6.4.4 Using a Non-Conformal Mesh in ANSYS FLUENT

If your multiple-zone mesh includes non-conformal boundaries, check if the mesh meets all the requirements listed in Section  6.4.3). This ensures that ANSYS FLUENT can obtain a solution on the mesh. Then do the following:

1.   Read the mesh into ANSYS FLUENT. If you have multiple mesh files that have not yet been merged, first follow the instructions in Section  6.3.15 to merge them into a single mesh.

2.   After reading in the mesh, change the type of each pair of zones that comprises the non-conformal boundary to interface (as described in Section  7.1.3).

Boundary Conditions

3.   Define the non-conformal mesh interfaces in the Create/Edit Mesh Interfaces dialog box (Figure  6.4.10).

Mesh Interfaces Create/Edit...

Figure 6.4.10: The Create/Edit Mesh Interfaces Dialog Box

(a)   Enter a name for the interface in the Mesh Interface text-entry box.

(b)   Specify the two interface zones that comprise the mesh interface by selecting one or more zones in the Interface Zone 1 list and one or more zones in the Interface Zone 2 list.

If one of your interface zones is much smaller than the other, you should specify the smaller zone as Interface Zone 1 to improve the accuracy of the intersection calculation.

(c)   Enable the desired Interface Options, if appropriate. There are three options:

• Enable Periodic Boundary Condition to create a non-conformal periodic boundary condition interface.
  • Select either Translational or Rotational as the periodic boundary condition Type to define the type of periodicity.

  • Retain the enabled default setting of Auto Compute Offset if you want ANSYS FLUENT to automatically compute the offset. After creating the interface, the offsets will be displayed in these fields. The fields will be uneditable when the Auto Compute Offset is enabled.

  • Disable Auto Compute Offset if you decide that you do not want ANSYS FLUENT to find the offset. In this case, you will have to provide the offset coordinates or angle in the required fields, depending on whether Translational or Rotational periodicity is selected.

    Auto computation means that the rotational angle or the translational offset will be automatically calculated and used while creating a non-conformal periodic boundary condition interface. However, it still relies on the Rotational Axis Origin and the Rotational Axis Direction that was entered for the cell zone in the cell zone condition dialog box (e.g. the Fluid dialog box). Therefore, before proceeding with the creation of the non-conformal periodic boundary condition interface, you have to correctly enter the rotational axis for the corresponding cell zone. Note that auto computation of the non-conformal periodic boundary condition offset does not mean that the Rotational Axis Origin and Rotational Axis Direction are also detected automatically and updated. It is still your responsibility to set up these values correctly.

  The Periodic Boundary Condition option is only valid when a single zone is selected in each of the Interface Zone 1 and the Interface Zone 2 selection lists.

• Enable Periodic Repeats when each of the two cell zones has a single pair of conformal periodics adjacent to the interface (see Figure  6.4.6). This option is typically used in conjunction with the sliding mesh model, when simulating the interface between a rotor and stator.

  The Periodic Repeats option is only valid when a single zone is selected in each of the Interface Zone 1 and the Interface Zone 2 selection lists.

• Enable Coupled Wall if you would like to model a thermally coupled wall between two fluid zones that share a non-conformal interface.

  Note that the following interfaces are coupled by default: the interface between a solid zone and fluid zone the interface between a solid zone and solid zone Therefore, no action is required in the Create/Edit Mesh Interfaces dialog box to set up such interfaces.

(d)   Click Create to create a new mesh interface. For all types of interfaces, ANSYS FLUENT will create boundary zones for the interface (e.g., wall-9, wall-10), which will appear under Boundary Zone 1 and Boundary Zone 2. If you have enabled the Coupled option, ANSYS FLUENT will also create wall interface zones (e.g., wall-4, wall-4-shadow), which will appear under Interface Wall Zone 1 and Interface Wall Zone 2.

(e)   If the two interface zones did not overlap entirely, check the boundary zone type of the zone(s) created for the non-overlapping portion(s) of the boundary. If the zone type is not correct, you can use the Boundary Conditions task page to change it.

(f)   If you have any Coupled Wall type interfaces, define boundary conditions (if relevant) by updating the interface wall zones using the Boundary Conditions task page.

Boundary Conditions

If you create an incorrect mesh interface, you can select it in the Mesh Interface selection list and click the Delete button to delete it. Any boundary zones or wall interface zones that were created when the interface was created will also be deleted. You may then proceed with the problem setup as usual.