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.
OpenSTREAM is designed to support collaborative physical-model development, implementation, assessment, and validation across users and institutions.
OpenSTREAM includes four solver frameworks:
- A mixture solver with hydrodynamic and thermal nonequilibrium capabilities.
- A generic two-fluid solver with separate liquid and vapor fields.
- A three-field solver for annular flow with liquid-film and entrained-droplet fields.
- A four-field solver for annular flow with base-film, disturbance-wave, entrained-droplet, and vapor fields.
The solvers support single-component, thermally expandable, steady-state and transient boiling two-phase flows in single straight channels under the assumptions associated with the selected solver frameworks and models.
OpenSTREAM includes physical and closure models, numerical methods, input handling, visualization and post-processing capabilities, tutorials, documentation, and automated environment, unit, integration, and regression tests.
Installation, MATLAB and Python compatibility, CoolProp configuration, and verification instructions are available in the Getting Started guide.
After installation, run the sample script to perform a complete mixture-solver calculation and confirm that the installation is functioning correctly.
The OpenSTREAM tutorials introduce the solver frameworks and principal workflows through MATLAB Live Scripts.
The tutorials cover:
- Quick-start calculations using all four solver frameworks.
- Mixture-, two-fluid-, three-field-, and four-field solver capabilities.
- Input-file construction and management.
- Numerical convergence and solver diagnostics.
- Mesh and time-step sensitivity.
- Advanced visualization and post-processing.
The companion OpenSTREAM-database repository provides an application and validation environment for OpenSTREAM using publicly available experimental datasets.
OpenSTREAM and OpenSTREAM-database are maintained as separate repositories. OpenSTREAM-database requires a compatible OpenSTREAM installation and is not included as a Git submodule.
Further information is available on the OpenSTREAM-database application page.
OpenSTREAM includes automated environment, unit, integration, and regression tests.
From the tests folder, run:
runOpenSTREAMTestsThe test runner discovers the available test classes, displays detailed diagnostics, produces a summary table, reports the total execution time, and raises an error if any test fails or does not complete.
The complete available test suite is also executed by MATLAB CI when changes are pushed to the repository.
The automated test suite is under active development and does not yet provide comprehensive coverage of every OpenSTREAM class, model, numerical option, solver path, or post-processing capability.
Further information is available in the Testing and verification guide.
The complete OpenSTREAM documentation includes:
- Installation and compatibility information.
- Solver theory and mathematical models.
- Tutorials and sample calculations.
- Input and package documentation.
- Testing and contribution guidelines.
- OpenSTREAM-database applications.
- Glossary, notation, and references.
If OpenSTREAM is used in research or published work, cite the relevant OpenSTREAM publications:
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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.
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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, August 31–September 5, 2025.
When OpenSTREAM is applied to experimental data provided through OpenSTREAM-database, the original experimental publications should also be cited.
Contributions to the OpenSTREAM solvers, physical and closure models, numerical methods, documentation, tutorials, examples, and automated tests are welcome.
Before contributing, review the OpenSTREAM contribution guidelines.
OpenSTREAM is distributed under the MIT License. This permits use, modification, and distribution of the software, provided that the original copyright notice and license text are retained.
See the LICENSE file for the complete terms.