an open source cfd-dem...

An Open Source CFD-DEM PerspectiveChristoph Goniva

Christoph KlossAlice Hager

Stefan Pirker

Christian Doppler Laboratory on Particulate Flow ModellingJohannes Kepler University Linz

www.cfdem.com | www.particule-flow.at

CD-Laboratory on Particulate Flow Modelling www.particulate-flow.atwww.cfdem.com

An Open Source CFD – DEM PerspectiveContents

1. Introduction of the Laboratory

2. Motivation

3. The Open Source code LIGGGHTS / LAMMPS

4. CFD – DEM coupling

5. Validation example


An Open Source CFD – DEM PerspectiveIntroduction of the lab

3

Founded in 2009 by Dr. Stefan Pirker at the Johannes Kepler University, Linz, Austria.

Governmental funding (50-70%) for application oriented fundamental research based on existing knowledge on particulate flows at the Institute of Fluid Mechanics and Heat Transfer of the JKU.

Our research focus covers: (a) solids charging, (b) offgas scrubbing, (c) industrial dust recycling, (d) sedimentation & erosion and (e) trickling beds

Current Industrial partners: Siemens VAI Metals Technologies, voestalpine Stahl, voestalpine Donawitz,Polysius (ThyssenKrupp group)


Industrial Partners

CD-Laboratory onParticulate Flow Modelling

Offgas Scrubbing

Solids Charging

Industrial Dust Recycling

Associated research

Sedimentation & Erosion

Tickling Bed

An Open Source CFD – DEM PerspectiveIntroduction of the lab

CD-Laboratory on Particulate Flow Modelling www.particulate-flow.atwww.cfdem.com 5

An Open Source CFD – DEM PerspectiveMotivation

Many applications require coupled CFD-DEM simulations !

Unfortunately, the CFD-DEM Approach is CPU intensive …

An efficient CFD-DEM solver is on need

Fast solver (both CFD and DEM)

Efficient parallelisation

Low license fees

Open access to source code

GPU acceleration for DEM is desirable to handle industrial scale processes

OpenFoam is already established as leading Open Source CFD toolbox…

LIGGGHTS is a parallel efficient DEM solver


An Open Source CFD – DEM PerspectiveLAMMPS / LIGGGHTS

LAMMPS =Large Atomic and Molecular Massively Parallel Simulator

OpenSource under GPL, provided by Sandia National Laboratories since themid 90‘s (http://lammps.sandia.gov/)

Widely used (over 500 journal publications 2000-2009 using LAMMPS)see http://lammps.sandia.gov/papers.html

LAMMPS has potentials for soft materials (biomolecules, polymers), solid-state materials (metals, semiconductors) and coarse-grained systems. It can be used to model atoms or, more generically, as a parallel particle simulator at the atomic, meso, or continuum scale.

LAMMPS is a C++ code, it runs on single processors or in parallel using message-passing techniques and a spatial-decomposition of the simulation domain. The code is designed to be easy to modify or extend with new functionality.

It is very fast and also used on huge clusters (e.g. on Sandia Red Storm with 16k Quadcore nodes, simulations with 2 billion particles performed)


Currently, LAMMPS offers a fast and efficient “GRANULAR” package for doing DEM simulations. Thereby, we profit from the fact that there are physicaland algorithmic analogies between DEM and MD

The key functionalities of this LAMMPS package are:

Pairwise interaction styles: Hooke and Hertz contact laws

with optional friction

Granular walls: (Hooke and Hertz, with optional friction) for

geometric primitives (box, cylinder)

Shear history for pairwise interaction and granular walls

An Open Source CFD – DEM PerspectiveLAMMPS / LIGGGHTS


The key functionalities of this package are (continued):

A function to insert/pour a stream of material into a

geometrical region

Functions to introduce gravity , freeze particles

and exert Stokes drag

Multibody dynamics which can be modified to use it

for handling of non-spherical particles

With pair style “hybrid/overlay”, other LAMMPS functionalities can be

added easily (e.g. adding bonds, point charges, dipole moments,...)

An Open Source CFD – DEM Perspective LAMMPS / LIGGGHTS


LIGGGHTS application example:



Goals of the CFDEM Project:

Creating a CFD-DEM framework for high performance computing

Make LAMMPS feasible for industrial applications

LIGGGHTS =

LAMMPS IMPROVED FOR GENERAL GRANULAR AND

GRANULAR HEAT TRANSFER SIMULATIONS

WWW.LIGGGHTS.COM | WWW.CFDEM.COM



The following challenges have been tackled with LIGGGHTS:

Feature LAMMPS LIGGGHTS 1.0 Complex wall import from CAD No YesImproved pair style No YesMoving mesh No YesPour nonspherical clumps(multisphere method)

No In progress...

Macroscopic cohesion model No YesHeat transfer model No YesParticle bonds with torques No In progress...Wall Stress Analysis No Yes6 dof solver No Yes



DEM with force on particles comingfrom CFD

f1

f2 f3

f4

= +

CFD with adaptedvoidfraction and momentum sources

-(f1 + f2)-(f3 + f4)

αf,1 αf,2

12

An Open Source CFD – DEM Perspective CFD – DEM coupling

Theoretical background:


( )( ) ( ) ( ) ( ) guuKuu

u

u

ffffffff

ffff

pt

t

ραααραρα

ραρα

+⋅∇+−−∇−=⋅∇+∂

∂

=⋅∇+∂

∂

τsffsfff

f 0

Navier-Stokes equations for the fluid in presence of a granular phase

αf fluid volume fractionuf fluid velocityτ, p stress tensor, pressureρf fluid densityKfs fluid solid momentum exchange term

comprises drag force, Magnus and Saffman force, virtual mass force,...

13




( )( )

.75.1150

Re15.01Re

24

,43

2

2

687.0

65.2

p

fs

pf

fs

pfpf

d

fp

ffpd

C

C

dd

d

pfsl

pfsl

uuK

,

uuK

−+=

+=

−= −

ρα

αμα

αα

αραα

Example for fluid solid momentum exchange Kfs :Gidaspow (1992): Hydrodynamics of Circulating Fluidized Beds, Kinetic Theory Approach. In Fluidization VII, Proceedings of the 7th Engineering Foundation Conference on Fluidization, pages 75‐82

14



:8.0>fα

:8.0≤fα


An Open-Source CFD – DEM Perspective„LammpsFoam“

flow data

particle datainit

end

LIGGGHTSOpenFoamSolver


An Open Source CFD – DEM Perspective Implementation

DEM solver calculates100 time-steps,

and transfers particle data to CFD solver

CFD solver calculates1 time-step

CFD solver fetches DEM particle data

CFD solver searches cell each particle is in

CFD solver transfers drag forces to DEM

start

CFD solver calculates volume fraction and momentum coupling


An Open-Source CFD – DEM PerspectiveImplementation

“Chimera” approach for momentum exchange

mesh for CFDcalculations

mesh for exchange fieldsKsl , α

DEM domain


An Open-Source CFD – DEM PerspectiveValidation example

Fluid boundary conditions Inital particle packing

Pressure drop and onset of fluidization in a cylindrical granular bed:

uf 0 – 0.02 m/sg 9.81 m/s2

μf 1.5 e-4 m2/sρs 200 kg/m3

ds 0.001 m (10000 particles)



validation case, onset of fluidization

inlet velocity void fraction


pressure drop


according to analytics, the minimum fluidization velocity is at 0.012 m/s


Performance:

excessive performance tests have not yet been carried out, a first hint:

10000 particles

1h for 1s simulation time

on 2 2.4 GHz processors



Fluid boundary conditions Inital particle packing

Partly fluidized bed (inhomogeneous velocity BC):




Partly fluidized bed (inhomogeneous velocity BC):

an open source cfd-dem...

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