• 제목/요약/키워드: Droplet spreading

검색결과 40건 처리시간 0.027초

SiO2 나노입자 현탁액의 충돌 및 퍼짐에 관한 실험적 연구 (Experimental study on impact and spreading of SiO2 nanoparticle colloidal suspension droplets)

  • 허형규;이상준
    • 한국가시화정보학회지
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    • 제11권3호
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    • pp.12-16
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    • 2013
  • The impact and spreading behaviors of silicon dioxide nanoparticle colloidal suspension droplets were quantitatively visualized using a high-speed imaging system. Millimeter-scale droplets were generated by a syringe pump and a needle. Droplets of different velocity were impacted on a non-porous solid surface. Images were consecutively recorded using a CMOS high-speed camera at 5000 fps (frames per second) for millimeter-scale droplets. Temporal variations of droplet diameter, velocity and maximum spreading diameters were evaluated from the sequential images captured for each experimental condition. Effects of Reynolds number, Weber number, and particle concentration were investigated experimentally.

고온 벽면과 충돌하는 단일 액적의 거동에 관한 연구 (A Study on the Behavior of a Droplet Impacting onto a Heated Surface)

  • 강보선;이동환
    • 대한기계학회논문집B
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    • 제23권7호
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    • pp.871-880
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    • 1999
  • In this paper an experimental study is presented of the problem of dynamic behavior of a water droplet impinging upon a heated surface. The experiments are mainly focused on the effects of impinging angle of a droplet and surface temperature on the impact dynamics of the droplet. It Is clarified that the droplet exhibits much different behavior depending on the normal momentum of an impinging droplet before impact. At surface temperature In the nucleate boiling regime. the disintegration of a droplet doesn't occur, whereas the deforming droplet adheres to the surface. The spreading and contraction of the liquid film is repeated a couple of times for the horizontal surface but the expanded droplet just slips without noticeable contraction for the inclined surfaces. In the film boiling regime, the impinging droplet spreads over the surface as a liquid film which is separated from the surface by produced vapor. Depending on the magnitude of the normal momentum of the droplet the disintegration into the several irregular shapes of liquid elements occurs for the horizontal and 30o-inclined surfaces, whereas the impinging droplet for the 60o-inclined surface doesn't break up and tends to recover the original spherical shape.

사스-코로나바이러스-2 공기 중 부유 전파이론과 에어로졸 제어기술 (Control Methods for Aerosols and Airborne Spreading Theory of SARS-CoV-2)

  • 이병욱
    • 한국환경보건학회지
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    • 제47권2호
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    • pp.123-130
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    • 2021
  • Objectives: Control methods against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) aerosols have been introduced. Airborne spreading theories for SARS-CoV-2 were analyzed in this study. Methods: Control methods for airborne microorganisms were discussed. Studies on theoretical estimations for airborne spreading of SARS-CoV-2 were presented and analyzed. Analytic calculations were conducted for explaining control techniques for airborne microorganisms. Results: Control methods for SARS-CoV-2 aerosols can include physical or biological procedures. Characterization of SARS-CoV-2 aerosols and massive clustering infection cases of COVID-19 support the airborne spreading theories of SARS-CoV-2. It is necessary to consider the disadvantages of control methods for airborne microorganisms. Conclusions: A study on control methods against bioaerosols is necessary to prevent the spreading of viruses. Airborne spreading theories of SARS-CoV-2 were supported by the current evidence, but further studies are needed to confirm these theories.

Liquid Crystal Droplet Patterns to Monitor Catalase Activity at Femtomolar Levels

  • Yoon, Stephanie;Jang, Chang-Hyun
    • Bulletin of the Korean Chemical Society
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    • 제35권9호
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    • pp.2704-2710
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    • 2014
  • Catalase (CAT) decomposes hydrogen peroxide that is toxic to the body. In this study, simple and sensitive detector has been developed for observing catalase activity using liquid crystal droplet system. Microscale LC droplet patterns are formed by spreading aldehyde-doped nematic liquid crystal on pre-treated glass slides. When hydrogen peroxide is added, aldehyde is oxidized and amphiphiles are formed. Dodecanoates cause the pattern to transit from bright to dark as they self-assemble to form a carboxyalte monolayer at the interface. When a drop of pre-incubated CAT and hydrogen peroxide mixture is placed onto the pattern, bright fan-shape is observed. This planar optical appearance indicates that catalase has decomposed hydrogen peroxide. Compared to the detectors that have been previously developed, this system is more sensitive with detection limit of 1fM. This research suggests further studies to be on LC droplet patterning to develop highly sensitive and methodologically simple sensors for various chemicals.

다양한 조건하에서 모세관력 불균형에 의해 구동되는 수평 표면 위의 액적 거동 (Behavior of Liquid Droplet Driven by Capillarity Force Imbalance on Horizontal Surface Under Various Conditions)

  • 명현국;권영후
    • 대한기계학회논문집B
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    • 제39권4호
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    • pp.359-370
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    • 2015
  • 본 연구는 다양한 조건하에서 모세관력 불균형에 의해 구동되는 수평 표면 위의 액적 거동을 수치해석적으로 연구한 것이다. 액적 거동은 자체개발 코드(PowerCFD)를 사용하여 수치해석하였다. 수치해석에 사용된 코드는 보존적인 압력기반 유한체적방법에 기초한 비정렬 셀 중심 방법 및 VOF 방법에 체적포착법인 CICSAM을 채용하고 있다. 상세한 액적 거동이 다양한 초기 액적형상, 접촉각 및 표면장력(또는 Bond 수)의 조건하에서 얻어졌다. 또한 액적 이송 메커니즘이 액적 형상에 대한 수치해석 결과로부터 검토되었다.

액적 열전달 향상에 미치는 Dissolved 가스의 영향에 관한 연구 (Effect of Dissolved Gases on Liquid Droplet Heat Transfer Enhancement)

  • 이정호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.1491-1498
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    • 2003
  • Droplet evaporation can be used to transfer large amounts of energy since heat is transferred across a thin liquid film. Spreading the drop over a larger area can enhance this heat transfer. One method of accomplishing this is to dissolve gas into the liquid. When the drop strikes the surface, a gas bubble nucleates and can grow and merge within the liquid, resulting in an increase in the droplet diameter. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally investigated. The local wall heat flux and temperature measurements were provided by a novel experimental technique in which 96 individually controlled heaters were used to map the heat transfer coefficient contour on the surface. A high-speed digital video camera was used to simultaneously record images of the drop from below. The measurements to date indicate that significantly smaller droplet evaporation times can be achieved. The splat diameter was observed to increase with time just after the initial transient dies out due to the growth of the bubble, in contrast to a monotonically decreasing splat diameter for the case of no bubbles. Bursting of the bubble corresponded to a sudden decrease in droplet heat transfer.

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고체 표면에 충돌하는 뉴턴 액적에 대한 최대 액막 직경 모델 검토 (Assessment of Maximum Spreading Models for a Newtonian Droplet Impacting on a Solid Surface)

  • 안상모;이상용
    • 대한기계학회논문집B
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    • 제36권6호
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    • pp.633-638
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    • 2012
  • 최대 액막 직경은 액적이 표면에 충돌한 이후에 최대로 퍼질 수 있는 정도를 의미하며, 분무기술과 관련된 다양한 응용분야에서 분무성능을 결정하는 중요한 인자 중의 하나이다. 본 연구에서는 고체표면에 충돌하는 뉴턴 액적에 대한 기존의 최대 액막 직경 모델들을 $4{\leq}Re{\leq}11700$, $23{\leq}We{\leq}786$, $37.9^{\circ}{\leq}{\theta}_s{\leq}107.1^{\circ}$ 범위에 해당하는 본 연구의 실험결과와 비교하여 검토하였다. 실험결과, 유체의 점도 및 충돌속도에 비하여 표면 젖음성이 최대 액막 직경에 미치는 영향은 미미한 것으로 나타났다. 한편, 기존의 모델 중에서 Roisman (2009) 모델은 최대 액막 직경에 대한 실험데이터의 80%를 ${\pm}5%$ 이내로 예측함으로써 가장 우수한 예측성능을 보였다.

해양유출기름의 확산 시뮬레이션 모델개발 (III) -3차원 디지털화상처리를 이용한 유적의 퍼짐 계측 - (Development of Simulation Model for Diffusion of Oil Spill in the Ocean (III) - Oil-droplet spreading measurement using 3-dimensional digital image processing technique-)

  • 이중우;도덕희;김기철;강신영
    • 해양환경안전학회지
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    • 제6권1호
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    • pp.47-55
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    • 2000
  • A three-dimensional digital image processing technique is proposed to quantitatively predict the dispersion phenomena of oil droplet onto the surface of the water. This technique is able to get the dispersion rate of an oil droplet three-dimensionally just below the surface of the water over time. The obtained dispersion rate obtained through this technique is informative to the investigation into the relationship among the gravity, surface tensions between oil, water, and air. This technique is based upon the three-dimensional PIV(Particle Imaging Velocimetry) technique and its system mainly consists of a three CCD(Charge Coupled Device) cameras, an image grabber, and a host computer in which an image processing algorithm is adopted for the acquisition of dispersion rate oil an oil droplet.

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수정된 CIP방법을 이용한 벽면 충돌 후 액적의 퍼짐 현상에 대한 수치해석 연구 (Numerical Study on Droplet Spread Motion after impingement on the wall using improved CIP method)

  • 손소연;고권현;이성혁;유홍선
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2010년 춘계학술대회논문집
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    • pp.109-114
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    • 2010
  • Interface tracking of two phase is significant to analyze multi-phase phenomena. The VOF(Volume of Fluid) and level set are well known interface tracking method. However, they have limitations to solve compressible flow and incompressible flow at the same time. CIP(Cubic Interpolate Propagation) method is appropriate for considering compressible and incompressible flow at once by solving the governing equation which is divided up into advection and non-advection term. In this article, we analyze the droplet impingement according to various We number using improved CIP method which treats nonlinear term once more comparison with original CIP method. Furthermore, we compare spread radius after droplet impingement on the wall with the experimental data and original CIP original CIP method, and it reduces the mass conservation error which is generated in the numerical analysis comparison with original CIP method.

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표면 결함이 있는 모재에 대한 용사 공정에서 용응 금속 액적의 충돌현상과 응고 과정 해석 (A Study on the Impact and Solidification of the Liquid Metal Droplet in the Thermal Spray Deposition onto the Substrate with Surface Defects)

  • 하응지;김우승
    • 대한기계학회논문집B
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    • 제26권11호
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    • pp.1597-1604
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    • 2002
  • In this study, numerical investigation has been performed on the impingement, spreading and solidification of a coating material droplet impacting onto a solid substrate in the thermal spray process. The numerical model is validated through the comparison of the present numerical result with experimental data fer the flat substrate without surface defects. An analysis of deposition formation on the non-polished substrate with surface defects is also performed. The parametric study is conducted with various surface defect sizes and shapes to examine the effect of surface defects on the impact and solidification of the liquid droplet on the substrate.