Analysis of particle dispersion and cavity formation during bulk particle water entry using fully coupled CFD-DEM-VOF approach

Abstract

This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid (CFD-DEM-VOF) model to simulate the complex behavior of particle-laden flows with free surfaces. The coupling between the fluid and particle phases is established through the implemented continuity, momentum, and alpha transport equation. The coupled particle forces such as drag, pressure gradient, dense virtual mass, viscous, and interface forces are also integrated, with drag and dense virtual mass forces being dependent on local porosity. The integrated conservative alpha transport equation ensures phase volume conservation during interactions between particles and water. Additionally, we have implemented a trilinear interpolation method designed to operate on unstructured hexahedral meshes. This method has been tested for its ability to properly resolve the coupling effects in the numerical simulations, particularly in cases with a relatively low cell-size ratio. The model is validated through three distinct test cases: single particle water entry, dam break with particles, and water entry of a group of particles case. The experimental setup is built to study the dynamics of the water entry of a group of particles, where three key flow features are analyzed: the evolution of average particle velocity, cavity shape, and particle dispersion cloud profiles in water. The tests involve four different scenarios, including two different water levels (16.1 and 20.1 cm) and two different particle densities (2650 and 4000 kg/m3). High-speed videometry and particle tracking velocimetry (using ImageJ/TrackMate) methods are employed for experimental data acquisition. It is demonstrated that numerical results are in excellent agreement with theoretical predictions and experimental data. The study highlights the significance of vortices in cavity shaping and particle dispersion. The validated CFD-DEM-VOF model constitutes a robust tool for simulating particle-laden flows, contributing valuable insights into the complex interplay between particles and fluids.