Dr. Fabian Schlegel

Head OpenFoam modelling of multiphase flows
Phone: +49 351 260 3467

Sustainable Development of Simulation Software for Modeling of Reactor Coolant Systems


Due to the growing importance of Computational Fluid Dynamics (CFD) for reactor safety research, there have been activities aimed at qualifying the associated methods for many years. This entails the development and validation of models on the basis of detailed experimental data, generated in comprehensive projects. There was and is a need for development, among other things, for multiphase flows, in particular for accident scenarios in the reactor coolant system. In order to be able to use the model developments and validation data generated throughout the various projects funded by the German Federal Ministry for Environment, Nature Conservation, Nuclear Safety and Consumer Protection in the long term, these are carried out using the software provided by the OpenFOAM Foundation, which is thereby qualified for application. The project presented here has the objective of gathering and maintaining software and simulation setups from partner institutions in a common repository.

Project description

The software released by the OpenFOAM Foundation, as a free, open source software, has the great advantage of enabling users to customize and extend the code according to their needs. However, with an increasing amount of customization, significant effort is required to maintain long-term compatibility with the main development line. Likewise, simulation setups can become incompatible with the source code over time. If, for various reasons, a development cannot be contributed to the main release, the task of maintenance lies with the authors. If maintenance is not done, the developments may be lost.

This situation is clearly unfavorable when it comes to the continuous validation for application to nuclear reactor safety research. The present project aims at supporting maintenance through  adopting a modern IT development environment, wherein institutions conducting research with the software released by the OpenFOAM Foundation can integrate and share their software and simulation setup developments in a sustainable manner. To this end, two GitLab repositories, containing software and setups, are made available to project partners. The software repository includes the customized code and constitutes an addon to software released by the OpenFOAM Foundation, which is regularly upgraded to keep track with the latest developments. The addon also features test and tutorial cases as well as a source code documentation. Validation cases are held in the setup repository and kept compatible as well. The process of merging new code and setups into the repositories and upgrading existing developments, respectively, is supported by CI/CD-pipelines, which allow for automized style and build checks and comparison of simulation results against stored reference solutions. Project partners have the possibility to communicate through a chat-service and, on demand, receive consultation and training with respect to developing and using the software released by the OpenFOAM Foundation.

Foto: Darstellung der Verknüpfung zwischen den OpenFOAM_RCS Projektpartnern und dem Helmholtz-Zentrum Dresden - Rossendorf. ©Copyright: Dr. Fabian Schlegel

Illustration of the linkage between NUSAR-RCS project partners and Helmholtz-Zentrum Dresden - Rossendorf.


This work is carried out in the frame of a current research project funded by the German Federal Ministry for Environment, Nature Conservation, Nuclear Safety and Consumer Protection, project number 1501658.

Picture: BMUV Logo with  funding notice


  • Helmholtz-Zentrum Dresden - Rossendorf
  • Framatome
  • Universität Rostock
  • Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH
  • Ruhr-Universität Bochum
  • Hochschule Zittau/Görlitz