiency and uniformity in a LCD-BLU are mainly determined by fine scattering patterns formed on the light guide panel. We propose a novel fabrication method of 3-dimensional scattered patterns based on anisotropic etching of silicon wafers. Micro-pyramid patterns with 70.5 degree apex-angle and micro-prism patterns with 109.4 degree apex-angle can be self-constructed by the wet, anisotropic etching of (100) and (110) silicon wafers, respectively, and those patterns are easily duplicated by the PDMS replica process. Experimental results on spatial and angular distributions of irradiation from the light guide panel with the micro-pyramid patterns were very consistent with the calculation results. Surface roughness of the silicon-based micro-patterns is free from any artificial defects since the micro-patterns are inherently formed with silicon crystal surfaces. Therefore, we expect that the silicon based micro-patterning process makes it possible to fabricate perfect 3-dimensional micro-structures with crystal surface and apex angles, which may guarantee mass-reproduction of the light guide panels in LCD-BLU.

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.1-8
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• 2015

An analytical model of liquid sloshing is developed to consider the energy-loss effect through a partially submerged porous baffle in a horizontally oscillating rectangular tank. The nonlinear boundary condition at the porous baffle is derived to accurately capture both the added inertia effects and the energy-loss effects from an equivalent non-linear drag law. Using the eigenfunction expansion method, the horizontal hydrodynamic force (added mass, damping coefficient) on both the wall and baffle induced by the fluid motion is assessed for various combinations of porosity, submergence depth, and the tank's motion amplitude. It is found that a negative value for the added mass and a sharp peak in the damping curve occur near the resonant frequencies. In particular, the hydrodynamic force and free surface amplitude can be largely reduced by installing the proper porous baffle in a tank. The optimal porosity of a porous baffle is near P=0.1.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.12
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• pp.3360-3371
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• 1995

Hydrodynamic characteristics of a stratified flow at a Y-junction were examined analytically. Gas is supplied through the main horizontal channel and liquid is introduced into the gas stream from the Y-shaped bottom branch. Analysis was performed with irrational flow and inviscid fluid assumptions. The Stokes' inverse transformation technique was adopted to convert the real x-y plane into the x-.psi. plane. The potential flow equation was solved numerically in the transformed (x-.psi.) plane and the interface profile, pressure distribution and the streamlines were obtained. The effects of the inlet conditions, injection angle and the gravity on the flow characteristics were also examined. To check the validity of the present method, the previous resultant the two-dimensional obtuse wedge flow was compared. The inverse transformation technique turned out to be also very useful to predict the hydrodynamic characteristics of a stratified flow with the pressure variation at a Y-shaped mixing junction.