Splashing Phenomena During Liquid Droplet Impact

Abstract

Splashing is a phenomenon often observed during liquid droplet impact onto a solid surface. The threshold of splashing is known to be related to droplet size, impact velocity, and physical properties of the liquid, but the mechanisms that initiate splashing are not understood completely. In accordance with the Kelvin-Helmholtz (K-H) instability analysis, recent studies have shown that ambient gas density has a significant effect on the threshold and trajectory of splashing. In this study, the effects of droplet velocity, impact angle, and ambient gas pressure (or density) on the threshold of splashing and the motion of the ambient gas surrounding the droplet were examined. Experimental observations of splashing were carried out with a droplet of 1.7 mm in diameter, while varying droplet velocity, impact angle, and ambient pressure. An empirical correlation was derived using our and other published data to determine the threshold of splashing based on the aforementioned parameters. Also, a numerical simulation using the volume of fluid method was carried out to calculate the gas velocities surrounding the droplet during impact. The results of this model gave supportive evidence that K-H instability is a suitable instability theory that helps explain the splash phenomenon with consideration of the gas motion surrounding the droplet.

Supercooled Water Droplet Impacting Superhydrophobic Surfaces in the Presence of Cold Air Flow

“…In fact, near the wall boundary layer thickness is not same as still air conditions. Secondly, K-H instability [31] which is promoted by increasing air speeds at either interface (solid-air or air-liquid) results in a more unstable spreading ligament. In fact, contribution of the full slip boundary condition along with K-H instability results in faster detachment of the water droplet during the recoiling phase.…”

“…Indeed, combination of both induced homogeneous nucleation through an evaporation cooling mechanism and imposing extra dynamic pressure of air flow on impacting drop totally changes the behavior of conventional drop impact dynamics on a superhydrophobic surface. Unlike the phenomenology of static pressure on wetting behavior of impacting drop on hydrophilic [31][32][33] and superhydrophobic surfaces [34], here the effect of extra pressure buildup due to incoming air flow on substrates such as superhydrophobic surface is evaluated, which might result in variation of droplet contact time below and above the critical temperature of heterogeneous ice nucleation (i.e., −24 • C).…”

Nanodroplets Behavior on Graphdiyne Membranes

“…Droplet splashing dynamics on surfaces is an important area in general science and industry [10][11][12][13], dealing with diverse aspects that a liquid could have (such as shapes and sizes) on impacting surfaces at different velocities. In this work, we have use fully atomistic molecular dynamics (MD) simulations to investiagate how water nanodroplets behave on impact at graphdyine membranes.…”

Theoretical and experimental study on mechanical characterisation of a water drop impact on a solid surface

“…The splashing phenomenon occurs when a liquid droplet impacts onto a solid or liquid surface (Liu et al, 2010). The physical mechanisms of splashing are still not completely understood, droplet impact against soil can be used to study many phenomena related to rainfall, runoff, irrigation, erosion of the soil and slopes.…”

“…Particularly this effect can be related to the drop diameter, velocity, shape, drop force and so impact pressure (Mouzai and Bouhadef, 2001). However Liu et al (2010) reported that the pressure field (distribution) inside the drop during impact is the key factor that produces splashing. As concerning the eroding pressure, different combinations of water drop characteristics such as mass, speed and diameter can differently affect the soil detachment.…”