Dynamics of viscoelastic drops impacting onto a hydrophobic solid substrate

Han, DingDing; Liu, Haoran; Liu, NanSheng; Ding, Hang

doi:10.1360/sspma2018-00167

Cited by 3 publications

(3 citation statements)

References 16 publications

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“…Chen et al pointed out that the adsorbed viscoelastic filements and the formation of the beads-on-a-string (BOAS) structures led to the imping droplets sticking on the substrate. Han et al investigated an Oldroyd-B fluid droplet numerically and interpreted the antirebound behavior as the generation of downward elastic stress near the droplet edge. Recently, Dhar et al systematically discussed the effects of impact velocity and polymer concentration on the inhibition of droplet rebound and considered the Weissenberg number as the critical parameter for determining the onset of antirebound behavior.…”

Section: Introductionmentioning

confidence: 99%

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Origin of Rebound Suppression for Dilute Polymer Solution Droplets on Superhydrophobic Substrate

et al. 2021

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Controlling droplet deposition with a minute amount of polymer additives is of profound practical importance in a wild range of applications. Previous work ascribed the relevant mechanisms to extensional viscosity, normal stress, wetting properties, etc., but the mechanism remains controversial. In this paper, we employ molecular dynamics simulations systematically for the first time to investigate the origin of rebound suppression for dilute polymer solution droplets on a flat superhydrophobic substrate. The results demonstrate that polymer−substrate interactions and impact velocities dominate the antirebound phenomenon. For low impact velocities, the dynamic characteristics of droplets are insensitive to polymer additives. However, large impact velocities will enhance the stretch behavior of polymer chains and make the chains closer to the substrate, increasing the probability of polymer molecules contacting the bottom substrate. With the cooperation of strong polymer−substrate interactions, polymer molecules can be absorbed easily by the bottom substrate, resisting the retraction process and leading to the onset of the antirebound behavior.

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Section: Introductionmentioning

confidence: 99%

“…Chen et al 18 pointed out that the adsorbed viscoelastic filements and the formation of the beads-on-astring (BOAS) structures led to the imping droplets sticking on the substrate. Han et al 19 the critical parameter for determining the onset of antirebound behavior.…”

Section: ■ Introductionmentioning

confidence: 99%

Origin of Rebound Suppression for Dilute Polymer Solution Droplets on Superhydrophobic Substrate

et al. 2021

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“…It has been suggested that the polymer dissipates energy during the stretching process, thus inhibiting the rebound of the droplets . However, a new theory has since been proposed, which suggests that the polymer interacts with the solid surface and the friction at the contact line dissipates the energy. , Up to now, there have been many reports on the regulation of droplet impact behavior by polymers, but there are still some controversies on the regulation mechanism. − In addition, nobody has studied the regulation and mechanism of polymer impact behavior from the perspective of the polymer structure.…”

Section: Introductionmentioning

confidence: 99%

Mechanism Study on the Alcoholysis and Polymerization Degree of Poly(vinyl alcohol) to Regulate Droplet Impact Behavior on Hydrophobic Surfaces

Wang,

Song,

Huang

et al. 2024

ACS Sustainable Chem. Eng.

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How to restrain the bounce behavior of droplets on hydrophobic surfaces is a problem in daily life, especially during pesticide spraying. Adding polymer is a constructive strategy to enhance the ability of pesticide deposition on plant leaves, but it lacks guidance about the relationship between molecular structure and regulation capacity. This study selected poly(vinyl alcohol) (PVA) with different degrees of alcoholysis and polymerization to explore physicochemical properties in different dimensions affecting the bounce behavior. The results revealed that PVA-1788 had the best regulatory ability according to suitable phase viscosity, good surface activity, high adhesion force, and tensile viscosity. Based on statistical analysis, breaking distance at the solid−gas−liquid three-phase line is quantitative sustainability metrics to promote droplet adhesion. Namely, the solution containing PVA-1788 were embedded in the micronano structures on the hydrophobic surfaces to form claw structures and then produced the pinning effect for enhancing energy consumption so as to inhibit the droplet retraction. This mechanism was verified by SEM and fluorescence microscopy, and the higher the release height, the faster the initial rate, resulting in the significant pinning effect, because of obvious bordered deposition and permeation. This study provides the mechanism into guiding polymer adjuvants added in pesticides in view of quantitative sustainability metrics, which can lead to economic and environmental benefits in the future.

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Numerical simulation of shear-thinning droplet impact on surfaces with different wettability

Xue-Feng¹,

Yu²,

Wang³

et al. 2020

Acta Phys. Sin.

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Controlling impact dynamics of droplets on solid surfaces is a significant problem in a variety of applications, such as inkjet printing, spray cooling and coating and so on. Most of fluids used in industries always contain various kinds of additives such as surfactants, polymers and particles. Therefore, these fluids exhibit non-Newtonian behaviors, for instance, yield-stress, viscoelastic, shear-thickening and shear-thinning. The impact dynamics of Newtonian droplets on solid surfaces has been extensively investigated. However, the number of researches about fluids with non-Newtonian properties is comparatively very small. In this work, we employ the finite element scheme coupled with level set method to simulate the impact process of droplets on solid surfaces. The numerical simulation models the presence of shear-thinning viscosity by using the truncated power-law rheological model. We first conduct a mesh convergence study and verify the numerical model. The simulation results are found to be in good agreement with experimental data in the literature. By performing extensive numerical simulations and varying the rheological parameters and surface wettabilities, the influences of these parameters on the impact dynamics are evaluated, and the dominant effects that govern the spreading and receding process are determined. The simulation results show that for the case of droplet impacting on surface with contact angle θ = 55°, the spreading is stronger with power-law index decreasing as evidenced by larger shape deformation and faster interface moving speed. As power-law index decreases, we expect the maximum dimensionless diameter to increase and the minimum dimensionless height to decrease during inertial spreading. For the case of droplet with lower power-law index (m = 0.85 and 0.80), which indicates lower viscous dissipation during impact, the dimensionless parameters have significant differences. After first receding, the impacting droplet is not balanced any more and it starts to spread again until its kinetic energy is completely damped by fluid viscous dissipation. For the case of droplet (m = 0.80) impacting on surface, the center breakage can be observed during droplet spreading, which results from the effect of strong shear-thinning property. When a shear-thinning droplet impacts on a surface with contact angle θ = 100°, the oscillation behavior can be observed and the oscillation amplitude increases as power law index decreases. Bouncing phenomenon can be observed when a droplet impacts on surface with contact angle θ = 160°, regardless of rheological property. Finally, we propose an empirical model to predict the maximum dimensionless diameter of shear-thinning droplet impacting on the surface with contact angle θ = 55° as a function of non-Newtonian Reynolds number Ren.

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Dynamics of viscoelastic drops impacting onto a hydrophobic solid substrate

Cited by 3 publications

References 16 publications

Origin of Rebound Suppression for Dilute Polymer Solution Droplets on Superhydrophobic Substrate

Origin of Rebound Suppression for Dilute Polymer Solution Droplets on Superhydrophobic Substrate

Mechanism Study on the Alcoholysis and Polymerization Degree of Poly(vinyl alcohol) to Regulate Droplet Impact Behavior on Hydrophobic Surfaces

Numerical simulation of shear-thinning droplet impact on surfaces with different wettability

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