On the submerging of a spherical intruder into granular beds

Chuan-Yu Wu,Ling Zhang,Lan Chen,F Radjai,S Nezamabadi,J.Y Delenne,S Luding

doi:10.1051/epjconf/201714002027

Chuan-Yu Wu, Ling Zhang + Show 5 more

Open Access

https://doi.org/10.1051/epjconf/201714002027

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Abstract

Granular materials are complex systems and their mechanical behaviours are determined by the material properties of individual particles, the interaction between particles and the surrounding media, which are still incompletely understood. Using an advanced discrete element method (DEM), we simulate the submerging process of a spherical projectile (an intruder) into granular materials of various properties with a zero penetration velocity (i.e. the intruder is touching the top surface of the granular bed and released from stationary) and examine its settling behaviour. By systematically changing the density and size of the intruder and the particle density (i.e. the density of the particles in the granular bed), we find that the intruder can sink deep into the granular bed even with a zero penetration velocity. Furthermore, we confirm that under certain conditions the granular bed can behave like a Newtonian liquid and the submerging intruder can reach a constant velocity, i.e. the terminal velocity, identical to the settling of a sphere in a liquid, as observed experimentally. A mathematical model is also developed to predict the maximum penetration depth of the intruder. The model predictions are compared with experimental data reported in the literature,good agreement was obtained, demonstrating the model can accurately predict the submerging behaviour of the intruder in the granular media.

Highlights

With the aim of investigating whether there is a liquid phase for granular materials through which a projectile can reach a terminal velocity and penetrate indefinitely, we employ an advanced numerical method, the discrete element method, and analyse the penetration of a spherical projectile of different sizes into granular media with zero initial speed, i.e. the projectile is placed on the top surface of the granular bed and released from rest
In contrast to the experimental study of PacheoVazquez et al ([4]) who used one particular granular material but varied the mass of the projectile, we systematically change the density of the particles in the granular materials for a given projectile, while keeping the initial packing structure of the granular bed identical, and examine how deep the projectile can sink into the granular materials and the kinematics of the projectile during the penetration process
We modeled a 2D system with the discrete element method (DEM), as detailed in Goey et al [5]

Summary

Introduction

With the aim of investigating whether there is a liquid phase for granular materials through which a projectile can reach a terminal velocity and penetrate indefinitely, we employ an advanced numerical method, the discrete element method (see the Methods section), and analyse the penetration of a spherical projectile of different sizes into granular media with zero initial speed, i.e. the projectile is placed on the top surface of the granular bed and released from rest. In contrast to the experimental study of PacheoVazquez et al ([4]) who used one particular granular material but varied the mass of the projectile, we systematically change the density of the particles in the granular materials for a given projectile, while keeping the initial packing structure of the granular bed identical, and examine how deep the projectile can sink into the granular materials and the kinematics of the projectile during the penetration process

Submerging kinematics

Penetration model

Model validation

Conclusions