Evaporation-induced saline Rayleigh convection inside a colloidal droplet

Kang, Kwan Hyoung; Lim, Hee-Chang; Lee, Hee Woong; Lee, Sang Joon

doi:10.1063/1.4797497

Cited by 76 publications

(64 citation statements)

References 42 publications

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“…[14]). Yet, even an initially uniform concentration profile will create a gradient due to evaporation, so the present definition is more useful here, and was adopted by Kang et al [6]. The problem analyzed in this section is a laterally infinite two-dimensional cuvette filled with a saline solution.…”

Section: Linear Stability Analysismentioning

confidence: 99%

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Evaporation-driven convective flows in suspensions of nonmotile bacteria

et al. 2018

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We report a novel form of convection in suspensions of the bioluminiscent marine bacterium Photobacterium phosphoreum. Suspensions of these bacteria placed in a chamber open to the air create persistent luminiscent plumes most easily visible when observed in the dark. These flows are strikingly similar to the classical bioconvection pattern of aerotactic swimming bacteria, which create an unstable stratification by swimming upwards to an air-water interface, but they are a puzzle since the strain of P. phosphoreum used does not express flagella and therefore cannot swim. Systematic experimentation with suspensions of microspheres reveals that these flow patterns are driven not by the bacteria but by the accumulation of salt at the air-water interface due to evaporation of the culture medium; even at room temperature and humidity, and physiologically relevant salt concentrations, the rate of water evaporation is sufficient to drive convection patterns. A mathematical model is developed to understand the mechanism of plume formation, and linear stability analysis as well as numerical simulations were carried out to support the conclusions. While evaporationdriven convection has not been discussed extensively in the context of biological systems, these results suggest that the phenomenon may be relevant in other systems, particularly those using microorganisms of limited motility.

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Section: Linear Stability Analysismentioning

confidence: 99%

“…The physical parameters used to solve the linear system are shown in Table II. The value of β was taken from Kang et al [6], and the evaporation speed was measured experimentally.…”

Section: Numerical Implementationmentioning

confidence: 99%

Evaporation-driven convective flows in suspensions of nonmotile bacteria

et al. 2018

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“…A study of the effect of saline Rayleigh convection on an evaporating sessile drop deposited on a nonsoluble substrate was recently carried out by Kang et al (2013). The authors investigated the evaporation dynamics using NaCl aqueous drops on a hydrophobic smooth substrate and showed that the evaporation-induced density gradient affects the evaporation dynamics.…”

Section: Evaporation In Presence Of Solute Concentration With or Withmentioning

confidence: 99%

“…Reproduced with permission fromKang et al (2013). The left half of the plane is for the concentration distribution, and the right half of the plane is for the velocity field.…”

mentioning

confidence: 99%

Soluble Substrate

Pirat

Colombani

Mailleur

2015

Droplet Wetting and Evaporation

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“…For instance, Kang et al (2013) investigated the evaporation-induced Rayleigh and Marangoni convections on the vertical cross-sectional plane in a sessile droplet. They used fluorescent particles and a cutoff filter to avoid laser light reflections, which may deteriorate image quality and alleviate the uncertainty.…”

Section: Introductionmentioning

confidence: 99%

Full-field spreading velocity measurement inside droplets impinging on a dry solid surface

Erkan

Okamoto

2014

Exp Fluids

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Liquid droplet impacts onto solid surfaces have attracted enormous amount of attention from wide range of research fields including experimental and numerical investigations. Unlike experimental efforts, numerical and analytical studies generated various sets of data. In this study, we investigated the spreading velocities inside the water droplets impinging onto a dry glass substrate using time-resolved PIV. The method, together with the high spatiotemporal resolution and the additional treatments improving the robustness, allowed us to resolve the radial velocity profiles efficiently in the spreading phase. Several impact velocity cases ranging from 0.40 to 0.96 m/s were studied. They correspond to low and moderate level Weber numbers (4.9-27.6). We observed that instantaneous radial velocity distributions exhibit linear and nonlinear modes. The nonlinearity is caused by the vortical flows formed at outer regions of the spreading liquid lamella. We demonstrated that even at low impact velocities the linear parts of the profiles obey a quasi-one-dimensional theory proposed in the literature. The comparison of obtained results with a literature-based numerical study, performed for high range of Weber numbers, confirmed the simultaneous existence of linear and nonlinear parts in the radial velocity profiles. In spite of the scale differences in terms of Weber number, the agreements in the tendencies of the profiles imply the validity of the mechanism considered in the numerical study even at low and moderate level range of Weber numbers.

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Evaporation-induced saline Rayleigh convection inside a colloidal droplet

Cited by 76 publications

References 42 publications

Evaporation-driven convective flows in suspensions of nonmotile bacteria

Evaporation-driven convective flows in suspensions of nonmotile bacteria

Soluble Substrate

Full-field spreading velocity measurement inside droplets impinging on a dry solid surface

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