Generating the Neutral Surface using Blade Faces

The Turbo Slicing Surface tool generates a neutral surface through a chosen blade in your turbomachinery geometry which represents the primary gas path.

Before using the Turbo Slicing Surface tool, make sure that your geometry has a suitable fluid domain. See Extracting the Overall Fluid Volume.

Note

The Turbo Slicing Tool focuses on generating the neutral surface and does not take into consideration the direction of flow. Radial geometry can consist of compressors or turbines, depending on the direction of the flow through the geometry. When defining the inlet and outlet faces for a radial geometry, define these faces so that they are consistent with a radial compressor, as shown in the example screenshots.

To extract the blade passage fluid volume:

In the Features toolbar, click the (Face Feature) option and select (Create Turbo Slicing Surface).
The Turbo Slicing Surface panel appears.
In the Turbo Slicing Surface panel, set Input Type to Blade Faces.
Specify the type of geometry:
- For axial geometries, set Blade Type to Axial.
- For radial geometries, set Blade Type to Radial or Radial Diffuser depending on the type of geometry you have.
In the 3D-CAD View scene, select the faces that make up a single blade.
To help with the selection, you can hide any obstructing faces. See Hiding Faces.

In some cases, small patches can cause problems. In these cases, omit the small patches from the blade selection. If patches exist, it is not necessary to fully capture the blade leading and trailing edge faces as the neutral surface is an approximate mid-surface.
- For axial geometries:
- For radial geometries:
Click inside the Hub Faces group box to activate it and in the 3D-CAD View scene, select the faces that make up the hub.
You are advised to only select the hub faces that envelop the selected blade, and that define the hub surface of revolution. It is not necessary to select all the faces that make up the hub. Do not select faces that are coincident with upstream or downstream boundaries.
- For axial geometries:
- For radial geometries:
Click inside the Shroud Faces group box to activate it and in the 3D-CAD View scene, select the faces that make up the shroud.
In cases without a shroud, for example open propellers, the shroud faces are the outer boundary of the extracted fluid domain.

If you hid any faces on the domain, restore them by right-clicking on a blank area in the scene and selecting Restore Hidden Faces. In many cases, the shroud is the domain wall.
- For axial geometries:
- For radial geometries:
Click inside the Inlet Faces group box to activate it and in the 3D-CAD View scene, select the faces that correspond to the inlets.
The inlet must be planar.
- For axial geometries:
- For radial geometries:
Click inside the Outlet Faces group box to activate it and in the 3D-CAD View scene, select the faces that correspond to the outlets.
- For axial geometries, the outlet must be planar. It is also good practice for the outlet to be parallel to the inlet.
- For radial geometries, the outlet is expected to be perpendicular to the inlet.
If the neutral surface can be calculated, a preview appears.
- For axial geometries:
- For radial geometries:
For geometries containing either non-planar inlets or outlets, or two or more small inlets or outlets, activate the Auto Extend Inlet/Outlet option.
For more information, see Turbo Slicing Surface Panel.
Set the turbo slicing surface parameters so that the neutral surface fits through the center of the blade. Also make sure that the areas where the neutral surface meet the inlet and outlet are normal to these boundaries.
The surface must fully intersect all domain walls so that you can use it to slice the single blade passage from the overall fluid domain.

See Turbo Slicing Surface Panel for a definition of the parameters.
- For axial geometries:
- For radial geometries:
Click OK.

The neutral surface is created and appears as a sheet body under the Bodies node of the feature tree.