• Title/Summary/Keyword: 충돌평판

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Analysis of Low-Speed Gas Flows Around a Micro-Plate Using a FDDO Method (FDDO 방법을 이용한 미소평판 주위의 저속 유동장 해석)

  • Chung, Chan-Hong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.8
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    • pp.12-19
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    • 2004
  • Low-speed gas flows around a micro-scale flat plate are investigated using a kinetic theory analysis. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the Discrete Ordinate method. Calculations are made for flows around a 5% flat plate with a finite length of 20 microns. The results are compared with those from the Information Preservation method and a continuum approach with slip boundary conditions. It is shown that three different approaches predict a similar basic flow patterns, while the results from the present method are more accurate than those from the other two methods in details.

Field Emission Display 개발동향 및 전망

  • 송윤호;이진호;권상직
    • Electrical & Electronic Materials
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    • v.15 no.12
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    • pp.11-18
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    • 2002
  • 전계 방출 디스플레이(Field Emission Display : FED)는 금속 또는 반도체로 만들어진 극미세 구조의 전계 에미터(field emitter)에 전기장을 인가하여 진공 속으로 방출되는 전자를 형광체에 충돌시켜 화상을 표시하는 디스플레이 소자로서, 원리적으로 브라운관(CRT)의 우수한 표시 특성을 그대로 가지면서 경량 박형화가 가능하기 때문에 'Thin CRT'라고 불리기도 한다 FED는 원리적으로 고휘도, 저소비전력, 빠른 응답속도, 광시야각, 고해상도, 우수한 칼라 표시. 넓은 사용온도 범위 등 CRT 및 평판 디스플레이의 장점을 모두 갖추고 있는 이상적인 디스플레이 소자로 평가되어 1990년대 초반부터 세계 유수의 연구 기관들이 본격 적 인 연구 개발을 추진하여 왔지만, 아직까지 평판 디스플레이 시장에 진입 할 만큼 기술 개발이 이루어지지 못하고 있다. 본 고에서는 FED의 근간이 되는 전계방출 소자의 원리 및 종류, FED의 핵심요소 기술, 최근 연구 개발 동향, FED의 응용 분야 및 상용화 가능성 등에 대하여 살펴보기로 한다.

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A Visualization of Smoke Front under a Horizontal Plate (평판하 연기선단의 가시화)

  • 한용식;김명배;오광철;유상필
    • Fire Science and Engineering
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    • v.15 no.1
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    • pp.41-46
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    • 2001
  • The flow induced by a vertically impinging circular jet under a horizontal plate is investigated by visualization technique, using kerosene smoke in nitrogen gas to visualize the vortex flow and impinging flow. The light source was the sheet beam of Ar-Ion laser. The vertical and horizontal images scattering of kerosene smoke were recorded by the high speed CCD camera and the video camera. The instantaneous velocity of the vortex and the mean velocity of the smoke front were measured from the acquisited images.

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NUMERICAL STUDY OF DROPLET IMPACT AND MERGING PROCESSES ON A FLAT SUBSTRATE WITH CONTACT ANGLE HYSTERESIS (동접촉각 이력 효과를 포함한 평판 위에서 액적의 충돌 및 결합 현상에 대한 수치적 연구)

  • Lee, W.;Son, G.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.103-108
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    • 2009
  • The droplet impact and merging process on a flat substrate with contact angle hysteresis is numerically studied. The droplet deformation is determined by an improved level-set method employing a sharp-interface technique for the stress condition at the liquid-gas interface and the contact angle condition at the liquid-gas-solid interline. Based on the computations, the droplet impact and merging pattern is investigated to find the optimal condition in manufacturing a micro-line. The effects of dynamic contact angles and droplet spacing on droplet motion are quantified.

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NUMERICAL ANALYSIS OF JET IMPINGING ON A MOVING PLATE (움직이는 평면으로의 충돌 제트에 대한 수치해석)

  • Kang, Soo-Jin;Seo, Seok-Won;Lee, Kwan-Soo
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.129-134
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    • 2011
  • In this paper, the confined single slot jet impingement is investigated numerically. Although the geometry of the jet impingement is simple, the flow pattern of the jet impingement is complex and the numerical results of the jet impingement is affected much by numerical methods. The first goal of this study is to analyze the effects of Reynolds models and numerical spatial discretization schemes on the results of heat transfer performance and the flaw characteristics and to select the best method. Various versions of the low Reynolds number k-epsilon turbulence models are compared. Using the selected numerical method, the flow field and heat transfer characteristics of confined single slot jet impingement on a moving plate are analyzed.

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Behavior of Impinging Droplet on a Solid Surface for the Variation of Fuel Temperature (연료 온도 변화에 따른 평판 충돌 액적의 거동에 관한 연구)

  • Lee, Dong-Jo;Kim, Ho-Yong;Chung, Jin-Taek
    • 한국연소학회:학술대회논문집
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    • 2003.12a
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    • pp.167-173
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    • 2003
  • An experimental study on the behavior of droplets impinging on a solid flat surface was carried out in the present study. Breakup of a liquid droplet impinging on a solid surface has been investigated experimentally for various fuels with different properties. The fuel temperature and incident angle were chosen as major parameters. And fuel temperature and incident angle varied in the range from $-20^{\circ}C$ to $30^{\circ}C$ and from $30^{\circ}$ to $60^{\circ}$, respectively, were investigated. It was found that the variation of fuel temperature influences upon droplet mean diameter which were bounced out from the solid surface. As the increases of incident angle, the break-out mass flow rate increases. This causes the decrease of liquid film flow rate. The larger incident angle gives less liquid film flow rate.

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A Study on the Heat Transfer Characteristics on Flat Plate Surface by Two-dimensional Impinging Air Jet (평판전열면(平板傳熱面)에 충돌(衝突)하는 2차원충돌분류계(二次元衝突噴流系)의 열전달특성(熱傳達特性)에 관(關)한 연구(硏究))

  • Lee, Y.H.;Kim, S.P.;Seo, J.Y.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.1
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    • pp.61-68
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    • 1991
  • The purpose of this study is to investigate the heat transfer characteristics and the flow structure in the case of rectangular air jet impinging vertically on the flat heating surface. The maximum value of Nusselt number at stagnation point is observed at H/B=10. It is found that this trend has been caused by the effect of stretching of large scale vortex in the stagnation region. For potential core region the Nusselt number distribution in the downstream of the stagnation point decreases gradually and begins to increase at about X/B=3. From the flow visualization it could be seen that small eddy produced from the nozzle edge grows in large scale and that large scale eddy disturbed the thermal boundary layer on the heating plate. The local average Nusselt number becomes maximum at X/B=0.5 regardless of H/B variation.

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A Numerical Study on Flow and Cooling Characteristics of Impinging Jets on a Moving Plate (이동하는 평판에서 충돌제트의 유동 및 냉각 특성에 대한 수치적 연구)

  • Jeon, Jin-Ho;Suh, Young-Ho;Son, Gi-Hun
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2562-2567
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    • 2008
  • Jet impingement on a moving plate, which is applicable to cooling of hot metals in a steel-making process, is investigated numerically by solving the Navier-Stokes equations in the liquid and gas phases. The liquid-gas interface or free surface is tracked by a level-set method which is improved by incorporating the ghost fluid approach based on a sharp-interface representation. The computations are made for multiple jets as well as a single jet to compare their flow characteristics. Also, the effects of the nozzle pitch, moving velocity of plate and jet velocity on the interfacial motion and the associated flow and temperature fields.

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A Study on the Behavior of an Impacting Droplet on a Wall Having Obstacles (방해물이 존재하는 평판 위 충돌 액적 거동에 관한 연구)

  • Yang, W.J.;Kang, B. S.
    • Journal of ILASS-Korea
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    • v.17 no.1
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    • pp.27-34
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    • 2012
  • In this paper an experimental study is presented to investigate the effect of a step edge and a stationary droplet on the dynamic behavior of impacting droplet on a wall. The main parameters are the distance from the edge and the center-to-center distance between two droplets. Photographic images are presented to show coalescence dynamics, shape evolution and contact line movement. The emphasis is on presenting the spreading length of droplet for the step edge and two coalescing droplets along their original centers. It is clarified that the droplet exhibits much different dynamic behavior depending on the location of the step edge. The momentum of impacting droplet was better transferred to the stationary droplet as the center- to-center distance between two droplets was reduced, which results in more spreading of coalescing droplet.

Experimental Study of the Supersonic Dual, Coaxial Jet Impinging on a Flat Plate (수직평판에 충돌하는 초음속, 이중, 동축 제트유동에 관한 실험적 연구)

  • 김중배;이준희;우선훈;이장창;김희동
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2002.04a
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    • pp.44-45
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    • 2002
  • 일반적으로 노즐이나 오리피스로부터 방출되는 초음속 단일 자유제트 유동의 경우, 제트내부에서 발생하는 충격파 시스템이나, 제트경계의 형상 그리고 제트코어의 길이 및 초음속 영역의 길이 등은 종래의 연구로부터 비교적 잘 알려져 있다. 이들 연구에 의하면, 제트의 압력비가 어느 정도 증가하게 되면, 노즐 하류에서 제트내부에는 마하 디스크가 발생하게 되며, 제트유동은 압축과 팽창을 반복하는 구조로 된다. 또 노즐 출구로부터 마하 디스크까지의 거리와 마하 디스크의 직경 등은 노즐의 압력비의 함수로 주어진다고 알려져 있다.

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