Record Details

Influence of Chemical Coating on Droplet Impact Dynamics

Electronic Theses of Indian Institute of Science

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Field Value
 
Title Influence of Chemical Coating on Droplet Impact Dynamics
 
Creator Gupta, Rahul
 
Subject Droplet Impact Dynamics
Low Energy Surface Coating
Surface Modification
Chemical Coating
Liquid Drop Impact
Solid Surfaces - Liquid Drop Impact
Aluminium Alloy Surfaces
Water Drop Impacts - Solid Surfaces
Superhydrophobic Surface
Water Droplets Impacting
Superhydrophobic Solid Surfaces
FAS-17
Impacting Water Drops
Drop Impact Dynamics
Aerospace Engineering
 
Description Dynamic behavior of impacting water drops on superhydrophobic solid surfaces provides important details on the stability/durability of such solid surfaces. Multi-scale surface roughness combined with a layer of low energy chemical is an essential surface modification process followed to create superhydrophobic capabilities on solid surfaces. The present work aims at studying the effect of low energy surface coating on droplet impact dynamics by carrying out experiments of water drop impacts on rough solid surfaces with and without chemical modification. A group of six aluminium alloy (Al6061) surfaces (three pairs) are prepared. Roughness, characterized in terms mean surface roughness, Ra, is introduced to these metallic surfaces using sand-paper polishing, electric discharge machining (EDM), and chemical based surface etching process. Low energy surface layer is laid on the rough surfaces by coating NeverWet hydrophobic solution, octadecyl-trichloro-silane (OTS), and perfluorodecyltricholorosilane (FAS-17). The impact dynamics of water drops is analyzed by capturing high speed videos for a range of drop Weber number from 1 to 570 and the salient features of drop impact process on the coated rough surfaces are compared with the corresponding uncoated rough surfaces. A one-to-one comparison on the spreading, fingering, receding, and final equilibrium of impacting drops on the coated and uncoated target surfaces is presented.
Upon coating NeverWet, the original surface features of the base aluminium surface are completely covered by the hydrophobic coating material resulting in a fresh top surface layer. The outcomes as well as the bounce-off characteristics of impacting water drops on the coated surface are comparable to those observed on lotus leaf. The surface morphology features of rough aluminium surfaces coated with OTS and FAS-17 are comparable to those of the corresponding uncoated surfaces. The quantitative measurements on primary spreading and maximum spread factor of impacting drops are largely unaffected by the presence of low energy chemical coating. The dominant effect of surface coating is seen on the receding of impacting drops and hence the final drop configuration. This behavior is more prominently seen on EDM fabricated rough surface (larger Ra) combined with OTS coating than that on etching based rough surface (smaller Ra) combined with FAS-17 coating highlighting the dependence of coating effect with roughness features.
 
Contributor Sivakumar, D
 
Date 2018-03-09T12:50:24Z
2018-03-09T12:50:24Z
2018-03-09
2016
 
Type Thesis
 
Identifier http://hdl.handle.net/2005/3262
http://etd.ncsi.iisc.ernet.in/abstracts/4123/G28219-Abs.pdf
 
Language en_US
 
Relation G28219