Numerical Study of the Wetting and Mobility of Liquid Droplets on Horizontal and Inclined Flat and Microgrooved Surfaces

Farhat, Nazia; Alen, Saif Khan; Rahman, Ashiqur

doi:10.1016/j.proeng.2015.05.035

Cited by 9 publications

(6 citation statements)

References 17 publications

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“…Because of the low surface wettability has extensive application in anti-corrosion, anti-icing, self-cleaning, drag reduction, and other fields. [6][7][8][9] At the same time, with the development of micromachining technology, such as mechanical micromachining, physical micromachining, and chemical micromachining, micro-structured surfaces with superhydrophobicity have been used to study the dynamic process of droplet collision.…”

Section: Introductionmentioning

confidence: 99%

Dynamic behavior of droplets impacting cylindrical superhydrophobic surfaces with different structures

Qian

Huang

et al. 2023

Physics of Fluids

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The dynamic behavior of droplets impacting cylindrical superhydrophobic surfaces with different structures (azimuthal groove, axial groove, pillar) is studied in this work. The rebound and splash thresholds with different structures were also proposed, which depended on D/D0 (where D is the ratio of cylinder diameter and D0 is the initial droplet diameter) and the surface structure of the substrate. Based on the energy conservation approach, a complete rebound threshold semi-empirical model is constructed for cylindrical superhydrophobic surfaces. The recovery coefficient is used to measure the energy loss during the droplet impacting the superhydrophobic cylindrical surface. At the same time, the energy loss was significant on the cylindrical superhydrophobic surface with different structures, and the surface structure of the substrate played a vital role in the energy loss of the collision process. Then a prediction formula for the maximum spread diameter on the cylindrical superhydrophobic surface with different structures is presented to understand the droplet collision behavior further. In addition, a level wing-like splash morphology could reduce contact time on grooved superhydrophobic surfaces. Based on the contact time as a function of the Weber number, the azimuthal grooved structure surface has the least contact time.

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Section: Introductionmentioning

confidence: 99%

Dynamic behavior of droplets impacting cylindrical superhydrophobic surfaces with different structures

Qian

Huang

et al. 2023

Physics of Fluids

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“…As a result, the retention force will differ from that observed by ElSherbini and Jacobi, who proposed a predictive retention force model based on a circular base area. Most prior researchers have used a simplified model for retention force that has assumed a spherical drop with a circular base area. − …”

Section: Introductionmentioning

confidence: 99%

Retention Forces for Drops on Microstructured Superhydrophobic Surfaces

et al. 2022

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Accurate models of retention forces between drops and superhydrophobic (SH) surfaces are required to predict drop dynamics on the surface. This retention force is, in turn, useful in modeling heat transfer rates for dropwise condensation on a SH surface. Drop contact angle distribution and base area on SH surfaces are essential factors for predicting retention forces. The present work measures the contact angle distribution and base area shapes of various drop sizes over a wide range of solid fraction for inclined microstructured SH surfaces at the point of drop departure. Base area shape was found to be well approximated using two ellipses with different aspect ratios, and the contact angle distribution was found to be best fit by a sigmoid function. At an incline near the roll-off angle, drop base area for surfaces with solid fraction close to 1 and close to 0 were found to be nearly circular, whereas the base area of drops on surfaces with an intermediate solid fraction deviated from circular behavior. In this work, maximum advancing and minimum receding contact angles were found as a function of solid fraction and used to calculate retention forces. Contact angle distribution and base area shapes are then used to calculate retention forces between drops and SH surfaces. These calculations are compared with the component of measured drop weight acting parallel to the plane on a tilted surface for validation. Previous retention force studies that investigate base area shape and contact angle distribution for smooth surfaces are not applicable for microstructured SH surfaces. The work shows that using a sigmoid contact angle distribution and modified base area shape yields retention forces that are on average 50% better than previously reported methods. Retention forces for smooth and SH surfaces calculated in this study were used to suggest retention force factor values for varying solid fraction surfaces.

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“…They found that the effect of inclination on droplet dynamics is more pronounced on hydrophobic substrates as compared to hydrophilic substrates. Farhat et al 20 performed threedimensional simulations to study the static and dynamic wetting of a liquid droplet on a horizontal microgrooved surface and compared the wetting patterns observed in microgrooved and flat surfaces.…”

Section: ■ Introductionmentioning

confidence: 99%

Motion of a Droplet on an Anisotropic Microgrooved Surface

2019

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We experimentally characterize the sliding angle of water droplets (volume 3.1–22.2 μL) migrating on inclined microgrooved surfaces along the longitudinal and transverse directions of the grooves. The rectangular microgrooves are manufactured on silicon wafers using standard photolithography techniques. We tilt the surface gradually using a rotating stage mechanism until the incipience of the sliding. The droplet migration in the longitudinal and transverse directions to the grooves is recorded using a high-speed camera. For the droplets migrating downward in the transverse direction, the contact line exhibits a “stick-slip” type motion, that is, the advancing contact line is attached to the surface, whereas the receding contact line is detached from the surface. However, no significant change in the relative position of the advancing and receding contact lines is observed in the case of the longitudinal migration of the droplets. The sliding behavior of the droplet in the longitudinal direction is similar to that observed in the case of a smooth surface. The sliding angle in the longitudinal direction of motion is found to be smaller as compared to that in the transverse motion of the droplet. In both longitudinal and transverse migrations, increasing the pitch of the grooves increases the contact angle, which in turn decreases the sliding angle. As the droplet volume is increased, the component of the gravitational force in the direction of inclination increases, which acts to decrease the sliding angle. A theoretical analysis is also conducted to predict the sliding angle of a droplet on microgrooved surfaces. The model predictions agree with the trends observed in our experiments and thus validate the proposed sliding mechanisms in the longitudinal and transverse migrations of the droplet.

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Numerical Study of the Wetting and Mobility of Liquid Droplets on Horizontal and Inclined Flat and Microgrooved Surfaces

Cited by 9 publications

References 17 publications

Dynamic behavior of droplets impacting cylindrical superhydrophobic surfaces with different structures

Dynamic behavior of droplets impacting cylindrical superhydrophobic surfaces with different structures

Retention Forces for Drops on Microstructured Superhydrophobic Surfaces

Motion of a Droplet on an Anisotropic Microgrooved Surface

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