# Status This page compares what femforge implements today with what its pipeline interfaces and its first solver backend, Elmer, offer. A row shows Implemented when the public config reaches it and the user guide documents it, Partial when a module or interface exists that the config cannot reach or the docs do not cover, and Not started when femforge has no model for it. ## Pipeline interfaces Each stage runs behind an interface, and one backend fills each interface today. [Concepts]() walks through the pipeline that connects them. | Stage | Today | Interface | What a new implementation needs | | --- | --- | --- | --- | | Geometry | A tagged STEP file from any CAD, or a Build123dGeometry subclass | GeometryArea | A `build_step(path)` that writes a STEP whose body names carry the tags. | | Mesh backend | GmshMesher in process, WorkerMesher in a child process | MeshBackend | A `mesh(job, out_dir)` that turns a `MeshJob` into Elmer mesh files and a `MeshReport`. | | Solver backend | Elmer, through the typed solver stack in `femforge.elmer.config` and the sif writer | None yet | Conditions and materials emit Elmer keywords directly, so a second solver needs a solver-neutral interface first; see [Solver objects](). | | Solver execution | NativeElmer for serial solves, DockerElmer for serial and MPI solves | ExecutionBackend | The `grid_convert`, `grid_partition` and `solve` methods and the `partitioned` flag of `src/femforge/elmer/runtime/backend.py`. | | Optimization | GridSearch, `find_max_current`, and the `convergence_ladder` and `richardson` mesh-convergence helpers in `femforge.run` | Parameterization, Objective, DriverLike | A search that evaluates configs from a `Parameterization` through a `DriverLike` and records them in a Study. | | Workbench | The trame workbench in `packages/femforge-workbench` | The `femforge.workbenches` entry point group | A function that returns a `Split`, declared as a WorkbenchSpec; see [Workbench](). | ## Frames Elmer names eight coordinate systems. femforge maps two of them to a frame; see [Frames](). | Elmer coordinate system | femforge | Status | | --- | --- | --- | | Cartesian 3D | Solid | | | Axi Symmetric | Axisymmetric | | | Cartesian 1D | | | | Cartesian 2D | | | | Polar 2D | | | | Polar 3D | | | | Cylindric | | | | Cylindric Symmetric | | | `CoordinateSystem` in `femforge.elmer.config` already names `Cylindric`, `Cylindric Symmetric` and `Polar` as keyword values, but no frame maps a model onto them. A new frame needs a model in `src/femforge/common/frame.py`, a geometry conversion in `src/femforge/geometry/frame.py` and a case in `Physics.in_frame`. ## Physics modules The rows follow the chapters of the Elmer Models Manual. The femforge column names the Physics preset or the module that wires the Elmer module. A `Not started` module can still run through GenericSolver, which writes a hand-built solver block whose keywords femforge does not check. [Conditions and physics]() documents each preset. ### Heat and thermal | Elmer module | Solves | femforge | Status | | --- | --- | --- | --- | | `HeatSolve`, `HeatSolveVec` | Heat conduction, with optional convection, radiation and temperature-dependent properties. | `Physics.THERMAL`, `Physics.JOULE_HEATING` | | | `PhaseChangeSolve` (transient) | The moving front between a liquid and a solid phase over time. | | | | `PhaseChangeSolve` (steady state) | The steady position of a liquid-solid phase boundary. | | | ### Electromagnetics | Elmer module | Solves | femforge | Status | | --- | --- | --- | --- | | `StatCurrentSolve` | The potential and current density in a conductor, and the Joule losses they produce. | `Physics.CURRENT_CONDUCTION`, `Physics.JOULE_HEATING` | | | `MagnetoDynamics` | The 3D magnetic field in A-V form on edge elements, static, time-harmonic or transient. | `Physics.MAGNETOSTATICS`, `Physics.COIL_MAGNETOSTATICS`; static only | | | `MagnetoDynamics2D` | The magnetic field of planar or axisymmetric problems from one component of the vector potential. | `Physics.MAGNETOSTATICS_2D`; axisymmetric static only | | | `CoilSolver` | A consistent current distribution through a coil, as a source for the magnetic solvers. | `Physics.COIL_MAGNETOSTATICS` | | | `StatElecSolve` | The electrostatic potential and field in dielectrics and conductors. | `Physics.ELECTROSTATICS` | | | `CircuitsAndDynamics` | Circuit equations coupled to a magnetoquasistatic model. | | | | `VectorHelmholtz` | Time-harmonic electromagnetic waves at high frequency. | | | | `EMWaveSolver` | Time-domain electromagnetic waves on edge elements. | | | | `MagneticSolve` | The magnetic induction equation in a conducting fluid. | | | | `StatElecBoundary` | Electrostatics between nearly parallel surfaces, reduced to one dimension. | | | | `PoissonBoltzmannSolve` | The electric potential with free charges that follow a Boltzmann distribution. | | | | `FourierLoss` | Electromagnetic losses from an on-the-fly Fourier series, in the Steinmetz style. | | | | `ElectricForce` | The electrostatic force on a surface from a solved potential. | | | | `StatMagSolve` | Axisymmetric magnetoquasistatics; Elmer marks it obsolete. | | | `Physics.ELECTROSTATICS` has a preset and documentation. `FixedPotential` feeds it only when its `physics` field is set to `ELECTROSTATICS`, and no guide page, example or test exercises that path. ### Structural mechanics | Elmer module | Solves | femforge | Status | | --- | --- | --- | --- | | `StressSolve` | Small displacements and stresses of a linear elastic solid. | `Physics.LINEAR_ELASTICITY` | | | `ElasticSolve` | Large deformations of an elastic solid. | | | | `ShellSolver` | Deformations of thin curved shells. | | | | `Smitc` | Bending of linear elastic plates. | | | | `BeamSolver3D` | Forces and moments in elastic beams. | | | | `SpringAssembly` | Point springs and masses added to a structural model. | | | | `RigidBodyReduction` | A displacement problem reduced by treating some blocks as rigid. | | | `Physics.LINEAR_ELASTICITY` is a scaffold: no condition targets it, and the material model has no Poisson ratio. ### Fluids | Elmer module | Solves | femforge | Status | | --- | --- | --- | --- | | `FlowSolve` | Incompressible or compressible viscous flow with the Navier-Stokes equations. | | | | `AdvectionDiffusion` | Transport of a species or scalar by convection and diffusion. | | | | `AdvectionReaction` | Transport of a passive scalar by a flow, with a reaction rate. | | | | `ReynoldsSolver` | Pressure in a thin fluid film. | | | | `Electrokinetics` | Flow of an electrolyte in small channels driven by electric surface charges. | | | | `ParStokes` | Steady incompressible flow with block preconditioning for large systems. | | | | `Stokes` | Incompressible flow in the rotational form of the Navier-Stokes equations. | | | | `LevelSet` | The position of a free surface tracked with a level-set function. | | | | `FreeSurfaceSolver` | A kinematic free surface, with limiters. | | | | `FreeSurfaceReduced` | A free surface found from a constant flux condition. | | | | `StructureFlowLine` (free surface) | A steady free surface in drawing and pulling processes, found along streamlines. | | | | `ArtificialCompressibility` | A stabilizing compressibility term for loosely coupled fluid-structure interaction. | | | | `FluidicForce` | The pressure and viscous force a flow exerts on a surface. | | | | `RichardsSolver` | Flow through variably saturated porous media. | | | | `ArteryOutlet` | An outlet boundary condition for blood flow in elastic arteries. | | | ### Acoustics and waves | Elmer module | Solves | femforge | Status | | --- | --- | --- | --- | | `HelmholtzSolve` | Time-harmonic acoustic pressure with the Helmholtz equation. | | | | `Acoustics` | Linearized Navier-Stokes acoustics with viscous and thermal losses, in the frequency domain. | | | | `WaveSolver` | A generalized scalar wave equation in the time domain. | | | | `CompressibleNS` | Large-amplitude, nonlinear waves in air. | | | | `HelmholtzBEM` | The Helmholtz equation with the boundary element method. | | | ### Particles and other | Elmer module | Solves | femforge | Status | | --- | --- | --- | --- | | `ParticleDynamics` | Trajectories of particles under forces and fields. | | | | `ParticleAdvector` | Diffusion-free advection of fields by tracking particles backward in time. | | | | `StructureFlowLine` (moving mesh) | Ordinary differential equations along an extruded mesh that moves with a draw velocity. | | | | `ModelMixedPoisson` | The Poisson equation with the flux as a second unknown. | | | | `PoissonBEM` | The Laplace equation with the boundary element method. | | | | `BatterySolver` | Charge and species transport in a lithium-ion cell. | | | | `DFTSolver` | Electronic structure with density functional theory; experimental in Elmer. | | | ### Utilities | Elmer module | Solves | femforge | Status | | --- | --- | --- | --- | | `SaveScalars` | Reductions and integrals of fields, written as scalar values to a file. | `src/femforge/elmer/config/output/save_scalars.py` | | | `ResultOutputSolve` | Field output in VTU and other formats. | `src/femforge/elmer/config/output/result_output.py` | | | `MeshSolve` | Mesh deformation that follows moving boundaries. | | | | `NonphysicalMeshSolve` | Mesh deformation where the mesh velocity does not matter. | | | | `RigidMeshMapper` | Rigid rotation and translation of mesh bodies. | | | | `StructuredMeshMapper` | A structured mesh fitted between given top and bottom surfaces. | | | | `ElementStats` | Quality statistics of the mesh elements. | | | | `StreamSolver` | Streamlines of a flow field. | | | | `FluxSolver` | The flux of a Poisson-type field, such as heat flux. | | | | `VorticitySolver` | The curl of a vector field. | | | | `DivergenceSolver` | The divergence of a vector field. | | | | `ScalarPotentialSolver` | The scalar potential whose gradient matches a given flux. | | | | `FilterTimeSeries` | Averages and Fourier filters over time-series results. | | | | `DataToFieldSolver` | A smooth field fitted to scattered data. | | | | `ProjectToPlane` | A 3D field projected onto a plane. | | | | `StructureProjectToPlane` | A field on a structured mesh projected onto its base surface. | | | | `FindOptimum` | New design parameters from a cost function, inside one Elmer run. | | | | `SaveLine` | Field values along lines through the mesh, written to a file. | | | | `SaveMaterials`, `SaveBoundaryValues` | Material and boundary parameters stored as fields. | | | | `SaveGridData` | Field values on a uniform Cartesian grid. | | | | `Isosurface` | Isosurfaces or isolines extracted to reduce output. | | | | `Elmer2OpenFoamIO`, `OpenFOAM2ElmerIO` | Field exchange with OpenFOAM through files. | | | | `Probes` | Integrals of expressions over bodies. | | | | `GmshOutputReader` | Fields read from a gmsh result file. | | | | `ReloadData` | Earlier results loaded back during a run. | | | | `ReloadInput` | The solver input reloaded while a run is in progress. | | | | `GridDataReader` | NetCDF grid data interpolated onto the mesh. | | | | Linear constraints (`SolverUtils`) | Linear constraints on a solve, enforced with Lagrange multipliers. | | | | `XdmfWriter` | Parallel results written as Xdmf and HDF5. | | | femforge runs its sweeps and optimizations outside Elmer, so it uses none of the Elmer optimization utilities. ## Solver capabilities The rows follow the chapters of the ElmerSolver Manual that describe a capability a user switches on. The chapters on fundamentals, the input file format, compilation and programming, and the appendices on file formats and element definitions are background and have no row. | Elmer capability | Solves | femforge | Status | | --- | --- | --- | --- | | Linear system methods | Direct, Krylov and multilevel solvers with their preconditioners. | LinearSystem fields on each solver | | | Nonlinear system options | Picard and Newton iteration, relaxation and convergence criteria. | NonlinearSystem fields on each solver | | | Parallel runs | Mesh partitioning and MPI solves. | DockerElmer with `mpi_processes`; see [Elmer: Native and Docker]() | | | Restart | A run that starts from saved solutions. | `SimulationSettings.output_file` writes a restart file; nothing reads one back | | | Time integration | Transient solves with BDF, Newmark and other schemes. | `SimulationType.TRANSIENT` and `TimesteppingMethod`; every preset is steady state | | | Dirichlet conditions and limiters | Fixed values on boundaries, and soft limits on a solution. | Fixed values through `FixedTemperature` and `FixedPotential`; no limiters | | | Generic solver utilities | Solver activation, variable naming, exported variables and passive elements. | `exec_solver` and `variable` fields on SolverBase | | | Eigenvalue problems | Modes and eigenfrequencies of a system. | | | | Shared boundary conditions | Periodic, mortar and conforming conditions between boundaries. | | | | Linear constraints | Extra linear equations that couple degrees of freedom. | | | | Constraint modes | The response to unit loads on chosen boundaries, as in a lumped model. | | | | Nodal loads | Point loads, and the reaction loads of a solved system. | | | | Block-matrix coupling | Tightly coupled multiphysics solved as one block system. | | | | Meshing utilities | Coordinate transformation, mesh multiplication, extrusion and discontinuous interfaces inside Elmer. | | | | Adaptive solution | Mesh refinement driven by an error estimate. | | | | Higher-order elements | p-elements of higher polynomial order. | | | ## Conditions and materials Every condition and material below is implemented. [Conditions and physics]() and [Materials]() document them. | Condition | Feeds | Target | | --- | --- | --- | | Magnetization | `MAGNETOSTATICS`, `MAGNETOSTATICS_2D`, `COIL_MAGNETOSTATICS` | body | | ForceComponent | `MAGNETOSTATICS`, `MAGNETOSTATICS_2D`, `COIL_MAGNETOSTATICS` | body | | CurrentDensity | `MAGNETOSTATICS_2D` | body | | CoilDrive | `COIL_MAGNETOSTATICS` | body | | CoilTerminal | `COIL_MAGNETOSTATICS` | outer shell | | FixedTemperature | `THERMAL`, `JOULE_HEATING` | boundary | | HeatFlux | `THERMAL`, `JOULE_HEATING` | boundary | | Convection | `THERMAL`, `JOULE_HEATING` | outer shell | | HeatSource | `THERMAL`, `JOULE_HEATING` | body | | FixedPotential | `CURRENT_CONDUCTION`, `JOULE_HEATING` | boundary | | JouleHeat | `JOULE_HEATING` | body | | Material | Tag | Notable properties | | --- | --- | --- | | Air | `Air` | μr = 1, near-zero conductivity | | Copper | `Copper` | Temperature-dependent conductivity | | N52, N42 | `N52`, `N42` | Temperature-dependent remanence and coercivity | | FR4 | `FR4` | εr = 4.5, glass transition temperature | | Steel\_1080 | `Steel1080` | Nonlinear B-H curve, or a linear μr | | Steel\_316 | `Steel316` | μr = 1.008, effectively non-magnetic | ## Picking a task A row marked or is a candidate task. [Contributing]() sets up a development checkout, and [Solver objects]() shows how a solver model, a preset and a condition slot into the sif writer. Open or claim a task on the [GitHub issues page]().