Numerical investigation of freely moving particle–droplet interaction with initial contact

Abstract

We simulated freely moving particle-droplet interaction with initial contact. Fluid-structure interaction was modeled by fictitious domain method, and two-fluid interface was tracked using Level Contour Reconstruction Method. For tracking movement of the solid object, additional object distance function was calculated at Eulerian grid center. Since simple geometry, i.e., circle, was used in this study, object distance function can be easily computed from center location updated by averaged velocity to constrain solid movement. The interaction phenomenon was simplified as center-to-center contact without initial velocity. The gravitational acceleration was also ignored. We choose the size ratio and Ohnesorge (Oh) number as main parameters. Two characteristic behaviors were captured: the merging and separation case. Each velocity of the particle and droplet was shown to see the detailed evolution for merging and separation. In addition, two major forces acting on the particle, a capillary force and inertial force, were analyzed.

Adaptive mesh axi-symmetric simulation of droplet impact with a spherical particle in mid-air

“…( 9), the centroid position of the particle is integrated with a 2 nd order Runge-Kutta method. We found that setting the viscosity of the solid to be 100 times that of the liquid is sufficient to represent the solid particle dynamics (Choi and Shin, 2019;Mirzaii and Passandideh-Fard, 2012). This treatment can be extended to more complex shaped solids by including rotational components.…”

“…Readers can find more detailed information about our existing numerical framework in our previous studies; Juric (2002, 2009), Shin et al (2005Shin et al ( , 2018, Shin (2021b, 2021c). It is also worthwhile mentioning that these numerical methods considered here have been rigorously validated with many existing experimental studies for a wide range of collision conditions (Choi and Shin, 2019;Yoon and Shin, 2021a, 2021b, 2021c and have also been applied to diverse studies of droplet collision phenomena which include collision with a stationary particle (Yoon and Shin, 2021a, 2021b, 2021c, a moving particle (Choi and Shin, 2019), a cylindrical wire (Han et al, 2020), a flat surface (Shin et al, 2018) and a liquid pool (Shin et al, 2017).…”

“…This treatment can be extended to more complex shaped solids by including rotational components. Several benchmark tests for the moving solid were performed in a previous paper and showed good accuracy compared with experimental data (Choi and Shin, 2019).…”

“…One of the popular strategies for reducing the computational cost is to employ an adaptive mesh refinement (AMR) technique, which generally incorporates regions of varying grid resolution within the overall computational domain (Berger and Colella, 1989;Popinet, 2003;Sussman et al, 1999). While well-known methods for the simulation of multiphase flows such as Volume-of-Fluid, Level-Set, and Front-Tracking have adopted a variety of appropriate AMR techniques (Agresar et al, 1998;Popinet, 2003), an AMR technique for our simulation framework has not yet been developed, even though our work has previously been widely applied to various droplet collision phenomena (Choi and Shin, 2019;Han et al, 2020;Shin et al, 2017;Yoon and Shin, 2021a, 2021b, 2021c and successfully parallelized (Shin et al, 2017).…”

Building pathways to full encapsulation processes

“…However, a hydrophilic particle can pass through and split the droplet. Choi et al, [23] investigated the freely moving drop-particle head-on impact with initial contact (i.e., gravitational force was ignored), and identified two main regimes including merging and separation. To address this knowledge gap, the present study utilises 3D (2D axisymmetric) simulations to examine the influence of drop-particle momentum transfer on the encapsulation outcomes, and how this momentum transfer can be optimised so that a stable coverage around particle is ensured.…”