Onset of Marangoni convection for evaporating sessile droplets

MacDonald, Brendan D.; Ward, C. A.

doi:10.1016/j.jcis.2012.06.046

Cited by 23 publications

(9 citation statements)

References 31 publications

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“…The threshold value for a flat fluid film is about 80 [67]. The onset of the Marangoni convection has been also confirmed in [68] for the particular case of droplets with contact angle θ = 90 • . Using the known estimates of the evaporation flux [69], we obtain the value Ma ≈ 0.4 for θ = 10 • and Ma ≈ 0.03 for θ = 3 • .…”

Section: Marangoni Flowsmentioning

confidence: 58%

Joint effect of advection, diffusion, and capillary attraction on the spatial structure of particle depositions from evaporating droplets

Kolegov

Barash

2019

Phys. Rev. E

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A simplified model is developed, which allows us to perform computer simulations of the particles transport in an evaporating droplet with a contact line pinned to a hydrophilic substrate. The model accounts for advection in the droplet, diffusion and particle attraction by capillary forces. On the basis of the simulations, we analyze the physical mechanisms of forming of individual chains of particles inside the annular sediment. The parameters chosen correspond to the experiments of Park and Moon [Langmuir 22, 3506 (2006)], where an annular deposition and snakelike chains of colloid particles have been identified. The annular sediment is formed by advection and diffusion transport. We find that the close packing of the particles in the sediment is possible if the evaporation time exceeds the characteristic time of diffusion-based ordering. We show that the chains are formed by the end of the evaporation process due to capillary attraction of particles in the region bounded by a fixing radius, where the local droplet height is comparable to the particle size. At the beginning of the evaporation, the annular deposition is shown to expand faster than the fixing radius moves. However, by the end of the process, the fixing radius rapidly outreaches the expanding inner front of the ring. The snakelike chains are formed at this final stage when the fixing radius moves toward the symmetry axis. arXiv:1903.06003v2 [cond-mat.soft]

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Section: Marangoni Flowsmentioning

confidence: 58%

Joint effect of advection, diffusion, and capillary attraction on the spatial structure of particle depositions from evaporating droplets

Kolegov

Barash

2019

Phys. Rev. E

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“…Numerous theoretical works were conducted in order to shed light on the underpinning physics of the internal flows in volatile drops and are now considered well understood. 29,30,31,32 On the contrary, the internal flows emerging in a drying water drop have received rather limited attention.…”

Section: Introductionmentioning

confidence: 99%

Influence of Local Heating on Marangoni Flows and Evaporation Kinetics of Pure Water Drops

et al. 2017

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The effect of localized heating on the evaporation of pure sessile water drops was probed experimentally by a combination of infrared thermography and optical imaging. In particular, we studied the effect of three different heating powers and two different locations, directly below the center and edge of the drop. In all cases, four distinct stages were identified according to the emerging thermal patterns. In particular, depending on heating location, recirculating vortices emerge that either remain pinned or move azimuthally within the drop. Eventually, these vortices oscillate in different modes depending on heating location. Infrared data allowed extraction of temperature distribution on each drop surface. In turn, the flow velocity in each case was calculated and was found to be higher for edge heating, due to the one-directional nature of the heating. Additionally, calculation of the dimensionless Marangoni and Rayleigh numbers yielded the prevalence of Marangoni convection. Heating the water drops also affected the evaporation kinetics by promoting the "stick-slip" regime. Moreover, both the total number of depinning events and the pinning strength were found to be highly dependent on heating location. Lastly, we report a higher than predicted relationship between evaporation rate and heating temperature, due to the added influence of the recirculating flows on temperature distribution and hence evaporation flux.

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“…The geometry of the sessile droplet is of critical importance for experiments performed to understand and quantify the evaporation behavior and the contribution from different energy transport modes. Experimental data from spherical caps is complicated to decipher because of the complex boundary conditions and lack of a convenient coordinate system, but experimental data for a spherical droplet can be analyzed in a straightforward manner using spherical coordinates and the corresponding boundary conditions [32,33] to calculate the energy transport by different modes. Another advantage of the spherical droplet shape is that temperature measurements can be taken that are directly normal to the interface (along the radial direction), which avoids any complex coordinate manipulation of the data and provides an accurate way to calculate the contributions from the energy transport modes.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of interfacial energy transport in an evaporating sessile droplet for evaporative cooling applications

Mahmud

MacDonald

2017

Phys. Rev. E

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In this paper we experimentally examine evaporation flux distributions and modes of interfacial energy transport for continuously fed evaporating spherical sessile water droplets in a regime that is relevant for applications, particularly for evaporative cooling systems. The contribution of the thermal conduction through the vapor phase was found to be insignificant compared to the thermal conduction through the liquid phase for the conditions we investigated. The local evaporation flux distributions associated with thermal conduction were found to vary along the surface of the droplet. Thermal conduction provided a majority of the energy required for evaporation but did not account for all of the energy transport, contributing 64±3%, 77±3%, and 77±4% of the energy required for the three cases we examined. Based on the temperature profiles measured along the interface we found that thermocapillary flow was predicted to occur in our experiments, and two convection cells were consistent with the temperature distributions for higher substrate temperatures while a single convection cell was consistent with the temperature distributions for a lower substrate temperature.

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Onset of Marangoni convection for evaporating sessile droplets

Cited by 23 publications

References 31 publications

Joint effect of advection, diffusion, and capillary attraction on the spatial structure of particle depositions from evaporating droplets

Joint effect of advection, diffusion, and capillary attraction on the spatial structure of particle depositions from evaporating droplets

Influence of Local Heating on Marangoni Flows and Evaporation Kinetics of Pure Water Drops

Experimental investigation of interfacial energy transport in an evaporating sessile droplet for evaporative cooling applications

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