Maximum number of iterations exceeded


Solver error: Maximum number of iterations exceeded by the solver

What happened?

The simulation stopped because the solver iterated 1000 times but could not reach the specified tolerances in the particular time step.

What could be the possible reason?

1- The mesh could have illegal/bad cells that are causing problems.

2- The flow variables reached extremely large or non-physical values. This could be caused by either incorrect boundary conditions or severe inflow/outflow conditions.

What can I do now?

1-) Please see the ‘Meshing Log’ under the ‘Mesh Operation’ for any errors in the mesh. Further, Also inspect the meshed body/surfaces visually to make sure there are no distorted cells near the surface.

SHM meshing log


2.1-) Make sure the Boundary Conditions are correct and have appropriate values. Please see Boundary Condition Documentation for details. Futher, see the sample Tutorials or Sample Projects for reference.

2.2-) Under “Numerics” entry in project tree, use lower values of ‘Relaxation factors’. for example:

relaxation factors
  • Lower the Solver tolerances e.g ‘absolute Tolerance = 1e-7’ and ‘relative Tolerance = 0.05’ or use default ones.
relaxation factors
  • In case of a transient simulation use ‘Automatic Time Stepping’ under “Simulation Control” and change ‘Number of outer correctors’ under “Numerics” to at least 4.

2.3-) If the flow conditions are severe e.g high inlet flow ‘Velocity’ or ‘Pressure’, try to ramp the values for the first few hundred steps using “Table Upload” (see TableUpload for details) option in boundary conditions.


If none of the above suggestions did solve your problem, then please post the issue on our forum or contact us.