Elmer

Franz Pichler

Virtual Vehicle Competence Center

2011-10-05

2011-10-05 Elmer 1 / 26

Gliederung

Elmer, what is that?

Solvers

Maybe an example?

2011-10-05 Elmer 2 / 26

Gliederung

Elmer, what is that?

Solvers

Maybe an example?

2011-10-05 Elmer 3 / 26

ELMER

Open Source Finite Element Software for Multiphysical ProblemsProject: http://www.csc.fi/english/pages/elmer

Forum: http://www.elmerfem.org

2011-10-05 Elmer 4 / 26

What can Elmer do?

I solving PDE’s with Finite Element Method

I Specializes on coupling of multyphysical problems (CouplingEquations)

I Coupling happens by Iteration of Solvers

I Works on HPC machines

2011-10-05 Elmer 5 / 26

What are the main parts of Elmer?

I ElmerGrid - Pre-Processor, Can convert/create/partitionmeshes

I ElmerGUI - GUI for setting up easy models and basis for morecomplicated models

I ElmerPost - Post-processor for Visualisation of results

I ElmerModels - Solvers of some important PDE’s and muchmore

2011-10-05 Elmer 6 / 26

HPC Capabilities

I Elmer works on Element formulation

I Local Matrices and rhs are assembled per Element

I Very little to no adjustment of the serial solvers needed to beused in parallel

I Uses mpi and supports some interfaces to the parallelenvironment

2011-10-05 Elmer 7 / 26

Some Technical Details:

I written in Fortran

I binaries available

I Compilation and Linking quite easy

I Uses Hypre, MUMPS, Metis,...

2011-10-05 Elmer 8 / 26

Gliederung

Elmer, what is that?

Solvers

Maybe an example?

2011-10-05 Elmer 9 / 26

Direct Solvers:

I Banded (Lapack)

I Umfpack (Multifrontal)

I MUMPS (Multifrontal in parallel)

2011-10-05 Elmer 10 / 26

Iterative Solvers: The Krylov subspace methods available inElmerSolver are

I Conjugate Gradient (CG)

I Conjugate Gradient Squared (CGS)

I Biconjugate Gradient Stabilized (BiCGStab)

I BiCGStab(l)

I Transpose-Free Quasi-Minimal Residual (TFQMR)

I Generalized Minimal Residual (GMRES)

I Generalized Conjugate Residual (GCR)

2011-10-05 Elmer 11 / 26

The Multigrid Methods are:

I GMG

I AMG

2011-10-05 Elmer 12 / 26

Preconditioners:

I None

I Diagonal

I ILUn, where the literal n may take values 0,1,...,9.

I ILUT

I Multigrid

2011-10-05 Elmer 13 / 26

Meshing Utilities:

I create simple 1D,2D,3D meshes with ElmerGrid

I convert meshes from known file formats to Elmer format

2011-10-05 Elmer 14 / 26

Gliederung

Elmer, what is that?

Solvers

Maybe an example?

2011-10-05 Elmer 15 / 26

Simple Example:Heat equation in a battery cell. The components of the battery are:

1. A passive housing Ωhouse

(gray)

2. A battery cell Ωcell (blue)

3. The electric ConductorsΩcond (brown/red)

2011-10-05 Elmer 16 / 26

The equation:

−∇ · (κ∇T ) = f

T = 270, x ∈ ΓD

f =

500, x ∈ Ωcell

1000, x ∈ Ωcond

0, else

2011-10-05 Elmer 17 / 26

Steps in Elmer (Possibility)

I Set up Model in ElmerGui

I Generate SIF File (input for Solver)

I Post-Process via ElmerPost

2011-10-05 Elmer 18 / 26

Refine Example: Couple “HeatSolver“ with “StaticCurrentSolver“The equation:

−∇ · (κ∇T ) = f

−∇ · (σ∇φ) = 0

T = 270, x ∈ ΓD

φ = 0, x ∈ ΓP1

φ = 10, x ∈ ΓP2

f = ∇φ · σ∇φ

2011-10-05 Elmer 19 / 26

Steps in Elmer (Possibility: Weak Coupling)

I Modify SIF File of the first example

I Add StaticCurrentSolver Section

I Add Keyword Joule Heat in Body Force

I Add ResultOutputSolver for VTK/VTU File output

I Post-Process via Paraview

2011-10-05 Elmer 20 / 26

Parallelization:

I Install with mpi (if not precompiled allready)

I Partition with ElmerGrid

I Adjustment of solvers (Not needed in Standard Cases)

I mpirun -np NP ElmerSolver

2011-10-05 Elmer 21 / 26

Installation:

I Use: svn co https://elmerfem.svn.sourceforge.net/

svnroot/elmerfem/trunk

to get trunk version

I Adjsut your Configure options:I modules="matc umfpack mathlibs elmergrid meshgen2d eio hutiter fem"

for m in $modules; do

cd $m ;\

./configure --prefix=/work/elmer_64\

--with-mpi=yes\

--with-64bits=yes\

--with-mpi-dir=/usr/local/lib\

--with-blas="/usr/lib64/libblas.so.3.0.3"\

--with-lapack="/usr/lib64/liblapack.so.3.0.3"\

--with-hypre="-L$HYPRE/lib -lHYPRE";

make -j2; make install ;

cd ..

done

2011-10-05 Elmer 22 / 26

Partition:

I Put mesh files in directory meshdir

I Type: ElmerGrid 2 2 meshdir -partition nx ny nz

I Using metis: ElmerGrid 2 2 meshdir -metis algorithm

NP

2011-10-05 Elmer 23 / 26

The Example:

I Using the metis PartGraphkway

I ElmerGrid 2 2 meshdir -metis 8 3

2011-10-05 Elmer 24 / 26

Solver Adjustment:

I None needed in that case

2011-10-05 Elmer 25 / 26

0 5 10

20

40

60

80

Number of Processors

Tim

e

0 5 10

100

200

300

400

2011-10-05 Elmer 26 / 26