Maximum Diameter of Impacting Liquid Droplets

Abstract

The maximum diameter a droplet that impacts on a surface will attain is the subject of controversy, notably for high-velocity impacts of low-viscosity liquids such as water or blood. We study the impact of droplets of simple liquids of different viscosities, and a shear-thinning complex fluid (blood), for a wide range of surfaces, impact speeds, and impact angles. We show that the spreading behavior cannot simply be predicted by equating the inertial to either capillary or viscous forces, since, for most situations of practical interest, all three forces are important. We determine the correct scaling behaviors for the viscous and capillary regimes and, by interpolating between the two, allow for a universal rescaling. The results for different impact angles can be rescaled on this universal curve also, by doing a simple geometrical correction for the impact angle. For blood, we show that the shear-thinning properties do not affect the maximum diameter and only the high-shear rate viscosity is relevant. With our study, we solve a longstanding problem within the fluid-dynamics community: We attest that the spreading behavior of droplets is governed by the conversion of kinetic energy into surface energy or dissipated heat. Energy transfer into internal flows marginally hinders droplet spreading upon impact.

Interplay between viscosity and elasticity in freely expanding liquid sheets

“…The importance of wettability for a yield stress fluid made of microgels [10], and of the dynamics of the contact line for dilute polymer solutions [14,15] have been clearly evidenced in the dynamics of non-newtonian drops. However, even for simpler fluids as low viscosity Newtonian liquids, providing a theoretical prediction for the maximal spreading of a drop as a function of the surface tension, contact angle, impact velocity and viscosity is not an easy task [13]. In the case of more viscous Newtonian fluids, the main difficulty in order to reach a theoretical prediction is to account for the viscous dissipation of the drop when it spreads, as complex flows are involved.…”

Jet dynamics post drop impact on a deep pool

“…This fame among the general public is undoubtedly due to its deeply attractive aesthetic, but drop impact also has a large field of applications. Inkjet printing [4], microfabrication of three-dimensional objects [5], underwater noise of rain [6], raindrop energy harvesters [7], forensic bloodstain pattern analysis [8], impact cratering [9], and the earthy smell, known as petrichor, present after a rain shower on a hot day [10] are a few among them. The diversity of these examples explains why drop impact has been studied by many authors [11,12].…”

Droplet Impact in Icing Conditions – Experimental Study for WE 540

“…During last years, the kinematic and the spreading phases have been widely described for the droplet impingement for room temperatures. The maximum diameter during spreading given by Laan et.al [8] and dependence of the droplet radius in the function of time described in the work by Stapelbroek [9] are not dependent on the surface properties. Fig.…”