CLUMP

Description

CLUMP is a collection of scripts to generate multi-sphere particles of overlapping or non-overlapping spheres, which approximate target geometries. Multi-spheres (a.k.a. clumps) are popular in numerical simulations using the Discrete Element Method (DEM), but these geometric object can find applications in a wider perspective, past numerical modelling. The motivation behind developing CLUMP stemmed from the need to compare different clump-generation techniques, both in terms of particle morphology and mechanical performance using the DEM. To this end, CLUMP offers two existing and well established clump-generation techniques and proposes a new one. The generated clumps can be exported in various formats, compatible with some of the most prominent DEM codes. Last, the surface of each generated clump can be extracted as a triangulated mesh and saved as an stl file, allowing for a full characterisation of particle morphology, using tools like SHAPE or 3D-printing of physical particle replicas. CLUMP was initially developed in MATLAB and has now been fully translated in Python. Both implementations will continue to be developed in parallel as the software evolves.

Architectural Features

CLUMP performs the following functions:

• GenerateClump

  • Favier et al (1999)
  • Ferellec and McDowell (2010)
  • Euclidean 3D (2021) and Extended Euclidean 3D (proposed in this code)

• ExportClump

  • YADE
  • MercuryDPM
  • LAMMPS
  • EDEM
  • PFC3D

• CharacteriseClump

  • Surface extraction

Installation

Running the following code in the terminal (for Linux and macOS) or in the Command Prompt (for Windows) will automatically set up the module along with its corresponding dependencies.

pip install clump-python

Quick Start

After the installation using pip install clump-python, CLUMP can easily be imported as

import CLUMP

This following examples demonstrate different approaches to generate clumps for the different target geometry. The variables below are documented within each function.

from CLUMP.examples import Example_Euclidean_3D

from CLUMP.examples import Example_Euclidean_3D_Extended

from CLUMP.examples import Example_Ferellec_McDowell

from CLUMP.examples import Example_Favier

The following example demonstrates the surface extraction method.

from CLUMP.examples import Example_ExtractSurface

Simple Examples

Here is an example of generating a clump from an STL file using Euclidean Distance Transform method.

from CLUMP import GenerateClump_Euclidean_3D  
  
inputGeom = "path_of_STL.stl"  
N = 21  
rMin = 0  
div = 102  
overlap = 0.6  
output = 'path_of_clump_output.txt'  
outputVTK = 'path_of_clump_vtk.vtk'  
visualise = True  
  
GenerateClump_Euclidean_3D(inputGeom, N, rMin, div, overlap, output=output, outputVTK=outputVTK, visualise=visualise)

To run the Extended Euclidean Transform, one needs to specify the maximum sphere radius which will trigger the extended version. The example is as follows:

from CLUMP import GenerateClump_Euclidean_3D  
  
inputGeom = "path_of_STL.stl"  
N = 21  
rMin = 0  
div = 102  
overlap = 0.6  
output = 'path_of_clump_output.txt'  
outputVTK = 'path_of_clump_vtk.vtk'  
visualise = True
rMax_ratio = 0.3 # Parameter to trigger the Extended Euclidean method
  
GenerateClump_Euclidean_3D(inputGeom, N, rMin, div, overlap, output=output, outputVTK=outputVTK, visualise=visualise, rMax_ratio=rMax_ratio)

Here is an example for the Ferellec-McDowell clump generation method:

from CLUMP import GenerateClump_Ferellec_McDowell

inputGeom = "path_of_STL.stl"  
dmin = 0.1  
rmin = 0.01  
rstep = 0.01  
pmax = 1.0  
seed = 5  
output = 'path_of_clump_output.txt'  
outputVTK = 'path_of_clump_vtk.vtk'  
visualise = True  
  
mesh,clump=GenerateClump_Ferellec_McDowell(inputGeom=inputGeom, dmin=dmin, rmin=rmin, rstep=rstep, pmax=pmax, seed=seed, output=output, outputVTK=outputVTK, visualise=visualise)

To generate a clump using the Favier method, you can use the following example:

from CLUMP import GenerateClump_Favier

inputGeom = "path_of_STL.stl"  
N = 10  
chooseDistance = 'min'  
output = 'path_of_clump_output.txt'  
outputVTK = 'path_of_clump_vtk.vtk'  
visualise = True  
  
mesh,clump=GenerateClump_Favier(inputGeom=inputGeom, N=N, chooseDistance=chooseDistance, output=output, outputVTK=outputVTK, visualise=visualise)

Consider a clump defined as follows:

import numpy as np

clump = np.array([[1, 0, 0, 1.1],  
                  [2, 1, 0, 1.1],  
                  [3, 0, 0, 1.2],  
                  [1, 0, 1, 1.2]])

To extract the surface of the clump, you can use ExtractSurface function as follows:

from CLUMP import ExtractSurface

N_sphere = 200  
N_circle = 100  
visualise = True  
  
faces, vertices = ExtractSurface(clump, N_sphere, N_circle, visualise)

BYOS (Bring Your Own Scripts)!

If you enjoy using CLUMP, you are welcome to require the implementation of new clump-generation approaches and features or even better contribute and share your implementations. CLUMP was created to provide a comparison of different methods, by collecting them in one place and we share this tool hoping that members of the community will find it useful. So, feel free to expand the code, propose improvements and report issues.