Molecular Dynamics Simulation on Behaviors of Water Nanodroplets Impinging on Moving Surfaces

Abstract

Droplets impinging on solid surfaces is a common phenomenon. However, the motion of surfaces remarkably influences the dynamical behaviors of droplets, and related research is scarce. Dynamical behaviors of water nanodroplets impinging on translation and vibrating solid copper surfaces were investigated via molecular dynamics (MD) simulation. The dynamical characteristics of water nanodroplets with various Weber numbers were studied at four translation velocities, four vibration amplitudes, and five vibration periods of the surface. The results show that when water nanodroplets impinge on translation surfaces, water molecules not only move along the surfaces but also rotate around the centroid of the water nanodroplet at the relative sliding stage. Water nanodroplets spread twice in the direction perpendicular to the relative sliding under a higher surface translation velocity. Additionally, a formula for water nanodroplets velocity in the translation direction was developed. Water nanodroplets with a larger Weber number experience a heavier friction force. For cases wherein water nanodroplets impinge on vibration surfaces, the increase in amplitudes impedes the spread of water nanodroplets, while the vibration periods promote it. Moreover, the short-period vibration makes water nanodroplets bounce off the surface.

Studies on Continuum Breakdown and Water Transport Behavior of Nanotubes for Water Purification: Impact of Temperature, Nanotube Material, and Diameter

“…Then, the density contour of the equilibrated water structure was determined, which was fitted to a circle, using expression 5. The radius and center of the fitted circle were used to evaluate the contact angle as per eqs 5and 6 35 x a z b R ( ) ( )…”

“…Then, the density contour of the equilibrated water structure was determined, which was fitted to a circle, using expression . The radius and center of the fitted circle were used to evaluate the contact angle as per eqs 5and false( x − a false) 2 + false( z − b false) 2 = R 2 θ = arcsin ( b − z sub R ) + 90 ° where a , b , and R denote the center and radius of the fitted circle. Z sub is the z coordinate of a virtual surface 5 Å above the solid surface.…”

“…The concept of Z sub was considered to avoid the effects of density fluctuations at the liquid−solid surface, which is basically connected to surface roughness. The details of this method can be found in the studies by Zhang et al 35 XI. Velocity Autocorrelation Functions.…”

Dynamical behaviors of nanodroplets impinging on solid surfaces in the presence of electric fields

“…In contrast to traditional thermodynamic methods and macroscopic experiments, molecular dynamics (MD) simulations can quantitatively and accurately determine the properties of nanodroplets throughout the spreading and bouncing processes, which is of tremendous practical value. [17][18][19] Zong et al, 20 utilized MD to investigate the early diffusion behavior of nanodroplets on a freeze-resistant nanopillar substrate. By modifying the structure of the substrate, they investigated the influence of surface tension and viscosity of the droplet on the freeze-resistant surface.…”

Heat Transfer and Fluids Properties of Nanofluids

“…In a different study, Zhang et al [ 9 ] performed a molecular dynamics simulation of the behaviors of water nanodroplets impinging on moving (translation and vibration) surfaces. They studied the dynamical characteristics of water nanodroplets under different factors such as Weber numbers, translation velocities, vibration amplitudes and vibration periods of the surface.…”