Coupling with NASTRAN

You can couple Simcenter STAR-CCM+ with Nastran using file-based coupling, for fluid-structure interaction (FSI) applications. In an FSI file-based coupled analysis, Simcenter STAR-CCM+ solves for the fluid loads and Nastran solves for the response of the solid structure. You can export the field data computed in each code to external files that are then used in the partner code to set appropriate boundary conditions.

An example application is structural design exploration, where you test different structural designs in Nastran using the fluid loads computed in a single Simcenter STAR-CCM+ run. In this example, the coupling is only one-way, that is, the structure response is not imported back into Simcenter STAR-CCM+. For more information on file-based coupling, see File-Based Coupling.

The following sections assume that you already prepared the Simcenter STAR-CCM+ fluid simulation and the Nastran structure model, as appropriate to your analysis. Simcenter STAR-CCM+ supports the import of shells, volumes (solids), and surface elements from Nastran model text files with the .nas, .bdf or .dat file extensions.

Exporting Simcenter STAR-CCM+ Data to NASTRAN

Simcenter STAR-CCM+ computes the fluid loads at the fluid-structure interface. You export the computed loads to external files that Nastran can read.

Export the fluid loads in one of the following ways:
  • In static analyses, first run the Simcenter STAR-CCM+ simulation until converged. Then, export the computed fluid loads to a .nas Nastran file and use the file as a static load for structural analysis. See Exporting Data to NASTRAN.
  • In transient analyses, you can export the fluid loads at regular intervals while the Simcenter STAR-CCM+ simulation is running. The fluid loads are saved to a .bdf file. You then use a java macro, which is provided in the Simcenter STAR-CCM+ installation, to convert the .bdf files to a transient load file that can be used in Nastran for structural analysis. See Exporting Data to NASTRAN (Transient Run).

Importing NASTRAN Solution Data

Once a Nastran model has been imported, its associated solution data can be imported into Simcenter STAR-CCM+ from the OUTPUT2 (.op2) binary file format.

Exporting a Model to NASTRAN

When you export a model to Nastran you can choose if patches with the same name are merged or not. Activating Merge Cell Types by Name exports the boundary/part surfaces after merging the patches with the same name. This typically leads to one Property ID (PID) for the whole boundary/part surface instead of one PID per patch.