Study of internal flow and evaporation characteristics inside a water droplet on a vertically vibrating hydrophobic surface

Park, Chang-Seok; Kim, Hun; Lim, Hee-Chang

doi:10.1016/j.expthermflusci.2016.05.018

Cited by 17 publications

(8 citation statements)

References 30 publications

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“…This is an advancement in the preliminary studies [21,23] on the near-wall fluorescent particle motion in a sessile droplet evaporation. Unlike the numerous numerical [50,51] or experimental and/or numerical [11,27,52,53] contact angle (CCA) modes of the droplet evaporation were followed recurrently during the evaporation process, which is consistent with the observation of some other researchers [28,[47][48][49], giving rise to asymmetrical deposition patterns. The nanoparticle concentration significantly influenced the droplet evaporation rate, leading to an irregular deposition patterns.…”

Section: Resultssupporting

confidence: 87%

“…Liquid droplet evaporation has a wide range of applications such as inkjet printing, thin film coating, spray drying, fuel injection and optoelectronic device manufacturing [1][2][3][4], as well as the diagnosis of diseases from drying the blood droplet and DNA microchips [5][6][7]. The deposition pattern of a droplet depends on the fluid flow within the droplet [8][9][10][11][12][13], temperature gradient [9,14,15], concentration and type of the nanoparticles [16][17][18]. The nature of the substrate [19][20][21][22][23] and type of base fluid [24,25] also have important roles on the formation of droplet deposition patterns.…”

Section: Introductionmentioning

confidence: 99%

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Deposition pattern and tracer particle motion of evaporating multi-component sessile droplets

Amjad

Yang

Raza

et al. 2017

Journal of Colloid and Interface Science

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The understanding of near-wall motion, evaporation behavior and dry pattern of sessile nanofluid droplets is fundamental to a wide range of applications such as painting, spray drying, thin film coating, fuel injection and inkjet printing. However, a deep insight into the heat transfer, fluid flow, near-wall particle velocity and their effects on the resulting dry patterns is still much needed to take the full advantage of these nano-sized particles in the droplet. This work investigates the effect of direct absorptive silicon/silver (Si/Ag) hybrid nanofluids via two experiments. The first experiment identifies the motion of tracer particles near the triple line of a sessile nanofluid droplet on a super-hydrophilic substrate under ambient conditions by the multilayer nanoparticle image velocimetry (MnPIV) technique. The second experiment reveals the effect of light-sensitive Si/Ag composite nanoparticles on the droplet evaporation rate and subsequent drying patterns under different radiation intensities. The results show that the presence of nanoparticle in a very small proportion significantly affects the motion of tracer particles, leading to different drying patterns and evaporation rates, which can be very important for the applications such as spray coating and inkjet printing.

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Deposition pattern and tracer particle motion of evaporating multi-component sessile droplets

Amjad

Yang

Raza

et al. 2017

Journal of Colloid and Interface Science

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“…In contrast, the flow pattern on the horizontal bi-phobic surface is Yshaped and bifurcated, with two symmetric vortices on both sides of the droplet. 54 Supplementary videos are available to visualize these flow fields. 49,55 Based on the observed velocities, we get 𝑅𝑎 3.3 10 and 𝑀𝑎 2.4 10 .…”

Section:  Results and Discussionmentioning

confidence: 99%

“…For the vertical biphobic surface, one small-size oval vortex is observed in the upper region of the droplet, with high fluid velocities in the upper region ( v > 2.2 m/s) and weaker flow in the lower region ( v < 0.75 m/s). In contrast, the flow pattern on the horizontal biphobic surface is Y-shaped and bifurcated, with two symmetric vortices on both sides of the droplet Videos S1 and S2 are available to visualize these flow fields.…”

Section: Resultsmentioning

confidence: 99%

Evaporation of Sessile Water Droplets on Horizontal and Vertical Biphobic Patterned Surfaces

Li²,

Weisensee³

2019

Langmuir

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ABSTACT: This paper presents an experimental study on thermal transport to single water droplets evaporating on heated bi-phobic surfaces consisting of a superhydrophobic matrix with a circular hydrophobic pattern with strong contact line pinning. A single water droplet of 8 µl volume is placed on a preheated surface and allowed to evaporate in an open laboratory environment. We investigate the influence of substrate orientation (horizontal and vertical) on evaporation dynamics. Using optical and infrared imaging, we report droplet fluid dynamics and heat transfer characteristics of the evaporating droplet. Overall, evaporation is more efficient on the vertical surface, exhibiting higher total heat transfer rates and up to 10% shorter evaporation times. Counterintuitively, on the vertical surface, the substrate-droplet interfacial heat flux was higher near the lower contact line than in the upper region, despite a high contact angle and an expected wedge effect at the bottom. At the same time, the temperature is colder in the lower part of the droplet. We attribute this apparent anomaly to the competition between sensible heating and evaporation, and a modified convective flow signature (both within the droplet and the gas phase) compared to a horizontal surface. We also show that the thermal signature becomes uniform once the contact angles at the upper and lower contact lines become equal towards the end of the evaporation process. Insights from this work can guide the design of spray cooling devices, or be used to alter particle deposition patterns during evaporation-based fabrication techniques and ink-jet printing.

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“…They demonstrated an axisymmetric internal flow for the oscillating droplets that is first pulled downwards along the symmetry axis, and subsequently folds back upwards along the surface of the drop towards the apex. However, opposite results were obtained by Lim's group (Shin and Lim, 2014;Kim and Lim, 2015) and Park et al (2016), they found that a vertically vibrating droplet attains various shapes at different modes, resulting in complicated vortices inside the droplet. In the visualization, the flow moves upwards starting from the bottom center of the droplet along the symmetric axis and then moves closer to the three phase contact line along the surface of the upper part of the droplet.…”

Section: Introductionmentioning

confidence: 77%

Experimental and CFD Study of Internal Flow inside a Sessile Microdroplet undergoing Lateral Vibration

Zhu¹,

Zhao²,

Lv³

et al. 2018

JAFM

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In this study, the internal flow pattern of a sessile microdroplet undergoing a lateral vibration was analyzed by using both the experimental and CFD simulation methods. By initially staining the droplet partially with fluorescent dye, the main flow inside the laterally vibrating microdrop was experimentally demonstrated to be that the main fluid flows downward along the central axis and ascends upward along the surface to form two counterflow circuits. Experimental evaluation of fluid mixing inside the droplets verified that the internal flowing velocity is dependent on the vibrating frequency, the main fluid flows faster at the resonant modes. CFD simulation using the VOF-CSF model showed that extra flow circuits exit inside the oscillating droplet besides the main flow. The diffusion of substrate momentum within the Stokes layer results in the two flow circuits near the bottom substrate, and the Laplace force due to the droplet deformation induces the two counter-current flow circuits near the surfaces of the microdroplet.

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Study of internal flow and evaporation characteristics inside a water droplet on a vertically vibrating hydrophobic surface

Cited by 17 publications

References 30 publications

Deposition pattern and tracer particle motion of evaporating multi-component sessile droplets

Deposition pattern and tracer particle motion of evaporating multi-component sessile droplets

Evaporation of Sessile Water Droplets on Horizontal and Vertical Biphobic Patterned Surfaces

Experimental and CFD Study of Internal Flow inside a Sessile Microdroplet undergoing Lateral Vibration

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