• 제목/요약/키워드: Laser sheet visualization

검색결과 74건 처리시간 0.035초

HDD의 동시 회전 디스크 내부 유동 패턴의 가시화 (Visualization of the Flow Pattern Between Co-rotating Disks in HDD)

  • 공대위;주원구;도덕희
    • 한국가시화정보학회:학술대회논문집
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    • 한국가시화정보학회 2003년도 추계학술대회 논문집
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    • pp.67-70
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    • 2003
  • Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. Laser sheet and digital camera was used for 2-dimensional visualization of the unsteady flow between the center pair of two co-rotating disks in air with a cylindrical enclosure (or shroud). Geometric parameters are gap height (H) between disks, and gap distance (G) between disk tip and shroud. The lobe-structured boundary between inner region and outer region was detected by inserted particles, and the number of dominant vortices was determined clearly It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on H which is defined as $Re_H={\Omega}RH/v$ ranging from $3.18\times10^3\;to\;1.43\times10^4$, and decreases as the disk speed increases. The lobe pattern by vortex cells is changed to a circular pattern for the wide gap than narrow one.

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LEX를 갖는 삼각날개의 와유동 가시화 (Visualization of Vortex Flow over a Delta Wing with LEX)

  • 손명환;장조원
    • 한국가시화정보학회지
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    • 제2권2호
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    • pp.52-57
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    • 2004
  • The development and interaction of vortices over a delta wing with leading edge extension (LEX) was investigated through off-surface flow visualization using micro water droplets and a laser beam sheet. Angles of attack of $20^{\circ}$ and 24$^{\circ}$ were tested at sideslip angles of $0^{\circ}$, $-5^{\circ}$, and $-10^{\circ}$ The flow Reynolds number based on the main-wing root chord was $1.82{\times}10^{5}$. The wing vortex and the LEX vortex coiled around each other while maintaining comparable strength and identity at a zero sideslip. The increase of angle of attack intensified the coiling and shifted the cores of the wing and LEX vortices inboard and upward. By sideslip, the coiling, the merging and the diffusion of the wing and LEX vortices were increased on the windward side, whereas they were delayed significantly on the leeward side. The present study confirmed that the sideslip angle had a profound effect on the vortex structure and interaction of a delta wing with LEX, which characterized the vortex-induced aerodynamic load.

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미세수소기포를 이용한 환기 터널내의 연기거동 모사 (Simulation of smoke movement in a ventilated tunnel by using fine hydrogen bubbles)

  • 박원희;이한수;장용준;정우성
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2008년도 춘계학술대회 논문집
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    • pp.1768-1772
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    • 2008
  • The authors previously presented that the experimental technique using fine bubbles generated by electrolysis simulated fire behavior in a tunnel. We improve this experimental setup to enable this to be considered tunnel-ventilation by circulation of salt water. In this paper we introduce the new experimental setup and the visualization of fine hydrogen bubbles simulated smoke in a ventilated tunnel by using a laser sheet are presented.

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가시화와 5공 프로브 측정을 통한 연장된 앞전을 갖는 편요된 델타형 날개에서의 와류 상호작용 관찰 (Observation of the Vortex Interaction over an Yawed Delta Wing with Leading Edge Extension by Flow Visualization and 5-hole Probe Measurements)

  • 손명환;이기영
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.388-393
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    • 2001
  • An experimental study is conducted to investigate the interaction of vortices over a delta wing with leading edge extension(LEX) through the off-surface flow visualization and the 5-hole probe measurements of the wing wake region. Especially, the application of a new visualization technique is employed by ultrasonic humidifier water droplet and laser beam sheet. The results, both the off-surface visualization and the 5-hole probe, show that LEX tends to stabilize the vortices of the delta wing up to the high angle of attack even though the model is yawed. With increasing yaw, the windward leading edge vortex moves inward, and closer to the wing surface, while the leeward vortex moves outwards and away from the wing surface. The vortex interaction is promoted in the windward side, and is delayed in the leeward side.

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미소 액적 내부 유동의 속도측정에 관한 연구 - 굴절영상의 이미지 보정 (Study on the Measurement of Fluid Velocity Within a Small Droplet - Compensation of Refracted Image)

  • 허영근;전영훈;서용권
    • 한국가시화정보학회지
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    • 제7권2호
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    • pp.42-46
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    • 2010
  • In this paper we report the method of visualizing and measuring the fluid flow within a small droplet of millimeter size. We use a vertical laser sheet in visualization of the micrometer size and special attention is given to the arrangement of microscope to obtain clear images. Then we use a PIV technique to measure the velocity of the internal flow from the images taken. Since the droplet is of spherical shape, the images represent highly deteriorated picture of the real objects due to the refraction phenomenon. In order to compensate the refraction, we in this study developed two kinds of methods for the real velocity. In the first method, the refracted images are directly used to obtain the velocity in the image space, and then the velocity is transformed to the real space. In the second method the images are first transformed to the real-space objects, and then the PIV is used to measure the velocity field. We compared the two results to prove the usefulness of the compensation technique.

원통형 케이스 내의 동시회전 디스크 내부 유동패턴의 가시화 (Visualization of the Flow Pattern Between Co-rotating Disks in Shroud)

  • 공대위;주원구
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1661-1665
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    • 2004
  • Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. Laser sheet and digital camera was used for 2-dimensional visualization of the unsteady flow between co-rotating disks in air with a cylindrical enclosure (or shroud). Geometric parameters are gap height (H) between disks, and gap distance (G) between disk tip and shroud. The lobe-structured boundary between inner region and outer region was detected by inserted particles, and the number of dominant vortices was determined clearly It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on H which is defined as $Re_H={\Omega}RH/v$ ranging from $7.96{\times}10^2$ to $1.43{\times}10^4$, and decreases as the disk speed increases. The lobe pattern by vortex cells is changed to a circular pattern for the wide gap than narrow one.

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APU 가스터빈 연소기내의 고속공기유동에 따른 연료 분무특성 연구 (Fuel Spray Characteristics of the APU Gas Turbine Combustor under high speed air flow conditions)

  • 김보라미;최채홍;이동호;최성만
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2009년도 춘계학술대회 논문집
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    • pp.285-288
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    • 2009
  • APU 가스터빈 연소기 내에서 공기 유동이 있는 경우의 연료 분무 특성을 알기 위하여 ND-Yag 레이저를 이용한 분무가시화 연구를 수행하였다. 분무형상 가시화를 하기 위하여 실물 연소기 1/6 크기의 분할 연소기를 제작하였으며, 연소기 부의 공기유속 조건을 모사하기 위하여 터보 블로워를 이용한 풍동장치를 제작하였다. 75 m/s 공기 유속 조건에서 분무가시화 결과 공기가 없는 경우에 비해 분무 각이 증가되었고 분무 입자도 넓게 분포됨을 알 수 있었다.

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인젝터 설계변수 및 분사조건에 따른 분무타겟팅 지점의 측정 및 예측 (Measurement and Prediction of Spray Targeting Points according to Injector Parameter and Injection Condition)

  • ;;박수한
    • 한국분무공학회지
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    • 제28권1호
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    • pp.1-9
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    • 2023
  • In the cylinder of gasoline direct injection engines, the spray targeting from injectors is of great significance for fuel consumption and pollutant emissions. The automotive industry is putting a lot of effort into improving injector targeting accuracy. To improve the targeting accuracy of injectors, it is necessary to develop models that can predict the spray targeting positions. When developing spray targeting models, the most used technique is computational fluid dynamics (CFD). Recently, due to the superiority of machine learning in prediction accuracy, the application of machine learning in this field is also receiving constant attention. The purpose of this study is to build a machine learning model that can accurately predict spray targeting based on the design parameters of injectors. To achieve this goal, this study firstly used laser sheet beam visualization equipment to obtain many spray cross-sectional images of injectors with different parameters at different injection pressures and measurement planes. The spray images were processed by MATLAB code to get the targeting coordinates of sprays. A total of four models were used for the prediction of spray targeting coordinates, namely ANN, LSTM, Conv1D and Conv1D & LSTM. Features fed into the machine learning model include injector design parameters, injection conditions, and measurement planes. Labels to be output from the model are spray targeting coordinates. In addition, the spray data of 7 injectors were used for model training, and the spray data of the remaining one injector were used for model performance verification. Finally, the prediction performance of the model was evaluated by R2 and RMSE. It is found that the Conv1D&LSTM model has the highest accuracy in predicting the spray targeting coordinates, which can reach 98%. In addition, the prediction bias of the model becomes larger as the distance from the injector tip increases.

선형터빈 케스케이드 통로내의 2차 유동과 손실에 관한 연구 (The Experimental Investigation of the Secondary Flow and Losses Within the Plane Turbine Cascade Passage)

  • 이기백;양장식;나종문
    • 대한기계학회논문집
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    • 제19권3호
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    • pp.784-795
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    • 1995
  • This paper represents the results of the experiments of the three-dimensional flow and the aerodynamic loss caused by the three-dimensional flow within the plane bucket blades. To research the secondary flow and the aerodynamic loss, the large-scale plane bucket blade of lst-stage in the low pressure steam turbine is made of FRP. The detailed investigation of the secondary flow and the aerodynamic loss using 5-hole pressure probe within turbine cascade has been carried out in the low speed wind tunnel. The limiting streamlines of the suction and endwall surface have been visualized by the oil film method. The flow visualization of the secondary flow has been performed by the laser light sheet technique and image processing system. By using the method mentioned above, it is possible to observe the evolution of the pitchwise mass-averaged flow deviation angle and total pressure loss coefficient, the secondary flow, and the aerodynamic loss through the cascade.

삼각날개/LEX에서의 와류 상호작용 특성 (Vortex Interaction Characteristics of a Delta Wing/LEX)

  • 이기영;손명환
    • 한국군사과학기술학회지
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    • 제5권3호
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    • pp.77-86
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    • 2002
  • An experimental study of the vortex interaction characteristics of a delta wing/LEX configuration was conducted in a wind tunnel using the micro water droplet and laser beam sheet visualization technique. The main focus of this study was to analyze the effect of the angle of attack and sideslip angle on the vortex interaction and vortex breakdown. These tests were accomplished at angles of attack between $16^{\circ}$ and $28^{\circ}$ and sideslip angle between $0^{\circ}$ and $-15^{\circ}$ at free-stream velocity of 6.2 m/s. Flow visualization data provide a description of the vortex interaction between LEX and wing vortices, and of the vortex breakdown. The introduction of LEX vortex stabilized the vortical flow, and delayed the vortex breakdown up to higher angle of attack. The vortex interaction and breakdown was promoted on the windward side, whereas they are suppressed on the leeward side.