Rebounding suppression of droplet impact on hot surfaces: effect of surface temperature and concaveness

Jowkar, Saeed; Morad, Mohammad Reza

doi:10.1039/c8sm02271b

Cited by 28 publications

(6 citation statements)

References 30 publications

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“…In agriculture, it is a challenging problem to suppress the bouncing of pesticide sprays for better efficiency without a large modification of the solution composition [62]. Among several strategies to suppress droplet rebound from a solvophobic surface [26,30,58], polymer additives are well-established. The first observation was that a few hundreds ppm of polyethylene oxide (PEO) in water suppresses the rebound when a droplet impacts on a hydrophobic leaf [6,36,54].…”

Section: Introductionmentioning

confidence: 99%

Stopping Droplet Rebound with Polymer Additives: A Molecular Viewpoint

Lee

Chilukoti

Müller‐Plathe

2022

Fluid Mechanics and Its Applications

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The origin of rebound suppression of an impacting droplet by a small amount of polymer additive has been tentatively explained by various physical concepts including the dynamic surface tension, the additional energy dissipation by non-Newtonian elongational viscosity, the elastic force of stretched polymer, and the additional friction on a receding contact line. To better understand the role of polymer on a molecular level, we performed multi-body dissipative particle dynamics simulations of droplets impacting on solvophobic surfaces. The rebound suppression is achieved by the elastic force of stretched polymer during the hopping stage, and the additional friction on the contact line during the retraction stage. Both slow-hopping and slow-retraction mechanisms coexist in a wide range of simulation parameters, but the latter is prevailing for large droplets, and for the strong attraction strength between polymer and surface. The increased polymer adsorption, which maybe achieved by a higher polymer concentration or a larger molecular weight, stimulates both mechanisms. Also, the molecular evidence of the additional friction on the receding contact line is shown from the relation between the contact angle and the contact line velocity where the slope of the fitted line is an indication of the additional friction.

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Section: Introductionmentioning

confidence: 99%

Stopping Droplet Rebound with Polymer Additives: A Molecular Viewpoint

Lee

Chilukoti

Müller‐Plathe

2022

Fluid Mechanics and Its Applications

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“…On the other hand, the impacted droplets on a superhydrophobic surface continuously bounce off from the surface due to low adhesion force. The bouncing phenomena reduces the contact time with the heated surface and results in the lower heat transfer performance [14] on superhydrophobic surface. The overall efficiency of spray cooling system relies on how long the impacted droplets are in contact with the heated surface and how fast the heated droplets drain from the surface.…”

Section: Introductionmentioning

confidence: 99%

Droplet Dynamics on a Wettability Patterned Surface during Spray Impact

et al. 2021

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Wettability patterning of a surface is a passive method to manipulate the flow and heat transport mechanism in many physical processes and industrial applications. This paper proposes a rational wettability pattern comprised of multiple superhydrophilic wedges on a superhydrophobic background, which can continuously remove the impacted spray droplets from the horizontal surface. We observed that the spray droplets falling on the superhydrophilic wedge region spread and form a thin liquid film, which is passively transported away from the surface. However, most of the droplets falling on the superhydrophobic region move towards the wedge without any flooding. The physics of the passive transport of the liquid film on a wedge is also delved into using numerical modelling. In particular, we elucidate the different modes of droplet transport in the superhydrophobic region and the interaction of multiple droplets. The observed droplet dynamics could have profound implications in spray cooling systems and passive removal of liquid from a horizontal surface. This study’s findings will be beneficial for the optimization of efficient wettability patterned surfaces for spray cooling application.

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“…Therefore, the droplet may spread, rebound, or splash away from the surface according to these physical conditions (Dunand et al, 2013). One of these conditions that have a strong influence on the droplet-surface interaction is the surface temperature (Jowkar & Morad, 2019). (Jowkar & Morad, 2019) stated that droplet rebound and secondary atomization postimpact to a solid heated surface are determined by the surface temperature and Weber number.…”

Section: Introductionmentioning

confidence: 99%

“…One of these conditions that have a strong influence on the droplet-surface interaction is the surface temperature (Jowkar & Morad, 2019). (Jowkar & Morad, 2019) stated that droplet rebound and secondary atomization postimpact to a solid heated surface are determined by the surface temperature and Weber number. Weber number is defined as the ratio between the inertial force of the droplet and the cohesive force of the liquid.…”

Section: Introductionmentioning

confidence: 99%

“…This in turn, lets the droplet to spread, recede, and then rebound from the surface post-impact. Whereas, at high Weber number, the kinetic energy of the droplet is high enough to initiate breakup (Jowkar & Morad, 2019). (Alizadeh et al, 2012) found that the surface temperature has a strong effect on the droplet dynamics post-impact on a heated surface, and recommended further investigations on this effect on variable surfaces.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Post-Impact Characteristics of a Diesel-in-Water Emulsion Droplet on a Flat Surface Below the Leidenfrost Temperature

Faik

Theeb

Zhang

2020

Int. J. Renew. Energy Dev.

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Droplet impingement on solid surfaces takes place in a variety of industrial and environmental applications. However, there are still some areas that are not fully comprehended; emulsion droplet impact on a heated surface is one of these areas that require further comprehension. Hence, the present work represents an experimental exploration for spread characteristics of diesel-in-water (DW) emulsion droplet impacting a heated flat plate. Three different emulsions in which water concentration is set to 10%, 20%, and 30% of the overall emulsion content by volume have been tested in addition to the neat diesel. The temperature of the flat plate is varied over the range 20, 40, 60, and 80ºC respectively. Magnified high speed direct imaging and shadowgraphy have been used simultaneously for tracking droplet spread over the heated surface post impact. Droplet spread rate, maximum diameter, rebound height and velocity represent the main evaluated parameters. The results show that the maximum spread diameter is proportional while spread rate is inversely proportional to the increase in plate temperature for all diesel concentrations including the neat diesel. Whereas, droplet rebound height and velocity are found to be more responsive to the variation in diesel concentration than the variation in plate temperature, so they are both minimum in the case of neat diesel and are increasing by the decrease of diesel concentration in the emulsions.

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Rebounding suppression of droplet impact on hot surfaces: effect of surface temperature and concaveness

Abstract: The focus of the present experimental study is on the maximum height of drop bouncing after impinging on flat and semicylindrical concave surfaces, in particular in terms of surface temperature.

Cited by 28 publications

References 30 publications

Stopping Droplet Rebound with Polymer Additives: A Molecular Viewpoint

Stopping Droplet Rebound with Polymer Additives: A Molecular Viewpoint

Droplet Dynamics on a Wettability Patterned Surface during Spray Impact

Post-Impact Characteristics of a Diesel-in-Water Emulsion Droplet on a Flat Surface Below the Leidenfrost Temperature

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