The following limitations apply to using the DO radiation model with the GPU solver:

The GPU solver is not available in the Ansys Workbench environment.

Larger reporting intervals for residuals and monitors is recommended for comparing the performance of the GPU solver to the CPU-driven Fluent solution. A reporting interval of 20 is recommended and can be specified with the following TUI command:

/solve set report-interval 20

Profiles in cylindrical coordinate systems, which includes those used for swirl inlets, are not supported.

Monitors and report definitions must be defined prior to solution initialization or before calculating the solution. Additionally, if the solver settings are changed from steady to transient, it may be necessary to redefine report definitions.

When monitoring mass flow rate at a non-conformal mesh interface where the fluxes are collected from intersected faces to the parent faces, the printed result will have the wrong sign (e.g -1 instead of 1).

When monitoring Dynamic Pressure (Pressure... category) at a stationary wall boundary, the resulting value will be zero as expected. However, results computed using a report (as outlined in Creating Output Parameters) will show an incorrect non-zero value.

Static expressions are supported by the GPU solver but are not recommended.

The Turbulent Viscosity Ratio is clipped to 10e5 in the same manner as the CPU-driven Fluent solver, however the GPU solver will not provide feedback to the transcript or console.

When thermal effects are defined for your case as outlined in Modeling Thermal Energy, using a steady-state solution to initialize a transient case does not work correctly when solving the energy equation. This limitation can be resolved by performing the procedure outlined in Transitioning from a Steady-State Solution to a Transient Calculation.

With the CPU-based Fluent solver, when modeling supersonic flow at a pressure inlet or velocity inlet all flow characteristics enter into the flow domain and the flow state must be fully specified. Similarly, when there is supersonic flow at a pressure outlet, all flow characteristics exit the domain and the specified pressure will be ignored by the solver. However, when modeling supersonic flow with the GPU solver, the flow will not be discretized correctly at pressure inlets, velocity inlets, and pressure outlets and the flow will be treated as subsonic at these boundary types. Supersonic static pressure at inlets will therefore be ignored, leading to an underspecified state which may produce an unreliable solution. Additionally, the specified static pressure on pressure outlets will still be enforced, which may lead to inconsistencies in the solution directly adjacent to the boundary.

With the CPU-based Fluent solver, if a fluid region is closed (has no pressure boundaries) and the flow is not compressible and not transient, the solver will set the pressure to zero at the cell closest to the pressure reference location ((0,0,0) by default). The GPU solver will instead constrain the pressure level by preserving the volume average of the initial condition for pressure. Therefore, there will be an offset in pressure between the CPU-based and GPU solver solutions. Additionally, since the pressure level is arbitrary for such flows, this offset will have no other effect on the solution but may affect force integrals on bodies which are not closed surfaces.

When modeling incompressible or incompressible ideal gas materials with the energy equation enabled, the temperature field calculated by the CPU-based Fluent solver and the GPU Solver may be different. This is due to different energy formulations (total energy and thermal energy) being used by the two solvers when computing incompressible flows. The CPU-based Fluent solver will use the thermal energy model when incompressible or incompressible ideal gas materials are defined and viscous heating is not enabled. However, for all other physics models the CPU-based Fluent solver will use the total energy model. Additionally, the GPU Solver will always use the total energy model for all physics models. While the thermal energy model is more likely to satisfy temperature boundedness conditions, the thermal energy model may yield a more robust solution than the total energy model in some cases.

When restarting a simulation using second-order transient, the solver uses the first-order Backward Euler scheme on the first timestep after restarting.

Restarting a GPU Solver solution on the CPU-driven Fluent solver will not restart correctly if the energy equation with a compressible material is calculated in the GPU Solver solution.