### 10.3.7. Stage Fluid Zone Feature

The “fluid zone” represents the 3D fluid region within the flow passage, and is used to define the extent of the CFD domain. In release 11.0, a fluid zone was automatically created for each ImportBGD feature, which included the fluid region around a single blade row. For multiple blade rows, the fluid zone must include separate regions for, and have distinct interfaces between, each blade row.

In release 12.0 and higher, a StageFluidZone feature takes as a reference the selected FlowPath feature, and creates solid bodies for the fluid region in every blade row of the flow path. The first stage fluid zone in the flow path will start at the inlet contour and extend to the first interface (or to the outlet contour if there is only one blade row). The last stage fluid zone starts at the last interface and extends to the outlet contour. All intermediate stage fluid zones start and end at the interfaces adjacent to the blade row. The individual bodies are “frozen” so that they are not merged to adjacent solid bodies, including adjacent stage fluid zone bodies. (Individual bodies can be suppressed or hidden using existing DM functionality.) All active bodies (blades, hub, etc.) are subtracted from the fluid zone.

The stage fluid zone upstream and downstream interfaces are located by default halfway between the closest extents of the adjacent blade rows. For this to work, the StageFluidZone feature assumes that there is no overlap between adjacent blade rows; the StageFluidZone feature reports an error if this condition is violated. (Overlapping blade designs should be created using a combination of the Blade and Splitter features.) You may adjust the relative location of the interface by using one value in the range 0-1.

The feature properties are as follows:

Table 10.1: Details View for StageFluidZone Feature

Details of [Feature Name]
StageFluidZone | [Feature Name]
Flow Path | [FlowPath feature selection]
Create Named Selections | [Yes | No]
Interface Detail 1:
Interface Location | [Value: 0-1, default 0.5][a]
Interface Detail 2:
Interface Location | [Value: 0-1, default 0.5][a]
[a] 0 corresponds to the aftmost trailing edge of the set of blades in the upstream blade row. 1 corresponds to the foremost leading edge of the set of blades in the downstream blade row.

The Create Named Selections property determines whether the feature will automatically create named selections for each stage fluid zone. The Interface Details groups are created dynamically depending on the number of interfaces involved (number of blade rows less one.)

Named selections are created automatically for each blade row of the StageFluidZone. The naming convention is Hub_[Main Blade Name], Shroud_[Main Blade Name], Blade_[Blade Name], etc. where Main Blade Name is the name of the main blade in the given blade row. For the Blade_ regions, each blade in the blade row will have a separate region defined.

Named selections will not appear in DesignModeler, but they will appear if you load the .agdb file into the Mechanical application or the Meshing application, provided that you have set the properties of the Geometry cell (in `Tools` > `Options` > `Geometry Import` in ANSYS Workbench) as follows:

- CAD Attributes is selected.

- Filtering Prefixes and Suffixes is cleared.

  (This setting appears when CAD Attributes is selected.)

- Named Selections is selected.

You can make the Geometry cell settings this way by default by selecting Tools > Options from the ANSYS Workbench main menu, browsing to the Geometry Import branch, and setting CAD Attributes (same as Attributes), CAD Attributes > Filtering Prefixes (same as Attribute Key), and Named Selections.

Note: If the StageFluidZone periodic interfaces do not appear to be trimmed appropriately on the hub or shroud boundaries, you can try increasing the Blade Extension property for the corresponding blade feature to remedy the problem. The StageFluidZone feature uses this property to control how the periodic interfaces are created.

Release 18.2 - © ANSYS, Inc. All rights reserved.