Phase diagram for nanodroplet impact on solid surfaces
Journal
Physics of Fluids
Journal Volume
33
Journal Issue
10
Date Issued
2021
Author(s)
Abstract
The impact dynamics of water nanodroplets on flat solid surfaces was studied by molecular dynamics simulations over a wide range of Weber numbers (We) and surface wettability (θ0), where θ0 is the Young contact angle. A phase diagram in the parameter space of We vs θ0 was established accommodating eight impact outcomes noted in the final stage of impact, with three of them, holes rebound, partial-rebound splash, and rebound splash, for the first time being identified and reported. The eight impact outcomes were classified into three categories, i.e., non-bouncing, bouncing, and splash. The results show that the splash is triggered only when Wecr > 140. The boundaries separating bouncing from non-bouncing were determined based on the phase diagram. When θ0 > 160°, the boundary is described as Wecr = a 1; when 110° < θ0 < 160°, the boundary depends on both We and θ0, with a larger We required to trigger bouncing on a less hydrophobic surface, expressed as Wecr = b + ccosθ0; when θ0 < 110°, bouncing never takes place, and hence, the boundary is determined only by the critical contact angle, expressed as θ0,cr = 110°. Here, a, b, and c are constants. ? 2021 Author(s).
Subjects
Contact angle
Hydrophobicity
Molecular dynamics
Surface chemistry
Classifieds
Hydrophobic surfaces
Impact dynamics
Nano-droplets
Parameter spaces
Solid surface
Surface wettability
Three categories
Water nanodroplets
Weber numbers
Phase diagrams
Type
journal article