Particle-Resolved Simulations of Flows Through Sphere, Cylinder or Spherocylinder Assemblies: Automatic Workflow

Abstract

We developed an OpenFOAM® application for generation of tri-periodic assemblies of fixed non-overlapping particles, intended for direct numerical simulations with body-fitted unstructured meshes.  The particles can be spherical, cylindrical or spherocylindrical, with random or pre-assigned positions and orientations, and mono- or polydisperse. The assemblies are optimized for meshing with snappyHexMesh: various meshing errors are minimized by using automatically generated edge meshes, as well as by controlling the interparticle distance and tangentiality to the boundaries. Further, we provide a new pressure boundary condition which improves the accuracy of the resulting hydrodynamic forces. The available post-processing function objects are extended to also calculate stresslets (i.e., resistance to the straining motion), relevant for rheology of suspensions. The workflow is validated against available analytical and numerical data, showing excellent agreement. With our present contribution, an OpenFOAM® user is able to significantly reduce the pre-processing efforts: typically, packings of solid fractions up to 0.3 are generated in the range of a few seconds to around a minute. This allows for efficient gathering of data needed for formulation of closure laws or for developing machine learning models, relevant for industrial applications such as pneumatic conveying and fluidized beds.