CFD Direct Year 7: 2021-2022

It is 7 years since OpenFOAM co-founders Henry Weller and Chris Greenshields launched CFD Direct with Jenya Collings to oversee the maintenance of OpenFOAM, on behalf of the OpenFOAM Foundation, and provide support, training and cloud services to users of OpenFOAM.  We summarise below our principal activities for our 7th year, ending March 2022.

Development

Developments introduce new functionality to the software, which then must be maintained into the future. We undertook 819 man-hours of new developments, with 662 code commits to the public development line of OpenFOAM (OpenFOAM-dev). Customer projects funded almost all of the work. Some examples of new developments include:

• a prototype general CPU load balancer which redistributes a mesh in parallel based on the computational load in local cell, initially working for chemistry loads;
• in the flowRateInletVelocity boundary condition, velocity profiles can be specified by laminar or turbulent boundary layers, and flow rate can be based on the mean velocity;
• new kOmega2006 turbulence model, the 2006 version of Wilcox’s k-omega RAS turbulence model;
• chemistry models solve mass fractions rather than concentrations to account for changes in reaction rate associated with thermal expansion;
• surface waves can now be specified with an input period which allows flow reversal at boundaries, so that waves can be specified in any direction and with zero mean flow.

Maintenance

Maintenance is the essential redesign, repair and publishing work that adds no new functionality to the software, but in instead targets the critical needs of users: accessibility, usability, robustness and extensibility. In year 7, we undertook 1373 man-hours of  maintenance work supported by 2021 maintenance funding at the OpenFOAM Foundation. Significant redesigns of components of OpenFOAM include:

• standardisation of fluid properties for flows which are incompressible, compressible, single and multi-phase, and single and multi-region;
• a new framework within fvMesh to handle run-time mesh redistribution, e.g. for load-balancing;
• the clouds fvModel which enables particles to be added to a simulation with various levels of coupling, with both incompressible and compressible solvers;

We resolved 169 issues on the Issue Tracking Site, with improvements to the software including:

• making the totalPressure boundary condition work reliably with an external tangential velocity, which can be specified in a freestream;
• adding a new nEcorr loop to conjugate heat transfer, which can improve cases where the thermal coupling between fluid and solid regions is dominant;
• improving the stabilisation of multiphase cases when phase fraction alpha → 0.

Unresolved issues were maintained at a level of ~25 during year 7. We expect to reduce these issues significantly, following the release of some long term developments to fix fundamental problems in critical areas, e.g. AMI. 

OpenFOAM Foundation

We continually manage the OpenFOAM Foundation, the copyright holder and licensor of OpenFOAM, to ensure it is distributed free and open source only.  It provides a focal point for the supporters of OpenFOAM, including the organisations who fund OpenFOAM through Maintenance Plans and individuals who contribute developments and maintenance.  Our work for the Foundation included:

• producing the major OpenFOAM v9 release and subsequent v9 patch releases, accompanied by release notes and documentation;
• packaging the development line, OpenFOAM-dev regularly for Ubuntu, other Linux distributions, Windows and macOS;
• publishing the openfoam.org website and the subdomain websites for Issue Tracking, Source Guide and Downloads;
• providing a Technical Guides resource;
• managing open source licensing issues, e.g. the OpenFOAM Foundation Contributor Agreement and enforcement.

CFD Book for OpenFOAM

In April 2022, CFD Direct published a book for CFD with OpenFOAM. Entitled Notes on Computational Fluid Dynamics: General Principles, the book provides essential knowledge to perform CFD analysis with confidence. During Year 7, we wrote the final three chapters on Turbulence, Reynolds-Averaged Turbulence Modelling and Sample Problems, and the cover, frontmatter, index and blurb.

The book is available:

• online in HTML format for free;
• as a print-on-demand paperback book for $29.95, self-published through Amazon KDP.

By self-publishing through Amazon, the book can be delivered to the doorsteps of CFD users worldwide at an affordable price, which supports our mission to make CFD accessible and inclusive.

Training

We hosted 56 days of OpenFOAM Training, updated for OpenFOAM v9, with our Essential CFD, Applied CFD, Programming CFD and Cloud CFD courses.  Courses were delivered exclusively as Virtual Training, introduced in response to COVID-19 and continued to provide wider access to training. With these measures, we have maintained the normal level of participation on our courses.

During 2021, we updated all our courses to the latest version of OpenFOAM, rewriting some topics in depth, e.g. on boundary conditions and matrix solution. We simplified some topics, e.g. numerical methods, where more detailed knowledge is now covered comprehensively in Notes on CFD.

Our goal is as always help participants learn effective CFD. We teach tools to build CFD competency with the aim to give participants:

• the confidence to deliver a good solution with CFD, rather than freeze at the keyboard;
• repeatable procedures to deliver the next good solution in a timely manner;
• the understanding to recognise a good solution from a bad one.

Cloud

CFD Direct From the Cloud™ (CFDDFC®) provides a turnkey platform including OpenFOAM v9 and related software, running in the cloud. CFDDFC reached  nearly 1000 subscribers running millions of core-hrs of AWS Elastic Cloud Compute (EC2). It offers low cost of running CFD in the cloud by using cheaper, spare capacity with EC2 Spot Instances, and provides cost estimates for instances and data transfer.

In Year 7, we added support for new C6i and M6i instance types to CFDDFC. We developed a new version of the product, with a browser-based remote desktop, which we have trialled successfully in training. In the coming months, we will release the browser version of CFDDFC and provide support for recent, new instance types on AWS.