Thomas Weinhart

Coarse-graining with MercuryCG – From Discrete Particles to Continuum Fields

Micro–macro transition methods are used to calibrate and validate
continuum models from discrete data, obtained from experiments or
simulations. Such methods generate continuum fields such as density,
momentum, stress, etc, from discrete data, i.e. positions, velocity,
orientations and forces of individual elements. Performing this
micro–macro transition step is especially challenging for
heterogeneous and dynamic situations. Here, we present a promising
technique, called coarse-graining, to perform this transition. This
novel method has several advantages: by construction the obtained
macroscopic fields are consistent with the continuum equations of
mass, momentum and energy balance. Additionally, boundary interaction
forces can be taken into account in a self-consistent way and thus
allow for the construction of locally accurate stress fields even
within one element radius of the boundaries. Similarly, stress and
drag forces can be determined for individual constituents, which is
critical for e.g. mixture and segregation models. Moreover, the method
does not require ensemble-averaging and thus can be efficiently
exploited to investigate static, steady and dynamic flows. The
resulting fields may serve various purposes: an in-depth analysis of
the material behaviour; extracting a problem-specific continuum model;
or even coupling of particle simulations with fluid solvers or other
continuum models.
We show how to practically use coarse-graining for both steady and
dynamic flows and mixtures, using our open-source coarse-graining tool
MercuryCG. The tool is available as part of an efficient discrete
particle solver MercuryDPM

Bio Sketch:

Thomas Weinhart studied Mathematics at the TU München, Germany (BSc) and Virginia Tech, USA (MSc, PhD). He is now Associate Professor in Thermal and Fluid Engineering at the University of Twente. He studies granular processes on all scales: he developed and experimentally validated contact laws for wetting, friction, cohesion and sintering; established coarse-graining as micro-macro method for extracting local macroscopic quantities from discrete particle data; modelled granular systems on the macroscale; and used FEM simulations to predicting the flow behaviour of large-scale systems. He now develops coupled methods for solving multi-scale, multi-physics problems, such as liquid migration, segregation of cohesive powders, sintering, 3D printing, tabletting, and wet granulation. In 2009, he co-founded MercuryDPM, a cutting-edge open-source software for particle simulations; and now leads the code development team. The code has several unique features that make it particularly apt to simulate complex industrial systems. All his research codes are publicly available in the software. For commercial use of the software, he co-founded MercuryLab, a spin-off company providing custom software, training and advice to companies on the design of process equipment.