A computional fluid dynamics (CFD) module for FreeCAD

by Qingfeng Xia, 2015 http://www.iesensor.com/HTML5pptCV

the team from CSIR South Africa, 2016

Oliver Oxtoby http://www.linkedin.com/in/oliver-oxtoby-05616835
Alfred Bogears http://www.csir.co.za/dr-alfred-bogaers
Johan Heyns http://www.linkedin.com/in/johan-heyns-54b75511

CSIR team has forked this repo into https://github.com/jaheyns/CfdOF, focusing on usability for new users and OpenFOAM. Meanwhile, this repo still targets at preparing real-world case files from FreeCAD goemetry for advanced users, which also means user needs to tweak the OpenFOAM case files in production environment. Features from CSIR fork will be picked up regularly in the future.

changelog and roadmap at Roadmap.md

LGPL license as FreeCAD

Features and limitation

This module aims to accelerate CFD case build up. Limited by the long solving time and mesh quality sensitivity of CFD problem, this module will not as good as FEM module. For engineering application, please seek support from other commercial CFD software.

Features

Python script and GUI to run a basic laminar flow simulation is supported by Cfd Workbench
An independent python module, FoamCaseBuilder (LGPL), can work with and without FreeCAD to build up case for OpenFOAMhttps://www.openfoam.com/
FenicsSolverhttps://github.com/qingfengxia/FenicsSolver, a multiphysics FEA solver set, has been demonstrated in early 2018.

Features comparison with CfdOF forked

missing features:

cfMesh, snappyHexMesh meshing (I will manually merged this feature later)
pure python fluid boundary class (my Cfd module using C++ corresponding class in Fem module)
dropped PyFoam dependency (I have a plan and it is half done)
porous model, multiphase model (I will not implement it)
support windows platforms by BlueCFD ( I support windows 10 only with WSL)
see also the CfdOF github

added features:

windows 10 WSL platform support
import external mesh (e.g. mesh generated from Salome)
Fenincs FEM solver
boundary layer supported via gmsh

Limitation:

turbulence model case setup is usable, but only laminar flow with dedicate solver and boundary setup can converge
OpenFOAM thermal sovler is under development

Platform support status

Linux:

  Ubuntu 16.04 as a baseline implementation, but should works for other linux distribution.

Windows 10 with Bash on Windows (WSL ubuntu 16.04) support (tested on windows 10 v1803):

 Official OpenFOAM  (Ubuntu deb) can be installed and run on windows via Bash on Windows (WSL) Since version 1803 can piped process output back python, which is needed to detect OpenFOAM installation.  There is a tutorial to install OpenFOAM on windows WSL: <https://openfoam.org/download/windows-10/>, make sure OpenFOAM bashrc is sourced in `~/.bashrc`.   On FreeCAD v0.17 for windows, gmsh has been installed, but 'PyFoam' is not included to the FreeCAD's python2.7 bundle. However, `pip` bundled with FreeCAD does not work, instead, 'PyFoam' is downloaded and extracted to "C:\Program Files\FreeCAD 0.17\bin\Lib\site-packages".

For paraview, it is recommended to uninstall WSL's paraview by sudo apt-get remove openfoam5paraview54, to use windows version (make sure paraview is installed and on PAHT) for better 3D performance. paraview on WSL just does not work for me, although fglgears works on software rendering viaexport LIBGL_ALWAYS_INDIRECT=1.

MAC (not tested):

  As a POSIX system, it is possible to run OpenFOAM and this module, assuming OpenFOAM/etc/bashrc has been sourced for bash

Relationship with official FEM workbench:

CFD is a pure Python wokbench based on FEM workbench. Code for meshing, material database capacity are shared. FemConstraintFluidBoundary is written in C++ and included in official FreeCAD FEM module, similar are VTK mesh and result IO C++ code.

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Installation guide

Prerequisites OpenFOAM related software

Debian/Ubuntu

see more details of Prerequisites installation in Readme.md in FoamCaseBuilder folder

OpenFOAM (3.0+) sudo apt-get install openfoam once repo is added/imported

see more OpenFOAM official installation guide, make sure openfoam/etc/bashrc is sourced into ~/.bashrc

PyFoam (0.6.6+) sudo pip install PyFoam (see platform notes for Windows). In the future, this dependency will be removed.
matplotlib for residual plot (it is bundled with FreeCAD on Windows), gnuplot is not needed any longer. On ubuntu/debian, sudo apt-get install python-matplotlib
paraFoam (paraview for OpenFOAM), usually installed with OpenFoam.

RHEL/Scientific Linux/Centos/Fedora: should work Installation tutorial/guide is welcomed from testers

Install freecad v0.17 stable

After Oct 2016, Cfd boundary condition C++ code (FemConstraintFluidBoundary) has been merged into official master in stable v0.17

Make sure Gmsh function is enabled and installed. gmsh 3 has been bundled with FreeCAD v0.17 on Windows.

Install Cfd workbemch

using FreeCAD 0.17 addon manager

from github for developers

git clone https://github.com/qingfengxia/Cfd.git

symbolic link or copy the folder into <freecad installation folder>/Mod, e.g, on POSIX system:

sudo ln -s (path_to_CFD) (path_to_freecad)/Mod

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Testing

Test FoamCaseBuider (only in Linux terminal mode)

There is a test script to test installation of this FoamCaseBuilder, copy the file FoamCaseBuilder/TestBuilder.py to somewhere writtable and run

python2 pathtoFoamCaseBuilder/TestBuilder.py

This script will download a mesh file and build up a case without FreeCAD.

tutorial to build up case in FreeCAD

Similar with FemWorkbench

make a simple part in PartWorkbench or complex shape in Partdesign workbench
select the part and click "makeCfdAnalysis" in CfdWorkbench

which creats a CfdAnalysis object, FemMesh object, and default materail

config the solver setting in property editor data tab on the left combi panel, by single click sovler object
double click mesh object to refine mesh
hide the mesh and show hte part, so part surface can be select in creatation of boundary condition
add boundary conditions by click the toolbar item, and link surface and bondary value
double click solver object to bring up the SolverControl task panel

select working directory, write up case, further edit the case setting up then run the case (currently, copy the solver command in message box and run it in new console)

Test with prebuilt case

A simple example of a pipe with one inlet and one outlet is included in this repo (test_files/TestCase.fcstd). The liquid viscosity is 1000 times higher than water, to make it laminar flow. The video tutorial is here

The test case is built on Linux, on windows you need to regenerate mesh, and change the case working folder to use the example case

Turbulence flow case setup is also usable, see (test_files/TestCaseKE.fcstd), but Reynolds number is set to be 1000, otherwise, calculation will diverge due to bad tetragen mesh. Better CFD meshing is planned for cfmesh, perhaps, snappyHexMesh.

Johan has built a case, see attachment test procedure on freecad forum

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Roadmap

see external Roadmap.md

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How to contribute this module

You can fork this module to add new CFD solver or fix bugs for this OpenFOAM solver.

There is a ebook "Module developer's guide on FreeCAD source code", there are two chapters describing how Fem and Cfd modules are designed and implemented.

https://github.com/qingfengxia/FreeCAD_Mod_Dev_Guide.git where updated PDF could be found on this git repo

This is an outdated version for early preview: https://www.iesensor.com/download/FreeCAD_Mod_Dev_Guide__20161224.pdf

Collaboration strategy

Cfd is still under testing and dev, it will not be ready to be included into official in the next 6 m.

Currently route I can imagine: CFD workbench new developers fork official FreeCAD and my Cfd githttps://github.com/qingfengxia/Cfd.git.

Cfd workbench depends on Fem for meshing and boundary(FemConstraint) and post-processing, most of them are coded in C++ so it is hard to split from Fem. If you need add feature on above, you branch FreeCAD official, not mime (but do let me know, pull request will only accepted if it is fully discussed on forum and reviewed by other dev like Bernd, me). see my ebook on how to pull request. Any other cfd python code, do pull request me (my Cfd.git) e.g. I developed vtk mesh and result import and export feature, git directly to official Fem workbench.

User can install freecad-daily, and git update/install Cfd.git so all got updated code without pain for installation.

KarlSoftware/Cfd