Altair AcuSolve 2026 Release Notes

New Features

Blast Furnace Chemical Reaction Modeling
Particle melting: In this release, melting of solid particles will be supported without tracking the resulting liquid mass in the CFD domain. This approach intentionally avoids introducing three-phase complexity. Melting will be handled at the particle level using conservation of mass principles, and any generated liquid mass will be removed from the system. To enable this functionality, the melting model must include heat transfer physics. The following parameters should be added to the field interaction model: edem_melting_no_mass_transfer and edem_melting_temperature.
Radiation for EDEM particles in AcuSolve EDEM coupling: In the AcuSolve–EDEM coupled simulation, radiation effects occurring between particles at elevated temperatures can be considered. This enhancement focuses solely on the heat transfer aspect within the particle domain, without introducing radiation modeling on the CFD side. The objective is to simulate particle-to-particle radiative heat flux accurately. To enable this, a new parameter must be added to the field interaction model: edem_particle_emissivity.
Battery Thermal Runaway Modeling
The following new features and improvements of the battery thermal runway modeling further enhance simulation fidelity and predictive capabilities:
  • SEI (Solid Electrolyte Interphase) decomposition modeling: The ARC (Accelerating Rate Calorimetry) reaction model now optionally includes a dedicated stage for SEI breakdown. By specifying enthalpy and Arrhenius parameters, you can capture early-stage battery thermal runaway processes.
  • Heat release tracking: Heat release from decomposition reactions is now reported directly during simulations, providing clearer insight into the battery thermal runaway dynamics.
  • Forchheimer-based venting formulation: A new mass flow rate venting model treats the vent as a thin, porous region where inertial losses dominate, delivering more accurate predictions of rapid gas release during venting events.
  • New electrolyte vapor pressure models: Two new electrolytes vapor pressure models are supported: EC (Ethylene Carbonate) and a DMC (Dimethyl Carbonate)/EC mixture. The latter allows you to define the mole fraction of the mixture for precise representation of the electrolyte.
  • Faster first-vent predictions: An enhanced adaptive time-stepping algorithm accelerates the critical first venting event by up to two times faster for the gas reaction based venting model. The routine now dynamically adjusts based on current pressure relative to the opening threshold, with the control window exposed as a user input for added flexibility.
  • Improved venting model robustness: General refinements to the pressure-based venting formulation enhance both performance and stability.
Optimization
Topology optimization input deck conversion: The utility acu2Topo.py can be used to convert a standard AcuSolve input deck to a topology optimization input deck with appropriate objectives and constraints for flow or thermal flow optimization problems. This makes it possible to generate a Topology Optimization deck based on any pre-processor supporting AcuSolve.
Streamlined shape optimization: Shape optimization is more streamlined with the AcuAutoShapes tool, which generates morph shape inputs based on an internal flow or topology flow results. This eliminates the need for manual shape creation in a pre-processor, simplifying the workflow for shape optimization simulations.

Enhancements

Thermal runaway heat source output
heat_src_trm is now available under element_integrated_output_variable (oeiv).
Documentation Additions
Two new tutorials have been introduced:
  • ACU-T: 3700 Brake Disc Cooling
  • ACU-T: 7203 Thermal topology optimization with heatsink, utilizing the acu2Topo utility script to convert the flow/thermal input file into the topology optimization input file.

Deprecated Features

  • Effective in the 2026 release, Platform MPI will be deprecated and removed from the list of supported parallel processing options in AcuSolve.

Resolved Issues

  • In previous versions, restarting cases with immersed boundary walls resulted in missing surface output in AcuProbe. This issue has been resolved in the current release.
  • Coupled simulations between AcuSolve and EDEM previously crashed with a negative particle volume error in the .Log file. This occurred when newly generated sphere particles failed to receive proper coupling force data from AcuSolve, alongside existing sphere-cylinder meta particles in EDEM. This issue has now been fixed.
  • AcuSolve–EDEM coupling runs using the porosity model in cylindrical coordinates previously crashed without providing a clear error message. This issue has been addressed and resolved in this version.

Known Issues

  • When coupling with EDEM and specifying a restart frequency in the AcuSolve input file (.inp), ensure the --wait flag is included either in your EDEM run script or within the additional option in Access. This flag is required for version 2025.1 and later, until a future enhancement is introduced. To terminate the AcuSolve-EDEM coupling jobs, use the acuSig utility.
  • Full restart type is not supported for cases involving immersed boundary walls. As a workaround, use the incremental restart type by appending the Restart Command with type = incremental to the end of the AcuSolve input file (.inp).
  • In the 2025.1 release, Qt libraries have been upgraded to version 6 across all products. These Qt6 libraries are now used for AcuSolve–EDEM coupling and are linked directly to the AcuSolve executable. Based on support feedback, some users encountered missing system libraries, such as the following error: error while loading shared libraries: libpcre2-16.so. This issue typically arises on systems running RHEL9, where the required library is not installed by default. In such cases, it is recommended to install the pcre2-utf16 package to resolve the dependency.