OpenFOAM 14: Rewritten Combustion Solver, Modular Lagrangian, and Units as a Standard Feature

OpenFOAM 14, released on July 14, 2026 by the OpenFOAM Foundation and produced by CFD Direct, marks a significant step forward for the world's most widely used open-source CFD toolbox. With approximately 938 code commits and 130 resolved issues, this release delivers meaningful improvements across combustion modeling, particle tracking, case configuration, and multiphase physics.

Rewritten XiFluid Combustion Solver

The headline feature of OpenFOAM 14 is a ground-up rewrite of the XiFluid solver — the primary tool for engine combustion and premixed flame simulations. The solver now operates as a two-phase system using the Multidimensional Universal Limiter with Explicit Solution (MULES) approach, treating unburnt and burnt gases as distinct phases with separately solved enthalpy equations.

This architectural change unlocks several capabilities that were previously unavailable:

• Multicomponent thermodynamics in the burnt gas zone, enabling accurate pollutant prediction and rich combustion reaction modeling
• Gaussian ignition rate model (GaussianbXiIgnition) for more physically realistic flame kernel growth
• Conjugate heat transfer support via the new ubCoupledTemperature boundary condition
• Access to the full range of transport models from the multiphaseEuler phase system

For engine simulation practitioners, the new multiValveEngineValveMotion and multiValveEnginePistonMotion mesh motion functions further streamline multi-valve engine case setup.

Modular Lagrangian Framework Reaches 80% Completion

OpenFOAM 14 continues the development of the modular Lagrangian framework, now 80% complete. Unlike the legacy particle-based approach, this framework stores particle data as fields — consistent with OpenFOAM's core design philosophy. The result is a more extensible, efficient, and maintainable particle tracking system.

New capabilities in this release include:

• Tracer cloud type for passive particle tracking in carrier flows
• Multicomponent thermodynamic models for particles with varying composition
• Mass transfer coupling to multiphase Eulerian solvers
• New velocity injection conditions: fanVelocity, flowRateConeDiskVelocity, and totalPressureConeVelocity

Units as a Standard Feature

A long-requested usability improvement arrives in version 14: physical units are now a first-class feature throughout the case configuration system. The new foamUnits utility allows engineers to specify input parameters with explicit units (e.g., diameter 500 [mm];) rather than relying on implicit SI conventions. Named dimensions replace numerical dimension arrays in example cases, and dimension checking is applied at field construction across all solvers.

The blockMesh utility gains a units control, and snappyHexMesh surfaces can now be specified with units or a scale factor — reducing a common source of setup errors.

Improved Case Configuration and Coded Input

The dynamic code framework for coded file input has been overhauled with several new directives:

• #codeBlock / #endCodeBlock — groups multiple #calc or #codeStream entries into a single compiled library for faster execution
• #codeDict — generates dictionaries from coded input
• #stream — a compact alternative to #codeStream
• #print — prints dictionary contents including default values, replacing the writeOptionalEntries function object
• #dump — writes expanded input file contents to the terminal for debugging

The new functionalFixedValue boundary condition provides a flexible, efficient mechanism for specifying non-uniform and time-varying inlet fields without pre-processing utilities like setFields.

Multiphase and Thermal Enhancements

The multiphaseEuler solver receives wall boiling and condensation improvements, including the new alphatPhaseChangeWallFunction boundary condition that allows both phenomena to operate simultaneously on a single patch. A new solidElectricalConduction fvModel calculates electrical conduction through solid regions and applies the corresponding Joule heating source — enabling coupled electro-thermal simulations.

Platform Support

OpenFOAM 14 is packaged for Ubuntu 22.04, 24.04, and 26.04 on both x86-64 and ARM64 hardware. Windows users can install via Windows Subsystem for Linux (WSL), and macOS users via Canonical Multipass. Source compilation is supported on any suitable Linux platform with GCC v5.5+ or Clang v14+.

Full release notes and download links are available at openfoam.org.