Overview

Ethos

The solids4foam project aims is to develop an OpenFOAM toolbox for solid mechanics and fluid-solid interactions that is:

• intuitive to use for new users
• easy to understand at the case and code level
• straightforward to maintain
• uncomplicated to extend

In addition, the toolbox aims to be compatible with all major OpenFOAM forks.

How the Pieces Fit Together

There is one solver, solids4Foam, and it contains no details of the physics or the discretisation. Instead it creates a run-time selectable physicsModel and advances it in time. The type entry in constant/physicsProperties chooses one of three families:

A solid model solves the momentum equation in a solid domain. The available models differ in whether the geometry is linear or nonlinear, whether a total or updated Lagrangian formulation is used, whether the discretisation is cell-centred or vertex-centred, and whether the solution algorithm is segregated, coupled or explicit.

A fluid model solves the flow equations; most are ports of a standard OpenFOAM solver into class form, for example pimpleFluid from pimpleDyMFoam and interFluid from interDyMFoam.

A fluid-solid interface owns one fluid model and one solid model and implements the partitioned coupling algorithm between them, for example fixedRelaxationCouplingInterface, AitkenCouplingInterface, IQNILSCouplingInterface, weakCouplingInterface and oneWayCouplingInterface. The differences between these are explored in tutorial 4.

The constitutive behaviour of a solid is kept separate from the solid model that uses it, so the two can be varied independently: constant/mechanicalProperties selects one or more mechanicalLaw objects, which return the stress for a given deformation, and constant/thermalProperties does the same for thermal behaviour.

Standard solvers in OpenFOAM can differ significantly between OpenFOAM forks.
solids4foam aims to include the fork-specific solver versions, e.g. when using
OpenFOAM-v2012, `pimpleFluid` is a port of `pimpleDyMFoam` from OpenFOAM-v2012.

Run-time post-processing is provided by the function objects, and the internal structure of the library is described under under the hood.

Toolbox Structure

The solids4foam toolbox follows the OpenFOAM structure:

solids4foam
├── Allwclean
├── Allwmake
├── README.md
├── ThirdParty
├── ...
├── applications
│   ├── scripts
│   ├── solvers
│   │   └── solids4Foam
│   ├── test
│   └── utilities
├── optionalFixes
├── src
│   ├── RBFMeshMotionSolver
│   ├── abaqusUMATs
│   ├── blockCoupledSolids4FoamTools
│   ├── higherOrderHelpers
│   └── solids4FoamModels
└── tutorials
    ├── Alltest
    ├── fluidSolidInteraction
    ├── fluids
    └── solids

• Allwmake and Allwclean compile and clean the toolbox:

  > ./Allwmake
  > ./Allwclean
  

• ThirdParty: solids4foam optionally uses some third-party code (e.g. Eigen, PETSc): for more details, see the installation guide.
• applications: contains the solids4Foam solver, a small number of helper utilities, and the Bash functions used by the tutorials; see applications.
• src: contains the libraries used by the solids4Foam solver, of which solids4FoamModels is the main one, defining the fluid, solid and fluid-solid interaction algorithms; see under the hood.
• tutorials: contains example cases for fluid, solid and fluid-solid interaction analyses; many of these are described in the tutorials guide.

The solids4FoamModels library is organised by the components above:

solids4foam
└── src
    └── solids4FoamModels
        ├── dynamicFvMesh
        ├── fluidModels
        ├── fluidSolidInterfaces
        ├── functionObjects
        ├── materialModels
        ├── numerics
        ├── physicsModel
        └── solidModels

A Note on Coding Style

solids4foam aims to follow the OpenFOAM Coding Style Guide closely. When a consistent style is not followed, reading code generated by others becomes tedious, painstaking and even impossible. Coding style is a crucial feature of software that is easy to read, understand, maintain and extend. For example:

Bad

Info <<"This is not good"
<< endl;

( a+b ) * ( c&d ) / (e&&f)

if(myName == "Philip"){
success = true;
}

…

Good

Info<< "That's better"
    << endl;

(a + b)*(c & d)/(e && f)

if (myName == "Philip")
{
    success = true;
}

…

Contributions are welcome; please see the contributing guide.