The sequential explicit coupling scheme (also referred to as the Gauss-Seidel coupling algorithm) is the only coupling scheme available for Abaqus/CFD to Abaqus/Standard or to Abaqus/Explicit co-simulation. In all of the predefined templates, the Abaqus/CFD analysis lags the co-simulation and the Abaqus/Standard or Abaqus/Explicit analysis leads the co-simulation. For conjugate heat transfer, the Abaqus/CFD analysis can either lag or lead the co-simulation. For fluid-structure interaction, the Abaqus/CFD analysis must lag the co-simulation and the Abaqus/Standard or Abaqus/Explicit analysis must lead the co-simulation.

The coupling step size is the period between two consecutive co-simulation data exchanges. The coupling step size is determined automatically based on the type of analysis and is used to obtain time-accurate solutions for the coupled physics problem. For fluid-structure interaction (FSI) and conjugate heat transfer (CHT) analyses that couple Abaqus/CFD and Abaqus/Standard, the coupling step size is the minimum of the time step sizes determined by the automatic time incrementation schemes of the individual analyses. For FSI problems that couple Abaqus/CFD and Abaqus/Explicit, Abaqus/Explicit imports the coupling step size from Abaqus/CFD; consequently, Abaqus/CFD exports the coupling step size to Abaqus/Explicit.

Depending on the type of analysis, Abaqus may either perform one increment (referred to as “lockstep”) or several increments (referred to as “subcycling”) per coupling step. For FSI analyses that couple Abaqus/CFD and Abaqus/Explicit, Abaqus/Explicit typically uses subcycling while Abaqus/CFD uses lockstep behavior.

You can use predefined templates to create a configuration file for the coupling schemes described above. Table 17.3.2–1 describes the predefined templates available for fluid-to-structural co-simulation and conjugate heat transfer and lists example configuration files that you can review.

To obtain an example configuration file, you can use the abaqus fetch utility. For example, to obtain the example for Abaqus/Standard to Abaqus/CFD conjugate heat transfer, use the following command:

abaqus fetch job=exa_std_cfd_cht

<?xml version="1.0" encoding="utf-8"?>
<CoupledMultiphysicsSimulation>
   <template_std_cfd_cht>
      <Standard_Job>standard_job_name</Standard_Job>
      <Cfd_Job>cfd_job_name</Cfd_Job>
      <duration>duration_value</duration>
   </template_std_cfd_cht>
</CoupledMultiphysicsSimulation>

In certain cases you may need to use co-simulation configuration features that are not described in the predefined templates. For example, you may wish to change the dissimilar mesh mapping search tolerances; these tolerances are available generally in the configuration file but are not described in the predefined templates. For these cases, you must create an elaborated configuration file; for more information, see “Using elaborated configuration files” in “Preparing an Abaqus analysis for co-simulation,” Section 17.2.1.