OpenSTREAM – Two-Phase Flow Solvers

Welcome

OpenSTREAM (Open Solvers for Two-phase flow Research, Engineering Analysis and Modeling) is an open-source, object-oriented computational environment designed for simulating one-dimensional, multi-field, two-phase flows in straigth geometries (Le Corre et al. [2025]) (Le Corre et al. [2025]). It supports phenomena such as wall boiling, phase interactions and non-equilibrium effects, making it a relevant tool for researchers working in thermal-hydraulics and two-phase flow systems.

What’s inside?

OpenSTREAM offers a suite of solver frameworks tailored to different modeling needs:

  • A mixture solver – with thermal non-equilibrium capabilities

  • A generic two-fluid solver – for generic separate-phase modeling

  • A three-field solver – for annular two-phase flow

  • An advanced four-field solver – for annular two-phase flow explicitly capturing disturbance waves

These solvers are designed to simulate single-component, thermally expandable, steady-state and transient boiling two-phase flows in straight multi-wall channels, which may be uniformly or non-uniformly heated. The implementation relies on a set of reasonable simplifying assumptions to ensure computational efficiency and stability. Each solver includes a set of baseline closure models, which can be customized by modifying the corresponding class methods in the source code.

Why OpenSTREAM?

OpenSTREAM is built to support open, transparent research and to lower the barrier to entry for developing and validating fundamental models in two-phase flow simulations. Its goal is to make advanced thermal-hydraulic modeling more accessible to engineers, scientists, and students alike. Whether you’re conducting research or learning the fundamentals, OpenSTREAM provides a collaborative and extensible environment for model development, performance evaluation, and cross-institutional validation, advancing the state of the art in multiphase flow simulation.

About this documentation

This guide will walk you through:

  • Installation and setup instructions

  • The design philosophy behind OpenSTREAM

  • How to run simulations and interpret results

  • Example applications and use cases

  • How to contribute

Looking for a printable version? You can download the full manual here: OpenSTREAM.pdf

[1]

Jean-Marie Le Corre, Jason Chan, Elisabeth Walter, Evan T. Hurlburt, and Roman W. Morse. Openstream: a new open-source platform for two-phase flow model development. In Proceedings of the 12th International Conference on Multiphase Flow (ICMF 2025). Toulouse, France, May 12–16 2025. URL: https://openstream-solvers.github.io/openstream/_static/publications/LeCorre2025ICMF.pdf.

[2]

Jean-Marie Le Corre, Jason Chan, Elisabeth Walter, Evan T. Hurlburt, and Roman W. Morse. Openstream: an open-source platform for two-phase flow modeling and simulation. In Proceedings of the 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21). Busan, Korea, August 31–September 5 2025. URL: https://openstream-solvers.github.io/openstream/_static/publications/LeCorre2025OpenSTREAM.pdf.

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