OpenSTREAM (Open Solvers for Two-phase flow Research, Engineering Analysis and Modeling) is an open-source computational environment for simulating one-dimensional, multi-field, two-phase flows, including phase change. It supports efficient and collaborative model development, performance evaluation, and validation across users and institutions.

OpenSTREAM and OpenSTREAM-database together form an open-source ecosystem for two-phase flow simulation, application, and validation.

Core simulation platform and solver frameworks. OpenSTREAM supports single-component, thermally expandable, multi-field two-phase flow simulations with phase change under steady-state and transient conditions, based on one-dimensional channel-flow formulations.

Companion repository providing applications, datasets, validation cases, and workflows. OpenSTREAM-database provides an application and validation environment for OpenSTREAM, enabling users to easily run and evaluate any solver using publicly available datasets.

Documentation is available at:

https://openstream-solvers.github.io/openstream/

Most users should begin with the OpenSTREAM repository and then use OpenSTREAM-database to access applications, examples, and validation cases.

To install and begin using OpenSTREAM, refer to the Getting started guide in the software documentation.

If you use OpenSTREAM in your research or activities, please cite the following publications:

• J.-M. Le Corre, J. Chan, E. Walter, E. T. Hurlburt, and R. W. Morse, “OpenSTREAM: A new open-source platform for two-phase flow model development,” 12th International Conference on Multiphase Flow (ICMF 2025), Toulouse, France, May 12-16, 2025.

• J.-M. Le Corre, J. Chan, E. Walter, E. T. Hurlburt, and R. W. Morse, “OpenSTREAM: An open-source platform for two-phase flow modeling and simulation,” 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21), Busan, Korea, Aug. 31 – Sept. 5, 2025.

OpenSTREAM is distributed under the MIT License. This permits free use, modification, and distribution of the software, provided that the original copyright notice and license text are included.