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Thomas Weinhart
Horstring Z117
P.O. Box 217
7500 AE Enschede, NL
Phone: +31 53 489 3301
Email: t.weinhart@utwente.nl
Skype: thomasweinhart
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MercuryCG
From discrete particles to continuum fields.
Discrete particle simulations create a large amount of data, like the position and velocities of each interactable (particle/wall), and the forces created by each interaction. This data completely describes the system you are simulating, but it is difficult to draw any physically relevant conclusions from it.
Therefore, granular assemblies are often described using continuum fields, like density, momentum and stress, which can often successfully describe the macroscopic physical behavior of the system.
MercuryCG is a package that provides this functionality. It is incorporated into MercuryDPM, but can be used with the output of pther codes as well.
For more information see the documentation of MercuryCG.

Figure: Flow height and Froude number of a shallow flow on an inclinde plane after impact of a stream of particles.

MercuryDPM
Fast, flexible particle simulations.
MercuryDPM is a code for discrete particle simulations. That is, it simulates the motion of particles, or atoms, by applying forces and torques that stem either from external body forces, (e.g. gravity, magnetic fields, etc...) or from particle interaction laws (e.g. LennardJones). For granular particles, these are typically contact forces (elastic, plastic, viscous, frictional), while for molecular simulations, forces typically stem from interaction potentials (e.g. LennardJones). The code has been developed extensively for granular applications, but could be adapted to include longrange interactions as well.
It was started by Anthony Thornton and Thomas Weinhart, and is currently actively developed by Thomas Weinhart, Anthony Thornton and Dinant Krijgsman with input from Stefan Luding and Onno Bokhove.
For more information see the MercuryDPM website.

Figure: Simulation of granular flow through a contraction with 400,000 particles. Two shocks are generated on either side of the contraction and there is interaction where the two shocks meet. The colour of the particles indicates the flow height.

Sintering – Modelling pressure, temperature, and timedependent contacts
A DFG project. Particles in contact (PiKo)
In most realistic situations, where particles come in contact, it can NOT be
assumed that the contact properties are independent of pressure, temperature
or time. Therefore, this project involves pressure, temperature, and
timedependent contact properties and their influence on the macroscopic
powder flow behavior. Sintering is chosen as one possible example and
starting point, where all these phenomena are relevant.
In realistic processes, a sintering process starts with many separate powder
particles that are, e.g., attracted by electrostatic forces, bound together
by capillary forces, or squeezed together by strong pressure. Leaving them
alone for long time, diffusion will set in and change the contact properties.
At elevated temperatures, the sintering works much faster and from the
originally isolated particles, a solid, possibly porous and fragile agglomerate is
formed.
The goal of this project is to model the particles in contact, before the
particles lose their identity. For this, temperature and pressuredependent
contact models have to be developed in parallel to contactmeasurements
(with M Kappl, Mainz). The manyparticle simulations will then be adapted to the
materials used and experimentally validated (with J Tomas, Magdeburg). As the
result of the project, the verified numerical model for the sintering process
of many particles will become available. This will then be used for the micro
macro transition in order to obtain better theoretical constitutive relations for
a macroscopic description based on the contactmechanics and physics.
More material:
Poster

Figure: Indenting of a weakly sintered granular bed. The sintering is so weak, that particle contacts easily break.
Rolling and torsion friction measured by rolling a particle along an inclined rail.

Computational multiscale modelling of superdispersed multiphase flows
A Strategic Innovative Project (SIP1) of the Institute of Mechanics, Processes and Control (IMPACT), Univ. of Twente
Developing good numerical models for dry granular flow is of interest in many industrial processes and geophysics. Granular material shows both solid and fluid behavior. Closed continuous models for granular flow only exist for certain cases, while Discrete Particle Models (DPM) are unfeasible for largescale simulations. Therefore I am working on a DG finite element model for heterogeneous multiscale modelling of polydisperse, nonuniform dry granular flows, which allows both efficient and reliable numerical simulations.

Figure: A rare view into the ironore melting furnace shows the inflow of pellets from an inclined, rotating chute (top left) during an inspection cycle. Improved control of the inflow of such granular matter isdesired by Corus (Photo courtesy: Corus).

A Posteriori Error Estimates of the DG Method for
Hyperbolic Systems
A posteriori error estimates are a useful tool to verify the
quality of ï¬nite element approximations and to control the
error in adaptive meshes. We apply the discontinuous Galerkin
method to ï¬rstorder linear hyperbolic systems in two and
three space dimensions. We explicitly write down the leading
error term and solve local ï¬nite element problems to obtain a
posteriori error estimates. We present convergence and
numerical results for problems from acoustics and
electromagnetism.
Collaborators: Slimane
Adjerid

Figure: hadaptive mesh refinement based on local error estimate. Source

Journal Articles

D. R. Tunuguntla, A. R. Thornton, T. Weinhart,
From discrete elements to continuum fields: Extension to bidisperse systems,
(submitted)
(arxiv).

S. Roy, S. Luding, T. Weinhart,
Micromacro transition and simpler contact models for wet granular materials,
(in prep.)

S. M. RubioLargo, F. AlonsoMarroquin, T. Weinhart, S. Luding, R. C. Hidalgo
Homogeneous cooling state of a system of 3D rod particles,
(submitted)

T. Weinhart, C. Labra, S. Luding, J. Ooi
Influence of coarsegraining parameters on the analysis of DEM simulation results,
(submitted)

K. Imole, D. Krijgsman, T. Weinhart, V. Magnanimo, C.B. Edgar, M. Ramaioli, S. Luding,
Experiments and Discrete Element Simulation of the Dosing of Cohesive Powders in a Simplified Geometry,
(submitted)

C.R. WindowsYule, T. Weinhart, D.J. Parker, A.R. Thornton,
The influence of thermal convection on density segregation in a vibrated binary granular system,
Physics Review E (2014)
(local copy).

WindowsYule, K.; Weinhart, T.; Parker, D.J.; Thornton, A.R.
Effects of system packing on the segregation behaviours of granular systems,
Physics Review Letters (2014)
(local copy).
 Slimane Adjerid, Thomas Weinhart,
Asymptotically Correct Discontinuous Galerkin error estimates for linear symmetric hyperbolic systems,
Applied Numerical Mathematics (2014)
(local copy).

R. Fuchs, T. Weinhart, J. Meyer, H. Zhuang, T. Staedler, X. Jiang and S. Luding
Rolling, sliding & torsion of micronsized silica particles  Experimental, numerical and theoretical analysis,
Granular Matter (2014)
(arXiv)

Weinhart, T., Hartkamp, R., Thornton, A.R., Luding, S.,
Coarsegrained local and objective continuum description of 3D granular flows down an inclined surface,
Phys. Fl. 25, 070605 (2013).

Thornton, A.R.; Weinhart, T.; Ogarko, V. and Luding, S.,
Multiscale modeling of multicomponent granular materials,
Computer Methods in Materials Science (2013). 13:2 p116 (Editor's choice).

Thornton, A.R., Weinhart, T., Luding, S., Bokhove, O.,
Friction dependence of shallow granular flows from discrete particle simulations ,
Eur. Phys. J. E 35:127 (2012).

Thornton, A.R., Weinhart, T., Luding, S., Bokhove, O.,
Modeling of particle size segregation: Calibration using the discrete particle method,
Int. J. Mod. Phys. C 23, 1240014 (2012).

Weinhart, T., Thornton, A.R., Luding, S., Bokhove, O.,
From discrete particles to continuum fields near a boundary,
Granular Matter 14(2), 289294 (2012).

Weinhart, T., Thornton, A.R., Luding, S., Bokhove, O.,
Closure Relations for Shallow Granular Flows from Particle Simulations,
Granular Matter 14(4), 531552 (2012).

R. Hartkamp, A. Ghosh, T. Weinhart and S. Luding,
A study of the anisotropy of stress in a fluid confined in a nanochannel,
J. Chem. Phys. 137, 044711 (2012).
 Slimane Adjerid, Thomas Weinhart,
Discontinuous Galerkin error estimation for linear symmetrizable hyperbolic systems,
AMS Journal of Mathematics of Computation, 80, 13351367 (2011).
 Slimane Adjerid, Thomas Weinhart,
Discontinuous Galerkin error estimation for linear symmetric hyperbolic systems,
Computer Methods in Applied Mechanics and Engineering, 198(3740), 31133129 (2009).
Other

T. Weinhart, D. Tunuguntla, A. R. Thornton, S. Luding
Physik der Lawinen,
(submitted).

Roy, S.; Luding, S.; Weinhart, T.,
Macroscopic bulk cohesion and torque for wet granular materials,
Proc. Conference for Conveying and Handling of Particulate Solids 2015,
(submitted).

Roy, S.; Luding, S.; Weinhart, T.,
Towards hydrodynamic simulations of wet particle systems,
WCPT7 Conf. Proc., in press (2014)
(local copy).

Weinhart, T., Luding, S., Thornton, A.R.,
From discrete particles to continuum fields in mixtures,
AIP Conf. Proc. 1542, 12021205 (2013)

Thornton, A.R.; Krijgsman, D.; de Voortwis, A.; Orgarko, O.; Luding, S.; Fransen, R.; Gonzalez, S.l Bokhove, O.; Imole, O.; Weinhart, T,
A review of recent work on the Discrete Particle Method at the University of Twente: An introduction to the open source package MercuryDPM,
Discrete Element Methods 6 (2013), Conference Proceedings.

A.R. Thornton, D. Krijgsman, R. Fransen, S. Gonzalez, D. Tunuguntla, A. ten Voortwis, S. Luding, O. Bokhove, T. Weinhart
MercuryDPM: Fast particle simulations in complex geometries,
EnginSoft Year 10, No. 1 (2013)
 Thornton, A.R., Weinhart, T., Bokhove, O., Zhang, B., van der Sar, D. M., Kumar, K., Pisarenco, M., Rudnaya, M., Savceno, V., Rademacher, J., Zijlstra, J., Szabelska, A., Zyprych, J., van der Schans, M., Timperio, V., Veerman, F. (2010) Modeling, optimization of algae growth.
Proceedings of the 72nd European Study Group Mathematics with Industry, 2529 Jan 2010, Amsterdam, Netherlands. pp. 5485. CWI.
 Weinhart, T.,
A Posteriori Error Analysis of the Discontinuous Galerkin Method for Linear Hyperbolic Systems of Conservation Laws,
PhD Thesis, Virginia Tech (USA), 2009.
 1820 September, 2013: Particles, Stuttgart, DE
 24 July, 2013: Swinbourne University, Melbourne, AUS
 18 July, 2013: University of Sydney, AUS
 812 July, 2013: Powders and Grains, Sydney, AUS
 7 May, 2013: University of Duisburg, DE
 712 April, 2013: EGU, Vienna, A
 2 April, 2013: Granular Workshop at DLR, Köln, DE
 3 March, 2013: PiKo Workshop, Siegen, DE
 17 January, 2013: DynSim, Hamburg, DE
 6 November, 2012: University of Edinburgh
 12 November 2012: EM symposium, Lunteren, NL
 12 October 2012: PiKo Workshop, Siegen, DE
 1013 September 2012: Conference for Conveying and Handling of Particulate Solids, Friedrichshafen, DE
 1013 July 2012: GRC Granular and granular fluid flow, Davidson, NC, USA (Poster)
 1718 January 2012: FOM, Veldhoven, NL
 13 January 2012: Burgersdag, Delft, NL
 26 October 2011: Particles 2011, Barcelona, ES
 23 October 2011: EM symposium, Lunteren, NL (Poster)
 27 September 2011: ISSI, Bern, CH
 11 April 2011: Bristol, UK
 3 April 2011: EGU 2011, Vienna (Poster)
 20 October 2010: FermatImpactGimfus, Sevilla, ES
 29 September 2010: SIP1 Workshop, Enschede, NL
 14 July 2010: ECCOMAS, Lisbon, PT (Poster)
 14 March 2010: Virginia Tech, Blacksburg, VA, US
University of Twente, Enschede
2014 (planned)
Advanced Programming in Engineering: lecturing 25% and grade.
Programming in Engineering: organize, lecture 50%.
Programming in Engineering summer course: organize, lecture 50%.
2013
Advanced Programming in Engineering: lecture 25% and grade.
Programming in Engineering: organized, lectured 50%.
Programming in Engineering summer course: organized.
2012
Advanced Programming in Engineering: lectured 25%, updated script and graded.
Programming in Engineering summer course: organized.
2011
Programming in Eng. summer course: organized, added material, lectured 50%, gave oral exams.
Programming in Engineering: lectured 50% and gave oral exams.
Advanced Programming in Engineering: lectured 25%, updated script and graded.
Particles to Continuum  MicroMacro Methods: lectured 25%
Complex Analyis: taught individual lecture.
Scientific Computation: tutored computer class and graded.
2010
Programming in Engineering summer course: lectured 50%, gave oral exams.
Advanced Programming in Engineering: lectured 25%, and graded.
Particles to Continuum  MicroMacro Methods: lectured 25%
Finite Elements: taught individual lectures.
Scientific Computation: tutored computer class and graded.
Virginia Polytechnic University, Blacksburg, VA, USA
2009
Integral Calculus Spring: lectured and assigned course grades, developed lesson plans and exams
2008
Integral Calculus Fall: lectured and assigned course grades, developed lesson plans and exams
Integral Calculus Spring: lectured and assigned course grades, developed lesson plans and exams
2007
Math Emporium: assisted math students in computer lab, administered online tests and quizzes.
Integral Calculus Fall: lectured and assigned course grades, developed lesson plans and exams
Integral Calculus Spring: lectured and assigned course grades, developed lesson plans and exams
2006
Differential Calculus: lectured and assigned course grades, developed lesson plans and exams, holding office hours, introducing programming in Mathematica.
Integral Calculus Fall: lectured and assigned course grades, developed lesson plans and exams
Integral Calculus Spring: lectured and assigned course grades, developed lesson plans and exams
2005
Math Lab: tutored for undergraduate math courses. Vector Geometry Recitation Fall: taught weekly recitation class supplementing lecture, graded
Vector Geometry Recitation Spring: taught weekly recitation class supplementing lecture, graded
2004
Vector Geometry Recitation Fall: taught weekly recitation class supplementing lecture, graded
Vector Geometry Recitation Spring: taught weekly recitation class supplementing lecture, graded
Math Emporium: assisted math students in computer lab, administered online tests and quizzes.
2003
Math Emporium: assisted math students in computer lab, administered online tests and quizzes.

Dr. Thomas Weinhart  Z117, Horstring, P.O. Box 217, 7500 AE Enschede, NL. email: t.weinhart@utwente.nl. +31 53 489 3301 

Last updated: Nov. 9, 2011 
(C) All rights reserved with Thomas Weinhart 

