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
• Assistant Professor in Multiscale Mechanics, Dept. of Thermal and
Fluid Engineering, University of Twente
• Developing simulation methods to understand, predict and optimize
complex multi-physics, multi-scale processes
• Focus on granular systems, using the Discrete Particle Method, CFD,
and coupled simulation techniques
• Cofounder of simulation software MercuryDPM, spin-off company MercuryLab
• Developed MercuryCG, an accurate and efficient technique to analyse
discrete simulations, and couple them with continuum models
• Developed microscopic contact models for frictional, wetted and
sintered particles, as well as rheological laws for granular and
atomistic flows and mixtures
• Applications: segregation and mixing, avalanche flows, additive
manufacturing, wet agglomeration, tableting, etc.