Restarting from a Previous Abaqus Simulation

An Abaqus restart must be performed when continuing from a previous Abaqus analysis, whether the analysis:
  • terminated due to an abort, for example in case of convergence failure in the Abaqus solver or a power failure
  • completed successfully (either a co-simulation analysis or an Abaqus stand-alone analysis to pre-load the structure)
  • terminated under Simcenter STAR-CCM+ control when the fluid mesh was remeshed in the middle of an analysis. See Remeshing the Fluid in Simcenter STAR-CCM+.
In order to restart, both the Simcenter STAR-CCM+ and Abaqus models must be in the same configuration at the point in time of the restart. Significant differences in configuration (such as a mismatch in the FSI boundary mesh positions) result in mapping errors (reported in the Simcenter STAR-CCM+ log window) or mapping inaccuracies. A good practice is to do both of the following steps when running an analysis:
  • Save restart frames at evenly spaced points in the Abaqus analysis. Do this using the *RESTART, WRITE, NUMBER INTERVAL=<n> command in the original Abaqus .inp file. See Specifying Co-Simulation Settings in Abaqus.
  • Synchronize the auto-save feature in Simcenter STAR-CCM+ to save at the same time intervals.

For analyses that were terminated before the end of the co-simulation analysis this practice ensures that there is a matching restart frame in Abaqus corresponding to a saved .sim file in Simcenter STAR-CCM+.

Select the displacement reference configuration based on the type of restart. For co-simulations where both the fluid and the structure are run together in all preceding analyses, set the configuration to Original Mesh Coordinates, of the coupled FSI boundary. Set this option under the relevant [Link] > Conditions > Displacement Reference Configuration Option node. In certain cases, there is a mismatch in the configuration that is represented by the original coordinates of each mesh. Examples of such cases are:
  • where the fluid analysis is remeshed
  • the Abaqus analysis is restarted from a stand-alone pre-loading step in Abaqus

In these cases, set Displacement Reference Configuration Option to Current Mesh Coordinates.

Define a restart from a point at which the models are in equilibrium. This condition is automatically satisfied when both analyses are started at the same point in time for the restart. If Abaqus is first run stand-alone to pre-load the structure and/or Simcenter STAR-CCM+ is run with a fixed FSI boundary to develop an initial flow field, then traction exported from Simcenter STAR-CCM+ and loads/boundary conditions applied in Abaqus may need to be ramped to allow a smooth transition to an equilibrium state at the fluid-structure interface.

To set up a restart analysis:

  1. Create an Abaqus .inp file with *RESTART, READ, ..., corresponding to the restart frame you are restarting from. If you wish to restart from a time point other than the time of completion of the previous step, include the END STEP parameter in the *RESTART definition. Also, include a new *STEP definition with the time duration of the new analysis and any additional structural loading or boundary conditions. Check the Abaqus .msg (Abaqus/Standard) or .sta (Abaqus/Explicit) files of the previous analysis for information about the restart frames that were written.
  2. In Simcenter STAR-CCM+, select the [Link 1] > Conditions > External Code Restart node and set Restart Option to New Step.
    A node called Abaqus Old Job Name appears under the [Link 1] > Values node.
  3. Within the Abaqus Execution properties, specify a new name for the Abaqus job (Current Job Name) and the new input file (Input File).
  4. Specify the old Abaqus job name using the [Link 1] > Values > Abaqus Old Job Name node.
    The Abaqus restart files from the analysis defined by Old Job Name are read at the start of the co-simulation and must be present in the same directory as the Input File of the restart analysis.
  5. Set the Displacement Reference Configuration Option to Current Mesh Coordinates if the original configurations of the structure and fluid do not match.
  6. Set the Simcenter STAR-CCM+ stopping time to the current time in Simcenter STAR-CCM+ plus the Abaqus restart step time. The co-simulation time corresponds to the Abaqus step time and starts from zero each time a co-simulation is restarted.
  7. Save the .sim file to a new name and click Run in Simcenter STAR-CCM+.