Simulation and Analysis of the GranuDrum Granular Material Flow Analyzer test

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

Introduction

The GranuDrum® methodology is a standardized version of the well-known rotating drum powder flowability characterisation methodology whereby the flow behavior and cohesive properties of granular materials are characterized using the Dynamic Angle of Repose (DAoR) and Cohesive Index (CI) measurements. By carefully controlling the rotation speed and capturing high-resolution images of the powder's surface, GranuDrum provides precise and repeatable measurements of powder flowability.

Key features of GranuDrum include:

Automated Measurement - GranuDrum automates the rotation and data acquisition process, reducing human error and increasing measurement consistency.
Data Analysis - GranuDrum processes the captured images to calculate the DAoR and CI without any human intervention.
Consistency and Repeatability - By using standardized testing methodology, GranuDrum ensures that measurements are consistent and repeatable across different batches of powder, which is crucial for accurate and reliable results.

The physical geometry and standard test procedures of GranuDrum are replicated in the provided EDEM simulation deck. A standard test consists of recording side-on images of the granular material flow in the drum after a steady state is achieved (5 seconds by default) at a fixed rotation rate between 0-250 RPM (30 RPM by default). The images are recorded at a constant frequency (1Hz by default) over a fixed period of time (45 seconds by default) as shown in Figure 1.

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

The DAoR and CI are computed using a complex analysis process that is based on the spatio-temporal characteristics of the granular bed surface. The calculation is conceptualized in Figure 2 and the complete equations are listed in the works of Neveu, Lumay and Francqui.

Figure 2. (a) The average air-powder interface determined from all images (b)Calculation of the DAoR (c) Calculation of the CI

Prerequisites

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

Using the kit

The simulation deck provided can be run directly in EDEM, and the AoR 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.
Analysis start time (s)	Specifies the lower limit of the simulation time range for which simulation data is included in the analysis. It is recommended to perform this analysis after the system has reached steady state, and this value must be set accordingly.
Analysis end time (s)	Specifies the upper limit of the simulation time range for which simulation data is included in the analysis.
Analysis step factor (Int)	Specifies the frequency of saved EDEM Time Steps included in the analysis. A value of n means every n^th saved Time Step is processed. Note: The image analysis frequency is the inverse of the product of the analysis step factor and the EDEM save interval. The default image analysis frequency for GranuDrum is 1Hz and it is recommended to maintain that frequency for all cases.
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 values 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 Rotating Drum tests. The analysis script automatically determines the drum 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 GranuDrum 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.