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What is Caelus?

Caelus is the next evolution in open-source computational continuum mechanics solutions. Caelus was originally forked from OpenFOAM-2.1.1 and was restructured to create a stronger foundation on which to build your open-source CFD solutions. The file formats are compatible but there have been many improvements to it such that it is now moving independently in its own direction.

Being a derivative of OpenFOAM, Caelus was released under the GPL. You can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. See the GNU General Public License for more details.

Why create Caelus?

For the past decade, OpenFOAM has been a pioneer in the field of open-source Computational Continuum Mechanics (CCM). Broader acceptance has been hampered by

  • difficulties using on it platforms other than a select few Linux distributions,
  • lack of documentation,
  • difficult installation,
  • dependencies on a large number of external applications, and
  • large library size due to unused and untested code.

The main highlights of how Caelus is different:

  • Compiles and runs in both serial and parallel on Windows 7/8/10, Redhat Enterprise Linux 6/7, Ubuntu LTS 16.04/18.04
  • Easy installation with GUI installer for all platforms
  • Removal of legacy code, unvalidated models and general library clean up
  • Only two external dependencies (Python and MPI)
  • Solvers and models validated against published data
  • Documentation

A summary of the main enhancements from each release are:


  • Updated thermophysical library
  • Updated Lagrangian library
  • Automatic parameterized simulations with CPL.
  • Run separate versions of Caelus side-by-side using CPL.
  • Compile Caelus and external applications using CPL.


  • Caelus Python Library (CPL)  provides utilities for pre and post-processing, as well as automating various aspects of the CFD simulation workflow.
  • wave library: a port of Niels Gjoel Jacobsen’s waves2Foam
  • Consistent and correction enhancements to the SIMPLE-based steady-state incompressible solver
  • Consolidation of static and dynamic mesh solvers into unified solvers
  • Published validation and verification papers from ASME FEDSM 2017


  • Fast, robust Cartesian, polyhedra, and tetrahedra meshing applications
  • New multiphase solvers and algorithm improvements
  • New gradient discretisation schemes
  • Multiple rigid body dynamics (nDoF) and mesh motion capabilities
  • Virtual Blade Model for high fidelity rotorcraft modeling


  • Performance and stability enhancements to linear solvers
  • New incompressible and compressible solvers
  • Updates to RANS, VLES, and LES turbulence models


  • Restructuring of interpolation schemes
  • Overhaul of limiters to ensure TVD compliance
  • Updates to pressure and density-based compressible solvers
  • New combustion solvers
  • New RAS, DES and VLES turbulence models


  • Further numerical improvements
  • New compressible solvers
  • New VLES turbulence model class
  • Coherent Structure LES
  • Multiphase VOF-LPT coupling
  • Update function objects


  • Improved numerical algorithms
  • Expression-based boundary conditions, initial conditions, sources, etc with the swak library and utilities
  • New solvers and models
  • Python-based execution environment


  • Compiles and runs in both serial and parallel on Windows 7/8, Redhat Enterprise Linux 6/7, Ubuntu LTS 12.04/14.04
  • Easy installation with GUI installer for all platforms that can also be run in text mode
  • Removal of legacy code, unvalidated models and general library clean up
  • Only two external dependencies (Python and MPI)
  • Solvers and models validated against published data
  • Documentation

Where can I get Caelus?

Installer packages are available at our public Bitbucket repository or alternatively, you can clone the repository and install from the source. Installation notes can be found here.

How do I use Caelus?

In a similar manner as you would OpenFOAM but much easier to set up and accessible on more platforms. It is also compatible with OpenFOAM’s file format. Check out the Caelus documentation for more details.

How do I contribute?

Caelus is an open-source, collaborative project. There is a publicly available source repository for the current Caelus release. A README file is provide with instructions for downloading and setting up Caelus. Please contact us if you encounter bugs, need help contributing, or have general feedback.

Technology subscription

Applied CCM offers a technology subscription which includes access to an industrial suites of solvers and applications. This suite of applications is compatible with the Caelus library.

SLIM Solver

SLIM technologySemi Linear Implicit Method (SLIM), a transient solver for both incompressible and compressible flows with superior performance and scalability compared to traditional pressure-based implicit transient solvers.

Adjoint Solver

Adjoint Vectors V8 SupercarA surface-based adjoint solver that provides both sensitivity magnitude and direction. It’s time-symmetry preserving, semi-discrete nature possesses the benefits of many traditional adjoint approaches while removing the drawbacks.

Technology subscription inclusions

Software and Installation Support

  • Permanent installation of all Applied CCM related software including custom codes and methods on customer’s hardware
  • Access to Applied CCM documentation and tutorials

Services and Technical Support

  • Support from a suitably qualified Applied CCM engineer that can be used for:
    • Direct user support of Applied CCM software
    • Training on Applied CCM methods
    • Installation and IT support of Applied CCM software
    • General support using Applied CCM software
    • Advice on best practice and methodologies
    • Testing of installation, codes and methods
  • Guaranteed 2 business day response to support inquiries


  • Free attendance for a pre-determined number of users once per calendar at any pre-scheduled Applied CCM training. Travel and accommodations costs not included.


  • Applied CCM will update software as needed, usually on an annual basis facilitated by an Applied CCM software repository
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