• 제목/요약/키워드: fine grid

검색결과 161건 처리시간 0.031초

Large eddy simulation using a curvilinear coordinate system for the flow around a square cylinder

  • Ono, Yoshiyuki;Tamura, Tetsuro
    • Wind and Structures
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    • 제5권2_3_4호
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    • pp.369-378
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    • 2002
  • The application of Large Eddy Simulation (LES) in a curvilinear coordinate system to the flow around a square cylinder is presented. In order to obtain sufficient resolution near the side of the cylinder, we use an O-type grid. Even with a curvilinear coordinate system, it is difficult to avoid the numerical oscillation arising in high-Reynolds-number flows past a bluff body, without using an extremely fine grid used. An upwind scheme has the effect of removing the numerical oscillations, but, it is accompanied by numerical dissipation that is a kind of an additional sub-grid scale effect. Firstly, we investigate the effect of numerical dissipation on the computational results in a case where turbulent dissipation is removed in order to clarify the differences between the effect of numerical dissipation. Next, the applicability and the limitations of the present method, which combine the dynamic SGS model with acceptable numerical dissipation, are discussed.

도시 규모의 대기오염 농도 예측 (Simulation of Atmospheric Pollutants Concentration in the Urban Scale)

  • 이상득;정일현
    • 한국대기환경학회지
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    • 제13권2호
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    • pp.137-145
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    • 1997
  • To predict the effects of air pollutant in the coastal region, we have developed the air pollutant model, the reaction model and the deposition of NO, $NO_2, and O_3$. And the numerical model of air pollutant concentration employed the nested technique to calculate with the higher resolution for the area. The nested technique used two grid systems, one for the large scale calculating region with the coarse mesh grid (CMG) and the other for the small scale region with the fine grid (FMG). In other to prove the validity of the simulation model the calculations were conducted for the present situation. The results of them reasonably agree with the observed data and proved the validity of the model.

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결정입계의 선택적 식각을 이용한 다결정 규소 태양전지의 제작과 특성 (Fabrication and Characterization of Polycrystalline Silicon Solar Cells using Preferential Etching of Grain Boundaries)

  • 김상수;김철수;임동건;김도영;이준신
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1997년도 하계학술대회 논문집 C
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    • pp.1430-1432
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    • 1997
  • A solar cell conversion effiency was degraded by grain boundary effect in polycrystalline silicon. To reduce these effects of the grain boundaries, we investigated various influencing factors such as preferential chemical etching of grain boundaries, grid design, transparent conductive thin film, and top metallization along grain boundaries. Pretreatment in $N_2$ atmosphere and gettering by $POCl_3$ and Al were performed to obtain polycrystalline silicon of the reduced defect density. Structural, electrical, and optical properties of solar cells were characterized. Improved conversion efficiencies of solar cell were obtained by a combination of Al diffusion into grain boundaries on rear side, fine grid finger, top Yb metal grid on Cr thin film of $200{\AA}$ and buried contact metallization along grain boundaries.

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Unstructured Grid Simulations of Supersonic Mixing Using Ramp Injectors

  • Kitazume, Yoshiyuki;Miyaji, Koji
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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    • pp.433-439
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    • 2004
  • This paper reports the grid resolution issues on the supersonic mixing simulation inside the engine for future aerospace vehicles. Unstructured finite volume method is used for the simulations. Three types of grids are used, namely, hybrid unstructured grids composed of prism and tetrahedron cells, locally refined grids, and hexahedral grids. Hexahedral grids are used to take advantage of fine distribution naturally behind the edge of the ramp where the vortex is generated. These latter two grids show much improved evaluations of the vortex motion and the mixing of the injected and the main flows.

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'그리드'(Grid)의 형성과 해체 -서양회화의 사적맥락과 그 해석을 중심으로 - (A Study on the Construction and Deconstruction of the 'Grid' : The Historical Context and Interpretation)

  • 김재관
    • 조형예술학연구
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    • 제1권
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    • pp.125-164
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    • 1999
  • The Grid, a lattice structure adapted in paintings, is one of thesimplest plastic structures based on the intersection of horizontal and perpendicular lines. Though mankind has, from the pre-history to the present day, put it to good use in everyday life as a traditional practice or a magical, esoteric, religious emblem in the case of the teciform of primitve art, it was in the paintings of Piet Mondrian that the Grid showed its modern, artistic transformation. As we suggest in the title, before I state the Grid as a plastic construction of modern painting, this dissertation inquires the Grid structure that extends over paintings through the ages as a painterly conept, especially focused on their formation and deconstruction. To begin with, my dissertation investigates, as a historical background, a general idea of the geometrical structure and phases of its transition in art, prior to dealing with the Grids as plastic strures in modern painting. the core of my study on formal Grids is permeated through the third chapter. The first chapter concentrates on, firstly, difining the notion of the Grid and geometrical structure, secondly, searching for a historical backgrounb with whict the so- called modern Grid-paintings come in, inquiring into the formation of the illusion-Grid as aresult of discovering the linear perpective and the situation of the conflict and reconciliaton between reality and illusion. Based on these considerations, the second cecond chapter will examine the various sitations of formation and adaptation of the paintery Grids in the Literalism-Grid, as we have already seen in the chapter one. And the cardinal third chapter devotes itself to the process of the formation of the so-called Object-Grid and Literal-Grid in the Literalism or Minimalism as its logical extension of the Painterly Grid. With it we can get to an interpretation and understanding of the meaning and qualites of Grid dwelt in Modernism thst transformed the structure of Painterly Grid originally as a plane concept to the third dimentionl structure. And then, the fourth chapter, we try to draw a new meaning andre-interpretation of the Formal-Grid as a representatuinnal structure appeared in the post-modernist paintings, going with its deconstructional situation. Therefore, we can, in our study on Grids, see the various points of view in the interpretation of them as illusion-structure, as plane-structure, and as cubic-structure; its concept differs form times, oscillating between its formation and deconstruction. The Grid, as we have seen in my dissertation, contains various problems and significations in art that deserve to investigate throughly, including some important plastic problem such as space and plane, and, in the case of do-grid, time. We may expect new concepts of it that will have difference meanings. 1 hope my study makes some contributions to understanding the coordination of the abstruse modern and contemporary art.

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태양전지를 이용한 지속 가능형 LTE 기반 IoT 미세먼지 측정 단말기 개발 (Development of the sustainable solar cell powered LTE based IoT fine dust detecting terminal)

  • 김호운;우동식
    • 전기전자학회논문지
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    • 제25권1호
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    • pp.109-115
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    • 2021
  • 본 논문에서는 환경문제로 높은 관심을 받고 있는 미세먼지를 측정하여 실시간으로 데이터를 전송하는 측정 단말기를 개발하였다. 단말기는 설치가 쉽도록 외부와의 데이터 연결은 전국에 퍼져 있는 LTE 망을 사용하도록 하였고 전원은 태양전지와 충전지를 사용하여 유선 전력망에 연결될 필요없이 지속 가능한 독립적인 형태로 개발하였다. 단말기를 통해 수집된 데이터는 공공 기관에서 제공하는 기상 데이터와 조합하여 미세먼지의 추세를 예측을 할 수 있음을 보였다. 개발된 단말기는 임의의 지역에서 간단한 설치 작업만으로 미세 먼지 측정 데이터를 얻을 수 있어 향후 미세먼지의 보다 정확한 흐름과 영향을 분석하는데 도움이 될 것으로 예상된다.

지형자료 해상도에 따른 대기 유동장 변화에 관한 수치 연구 (Numerical Study on Atmospheric Flow Variation Associated With the Resolution of Topography)

  • 이순환;김선희;류찬수
    • 한국환경과학회지
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    • 제15권12호
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    • pp.1141-1154
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    • 2006
  • Orographic effect is one of the important factors to induce Local circulations and to make atmospheric turbulence, so it is necessary to use the exact topographic data for prediction of local circulations. In order to clarify the sensitivity of the spatial resolution of topography data, numerical simulations using several topography data with different spatial resolution are carried out under stable and unstable synoptic conditions. The results are as follows: 1) Influence of topographic data resolution on local circulation tends to be stronger at simulation with fine grid than that with coarse grid. 2) The hight of mountains in numerical model become mote reasonable with high resolution topographic data, so the orographic effect is also emphasized and clarified when the topographic data resolution is higher. 2) The higher the topographic resolution is, the stronger the mountain effect is. When used topographic data resolution become fine, topography in numerical model becomes closer to real topography. 3) The topographic effect tends to be stronger when atmospheric stability is strong stable. 4) Although spatial resolution of topographic data is not fundamental factor for dramatic improvement of weather prediction accuracy, some influence on small scale circulation can be recognized, especially in fluid dynamic simulation.

A Parameter Selection Method for Multi-Element Resonant Converters with a Resonant Zero Point

  • Wang, Yifeng;Yang, Liang;Li, Guodong;Tu, Shijie
    • Journal of Power Electronics
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    • 제18권2호
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    • pp.332-342
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    • 2018
  • This paper proposes a parameter design method for multi-element resonant converters (MERCs) with a unique resonant zero point (RZP). This method is mainly composed of four steps. These steps include program filtration, loss comparison, 3D figure fine-tuning and priority compromise. It features easy implementation, effectiveness and universal applicability for almost all of the existing RZP-MERCs. Meanwhile, other design methods are always exclusive for a specific topology. In addition, a novel dual-CTL converter is also proposed here. It belongs to the RZP-MERC family and is designed in detail to explain the process of parameter selection. The performance of the proposed method is verified experimentally on a 500W prototype. The obtained results indicate that with the selected parameters, an extensive dc voltage gain is obtained. It also possesses over-current protection and minimal switching loss. The designed converter achieves high efficiencies among wide load ranges, and the peak efficiency reaches 96.9%.

덕적도 지형을 고려한 소형풍력발전기 발전량 평가 (Evaluation of Energy Production for a Small Wind Turbine by Considering the Geometric Shape of the Deokjeok-Do Island)

  • 장춘만;이상문;전완호;임태균
    • 한국수소및신에너지학회논문집
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    • 제25권6호
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    • pp.629-635
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    • 2014
  • This paper presents annual energy production (AEP) by a 1.5kW wind turbine due to be installed in Deokjeok-Do island. Local wind data is determined by geometric shape of Deokjeok-Do island and annual wind data from Korea Institute of Energy Research at three places considered to be installed the wind turbine. Numerical simulation using WindSim is performed to obtain flow pattern for the whole island. The length of each computation grid is 40 m, and k-e turbulence model is imposed. AEP is determined by the power curve of the wind turbine and the local wind data obtained from numerical simulation. To capture the more detailed flow pattern at the specific local region, Urumsil-maul inside the island, fine mesh having the grid length of 10m is evaluated. It is noted that the input data for numerical simulation to the local region is used the wind data obtained by the numerical results for the whole island. From the numerical analysis, it is found that a local AEP at the Urumsil-maul has almost same value of 1.72 MWh regardless the grid resolutions used in the present calculation. It is noted that relatively fine mesh used for local region is effective to understand the flow pattern clearly.

저레이놀즈수 k-$\varepsilon$난류모형 개선에 관한 연구 (A Study on the Development of Low Reynolds Number k-$\varepsilon$ Turbulence Model)

  • 김명호;신종근;최영돈
    • 대한기계학회논문집
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    • 제16권10호
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    • pp.1940-1954
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    • 1992
  • 본 연구에서는 가공기 자체의 파라메터와 성능에 관한 연구로서 출력 에너지 가 서로 다른 가공기를 사용하여 SUS 304 스테인리스 시험편을 관통, 절단하면서 출력 에너지와 최대 출력을 비교하여 보고, 시험편 관통시 주파수와 출력 에너지와의 관계, 시험편 관통시 응융 금속 제거량에 의한 절단 속도의 예측, 서로 다른 출력의 가공에 있어서 슬릿 절단 폭, 커프 폭, 드로스 길이, 절단면의 표면 거칠기 등을 비교하여 출 력차에 따른 가공 특성을 고찰하였다.