Water droplet on inclined dusty hydrophobic surface: influence of droplet volume on environmental dust particles removal

Abdelmagid, Ghassan; Yilbaş, Bekir Sami; Al‐Sharafi, Abdullah; Al‐Qahtani, Hussain; Al-Aqeeli, N.

doi:10.1039/c8ra10092f

“…The rotational kinetic energy of the rolling droplet over inclined hydrophobic surfaces is influenced by the forces of pinning (under surface tension), air drag, and interfacial shear (created over the wetted surface) 34 . The pinning force is proportional to the droplet wetting diameter ( D w ), the solid fraction ( ϕ s ), droplet fluid surface tension ( γ ), and advancing ( θ A ) and receding ( θ R ) angles during rolling.…”

Section: Resultsmentioning

confidence: 99%

Water droplet can mitigate dust from hydrophobized micro-post array surfaces

Abubakar

¹

,

Yilbaş

²

,

Al‐Qahtani

³

et al. 2021

Sci Rep

Self Cite

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Water droplet rolling motion over the hydrophobized and optically transparent micro-post array surfaces is examined towards dust removal pertinent to self-cleaning applications. Micro-post arrays are replicated over the optically transparent polydimethylsiloxane (PDMS) surfaces. The influence of micro-post array spacing on droplet rolling dynamics is explored for clean and dusty surfaces. The droplet motions over clean and dusty micro-post array surfaces are monitored and quantified. Flow inside the rolling droplet is simulated adopting the experimental conditions. Findings reveal that micro-post gap spacing significantly influences droplet velocity on clean and dusty hydrophobized surfaces. Air trapped within the micro-post gaps acts like a cushion reducing the three-phase contact line and interfacial contact area of the rolling droplet. This gives rise to increased droplet velocity over the micro-post array surface. Droplet kinetic energy dissipation remains large for plain and micro-post arrays with small gap spacings. A Rolling droplet can pick up dust particles from micro-post array gaps; however, few dust residues are observed for large gap spacings. Nevertheless, dust residues are small in quantity over hydrophobized micro-post array surfaces.

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“…The rotational kinetic energy of the rolling droplet over inclined hydrophobic surfaces is influenced by the forces of pinning (under surface tension), air drag, and interfacial shear (created over the wetted surface). 32 The pinning force is proportional to the droplet wetting diameter (Dw), the solid fraction (s), droplet fluid surface tension (), and advancing (A) and receding (R) angles during rolling. It takes the form:…”

Section: Droplet Rolling Over Hydrophobic Micro-post Arraysmentioning

confidence: 99%

“…. 32 The air-drag force acting over rolling droplet can be formulated via ≅ 1/2 2 , here, Cd is drag coefficient and air velocity is Uf , which can be considered as rolling droplet translational velocity (Vd). 33 The interfacial shear force created over the wedded area can be simplified to take the form of: = ( ), here Aw is wetted area,  is fluid viscosity, y is distance normal to the wetted area.…”

Section: Droplet Rolling Over Hydrophobic Micro-post Arraysmentioning

confidence: 99%

Water Droplet Can Mitigate Dust from Hydrophobized Micro-Post Array Surfaces

Abubakar

¹

,

Yilbas

²

,

Al‐Qahtani

³

et al. 2021

Preprint

0

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Water droplet rolling motion over the hydrophobized and optically transparent micro-post array surfaces is examined towards dust removal pertinent to self-cleaning applications. Micro-post arrays are replicated over the optically transparent polydimethylsiloxane (PDMS) surfaces. The influence of micro-post array spacing on droplet rolling dynamics is explored for clean and dusty surfaces. The droplet motions over clean and dusty micro-post array surfaces are monitored and quantified. Flow inside the rolling droplet is simulated adopting the experimental conditions. Findings reveal that micro-post gap spacing significantly influences droplet velocity on clean and dusty hydrophobized surfaces. Air trapped within the micro-post gaps acts like a cushion reducing the three-phase contact line and interfacial contact area of the rolling droplet. This gives rise to increased droplet velocity over the micro-post array surface. Droplet kinetic energy dissipation remains large for plain and micro-post arrays with small gap spacings. A Rolling droplet can pick up dust particles from micro-post array gaps; however, few dust residues are observed for large gap spacings. Nevertheless, dust residues are small in quantity over hydrophobized micro-post array surfaces.

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“…Environmental dust settles on surfaces and alters surface optical characteristics while influencing performance of a renewable energy devices such as photovoltaics, which becomes significant over the time 1 . This is because of the composition of the environmental dust, which is consisted of various elements and oxides while lowering the UV visual transmittance of solar radiation 6 . Surface cleaning of such devices becomes essential for effective and sustainable operations.…”

Section: Introductionmentioning

confidence: 99%

“…However, the dust particles with sharp edges can anchor on the surface and they are difficult to pick up by the droplet. The low surface energy dust particles are unable to be cloaked by the droplet fluid and mostly they remain as residues on the surface while adversely affecting the cleaning performance 6 . In addition, the dust thickness influences the droplet fluid cloaking and the amount of dust picked up by the droplet may reduce with increasing dust thickness on the surface.…”

mentioning

confidence: 99%

A water droplet-cleaning of a dusty hydrophobic surface: influence of dust layer thickness on droplet dynamics

Hassan

¹

,

Yilbaş

²

,

Bahatab

³

et al. 2020

Sci Rep

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Water droplet cleaning of a dusty hydrophobic surface is examined. Environmental dust are used in the experiments and cloaking velocity of a dust layer by a droplet fluid is measured and hemi-wicking conditions for the dust layer are analyzed adopting the pores media wick structure approach. A droplet motion on dusty and inclined hydrophobic surface is analyzed using a high speed digital imaging system. Influences of dust layer thickness, droplet volume, and surface inclination angle on the mechanisms of dust removal by a rolling droplet are evaluated. The findings revealed that dust cloaking velocity decreases exponentially with time. The droplet fluid can cloak the dust layer during its transition on the dusty surface. The transition period of droplet wetted length on the dusty surface remains longer than the cloaking time of the dust layer by the droplet fluid. Translational velocity of rolling droplet is affected by the dust layer thickness, which becomes apparent for small volume droplets. Small volume droplet (20 µL) terminates on the thick dust layer (150 µm) at low surface inclination angle (1°). The quantity of dust picked up by the rolling droplet increases as the surface inclination angle increases. The amount of dust residues remaining on the rolling droplet path is relatively larger for the thick dust layer (150 µm) as compared to its counterpart of thin dust layer (50 µm).

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Water droplet on inclined dusty hydrophobic surface: influence of droplet volume on environmental dust particles removal

Abstract: A water droplet's behavior on an inclined hydrophobic surface in the presence of environmental dust particles is considered and the droplet's dynamics are analyzed pertinent to self-cleaning applications.

Cited by 28 publications

References 49 publications

Water droplet can mitigate dust from hydrophobized micro-post array surfaces

Water droplet can mitigate dust from hydrophobized micro-post array surfaces

Water Droplet Can Mitigate Dust from Hydrophobized Micro-Post Array Surfaces

A water droplet-cleaning of a dusty hydrophobic surface: influence of dust layer thickness on droplet dynamics

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