Viscoplastic water entry

Abstract

The impact of viscoplastic droplets on a free surface of water is studied. The droplet undergoes an elasto-plastic deformation at the early stages of water entry. At large time, the yield stress dominates; therefore, the droplet solidifies and reaches an equilibrium shape. Depending on the impact velocity and the rheology of the droplet, the final morphologies vary from pear-shaped to capsules that contain bubbles. We perform an analysis of the orders of magnitude of the forces and introduce the relevant dimensionless groups. Furthermore, we categorize the final shapes in a phase diagram and analyse their geometrical properties. The process presents a method of making non-spherical beads and capsules with tunable shapes and provides information on the general problem of the impact of highly deformable objects on a liquid surface.

Deep pool water-impacts of viscous oil droplets

“…Drop impacts on a deep pool of liquid [1][2][3][4][5][6] and on different types of solid substrates [7][8][9] have been an active subject of research for a long time. This finds its place in a wider tradition of the work on water entry comprehensively covered by Truscott et al 10 Drop impact studies differ from solid projectile impacts in that, in the former, the impacting projectile is deformable, which has also become of interest as evidenced by recent works of Hurd et al 11 and Jalaal et al 12 Upon the impact of a drop on a deep liquid pool, a crater is formed below the free surface of the target, whose collapse can result in phenomena such as bubble entrainment and formation of a Worthington jet, depending on the physical conditions. 6 To understand these common features, which constitute fundamental questions about cavity formation, collapse and jet formation, the experimental focus has been almost exclusively on impacts where the drop and pool consist of the same liquid.…”

Air evolution during drop impact on liquid pool

“…The change in air viscosity significantly affects the whole dynamics of drop impact 53 and thus it would be crucial to investigate the effect of air viscosity on air entrapment during drop impact on a liquid pool. Further studies should be expanded to understand the oblique impact of droplets on deep liquid pools [54][55][56] , the impact of viscoelastic or viscous droplets [57][58][59] , and the impact-induced fabrication 60,61 , with more facilitating of numerical 62 , theoretical 63 , and experimental approaches 64,65 .…”

Viscoplastic drop impact on thin films

“…More weakly shear-thinning fluids (those without an apparent yield stress) tested were formulations of xanthan gum in water [24]. Some of these scaling laws have also been verified experimentally for Carbopol [26], including water-entry problems [27].…”