Linux Operating System

• No known issues, limitations, or documentation inaccuracies.

Parallel Processing

• When running the meshing mode of Fluent in shared memory on Windows with more than 64 logical cores and the default Microsoft MPI, you may receive an error message stating that you have run out of memory during mesh generation. Workaround: specify the use of the Intel MPI (for example, by including the -mpi=intel command line option when launching). (1124265)

Fluent Meshing in Workbench

• When running on Linux or using the LSF job scheduler, the core count per job should be limited to the maximum number of cores available on a single machine. (913594)

  Parallel Processing

  • When running the meshing mode of Fluent in shared memory on Windows with more than 64 logical cores and the default Microsoft MPI, you may receive an error message stating that you have run out of memory during mesh generation. Workaround: specify the use of the Intel MPI (for example, by including the -mpi=intel command line option when launching). (1124265)

  For a list of ongoing Fluent limitations, refer to Known Limitations in Ansys Fluent in the Getting Started section.

  2D Workflow

  • The last-ratio offset method type for 2D boundary layers may lead to uneven prism cap (jagged/uneven inflation). (1163166)

Solver

• For single phase flows, the use of multiple materials in the same simulation with a large variation (for example, orders of magnitude differences) in the density values with gravity enabled is not recommended, and may result in convergence difficulties. Workaround: the following Scheme command may help improve the convergence behavior by setting the operating density according to each material independently: (rpsetvar 'calculate-material-operating-density-sp? #t). The default method averages over the entire domain to set a reference density, and may not be appropriate. For further details about setting operating conditions, see Operating Conditions in the Fluent User's Guide. (1053911)

Graphics, Reports, and Postprocessing

• No known issues, limitations, or documentation inaccuracies.

Radiation/Heat Transfer

• Some cases involving shells on NCI may see non-physical results. In these cases, you should set the rpvar controlling secondary gradients for shells to false using the following command:

  (rpsetvar temperature/shell-secondary-gradient? #f))(1094000)

• Invalid characters (such as '?') are being printed for the GT-POWER version display in the Fluent console for windows only. This information is being printed from GT. For more information, contact GT support. This is purely a printing issue and does not affect results in any way. (1117952)

Reacting Flows

• No known issues, limitations, or documentation inaccuracies.

Discrete Phase Model

• No known issues, limitations, or documentation inaccuracies.

PBNS Solver

• Porous media cases with the following flow conditions may experience convergence difficulties when running in Ansys Fluent 2022R1 or later:

  • Flow in porous media is not one-dimensional.

  • Porous and non-porous regions are separated by non-conformal interfaces (that is, the porous interfaces coincide with non-conformal fluid-fluid interfaces).

  As a workaround for cases where the flow in the porous media is not one-dimensional, you may invoke the following scheme command in the console:

  (rpsetvar ‘pressure/porous-zone-presto-dissipation? #f)

  This command provides the independence of the pressure interpolation scheme. However, in general, using this command is not recommended. (1120629)

Parallel Processing

• Open MPI may fail to run and throw the following error in the shared memory mode on a machine that is disconnected from any network: No network interfaces were found for out-of-band communications. We require at least one available network for out-of-band messaging. Workaround: include the following command line option when launching Fluent: -mpiopt=" --mca oob_tcp_if_include lo ". (1143162)

Load Managers

• The defaults for Fluent 2025 R1 are configured to work with Slurm 24.05.3, which uses srun by default for the remote node access mechanism. When running older Slurm versions (which use SSH by default), you may be required to specify the use of SSH for the remote node access mechanism by including -scheduler_tight_coupling=0 as a command line option or by entering SCHEDULER_TIGHT_COUPLING=0 in the Environment tab of Fluent Launcher. (1168161)

ACT

• No known issues, limitations, or documentation inaccuracies.

Fluent in Workbench

• Fluent sessions running with distributed memory may fail to launch properly. As a workaround you can run Fluent with distributed memory in standalone mode (outside of Workbench). (1147264)

• Fluent design point studies using the Remote Solve Manager may not completely update due to errors. Should this happen, you can rerun the affected design points with a lower or the same number of cores and they will update as expected (you may have to rerun failed design points multiple times). (1012512)

Fluent Python Console

• No known issues, limitations, or documentation inaccuracies.

Parametric Studies

• No known issues, limitations, or documentation inaccuracies.

Simulation Reports

• No known issues, limitations, or documentation inaccuracies.

Simulation Environment

• Enabling the Console Auto Completer causes a significant slowdown in command execution, such as when using Execute Commands via the graphical user interface, Fluent scheme, or the Python console. It also impacts the performance of Fluent client applications like Fluent Aero and Fluent Icing. To work around this issue, disable the Console Auto Completer feature. (1199044)

Fluent Aero

• The Parametric Graph tool, available in the Results ribbon and under Results → Simulation → Graphs in the Outline View, encounters an error when reading a .csv file that contains non-numeric data columns. This prevents the tool from plotting the graph. Before using the Parametric Graph tool, remove any columns that contain non-numeric data from the .csv file. (1201862)

• Enabling the Console Auto Completer causes a significant slowdown in command execution, such as when using Execute Commands via the graphical user interface, Fluent scheme, or the Python console. It also impacts the performance of Fluent client applications like Fluent Aero and Fluent Icing. To work around this issue, disable the Console Auto Completer feature. (1199044)

Fluent Icing

• When a wall thread assigned a heat flux file is not included in all partitions, the program may hang during setup, especially in small cases with a high CPU count. To work around this issue, reducing the CPU count may help resolve the problem. (1171244)

• When using an input file with the .msh extension, the Droplets and Ice icons in the Project View do not update correctly and appear broken. To workaround this, rename the .msh input file to .cas.h5 before running the simulation to ensure proper icon functionality. (1208180)

Polyflow

• No known issues, limitations, or documentation inaccuracies.