OpenFOAM sustainability involves developing software that meets critical needs of users, through a balance of resources, technology, investment and institutional support. The critical needs are availability, usability, robustness and extensibility. The critical work required to meet those needs are publishing, repair and redesign. Employers rarely allocate time to individuals to contribute critical work, so it is generally left to “career maintainers” at CFD Direct. With limited funding, decisions about the critical work are made by those who fund and/or contribute the work, via The OpenFOAM Hub.
CFD Direct manages and maintains OpenFOAM on behalf of the OpenFOAM Foundation which owns the OpenFOAM software which it distributes free and open source only. CFD Direct includes Chris Greenshields and Henry Weller who have been managing OpenFOAM since its first release in 2004. Management and maintenance is a considerable undertaking with 1 million lines of code and supporting infrastructure, including 4 websites, documentation etc. It requires a funded team of specialist software engineers with expertise in numerics, geometry and meshing, data processing, fluid dynamics and physical modelling. The articles below describe our recent management and maintenance activities, and analysis supporting a sustainable future for OpenFOAM.
In Year 3 of CFD Direct, we developed new functionality in OpenFOAM and maintained critical components of the code base, reducing the number of unresolved issues by 45%. We managed the OpenFOAM Foundation: promoting sustainable development, releasing OpenFOAM v5, packaging OpenFOAM-dev and publishing websites and documentation. We delivered 60 days of OpenFOAM Training, introducing our new “hybrid” classroom-virtual courses to host participants in person and remotely. We launched the new Cloud CFD course to teach inexpensive, secure, efficient CFD with CFD Direct From the Cloud™.
OpenFOAM is free, open source software for computational fluid dynamics (CFD). At the heart of OpenFOAM is a development kit (“SDK”), providing software and tools to build CFD applications, enabling users to customise their CFD, quickly and conveniently. CFD Direct includes OpenFOAM developers who maintain the SDK. We manage an environment for sustainable OpenFOAM development that involves: early public code release with rapid-turnaround user feedback; a network of developers, funding companies and users; and, co-ordinated code integration and maintenance.
During Year 2, CFD Direct made over 1000 code commits to the public development line of OpenFOAM, making us by far the largest contributor of code to OpenFOAM. We produced the major new version 4.0 release of OpenFOAM and the minor update version 4.1 release. We transformed OpenFOAM-dev into stable software of “always-releasable” quality and package it weekly for Ubuntu. Ubuntu packs can now be installed directly on Windows 10 and we also provide “containerized” versions, hosted on Docker Hub, accompanied by launch scripts for easy installation of OpenFOAM on Linux and macOS.
In Year 2, CFD Direct handled almost 500 issues on the OpenFOAM issue tracking system. We upgraded the system and and analyzed metrics relating to timely resolution of issues which concluded that current unresolved issues relate to badly designed components of OpenFOAM that require significant code rewriting. To fund that repair work and ongoing maintenance, we ran a successful campaign to raise €100 k from companies that benefit from OpenFOAM. We carried out substantial maintenance to OpenFOAM websites, significant updates to documentation, and administration for the OpenFOAM Foundation.
OpenFOAM is free, open source software in computational fluid dynamics for real-world engineering and scientific applications. CFD Direct is committed to maintain OpenFOAM, demonstrated by the thousands of code commits to OpenFOAM-dev, with support from contributors. Maintenance concerns the evolution of software in response to changes in user expectation and environment. We have introduced an agile strategy suitable to the feedback process of software evolution and have identified key areas of OpenFOAM that requiring significant redesign, e.g. AMI and particles.
A breakdown of outstanding issues in OpenFOAM (2016-10-26) shows 90% of unresolved issues falling within only 7 categories. The two worst offenders account for almost half of all unresolved issues: 1) AMI, ACMI and cyclic interfaces; and, 2) heat transfer, including conjugate heat transfer (CHT). These categories, and “particles and tracking” and “sources/constraints” in particular, require significant refactoring and/or rewriting. Their current state of disrepair was caused by poor funding under a roadmap development strategy. Funding of agile development of OpenFOAM is now needed to support our aim to improve quality, with a target 50% reduction in unresolved issues in 2017.
Agile development of OpenFOAM emerged following the public distribution of the development line in December 2014. It relies on user participation, which is encouraged by rewarding users for reporting issues with timely resolution. OpenFOAM was in poor health at version 2.3.0, with unresolved issues increasing rapidly and long resolution times. Following the move to agile development, unresolved issues are reduced and under control, with ~70% of issues resolved in 1 day and ~90% resolved in 1 week, taking OpenFOAM to a new level of quality and maturity (always releasable) by version 4.0.
The OpenFOAM Issue Tracking system exists to enable users to report issues. An issue exists when OpenFOAM behaves in a manner that does not meet reasonable expectations, including in design and usability. OpenFOAM is mature, quality software, whose successful development demands that issues are resolved in a timely manner. Roadmap development obstructs issue resolution, resulting in unreliable software and inefficient development. Instead, free, open source software can exploit agile development with frequent code release, as the best strategy for CFD development. Users should adopt continuous upgrade to minimize cost and to benefit the agile development strategy.
OpenFOAM version 4.0 is the latest major version of OpenFOAM, released on 28th June 2016. CFD Direct was by far the largest contributor to OpenFOAM 4.0, contributing the vast majority of new functionality including post-processing, numerous boundary conditions and physical models. Additionally, we contributed across all other aspects of software engineering that make OpenFOAM a mature, modern environment for CFD. This article provides the inside view of that work on the software engineering behind OpenFOAM 4.0, contributed largely during a 3 month period from April-July, 2016.