• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.53-59
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• 2004

A general purpose program NUFLEX for the analysis of 3-D heat/fluid flow in complex geometry with pre/post processor have been developed, which consists of a flow solver based on FVM and a dedicated pre/post processor. The program employs a general non-orthogonal grid system and solve laminar and turbulent (lows with standard and RNG $\kappa-\epsilon$ turbulence models. NUFLEX is capable of analysing two-phase flow with topologically complex interface, turbulent diffusion combustion, solidification problems and magnetic flow. For the purpose of verification of the program and testing the applicability, several practical problems are solved and compared with the available data. Comparison of the NUFLEX results with that by the STAR-CD program has been also made for the same flow configuration and grid structure.

• Journal of Mechanical Science and Technology
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• 제14권4호
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• pp.448-455
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• 2000

The bow wave breaking and the viscous interaction of stern wave are studied by simulating the free-surface flows. The Navier-Stokes equation is solved by a finite difference method in which the body-fitted coordinate system, the wall function and the triple-grid system are invoked. After validation, the calculations are extended to turbulent flows. The wave elevation at the Reynolds number of $10^4$ is much less than that at $10^6$ although the Froude number is the same. The numerical appearance of the sub-breaking waves is qualitatively supported by experimental observation. They are also applied to study the stern flow of S-103 for which extensive experimental data are available. Although the interaction between separation and the stern wave generation are not yet clear, the effects of the bow wave on the development of the boundary layer flows are concluded to be significant.

• 한국전산유체공학회지
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• 제11권1호
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• pp.1-7
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• 2006

Numerical investigation of a centrifugal compressor volute having a modified straight conical duct hill been made. Three-dimensional Reynolds-Averaged Navier-Stokes equations with $k-{\varepsilon}$ turbulence equation are solved To avoid coordinate singularity at the central axis of the duct, multi-block H-type grid is generated on the circular cross-sections of the volute and stretched toward the solid wall boundary. We obtained numerical results with three different mass flow rates at the volute inlet, namely, with the inlet conditions that give small, medium and large mass flow rates at the outlet of the conical duct. Agreement with the experimental results is observed.

• 설비공학논문집
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• 제12권11호
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• pp.1004-1011
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• 2000

Experimental and computational studies were carried out to confirm the turbulent enhancement of the cooling system of nuclear reactor by large scale vortex generation in nuclear fuel bundle. The large scale vortex motions were generated by rearranging the inclination angles of mixing vanes to the coordinate directions. Axial development of mean and turbulent velocities in the subchannels were measured by the 2-color LDV system. Eddy diffusivity heat flux model and $k-varepsilon$ model were employed to analyze the turbulent heat and fluid flows in the subchannel. The turbulence generated by split mixing vanes has small length scales so that they maintain only about $10 D_H$ after the spacer grid. On the other hand, the turbulences generated by the large scale vortex continue more and remain up to $25 D_H$after the spacer gird.

• 한국멀티미디어학회논문지
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• 제25권11호
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• pp.1557-1563
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• 2022

Currently Spatial Data is collected and processed in various methods, and its usability is very high. However, the existing Spatial Data analysis Software usually requires professional knowledge in the collection, refinement, and application of spatial Date, making it difficult to access and apply it. Therefore, this study established a new WebGIS platform with improved accessibility and usability to solve these problems. This platform supports various services such as master map sharing, spatial data generation, automatic coordinate system conversion, WMS issuance, grid generation, and grid analysis. These services increase operational convenience, such as simplifying repetitive tasks and automatically expressing text files. While it is believed that non-experts can easily and conveniently because of them to simplify and express the results. In addition, it is judged to have high accuracy and reliability compared to the analysis results using the existing Open Source-based GIS software.

• 대한조선학회논문집
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• 제29권3호
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• pp.59-70
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• 1992

2차원 비압축성, 정상, 층류 Navier-Stokes 방정식을 일반 곡선 좌표계에서 계산하기 위한 유한체적법을 개발하였다. 수치해석은 정규 격자구조를 채택하였으며, 이때 압력의 불안정한 거동은 모멘텀 보간법에 의하여 제거하였다. NACA0012 날개 단면 주위의 유동을 개발된 컴퓨터 프로그램으로 계산한 결과들은 실험 및 다른 계산결과와 잘 일치하였다.

• 한국습지학회지
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• 제16권3호
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• pp.327-336
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• 2014

물에 잠긴 얇은 벽은 잠제 사각형 블록의 극단적인 경우라고 할 수 있으며, 하천이나 해안지역에서 다양한 목적으로 사용될 수 있다. 잠제구조물의 얇은 벽 주위 흐름과 압력을 계산하기 위하여 동수압이 포함된 ${\sigma}$-격자체계의 3차원 수치모델을 수행하였고, 그 주변의 유속 흐름을 파악하였다. ${\sigma}$-격자체계는 완경사 하상에 유동 시뮬레이션을 적용할 수 있는 강력한 장점을 가지고 있다. 반면에 ${\sigma}$-격자체계는 하상에 날카로운 구조물등에 대한 해석에는 한계를 갖고 있다. 동압력 계산은 직교격자 시스템에서만 유효하다. CST3D시스템 내에 SOLA 기법을 ${\sigma}$-격자체계에 맞게 수정하여 채택하였다. 모델은 2차원 수조에서의 1차원 전자자기식유속계를 통한 관측자료를 통하여 검증하였고, 정수압 가정의 ${\sigma}$-격자체계 수치모형과의 비교를 통하여 정량적인 비교 검토를 수행하였다. 전체적으로 계산된 수평유속과 측정된 수평유속이 유사한 것으로 나타났다. 수리모형실험을 통한 관측자료의 결과를 수치모형이 10% 이내로 정확하게 모의하였고, 관측자료와 대조하였을시 와도의 분포를 유사하게 재현하였다. 수정 SOLA 방식을 채택하여 동수압이 고려되었고, ${\sigma}$-격자체계에 적용한 본 연구는 실제 관측자료를 잘 재현하였으며, 하구, 하천등의 구조물 주변에서의 유속분포를 검증할 시 매우 유용한 것으로 판단된다.

• Korean Journal of Geomatics
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• 제2권1호
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• pp.83-89
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• 2002

The cadastral maps as many as about 750,000 map sheets to cover 34,751,000 parcels of land of Korea, are being digitalized. The problem of shrinkage-expansion of the paper cadastral maps has to be resolved for the new digital maps, where the nodes and vertices of the parcel boundaries are represented by coordinates. The photo coordinate refinement techniques, two dimensional projective transformation and local area transformation as in the reseau grid method, were introduced for this distortion correction. Using the fact that original maps drawn on the plane tables in field from 1910 to 1918 have grid lines and have been preserved well, a strategic flow to apply the refinement techniques to the digital maps with the original maps as controls was developed. To accommodate the presence or absence of the original maps and grid lines, and different scales and sizes of the maps, the strategy was implemented by a computer program package. Various distortions and corrections were simulated and errors were evaluated. The RMS errors in the corrected digital maps were allowable, thus, the method developed in this study was to be applicable for the digital cadastral maps.

• 한국측량학회지
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• 제31권2호
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• pp.151-157
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• 2013

1997년부터 도로명을 기준으로 주소를 나타내는 법적 근거가 마련되었다. 지번 방식의 주소에서 도로의 왼쪽에 위치한 건물에 홀수번호를 오른쪽에 위치한 건물에는 짝수번호를 부여하는 도로명 기준의 주소로 변화하는 것이다. 사람들이 거주하는 지역에 대해서는 도로명주소에 의한 위치표시는 가능하나, 전 답 산악 지역에 대한 위치표시체계는 미흡하여 범죄와 응급 구조에 신속히 대처할 수 없다. 이러한 비거주지역에서의 위치찾기 어려움의 도로명주소 약점을 보완하기 위해 국가지점번호가 도입되었다. 연구의 목적은 국가지점번호 도입을 돕기 위함이다. 본 연구에서는 국가지점번호를 위한 영토 중심의 기준점과 격자 범위, 그리고 부여체계로 두 글자의 한글과 x, y 좌표체계를 제안하였다. 또한, 지점번호 고시대상지역, 지점번호판 설치위치와 민간 및 공공분야 활용방안을 제시하였다.

• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.95-104
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• 2007

A new design approach of complex geometries such as wing/body configuration is arranged by using overset mesh techniques under large scale computing environment. For an in-depth study of the flow physics and highly accurate design, several special overlapped structured blocks such as collar grid, tip-cap grid, and etc. which are commonly used in refined drag prediction are adopted to consider the applicability of the present design tools to practical problems. Various pre- and post-processing techniques for overset flow analysis and sensitivity analysis are devised or implemented to resolve overset mesh techniques into the design optimization problem based on Gradient Based Optimization Method (GBOM). In the pre-processing, the convergence characteristics of the flow solver and sensitivity analysis are improved by overlap optimization method. Moreover, a new post-processing method, Spline-Boundary Intersecting Grid (S-BIG) scheme, is proposed by considering the ratio of cell area for more refined prediction of aerodynamic coefficients and efficient evaluation of their sensitivities under parallel computing environment. With respect to the sensitivity analysis, discrete adjoint formulations for overset boundary conditions are derived by a full hand-differentiation. A smooth geometric modification on the overlapped surface boundaries and evaluation of grid sensitivities can be performed by mapping from planform coordinate to the surface meshes with Hicks-Henne function. Careful design works for the drag minimization problems of a transonic wing and a wing/body configuration are performed by using the newly-developed and -applied overset mesh techniques. The results from design applications demonstrate the capability of the present design approach successfully.