Using Material Databases

Importing Thermodynamic and Transport Properties

By default, a material database object named Standard is loaded automatically in a new simulation once you select a material model. This object accesses the props.mdb file that is located in your main Simcenter STAR-CCM+ installation directory (Windows) or in the star subdirectory of that directory (Linux).

To add a material or change the property of one, you can load a separate material database file. Alternatively, you can modify a database file for this purpose and reload it into the simulation. (If you are working with the database file supplied with Simcenter STAR-CCM+, be sure to make a copy and then move the original to another location.)

Simcenter STAR-CCM+ can accommodate multiple material databases, making them all available in the material model selection process.

The simplest way to prepare to load an additional database file is to place it in the same directory as the ones supplied by default, but with a different name. This location would be your main Simcenter STAR-CCM+ installation directory (Windows) or the star subdirectory of that directory (Linux). Make these preparations before opening your simulation file.

Reloading a Database File

This action updates all the information in the simulation for that database.

To reload the material database file, right-click the material database node and select Reload.

Importing Thermodynamic and Transport Properties

Simcenter STAR-CCM+ can import files with NASA thermal and transport properties.

To import this type of file:

1. Create a new (empty) material database object.
2. Right-click on that object and select Import Thermodynamic and Transport Properties...
   
   
   
3. Navigate to your file and click Open.

The first option imports the contents of the entire file. The second imports properties only for the materials that are already represented in the database object. This action populates the material database node with three database folders, similar to the structure of the Standard database object. You can also add more properties to the database object by selecting Import Thermodynamic and Transport Properties... again and selecting other files.

Changing Database Material Properties

Generally material properties can be changed by opening the database material property nodes and entering values in the properties of the sub-nodes. However, your actions in the GUI affect how permanent these changes are.

In principle, changes are made permanently to the material database by modifying a copy of that database. (Take care not to overwrite the original supplied file.) The simulation file itself only retains changes that are made to properties of the database materials that are used to create substances in the continuum (within single, multiphase, or multi-component material models). Therefore, if you modify a group of database materials, and then select only part of them in your continuum, the other modified database materials revert to their original values when you close and reopen the simulation file.

A good approach for modifying properties is as follows:

1. For a trial run, change material properties in the continuum.
2. Run the simulation.
3. If you are satisfied with the results from the new property values of the materials in the continuum:
   1. Make a copy of the external database file for use by the simulation.
   2. In the database material, enter the custom values that you used in the continuum. Specifically, enter the values in the database material properties values of the database material (for example Tools > Material Databases > Standard > Gases > Air > Density > Constant).
   3. Save the values to the database file by right-clicking the material database node and selecting Save.

Changing the Units of the Database Material Properties

By default the database materials have properties that are measured in SI (Systeme Internationale) units. However, you can change the units as they are represented in the database material properties, using the standard technique for changing units in Simcenter STAR-CCM+.

After making the switch once, you will have the added option of changing the units used for individual database material property values. To access this option for a particular value, click the property customizer () in the Value property of the node to activate the Customizer dialog. The properties within that dialog include a drop-down list with a choice of units.

What If the Database File Is Missing?

Most of the work you would do with material models depends on the supplied props.mdb file residing in its normal place. That place is your main Simcenter STAR-CCM+ installation directory (Windows) or the star subdirectory of that directory (Linux). You can load a material database into an open simulation.

Without a database, you cannot select materials in a new simulation, or change the material selections in an existing simulation. Your only option is to modify properties of material selections that were saved previously in a simulation file.

In a new or existing simulation, Simcenter STAR-CCM+ lets you know in several ways that the database is missing (in the following example, the standard material database is missing):

• When you attempt to select a new or alternate material model, you get an empty selection dialog, except for any materials selected in a previously saved simulation. (In this example, the simulation file contains only the material Air.)
  
  
• After you attempt to select a material model, the material database node appears in the object tree, but with no database folder nodes. (In an existing simulation file, the database folder nodes are also empty except for the referenced materials.)
  
  

Modifying a Copy of the Material Database

Located in your main Simcenter STAR-CCM+ installation directory (Windows) or in the star subdirectory of that directory (Linux), the props.mdb file is modified through the Simcenter STAR-CCM+ GUI, rather than opening it with another program.

Possible reasons for changing the material database include:

• Adding material data
• Importing a PPDF table (equilibrium or flamelet)
• Importing Chemkin-formatted data

After you make a copy of the external props.mdb file and relocate the original, change properties of database materials and/or add new materials with new properties and enter values for them. Once you are finished, right-click the node of the material database and select Save. (Saving the simulation file alone does not save your database material properties changes to the external database file.)