Visual analysis of density and velocity profiles in dense 3D granular gases

Dmitry Puzyrev,Torsten Trittel,Nicolas Vandewalle,David Fischer,Eric Falcon,Fabien Palencia,Yves Garrabos,Ralf Stannarius,Raúl Cruz Hidalgo,Carole Lecoutre,Martial Noirhomme,Eric Opsomer,Kirsten Harth

doi:10.1038/s41598-021-89949-z

Abstract

Granular multiparticle ensembles are of interest from fundamental statistical viewpoints as well as for the understanding of collective processes in industry and in nature. Extraction of physical data from optical observations of three-dimensional (3D) granular ensembles poses considerable problems. Particle-based tracking is possible only at low volume fractions, not in clusters. We apply shadow-based and feature-tracking methods to analyze the dynamics of granular gases in a container with vibrating side walls under microgravity. In order to validate the reliability of these optical analysis methods, we perform numerical simulations of ensembles similar to the experiment. The simulation output is graphically rendered to mimic the experimentally obtained images. We validate the output of the optical analysis methods on the basis of this ground truth information. This approach provides insight in two interconnected problems: the confirmation of the accuracy of the simulations and the test of the applicability of the visual analysis. The proposed approach can be used for further investigations of dynamical properties of such media, including the granular Leidenfrost effect, granular cooling, and gas-clustering transitions.

Highlights

Ensembles of macroscopic, hard particles that interact by inelastic collisions are of considerable academic interest as a test for analytical and numerical treatments of multiparticle systems
Experimental and theoretical investigations of granular gases can be roughly grouped into two classes: The first one deals with granular gases in absence of external forcing, while the second one investigates stationary states under permanent energy entry from the exterior that compensates the dissipative losses of kinetic energy
The aim of this study is to develop methods to extract local velocity, kinetic energy, and particle number density data from densely packed, periodically excited granular ensembles of cylindrical rods

Summary

Introduction

Hard particles that interact by inelastic collisions are of considerable academic interest as a test for analytical and numerical treatments of multiparticle systems They are of fundamental importance, e.g. for the understanding of fluidization of granular materials, of granular flow and behaviour under shear. Experimental and theoretical investigations of granular gases can be roughly grouped into two classes: The first one deals with granular gases in absence of external forcing, while the second one investigates stationary states under permanent energy entry from the exterior that compensates the dissipative losses of kinetic energy The investigation of the former scenario, granular cooling of granular g ases[2], has attracted considerable theoretical efforts, while experimental studies remained comparably scarce. The interesting aspects of such experiments are, among others, the distribution of mean kinetic energies among the individual degrees of freedom of the particles, the velocity distribution functions, and the spatial distribution of the particles in the observed volume

Objectives

Methods

Conclusion