Elmer under the hood

You never need this page to build and solve models. It explains what Elmer Studio does on your behalf, for checking its work, running a case outside the GUI, or reporting a problem.

From model to Elmer case

When you compute a study, each run (each parameter value of a sweep) gets its own case folder:

File Contents

File	Contents
`case.sif`	The Elmer solver input file: header, simulation settings, constants, bodies, materials, body forces, initial conditions, equations, solvers and boundary conditions.
`ELMERSOLVER_STARTINFO`	Tells ElmerSolver which `.sif` to run.
`mesh/`	The Elmer mesh: `mesh.header`, `mesh.nodes`, `mesh.elements`, `mesh.boundary`, `mesh.names`.
`results/`	Elmer’s output, as VTU files (`.pvtu` for parallel runs).
`solver.log`	ElmerSolver’s complete output.
`meta.json`, `mesh.npz`	What Elmer Studio needs to read the results back: the study, sweep values, selections and the mesh topology.

case.sif

The Elmer solver input file: header, simulation settings, constants, bodies, materials, body forces, initial conditions, equations, solvers and boundary conditions.

ELMERSOLVER_STARTINFO

Tells ElmerSolver which .sif to run.

mesh/

The Elmer mesh: mesh.header, mesh.nodes, mesh.elements, mesh.boundary, mesh.names.

results/

Elmer’s output, as VTU files (.pvtu for parallel runs).

solver.log

ElmerSolver’s complete output.

meta.json, mesh.npz

What Elmer Studio needs to read the results back: the study, sweep values, selections and the mesh topology.

Study Open Case Folder opens the folder of the selected study. The folders live in a temporary working directory while the model is open. Saving the model stores the solutions in the .esm file. The working directory is removed when you close the model.

How the model is translated

Model Elmer

Model	Elmer
Domains with the same material and physics features	Bodies, each with its `Material`, `Equation`, `Body Force` and `Initial Condition`
Boundary features	`Boundary Condition` sections on the selected boundaries (later features override earlier ones)
Physics interfaces	`Solver` sections: the Elmer module, its variable, linear and nonlinear settings, and the extra keywords you added
Multiphysics couplings	Keywords that connect the solvers (for example a Joule heat source), solved in one steady-state or time loop
Parameters	Numbers in SI, written into the expressions
Expressions that depend on space, time or the solution	MATC functions (`Variable … Real MATC "…"`), with `stmin`/`stmax` helpers for two-argument min/max
Interpolation functions	Elmer tables (`Real` with pairs of values)
Study step	`Simulation Type` Steady state / Transient / Scanning, eigen analysis settings

Domains with the same material and physics features

Bodies, each with its Material, Equation, Body Force and Initial Condition

Boundary features

Boundary Condition sections on the selected boundaries (later features override earlier ones)

Physics interfaces

Solver sections: the Elmer module, its variable, linear and nonlinear settings, and the extra keywords you added

Multiphysics couplings

Keywords that connect the solvers (for example a Joule heat source), solved in one steady-state or time loop

Parameters

Numbers in SI, written into the expressions

Expressions that depend on space, time or the solution

MATC functions (Variable … Real MATC "…"), with stmin/stmax helpers for two-argument min/max

Interpolation functions

Elmer tables (Real with pairs of values)

Study step

Simulation Type Steady state / Transient / Scanning, eigen analysis settings

The Elmer solver behind each interface is listed on Physics interfaces. Where it matters, Elmer Studio also chooses:

the linear solver: direct (UMFPACK) for small models, iterative (BiCGStab with ILU) for large 3D ones;
nonlinear iteration when a property or a boundary value depends on the solution;
Newton linearization for electrode kinetics, with line search (see Electrochemistry);
boundary fluxes from reaction loads, which are exactly conservative, for heat flow and electrode currents.

Seeing and exporting the input

Study Show Elmer Input File shows the .sif of a study without running it.
File Export Elmer Case (also on the Developer tab) writes a self-contained case folder: mesh/, case.sif and ELMERSOLVER_STARTINFO. Run it anywhere with Elmer installed:
```
cd my_case
ElmerSolver case.sif
```

The exported case is plain Elmer, with nothing specific to Elmer Studio, so you can hand it to colleagues who use Elmer directly, run it on a cluster, or study and edit it.

Adding Elmer keywords the GUI doesn’t have

Two places take raw Elmer keywords:

the physics interface’s Additional Elmer solver keywords, for its Solver section;
a Solver node’s Additional SIF keywords under the study’s Solver Configurations.

The lines are appended verbatim, so any Elmer feature can be reached without leaving the GUI.

The Elmer installation

File Preferences… (or Developer Elmer Installation) shows which Elmer is used and lets you change it. Elmer Studio supports:

the official CSC installers and distribution packages;
MPI builds (ElmerSolver_mpi) for parallel runs;
a from-source CMake build tree of elmerfem. Elmer Studio finds the solver, its modules and runtime libraries inside it. This is how you use a newer Elmer, or one with your own changes, without installing it.

Detect reports the solver version and what it can do beyond Elmer 9.0 (for example the diffusion-current term of StatCurrentSolve, or a Fortran compiler for user solvers). Elmer Studio uses such features only when they are present.

When Elmer stops with an error

The Messages pane quotes Elmer’s own ERROR:: line, and Log has the full output. The case folder keeps the .sif, the mesh and solver.log. Those three files are what to attach to a bug report.