• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.231-236
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• 2008

A method of moments model for the resistive vee dipole has been established. In order to validate the numerical model, an experimental model is built and reflections from the antenna in the feed line are measured. The measured data and the numerical data agree closely validating the numerical model. Based on the numerical model, efficiency of the antenna and the power dissipated in the resistors are analyzed. The results show that the antenna has low radiation efficiency because of the loading resistors and that the resistors near the drive point of the antenna dissipate more power than do the resisters far from the drive point. The results can be used to determine the amount of power that can be accepted by the resistive vee dipole, to determine the power rating of the loading resistors for a desired application, or to estimate the operation range of the antenna.

• Journal of the Korean earth science society
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• v.25 no.8
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• pp.784-798
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• 2004

Microscale wind fields were simulated by MUKLIMO at the Naro Space Center, where complicated mountainous terrain and trees exist. In order to test the model's sensitivity with the effects of terrain and trees, experimental simulations were conducted under the various initial conditions. The experiments showed that the effects of trees were more significant on flat surfaces than on mountain cliffs. Based on the results, an actual 10 m level microscale wind field was simulated at the Naro Space Center, which has complicated mountainous terrain. Simulations of wind fields before and after the construction of the launching site were also conducted. It was found that MUKLIMO was of the mesoscale wind fields at the Naro Space Center.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.1
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• pp.87-102
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• 1990

개방식과수로는 낮은 압력으로 다량의 용수를 수송할 수 있는 장점을 갖고 있으나 유량변동에 의한 서어징현상이 현저한 것이 단점이다. 관로내의 흐름을 안정시키기 위해서는 이 서어징의 특성이 규명되어 대규모의 서어징에 대한 대책이 강구되어야 할 것이다. 개방식관수로계의 서어징을 강성수주이론으로 계산하기 위하여 운동방정식 연속방정식가 스탠드 수조의 중간벽에 설치된 언의 월유공식등을 조합한 기초방정식이 유도되었다. 본 연구의 수치해석 모델은 가장 일반적인 4차의 Runge-Kutter 방법을 사용하였으며, 이 모델의 정당성과 프로그램의 유통성을 검증하기 위하여 수리모형실험치와 수치해석치가 비교되었다. 그 결과 관로에 공기의 혼입이 없는 경우에는 실험치와 해석치가 실용상의 지장이 없는 정도로 잘 일치되었지만, 공기의 혼입이 발생되는 경우에는 실험치가 해석치에 비해 약간 크게 나타나서 이 경우에도 서러징의 해석이 가능한 새로운 모델의 개발이 필요한 것으로 생각된다. 또한 본 강성수주 모델을 이용하여 현재 서어징 문제로 곤란을 받고 있는 일본 자하연 비파호 부근의 용수간선을 대상으로 그 서어징의 특성과 개선방법을 경계한 결과 개설 개방식관수로계의 스탠드 중 매3개소 스탠드마다 1개소 스탠드의 하류측 수조 수면적 확장하는 것이 타당성이 있는 것으로 해석되었다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.1
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• pp.119-132
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• 1998

For the purpose of producing of grid D.E.M based on National Digital Map accurately and efficiently, We must carefully consider arrangement and numbers of it's elevation information, supplement interpolation method of control point information for maintaining accuracy. According to each combination, each of them has an effect on estimate elevations. This study, after finishing experimental analysis of several grid distance and interpolation methods, aims at presenting the optimal grid distance and interpolation method in the production of grid D.E.M by using of National Digital Map. The results are as follows: First, The result of experimental analysis shows that the method of Kriging is a very excellent interpolation method in the production of grid D.E. M by using National Digital Map. Second, For the purpose of determining grid distance, this study present that twice of the amount of contour interval to make producing grid D.E.M is optimal distance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1463-1476
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• 2014

In order to understand hydrodynamic and morphodynamic characteristics under wave-current interactions in an estuary, a coupled model for two-way analysis between existing 3-d numerical wave tank and newly-developed 3-d morphodynamic model has been suggested. Comparing to existing experimental results it is revealed that computed results of the newly-suggested model are in good agreement with each laboratory test result for wave height distribution, vertical flow profile and topographical change around ocean floor pipeline in wave-current coexisting field. Also the numerical result for suspended sediment concentration is verified in comparison with experimental result in solitary wave field. Finally, it is shown that the 3-D coupled Hydro-Morphodynamic model suggested in this study is applicable to morphological change under wave-current interaction in an estuary.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.4
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• pp.77-85
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• 1987

본 논문은 단기통 4사이클 전기점화기관에서 가스교환 과정이 체적효율에 미치는 영향에 대하여 연구한 것이다. 가스교환 과정의 수학적 모델을 설정하고 수치해석을 수행한 결과 체적효율은 가스교환과정과 관련되는 밸브 개폐시기(1,2)보다는 흡배기관의 압력에 의하여 더 큰 영향을 받는 다는 것을 알 수 있었다. 실험에 있어서는 각각 밸브 개폐시기가 다른 3종류의 캠을 사용하였 으며 수치 해석결과와 실험결고가 비교적 잘 일치하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.257-264
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• 2021

This study established a numerical model capable of calculating the wave overtopping rate of coastal structures by nonlinear irregular waves using the FUNWAVE-TVD model, a fully nonlinear Boussinesq equation model. Here, a numerical model was established by coding the mean value approach equations of EurOtop (2018) and empirical formula by Goda (2009), and adding them as subroutines of the FUNWAVE-TVD model. The verification of the model was performed by numerically calculating the wave overtopping rate of nonlinear irregular waves on vertical wall structures and comparing them with the experimental results presented in EurOtop (2018). As a result of the verification, the numerical calculation result according to the EurOtop equation of this model was very well matched with the experimental result in all relative freeboard (R_c/H_mo) range under non-impulsive wave conditions, and the numerical calculation result of empirical formula was evaluated slightly smaller than the experimental result in R_c/H_mo < 0.8 and slightly larger than the experimental result in R_c/H_mo > 0.8. The results of this model were well represented in both the exponential curve and the power curve under impulsive wave conditions. Therefore, it was confirmed that this numerical model can simulate the wave overtopping rate caused by nonlinear irregular waves in an vertical wall structure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1325-1333
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• 2011

An analytical, numerical, and experimental comparison of the hydraulic and thermal performance of new vascular channels with semicircular cross sections was conducted. The following conditions were employed in the study: Reynolds number, 30-2000; cooling channels with a volume fraction of the cooling channels, 0.04; and pressure drop, $30-10^5$ Pa. Three flow configurations were considered: first, second, and third constructal structures with diameters optimized for hydraulic operations. To validate the proposed vascular designs by an analytical approach, 3-D numerical analysis was performed. The numerical model was also validated by the experimental data, and the comparison results were in excellent agreement in all cases. The validation study against the experimental data showed that compared to traditional channels, the optimized structure of the cooling plates could significantly enhance heat transfer and decrease pumping power.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.275-281
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• 2016

Subcooled boiling under low pressure was numerically investigated using computational fluid dynamics(CFD). The wall boiling model was used for simulating the subcooled boiling; this model requires sub-models consisting of bubble departure diameter, nucleation site density and bubble departure frequency. The CFD code CFX provides the default models based on experimental data. Because these models are mostly developed under high pressure conditions, it would not be predicted well in low pressure conditions. Thus in this study, CFD validation for subcooled boiling under low pressure was analyzed. The numerical results were compared with experimental data from published paper. Simulations were performed with mass flux ranging from 250 to $750kg/m^2s$, heat flux ranging from 0.37 to $0.77MW/m^2$ and constant outlet pressure of 0.11 MPa. Employing the empirical correlation developed under low pressures could increase the accuracy of numerical analysis.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.29-38
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• 2018

Three-dimensional continuum modeling of dynamic soil-pile-structure interaction embedded in a liquefiable sand was carried out. Finn model which can model liquefaction behavior using effective stress method was adopted to simulate development of pore water pressure according to shear deformation of soil directly in real time. Finn model was incorporated into Non-linear elastic, Mohr-Coulomb plastic model. Calibration of proposed modeling method was performed by comparing the results with those of the centrifuge tests performed by Wilson (1998). Excess pore pressure ratio, pile bending moment, pile head displacement-time history according to depth calculated by numerical analysis agreed reasonably well with the test results. Validation of the proposed modeling method was later performed using another test case, and good agreement between the computed and measured values was observed.