Simulation and Analysis of the GranuHeap Granular Material Heap Analyzer test

This section provides instructions on running an EDEM simulation of the GranuHeap® Granular Material Heap Analyzer developed by GranuTools and computing the standard measurements of the instrument from the simulation data using the GranuHeap calibration kit.

Introduction

The GranuHeap® methodology is a standardized version of the well-known Angle of Repose (AoR) powder flowability characterization methodology, where, the flow behavior and cohesive properties of granular materials are characterized using the AoR and Static Cohesive Index (SCI) measurements. The AoR is defined as the maximum stable angle of a pile of granular material under static conditions, and the SCI is a measure of the difference between the actual heap shape and an ideal (triangular) heap shape. Both are determined from image analysis. The instrument uses the lifting cylinder method to form the granular pile. A hollow cylinder is placed on a base plate such that there are no gaps and is filled with granular material. The granular heap is then formed by raising the cylinder at a constant rate allowing some of the material to shear off.

Key features of GranuHeap include:
  • Automated Process - GranuHeap automates the lifting of the cylinder, ensuring a consistent and controlled release of the material, which enhances the repeatability and reliability of the measurements.
  • Data Analysis - The AoR and SCI are automatically determined via image analysis and without human intervention.
  • Consistent and Repeatable Results - By using a standardized testing methodology, GranuHeap ensures that results are consistent and repeatable.

The physical geometry and standard test procedure of GranuHeap are replicated in the providedEDEM simulation deck. A standard test consists of recording side-on images of the granular material under static conditions (after 5 seconds by default) at different angles around the pile as shown in Figure 1.

Figure 1. a. EDEM simulation of the GranuHeap b) Corresponding side-on image for analysis


The AoR and SCI are computed using a complex analysis process that is based on the geometric characteristics of the granular bed surface. The calculation is conceptualized in Figure 2.
Figure 2. The average air-powder interface determined from all images and the definition of the AoR


Note: The parts in red show the fluctuations of the heap interface around the ideal heap shape which are used to measure the SCI.

Prerequisites

All the requisite files are located at: <Altair installation folder>\EDEM <version>\examples\Calibration Kits\GranuHeap.

Using the kit

The simulation deck provided can be run directly in EDEM, and the AoR and SCI can be automatically obtained via the provided Python script which uses the EDEMpy library of functions to find all EDEM decks in its folder tree and generate plots and results reports per simulation deck, as well as a summary results report for all decks. The analysis settings for the script are defined in the provided text file and listed in Table 1 as follows:
Table 1. Python script settings
Parameter Description
Number of Images (-) Specifies the number of images taken around the granular pile for the determination of the AoR and CI. The orientation angles are equally spaced between 0 and 180 degrees. The minimum value is 1.
Save images? (Yes/No) Specifies whether the analysis images are retained. If you select Yes, the images are stored in a sub folder within the simulation deck folder.
Individual report? (Yes/No) Specifies whether an individual results report is written out for every simulation deck. If you select Yes, a report containing all relevant results is generated per simulation deck in its corresponding folder in .csv format.
Summary report? (yes/no) Specifies whether a summary report with the key results for all simulation decks will be produced. The results are written out in the Summary.csv file in the Python script folder.

The default settings correspond to the standard test procedure of the instrument. A settings text file is required for each folder containing EDEM simulation decks, and the settings are used to post-process all simulation decks in that folder.

The provided Python script can be executed from EDEM Analyst > File > Run EDEMpy Script, or from the command line. To run the script from the command line, you must ensure that EDEMpy is installed in the relevant Python distribution. For more information about installing EDEMpy, see Install EDEMpy.

Note: Geometric and/or contact model parameter scaling may be required to achieve practical simulation times for the AoR tests. The analysis script automatically determines the base diameter to accommodate geometric scaling, and will maintain its functionality, provided all the geometry is scaled around the origin of the coordinate system, and the base is not renamed.

Acknowledgement

The development of the GranuHeap calibration kit was made during the PhD thesis of Ben Jenkins in the framework of a collaboration between GranuTools and the University of Birmingham under the academic supervision of Dr. Kit Windows-Yule and Prof. Jonathan Seville.