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Effect of low energy surface coating on droplet impact dynamics on rough aluminum

Gupta, R and Vaikuntanathan, V and Sivakumar, D (2015) Effect of low energy surface coating on droplet impact dynamics on rough aluminum. In: ICLASS 2015 - 13th International Conference on Liquid Atomization and Spray Systems, 23-25 August 2015, National Cheng Kung UniversityTainan; Taiwan.

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Fabrication of long-lived superhydrophobic surfaces (SHS) received considerable academic interest in recent years due to their use in practical applications involving self-cleaning, anti-icing, reduced adhesion, and drag reduction. SHS exhibiting high contact angle (> 150o) and low roll-off angle (< 10o) for a water drop are obtained by means of a surface morphology with multi-scale roughness and a low energy surface. Wet-chemistry grafting involving the deposition of a low energy coating on a rough surface is one of the effective methods to fabricate such surfaces. The present work investigates the impact of water droplets with impact Weber number varying in the range 24-520 on a rough aluminum surface coated with Octadecyl-Trichloro-Silane (OTS). The deduced results of droplet impact are compared with those obtained for an almost identical rough aluminum surface without coating to record the effect of OTS coating on the impact dynamics. Quantified measurements of surface morphology and static contact angle obtained for the uncoated and coated rough target surfaces show negligible differences. However, the droplet impact dynamics on the target surfaces exhibits significant differences at almost all impact conditions. A one-to-one comparison on the spreading, fingering, receding, and final equilibrium of impacting droplets on the target surfaces is carried out. On the uncoated rough target surface, the spreading droplet liquid gets pinned onto the surface due to its penetration into the roughness valleys resulting in a low droplet activity time. The low energy surface coating increases the activity time of droplet liquid on the target surface by altering the receding dynamics of impacting droplets. However, the fraction of droplet volume participating in the receding process decreases with the increasing Weber number. The role of surface coating on the dynamics of fingers ejecting from liquid lamella is discussed. The findings are useful to enhance modeling efforts on droplet impact phenomenon on coated rough surfaces. © 2015 International Conference on Liquid Atomization and Spray Systems. All rights reserved.

Item Type: Conference Paper
Publication: ICLASS 2015 - 13th International Conference on Liquid Atomization and Spray Systems
Publisher: Europe, Institute for Liquid Atomization and Spray Systems
Additional Information: cited By 0; Conference of 13th International Conference on Liquid Atomization and Spray Systems, ICLASS 2015 ; Conference Date: 23 August 2015 Through 27 August 2015; Conference Code:160081
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 29 Oct 2020 10:58
Last Modified: 29 Oct 2020 10:58
URI: http://eprints.iisc.ac.in/id/eprint/67059

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