• Title/Summary/Keyword: Droplet shape

Search Result 165, Processing Time 0.033 seconds

Micro droplet driven by thermocapillary and capillary valve (열모세관에 의한 미소액적 구동과 모세관 밸브)

  • Lim, Nam-Hyuk;Kim, Sung-Wook;Yoo, Jung-Yul
    • Proceedings of the KSME Conference
    • /
    • 2003.04a
    • /
    • pp.1777-1782
    • /
    • 2003
  • This paper presents the design, fabrication, and testing of the capillary-induced pressure drop valve, thermocapillary pumping of liquid droplet in hydrophilic channels and the splitting of droplet. The capillaryinduced pressure drop is derived with thermodynamic approach considering three-dimensional meniscus shape which is essential for calculating pressure drop in the diverging shape channel when the aspect ratio is close to one. The micro channel is fabricated via MEMS processes, which consists of the liquid stop valve to retard the liquid droplet, thermocapillary pumping region and the bifurcation region. Also the micro heaters are fabricated to drive the droplet by thermocapillary. The theoretical approaches agree well with the experimental data. The functionality of capillary valve is confirmed to be valid when the aspect ratio is smaller than one. To overcome the difficulty in splitting of the droplet due to the pressure drop in the general Y-shape channel, the protrusion shape is employed for easy splitting in the bifurcation channel.

  • PDF

Transport Mechanism of an Initially Spherical Droplet on a Combined Hydrophilic/Hydrophobic Surface (친수성/소수성 복합표면상에서 초기 구형 액적의 이송 메커니즘)

  • Myong, Hyon Kook;Kwon, Young Hoo
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.39 no.11
    • /
    • pp.871-884
    • /
    • 2015
  • Fluid transport is a key issue in the development of microfluidic systems. Recently, Myong (2014) has proposed a new concept for droplet transport without external power sources, and numerically validated the results for a hypothetical 2D shape, initially having a hemicylindrical droplet shape. Myong and Kwon (2015) have also examined the transport mechanism for an actual water droplet, initially having a 3D hemispherical shape, on a horizontal hydrophilic/hydrophobic surface, based on the numerical results of the time evolution of the droplet shape, as well as the total kinetic, gravitational, pressure and surface free energies inside the droplet. In this study, a 3D numerical analysis of an initially spherical droplet is carried out to establish a new concept for droplet transport. Further, the transport mechanism of an actual water droplet is examined in detail from the viewpoint of the capillarity force imbalance through the numerical results of droplet shape and various energies inside the droplet.

Uniform metal droplet generation using laser (레이저를 이용한 균일 금속 액적 생성)

  • 강대현;양영수;김용욱;조성규;박성민
    • Laser Solutions
    • /
    • v.5 no.1
    • /
    • pp.23-31
    • /
    • 2002
  • The uniform metal droplet generation using Nd-YAG laser was studied and experiment was carried out. The shape and volume of developed droplet was measured and the Young-Laplace equation and equilibrium condition of force were applied this model. The differential equation predicting shape of droplet using equilibrium condition of force instead of Navier-stokes equation was induced and numerical solution of differential equation compared with experimentation data. The differential equation was solved by Runge-Kutta method. Surface tension coefficient of droplet was determined with numerical solution relate to experimental result under the statical condition. In case of dynamic vibration, metal droplet shape and detaching critical volume are predicted by recalculating proposed model. The result revealed that this model could reasonably describe the behavior of molten metal droplet on vibration.

  • PDF

The Evaporation Shape of Deposited Droplet on the Hot Surface (고온표면에 부착된 액적의 증발형상 변화)

  • Bang Chang-Hoon
    • Journal of the Korean Society of Safety
    • /
    • v.20 no.1 s.69
    • /
    • pp.68-74
    • /
    • 2005
  • The objective of the present work is to examine the evaporation shape of deposited droplet on the hot surface. this paper performed the experiments as following conditions: (a) the surface temperature is within the range between $80^{\circ}C$ and $95^{\circ}C$ in the conduction and radiation, (b) droplet diameter is 3.0mm. The results are as follows; while droplet evaporates, droplet's radius is kept changelessly to $70\%$ evaporation time and droplet's shape is kept changelessly after. In case use Constant radius model, about $10\%$ is appearing high than value that time-averaged heat flux applies Inverse heat conduction.

A LIQUID DROPLET SIMULATION ON ZIG-ZAG MOTION (단일 액적의 Zig-Zag 운동 시뮬레이션)

  • Jung, Rho-Taek
    • Journal of computational fluids engineering
    • /
    • v.14 no.3
    • /
    • pp.63-68
    • /
    • 2009
  • The motion of a rising liquid droplet is different that of a bubble motion. Treatment of liquid drops is more complex because internal motion must be considered. A 3D unstructured CFD code has been developed to solve incompressible N-S equation for the droplet simulation. This front-tracking consideration which the interface is tracked explicitly is very available to apply for not only exact interface topology but also the high schmidt number issue, such as $CO_2$ dissolution. This paper is forced on the zig-zag motion of the liquid droplet. The simulation shows that if the rising droplet is located at the corner of the zig-zag path, the velocity is low and shape of the droplet is more spherical shape, results in the less drag coefficient. Twin horse shoe vortexes behind the rising droplet are presented and the topology of the droplet is compared with an experimental result during one period of the path.

Shape Oscillation and Mode Characteristic of Droplet on Vibrating Flat Surface (진동 평판 위 액적의 형상 진동 변화 및 모드 특성)

  • Shin, Young-Sub;Lim, Hee-Chang
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.37 no.5
    • /
    • pp.489-494
    • /
    • 2013
  • This study aims to understand the mode characteristics of a droplet under a periodic forced vibration. To predict the resonance frequency of a droplet, theoretical and experimental approaches were employed. A high-speed camera was used to capture the various deformation characteristics of a droplet-mode shape, detachment, separated secondary droplet, and skewed deformation. The comparison between the theoretical and the experimental approaches shows a ~10% discrepancy in the prediction of the resonance frequency, which appears to be caused by the effect of contact line friction, nonlinear wall adhesion, and experimental uncertainty. Owing to contact-line pinning and smaller amplitude, the droplet shape becomes symmetric and the size of each lobe at the resonance frequency exceeds that at the neighbor, which is out of resonance.

An Experimental Study on Shape Oscillation Mode of a Pendant Droplet by an Acoustic Wave (음향 가진을 이용한 매달려 있는 액적의 형상 진동 모드에 관한 실험적 연구)

  • Kang Byung-Ha;Moon Jong-Hoon;Kim Ho-Young
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.30 no.6 s.249
    • /
    • pp.523-530
    • /
    • 2006
  • One of the fascinating prospects is the possibility of new hydrodynamics technology on micro-scale system since oscillations of micro-droplets are of practical and scientific importance. It has been widely conceived that the lowest oscillation mode of a pendant droplet is the longitudinal vibration, i.e. periodic elongation and contraction along the longitudinal direction. Nonlinear and forced oscillations of supported viscous droplet were focused in the present study. The droplet has a free contact line with solid plate and inviscid fluid. Natural frequencies of a pendant droplet have been investigated experimentally by imposing the acoustic wave while the frequency is being increased at a fixed amplitude. It is found that a pendant droplet shows the resonant behaviors at each mode similar to the theoretical analysis. The rotation of the droplet about the longitudinal axis is the oscillation mode of the lowest resonance frequency. This rotational mode can be invoked by periodic acoustic forcing and is analogous to the pendulum rotation. It is also found that the natural frequency of a pendant droplet is independent of the drop density and surface tension but inversely proportional to the square root of the droplet size.

Water droplet behavior on a solid-infused surface cured with commercial Gentoo polymer (상용 Gentoo 폴리머가 경화된 고체주입표면에서 물방울 거동)

  • Hyeongwon Kim;Jeong-Hyun Kim
    • Journal of the Korean Society of Visualization
    • /
    • v.22 no.1
    • /
    • pp.61-67
    • /
    • 2024
  • In this study, the behavior of water droplets on a solid-infused surface was evaluated by quantifying a water droplet's contact angle, sliding angle, and terminal velocity. The contact angle hysteresis and sliding angle of water on the solid-infused surface were measured to be lower than those of the hydrophobic PTFE surface. It led to the enhancement of the initiation of the water droplet's movement. When the capillary number was lower than Ca < 0.004, the terminal velocity of the water droplet on the solid-infused surface was higher than the PTFE surface due to the low contact line resistance. However, the transition of the droplet morphology from a hemispherical shape to a streamlined teardrop shape beyond Ca > 0.004 lost the effect of reducing frictional resistance on the solid-infused surface.

Heat and Mass Transfer Enhancement of a pendant droplet on heated horizontal surface by acoustic resonance (가열된 평판위에 매달려 있는 액적의 음향공진에 의한 열 및 물질 전달 촉진에 관한 연구)

  • Moon, Jong-Hoon
    • Proceedings of the SAREK Conference
    • /
    • 2005.11a
    • /
    • pp.335-340
    • /
    • 2005
  • Nonlinear and forced oscillations of supported viscous droplet were focused in the present study. The droplet has a free contact line with solid plate and inviscid fluid. Natural frequencies of a pendant droplet have been investigated experimentally by imposing the acoustic wave while the frequency is being increased at a fixed amplitude. The evaporation was observed at atmosphere pressure. The droplet was recorded throughout the entire evaporation process and transient variations of the volume was measured. The evaporation process of oscillating droplet with thermofoil has been also observed to investigate analyzing the resonance effect on the thermal characteristics of droplet. It is found that a pendant droplet shows the resonant behaviors at each mode similar to the theoretical analysis. During imposing the acoustic wave, the pendant droplet makes a rotating motion in its longitudinal axis which is a new shape oscillation mode. The evaporation rate of a pendant droplet at resonant frequency is significantly enhanced.

  • PDF

Shape Oscillation and Detachment of Droplet on Vibrating Flat Surface (진동하는 평판 위의 액적의 형상 진동 및 제거 조건에 대한 연구)

  • Shin, Young-Sub;Lim, Hee-Chang
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.38 no.4
    • /
    • pp.337-346
    • /
    • 2014
  • This study aimed to understand the mode characteristics of a droplet subject to periodic forced vibration and the detachment of a droplet placed on a plate surface. An surface was coated with Teflon to clearly observe the behavior of a droplet. The contact angle between the droplet and surface and the hysteresis were found to be approximately $115^{\circ}C$ and within $25^{\circ}C$, respectively. The coating process was performed in a clean room that had an environment with a low level of contaminants and impurities such as air dust, detergents, and particles. To predict the resonance frequency of a droplet, theoretical and experimental approaches were applied. Two high-speed cameras were configured to acquire side and top views and thus capture different characteristics of a droplet: the mode shape, the detachment, the separated secondary droplet, and the waggling motion. A comparison of the theoretical and experimental results shows no more than 18 discrepancies when predicting the resonance frequency. These differences seem to be caused by contact line friction, nonlinear wall adhesion, and the uncertainty of the experiment. For lower energy inputs, the contact line of the droplet was pinned and the oscillation pattern was axisymmetric. However, the contact line of the droplet was de-pinned as the oscillation became more vigorous with increased energy input. The size of each lobe at the resonance frequency is somewhat larger than that at the neighboring frequency. A droplet in mode 2, one of the primary mode frequencies, exhibits vertical periodic movement as well as detachment and secondary ejection from the main droplet.