Analysis of high-energy drop impact onto deep liquid pool

TL;DR

This study uses advanced numerical simulations to analyze high-energy drop impacts on deep liquid pools, revealing detailed flow dynamics, bubble entrapment, and droplet formation mechanisms with good experimental agreement.

Contribution

It introduces a comprehensive DNS approach with adaptive mesh refinement and VOF for modeling high-energy drop impacts, providing new insights into splash dynamics and droplet production.

Findings

Numerical results match experimental visualizations of splash phenomena.

Detailed internal flow analysis reveals mechanisms of bubble entrapment and ligament formation.

Droplet size distribution is bimodal, indicating multiple droplet production mechanisms.

Abstract

The present work is devoted to the analysis of drop impact onto a deep liquid pool. It is focused on the effects of high-energy splash regimes, caused by the impact of large raindrops at high velocities. Such cases are characterized by short time scales and complex mechanisms, and they have thus received little attention until now. The BASILISK open-source solver is used to perform three-dimensional Direct Numerical Simulations (DNS). The capabilities of the octree adaptive mesh refinement techniques enable to capture the small-scale features of the flow, while the Volume of Fluid (VOF) approach combined with a balanced force surface tension calculation is applied to advect the volume fraction of the liquids and reconstruct the interfaces. The numerical results compare well with experimental visualizations: both the evolution of crown and cavity, the emanation of ligaments, the formation of bubble canopy, and the growth of the downward spiral jet that pierces through the cavity bottom, are correctly reproduced. Reliable quantitative agreements are also obtained regarding the time evolution of rim positions, cavity dimensions and droplet distributions through an observation window. Furthermore, simulation gives access to various aspects of the internal flows (velocity, vorticity, pressure, energy budget), which allows to better explain the corresponding physical phenomena. Details of the early dynamics of bubble ring entrapment and splashing performance, the formation/collapse of bubble canopy, and the spreading of drop liquid, are discussed. The statistics of droplet size show the bimodal distribution in time, corroborating distinct primary mechanisms of droplet production at different stages.