• Journal of Mechanical Science and Technology
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• 제20권1호
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• pp.147-157
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• 2006

This paper represents a numerical study of the flow field due to the interactions between a pair of vortices produced by vortex generators in a rectangular channel flow. In order to analyze longitudinal vortices induced by the vortex generators, the pseudo-compressibility method is introduced into the Reynolds-averaged Navier-Strokes equations of a 3-dimensional unsteady, incompressible viscous flow. A two-layer $k-{\epsilon}$ turbulence model is applied to a flat plate 3-dimensional turbulence boundary to predict the flow structure and turbulence characteristics of the vortices. The computational results predict accurately the vortex characteristics related to the flow field, the Reynolds shear stresses and turbulent kinetic energy. Also, in the prediction of skin friction characteristics the computational results are reasonably close to those of the experiment obtained from other researchers.

• 한국전산유체공학회지
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• 제13권4호
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• pp.24-32
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• 2008

Environmental test is divided into operation test and storage test. The temperature of storage test is induced temperature which is considered with all sort of the heat source. Induced temperature is the temperature to be adapted to each item and platform and can be induced by computer simulation, laboratory, and real field test. We considered the induced temperature to be associated with solar heat source. In this research. First, we compared the induced temperature which be occurred by one experiment for thin plate in solar test chamber with the other one which be occurred by computer simulation to be SolidWorks 2007 COSMOS FloWorks. After this verification, we showed induced temperature which can be occurred when the test item is stored. Especially, we bring out the induced temperature by applying the ambient temperatures which is presented by MIL-STD-810F and brought out in preceding research.

• International Journal of Air-Conditioning and Refrigeration
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• 제16권3호
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• pp.89-99
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• 2008

Indoor ozone has received attention because of its well-documented adverse effects on health. In addition to the inherently harmful effects of ozone, it can also initiate a series of reactions that generate potentially irritating oxidation products, including free radicals, aldehydes, organic acids and secondary organic aerosols (SOA). Especially, ozone reacts actively with terpene. The overarching goal of this work was to better understand ozone and terpene distributions within rooms. Towards this end, the paper has two parts. The first describes the development of a cylindrical test chamber that can be used to obtain the second order rate constant $(k_b)$ for the bi-molecular chemical reaction of ozone and terpene in the air phase. The second consists of model room experiments coupled with Computational Fluid Dynamics (CFD) analysis of the experimental scenarios to obtain ozone and terpene distributions in various turbulent flow fields. The results of CFD predictions were in reasonable agreement with the experimental measurements.

• 한국유체기계학회 논문집
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• 제11권5호
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• pp.30-36
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• 2008

Axial fan without static blades requires the duct as a guidance for unskewed inflows. This work examined the geometric effects of a duct guided the in and out flows through an impeller. The present methodologies are computational predictions with parallel work by experimental validation. Several different positions of a rotor in a duct are proposed for plausible models of a rotor inside a duct. The optimum axial position of an impeller in a duct is found at the #4 model where the impeller lies on the inlet edge of a circular duct. The model shows a wider inlet area. The result of computational prediction is in good agreement with experiment measurement.

• 한국항만학회지
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• 제13권1호
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• pp.175-182
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• 1999

The ocean wave is hydrodynamically investigated to get more reliable solution. To improve the computational accuracy more fine grids are used with relatively less computer storage on the free surface. One element of the free surface is discretized into more fine grids because the free-surface waves are much affected by the grid size in the finite difference scheme. Here the multi-grid method is applied to confirm the efficiency for the S103 ship model by solving the Navier-Stokes equation for the turbulent flows. According to the computational result approximately 30% can be improved in the free surface generation, Finally the limiting streamlines show numerical result is similar to the experiment by twin tuft.

• 한국전산유체공학회지
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• 제15권2호
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• pp.14-20
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• 2010

Shock-focusing concave reflectors can have parabolic, circular or elliptic cross-sections. They produce effectively a very high pressure at the focusing point. In the past, many optical images have been obtained on shock focusing via experiments. Measurement of field variables is, however, difficult in the experiment. Using the wave propagation algorithm and the Cartesian embedded boundary method, we have successfully obtained numerical Schlieren images that appear very much like the experimental results. In addition, we obtained the detailed field variables such as pressure, velocity, density and vorticity in the unsteady domain. The present numerical results have made it possible to understand the shock focusing phenomenon in more detail than before.

• 한국전산유체공학회지
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• 제12권1호
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• pp.16-21
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• 2007

This paper presents numerical results of fluid flows and mixing in a microfluidic device with AC electroosmotic flows (AC-EOF) around coplanar electrodes attached on the top and bottom walls. To obtain the flow and mixing characteristics, numerical computations are performed by using a commercial code, CFX10. Experiment was performed to confirm the generation of the drift velocity around the electrodes. It was found that near the coplanar electrodes 3-D complex flows are generated. The AC-electroosmotic flow on the electrodes plays an important role in mixing the liquid.

• ETRI Journal
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• 제35권3호
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• pp.469-479
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• 2013

This paper proposes an efficient computation-aware mode decision and search point (SP) allocation algorithm for spatial and quality scalabilities in Scalable Video Coding. In our proposal, a linear model is derived to allocate the computation for macroblocks in enhancement layers by using the rate distortion costs of the base layer. In addition, an adaptive SP decision algorithm is proposed to decide the number of SPs for motion estimation under the constraint of the allocated computation. Experiment results demonstrate that the proposed algorithm allocates the computation resource efficiently and outperforms other works in rate distortion performance under the same computational availability constraint.

• 전산구조공학
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• 제5권1호
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• pp.83-89
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• 1992

사용하중하의 철근콘크리트 스래브의 비탄성 처짐을 산정하는 실용적인 방법을 제시하였다. 선형 유한요소 해석의 탄성해석결과와 설계된 철근량을 이용하여 비탄성 처짐계수(.betha.)를 결정하고, 이를 이용하여 설계된 슬리브의 사용성을 검토하기 위한 사용하중하의 처짐을 구할 수 있도록 하였다. 모서리에 지지된 슬래브 예에서 제시한 방법으로 구한 비탄성처짐과 실험 및 비선형해석 결과와 비교해 본 결과 서로 매우 잘 일치함을 보여주었다. 제시된 방법을 비정형 슬래브 설계에 응용한 문제도 고려하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.111-118
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• 2004

For the precise analysis of high velocity impact problem though FEM with element erosive method, the adequate mesh size and critical equivalent plastic strain(EQPS) is chosen prior to the simulation. In this research, it is strongly required from a standpoint that critical EQPS is used to decide whether perforation occurs or not. The optimization of dual armor plate consisting of 4340 steel and 2024 aluminium against a die steel sphere with high-velocity has been suggested using Lagrangian explicit time-integration code, NET2D. The response surface method based on the design of experiment is utilized for the size optimization. The optimized thickness of each layer, in which perforation does not occur, the strength of multi-layer is maximized and total weight is minimized, is obtained at a constant velocity of a pellet with a designated total thickness.