Ensure that any enabled models, boundary conditions, or solver settings are supported by the GPU solver. If performing the calculation after reading in a Fluent case file, ensure that all unsupported features have been properly converted (see Reading Fluent Case Files Into the Fluent GPU Solver).

If the flow solver is having difficulty when calculating a linear solution, you may encounter the following messages in the console:

AMG (energy/solver/solve) It 5, Diverged.

or

AMG (energy/solver/solve) It 8, Stalled.

Depending on the severity, you can increase the verbosity of the AMG solver within the Advanced Solution Controls dialog box as described in Setting Algebraic Multigrid Parameters and restart the calculation. During the calculation, information similar to the following will be printed in the console:

AMG (energy/solver/solve) residual history:
  It 0: Residual [rel,abs] = 1.0000e+00,6.4496e+04
  It 1: Residual [rel,abs] = 6.4405e-01,4.1539e+04
  It 2: Residual [rel,abs] = 7.8587e-01,5.0686e+04
  It 3: Residual [rel,abs] = 1.1034e+00,7.1168e+04
  It 4: Residual [rel,abs] = 1.6327e+00,1.0530e+05
  It 5: Residual [rel,abs] = 2.4890e+00,1.6053e+05
AMG (energy/solver/solve) It 5, Diverged.

If the residual values decrease at the beginning of the linear iterations but then stall, the warning printed in the console may not be indicating an issue with the solver settings. However, if the residual values increase as the solution progresses, this may indicate that the nonlinear residual convergence is poor and the solution may not be reliable. Performing either of the following steps may resolve this issue :

Decrease the Under-Relaxation Factor values within the Solution Controls task page. If using the SIMPLE scheme for a steady-state flow, the following under-relaxation factor adjustments may be beneficial:

Note that the above uner-relaxation factor adjustments may lead to slower convergence in some cases. For more information on adjusting solution controls settings for turbulent flows see Solution Strategies for Turbulent Flow Simulations.

Change the Spatial Discretization Schemes from second order to first order (see Choosing the Spatial Discretization Scheme). Switching to first order schemes will affect the solution accuracy. However, the decrease in accuracy is negligible when modeling turbulence.

Check the mesh quality and improve the mesh quality if the quality is poor or if there are any left-handed faces. The mesh can be improved either by regenerating the mesh with higher quality or by using the Fluent mesh improvement capability with the following text command:

/mesh/repair-improve/improve-quality