Numerical study of head-on droplet collisions at high Weber numbers

Abstract

Head-on collisions of binary water droplets at high Weber numbers are studied by means of direct numerical simulations (DNS). We modify the lamella stabilization method of Focke & Bothe (J. Non-Newtonian Fluid Mech., vol. 166 (14), 2011, pp. 799-810), which avoids the artificial rupture of the thin lamella arising in high-energy collisions, and validate it in the regime of high Weber numbers. The simulations are conducted with and without initial disturbances and the results are compared with the experimental work of Pan et al. (Phys. Rev. E, vol. 80 (3), 2009, 036301). The influence of initial white noise disturbance on the collision dynamics is identified and good agreement between the simulation results and the experimental results is obtained when the initial noise disturbances are properly exerted. In order to include the stochastic nature of the disturbance, we conduct several simulations with white noise disturbance of same strength and average the spectrum diagram for the unstably developing rim of the collision complex. We show that the magnification of rim perturbation can be predicted by Plateau-Rayleigh theory over a long time span.

On the splashing of high-speed drops impacting a dry surface

“…A number of studies focus on clarifying the mechanisms leading to the loss of stability of a rim formed at the edge of an uprising corona (Taylor 1959). These attempts include linear long-wave analysis of transverse rim stability (Roisman, Horvat & Tropea 2006;Krechetnikov & Homsy 2009;Krechetnikov 2010;Roisman 2010) and numerical studies of this phenomenon (Agbaglah, Josserand & Zaleski 2013;Liu & Bothe 2016). At later stages of the impact, the rim-bending disturbances become nonlinear and consequently form several cusps (Yarin & Weiss 1995), which then become the sources of multiple FIGURE 1.…”

Contact line advection using the geometrical Volume-of-Fluid method

“…The numerical studies in the present work are carried out with the Volume of Fluid in-house code Free Surface 3D (FS3D) originally developed by Martin Rieber [39]. Since then, FS3D has been further developed at the University of Stuttgart(see, e.g., [40] and more references given there) and at the Technical University of Darmstadt (see [9], [41][42][43][44][45][46][47]). It has been applied successfully to a variety of multiphase flow problems including falling films [41], thermocapillary effects [42], thermocapillary effects in wetting [9], (reactive) mass transfer processes at fluid interfaces [43], [44], [45], multi-component mass transfer at fluid interfaces [46] and droplet collisions at high Weber numbers [47].…”

Experimental and Computational Investigation of binary drop collisions under elevated pressure

“…A recent overview of FS3D is given in [16]. FS3D has been validated in [15,17,18,19] for the simulation of binary droplet collisions. In FS3D, for integrating the surface tension force, the balanced-CSF [20] and CSS models [21] are implemented.…”