Brazil nut effect simulation for dry size classification under lunar gravity conditions

Miguel Maria Picão Caldeira Martins Albino

Key information

Authors:

Miguel Maria Picão Caldeira Martins Albino (Miguel Maria Picão Caldeira Martins Albino)

Supervisors:

Gustavo André Paneiro (Gustavo Paneiro); Joshua Nicholas Rasera

Published in

April 29, 2025

Abstract

This project investigates the Brazil Nut Effect (BNE) – a physical phenomenon where larger particles rise to the top of a vibrating granular mixture - through the creation of physically accurate 3D simulations. Using YADE, an open-source Discrete Element Method (DEM) software, the study explores particle segregation under both terrestrial and lunar gravity conditions. The work was divided into three stages: validation, calibration, and the lunar case study analysis. Validation involved replicating previous BNE studies using an intruder model, while calibration introduced experimental data from tests conducted at Imperial College of London with varying amplitudes and two different sample types. The final stage focused on lunar gravity, revealing that BNE is more pronounced under reduced gravity, with all tests showing segregation - unlike some under Earth gravity conditions. A key part of the study analysed frequency variation, demonstrating that both extremely low and high frequencies hinder effective particle segregation. Results suggest that the amplitude-frequency relationship follows an inverse proportionality close to 1:1 for the maximization of segregation efficiency. Further findings indicate that more balanced particle mixtures resist overfluidization, maintaining better segregation quality. The simulation results also align with the critical dimensionless acceleration (Γ_crit = 1) found in literature but suggest the existence of an upper threshold - an optimal Γ - beyond which segregation quality declines. This research contributes valuable insights into particle behaviour in low-gravity environments, with implications for future lunar resource beneficiation.