• Title/Summary/Keyword: Droplet spreading

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

  • Huh, H.K.;Lee, S.J.
    • Journal of the Korean Society of Visualization
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    • v.11 no.3
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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.

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

  • Kang, Bo-Seon;Lee, Dong-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.7
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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.

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

  • Lee, Byung Uk
    • Journal of Environmental Health Sciences
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    • v.47 no.2
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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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    • v.35 no.9
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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.

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

  • Myong, Hyon Kook;Kwon, Young Hoo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.4
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    • pp.359-370
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    • 2015
  • The present study aims to numerically investigate the behavior of liquid droplet driven by capillarity force imbalance on horizontal surfaces ranging from hydrophilic to hydrophobic, under various conditions. The droplet behavior has been simulated using an in-house solution code(PowerCFD), which employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The detailed droplet behavior was obtained under various conditions for droplets with different initial shapes, contact angles and surface tension forces(or Bond number). The mechanism of droplet transport was examined using the numerical results on the droplet shapes.

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

  • Lee, Jung-Ho;Kim, Jung-Ho;Kiger, Kenneth T.
    • Proceedings of the KSME Conference
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    • 2003.04a
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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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Assessment of Maximum Spreading Models for a Newtonian Droplet Impacting on a Solid Surface (고체 표면에 충돌하는 뉴턴 액적에 대한 최대 액막 직경 모델 검토)

  • An, Sang-Mo;Lee, Sang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.6
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    • pp.633-638
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    • 2012
  • The maximum spreading is the maximum extent to which a drop can spread after impacting on a surface. It is one of the crucial factors determining the spraying performance in many applications. In this study, the existing maximum spreading models for a Newtonian liquid droplet impacting on a dry solid surface were reviewed and compared with the experimental results over the ranges of $4{\leq}Re{\leq}11700$, $23{\leq}We{\leq}786$, and $37.9^{\circ}{\leq}{\theta}_s{\leq}107.1^{\circ}$. The surface wettability was found to have only a minor influence on the maximum spreading, compared to the liquid viscosity and impact velocity. Among the models tested, the Roisman (2009) model showed the best agreement with the experimental results, matching 80% of the measured data within ${\pm}5%$.

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

  • 이중우;도덕희;김기철;강신영
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.6 no.1
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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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Numerical Study on Droplet Spread Motion after impingement on the wall using improved CIP method (수정된 CIP방법을 이용한 벽면 충돌 후 액적의 퍼짐 현상에 대한 수치해석 연구)

  • Son, S.Y.;Ko, G.H.;Lee, S.H.;Ryou, H.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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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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A Study on the Impact and Solidification of the Liquid Metal Droplet in the Thermal Spray Deposition onto the Substrate with Surface Defects (표면 결함이 있는 모재에 대한 용사 공정에서 용응 금속 액적의 충돌현상과 응고 과정 해석)

  • Ha, Eung-Ji;Kim, Woo-Seung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.11
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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.