• Journal of the KSME
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• v.25 no.3
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• pp.236-241
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• 1985

본 고에서는 일반적으로 노즐 부위 열해석에서 무시되는 복사열전달율과 점성소산효과를 수치적 모델을 통하여 그 필요성 여부를 조사한 것이며 다음과 같은 결론을 얻었다. (1)연소실 및 수 렴부위에서는 복사열전달율이 대류열전달율과 같은 차수의 크기로 나타나고 있어서 고 복사율을 갖는 연소가스에서는 특히 중요하다. 특히 최근에 많이 사용되는 연료에는 연소가스에 산화알 루미늄 성분이 증가하는 추세이므로 노즐부위 열해석에는 복사열전달이 차지하는 비중이 커질 것이다. (2)노즐의 확산부위에서는 고속으로 인하여 가스자체의 점성소산이 일어나 특성치 보 정계수 값이 감소한다. 따라서 Bartz의 예측치 보다는 열전달계수의 값이 적어지고 있다. (3) 따라서 노즐수렴부위에서는 일반적으로 Bartz의 예상치보다 높고 확산부에서는 낮은 결과를 얻 었던 실험결과와를 비교할 때 고온고속 노즐에서의 열전달해석은 복사 열전달과 점성열 소산을 고려함으로써 정확하게 될 수 있다. (4)이상 고려된 실험 데이터와 수치모델의 고찰은 노즐내의 침식이 없는 경우이나 실제의 경우 노즐벽 표면에서 화학적 반응이 일어난다. 그러나 이때 발 생될 수 있는 순수한 발한효과는 미미하며 단지 전체적인 단면의 열 해석시 상기에서 예측된 열전달율을 근간으로 화학반응열 및 온도분포를 계산하여야 할 것이다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1997.10a
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• pp.93-98
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• 1997

도시폐기물의 효율적인 소각 처리를 위해서 폐기물 처리량 50 ton/day의 화격자 소각로를 대상으로 화학반응을 고려하여 연소실 내부의 열유동 현상을 전산모사하였다. 수치해석 프로그램으로 상용코드인 PHOENICS를 사용하여 3차원 모사를 하여 실험으로 파악할 수 없는 연소실 내부의 유동 및 폐기물과 산화제와의 반응을 계산하였다. 건조부, 주연소부, 후연소부에 1차연소용공기, 연료의 분포 및 폐기물의 발열량이 노내 열유동 현상에 미치는 영향을 조사하였다. 1차연소용 공기의 분포에 따라 노내 유동장의 형태에 변화가 있었으며, 벽면에서의 복사열전달을 고려한 경우 2차연소실과 출구근처에서 온도분포가 파일롯트 플랜트 실험결과와 잘 일치하는 r서으로 나타났다.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.33-44
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• 1992

In the present paper, three types of analytic and numerical method are applied to the analysis of sloshing problem. Analytic solution with linear free-surface boundary condition is introduced and numerical methods are used to analyze flued flow trapped in two-and three-dimensional tanks. Source-distribution method is applied to two- and three-dimensional rectangular tanks and sphere tank. Finite difference method is utilized to compute fluid motion and pressure evolution in two dimensional tanks with girders or slopes. Calculated results are compared with those of experiment or other numerical techniques.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.489-495
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• 2001

We developed a design code for a diode side-pumped Nd:YAG laser with a diffusive reflector to investigate the optimum design conditions resulting in homogeneous absorption distribution and efficient laser output power. By including the thermal tensing effect in the calculation of the laser output power, the calculated output powers were in fairly good agreement with the experimental results within the stable resonator condition. The calculation method can be used effectively for a diode side-pumped Nd:YAG laser in choosing the optimum design parameters and in predicting the laser output power.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.655-663
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• 2008

In this research, the fire resistance of Concrete-Filled Circular Steel Tube Columns (CFT) was evaluated by numerical analysis. As the materials of CFT columns, the steel of SPSR 400 grade and the concrete of 27.5MPa, 37.8MPa strengths were used. Significant parameters,such as concrete strength, axial load, and cross-sectional dimensions were determined. To verify the accuracy of the numerical analysis,the analysis results were compared with the former experiment results. The effect of the fire resistance time, axial load ratio, cross-sectional dimensions and concrete strength was evaluated by comparison with the fire resistance of the square CFT columns. This research showed that the structural behavior and fire resistance from the findings of numerical parametric studies showed a similarity to that of the experimental results. Therefore, this numerical analysis is reasonable in estimating the fire resistance of the circular CFT column.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.831-838
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• 2016

The disaster preventing system using vegetation has been growing in the field of coastal engineering in recent years. To analyze wave and flow fields under nonlinear interactions between tsunami and vegetation, the purpose of this study is to evaluate newly-developed 3-D numerical wave tank including energy dissipation by tsunami-vegetation interaction based on existing N-S solver with porous body model. Comparing numerical results using mean drag coefficient and dynamic drag coefficient due to Reynolds number to existing experimental results it is revealed that computed results considering the dynamic drag coefficient are in good agreement with the laboratory test results for time-domain waveform. In addition, the calculated transmission coefficients of solitary waves in various vegetation densities and incident wave heights are also in good agreement with the experimental values. This confirms the validity and effectiveness of the developed 3-D numerical wave tank with the fluid resistance by vegetation.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.3
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• pp.191-199
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• 2000

In this paper, a numerical analysis using the finite element method (FEM) is presented which models the eddy current testing (ECT) of tubes with 3-dimensional defects. For the description of 3-dimensional eddy current problems, the governing equation is derived from the Maxwell's equations. The 3-dimensional FEM formulation with hexahedral elements is carried out using the Galerkin weighted residual method. The INCONEL 600 steam generator tube with inner and outer diameter defects is adopted for the numerical analysis, and the ECT signal, which is the trajectory of the probe impedance, is calculated. For the verification of the numerical analysis method, results of numerical calculations and experiments are compared and they show good agreements. Based on this verification, several defect signals are predicted and their characteristics are investigated with the variation in the defect depth and the circumferential angle of the defect.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.699-702
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• 2007

보다 효과적인 색인어 추출 및 색인어 가중치 결정을 위하여 문서의 내용뿐 아니라 구조를 이용하여 색인을 추출하는 연구가 이루어지고 있는데, 대부분의 연구들이 XML 태그의 중요도가 아닌, 문맥상의 단락에 대한 중요도를 계산하거나 HTML 문서 태그의 중요도 결정에 관한 연구들이다. 이러한 기존 연구들은 대부분이 객관적인 실험을 통해서 중요도를 입증하기보다는 상식적인 관점에서 단순한 수치로 중요도를 결정하고 있다. 본 논문에서는 웹 문서 관리를 위한 표준으로 자리잡아가고 있는 XML 문서의 태그 정보를 이용한 자동색인을 위하여, 논문을 구성하는 주요 태그의 가중치를 계산하는 방법을 제안한다. 보다 객관적인 가중치 결정을 위하여 인용된 문서간의 관계를 알아보고 서로 연관이 있을 확률을 계산하여 그 기대치만큼 색인어에 대한 가중치에 반영한다. 그리고 기존 태그 중요도 결정 방법을 적용하여 계산된 색인어 가중치를 이용한 검색성능과 비교함으로써 본 논문에서 제안한 방법을 적용하여 계산된 색인어 가중치의 효과를 검증한다.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.741-746
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• 2010

It is necessary to estimate more accurately the resistance of barge in still water and waves to compute the break load of towline and towing power for safety towing performance. The method proposed by government has calculated the total resistance of barge which is composed of frictional resistance, wave making resistance and air resistance considering the shape of hull and towing speed. However, the added resistance is equally applied with the significant wave height regardless of the type of vessels. In this study, we have carried out the numerical calculation to estimate the added resistance of wigley model in waves and compared with the experiment data to confirm the accuracy of the method. Then the computation was executed for the barge varying shape of the bow. As a result, added resistance of barge was differently occurred i.e. 0.3∼1.1 ton according to encounter angle, 0.4∼1.2 ton according to towing speed and 0.5∼1.1 ton according to shape of bow.

• Journal of Korea Water Resources Association
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• v.45 no.2
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• pp.217-227
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• 2012

This paper presents a quasi-steady model for numerical simulations of reservoir sedimentation and reservoir flushing. The quasi-steady model is based on the assumption that the flow is steady with time-dependent stream morphology change. This is reasonable because stream morphology changes over a long period, while the flow changes rapidly. The proposed model is first applied to two laboratory experiments for reservoir sedimentation. The channel is shown to be adjusted to new sediment supply at the upstream by changing both the flow depth and slope. Simulated water surface and bed profiles compare favorably to measured data. The model is also applied to reservoir flushing. Good agreement between simulated and measured data is not obtained due to time variation of outflow generated to facilitate the flushing in the experiment. Finally, relationships for equilibrium flow depth and bed slope are proposed and tested through numerical experiments.