### 10.3.2. FlowPath Feature

The FlowPath feature specifies the flow path. The contour sketches described in Flow Path Contour Creation are used in the definition of this feature. The FlowPath feature also creates the layer contours used to define the blade profiles, and automatically creates the LayerContour sketch, which shows the locations of the layers. The feature properties are listed in the table below. Note that all items under each bold heading in the table are grouped under that heading.

Details of [Feature Name]
FlowPath | [Name]
Machine Type | [Pump | Centrifugal Compressor | Axial Compressor | Fan | Radial Turbine | Axial Turbine | Hydraulic Turbine | Undefined]
Theta Direction | [Right-handed | Left-handed]
Hub Contour | [Sketch selection]
Shroud Contour | [Sketch selection]
Inlet Contour | [Sketch selection]
Outlet Contour | [Sketch selection]
Hub Cut? | [Yes | No]
(If “Hub Cut?” = “Yes”) Hub Cut | [Sketch selection]
Shroud Cut? | [Yes | No]
(If “Shroud Cut?” = “Yes”) Shroud Cut | [Sketch selection]
Number of Layers | Implicitly defined number of layers
Sketches for Defined Layer | [Sketch selection]
Advanced Property
Interpolation Mesh Size | The interpolation mesh is used to establish spanwise and streamwise coordinates in the flow path. It is important that the interpolation mesh sufficiently resolves the flow path in order to avoid adversely affecting geometry creation. The default interpolation mesh size is 2000. If the flow path is long and contains sharp bends (low-radius bends as viewed in the meridional plane), you should specify a higher interpolation mesh size. As a guideline, the mesh size should be 2000 multiplied by the number of blade rows.
Sketches of User Defined Layers:
Sketch Name | [Sketch name]
Sketch Name | [Another sketch name]
Layer Details: 1
Layer Type | [Fixed Span | User Defined Layer]
Span Fraction 1 | 0
Layer Details: 2
Layer Type | [Fixed Span | User Defined Layer]
Span Fraction 2 | [0 < Value < 1]
Layer Details: 3
Layer Type | [Fixed Span | User Defined Layer]
Span Fraction 3 | [0 < Value < 1]
Layer Details: 4
Layer Type | [Fixed Span | User Defined Layer]
Span Fraction 4 | 1

The Machine Type is used by downstream applications, for example in CFD-Post, for determining the appropriate default postprocessing report. The Theta Direction specifies the interpretation of the theta direction for the CamDef angle definitions. The theta direction can be specified as either right-handed or left-handed relative to the direction of the global Z axis (the machine axis).

By default, the flow path starts with two layers: one for the hub and one for the shroud. You can insert or delete layers. The first and last layers must be at span fractions of 0 and 1, respectively; these will always exist and cannot be deleted or changed. A given blade does not need to have defined profiles on all layers. The layers are defined in the context of the FlowPath feature for consistency between blade rows.

A layer can be defined by a fixed value of span fraction, or it can be defined by a sketch:

- To insert a new fixed-span-fraction layer, right-click an existing fixed-span-fraction layer in the details view and select Insert Layer Above or Insert Layer Below. To delete a fixed-span-fraction layer, right-click it and select Delete.

- To add one or more layers using sketches, specify the applicable sketches (which must be created beforehand) in the Sketches for Defined Layer property. Each sketch should contain one or more (separate) curves. Each curve in each specified sketch is used to create one layer. For example, if you select two sketches, one having one curve and the other having four curves, then five sketch-based layers will be generated.

  After you apply your sketch selection, a new category, Sketches of User Defined Layers, appears and lists the sketches that were selected. You can remove a sketch listed under Sketches of User Defined Layers by right-clicking the sketch and selecting Remove from selection.

  After you select sketches, or if you make any changes to the sketch selection in general, you must then regenerate the FlowPath feature. After regeneration is complete, the user-defined layers will appear in the “Layer Details” portion of the FlowPath details view.

Note: After the FlowPath feature has been generated, you will not be able to edit the Sketches for Defined Layer property until you right-click the FlowPath feature in the tree view and select Edit Selections from the shortcut menu.

All layers are presented in the details view in the order of average fractional span value. If you change a layer’s sketch curve or span fraction value such that the order of layers changes, then:

- The layers are renumbered (in accordance with their average fractional span values), and

- Any objects that refer to layers will continue to refer to the same layers under their new numbers.

For example, if the Blade sub-feature Blade1_Camberline6 refers to layer 6 and you subsequently insert a layer before layer 6, then the original layer 6 will be renumbered to become layer 7 and Blade1_Camberline6 will then automatically change so that it refers to layer 7 (and it will be renamed to Blade1_Camberline7).

Note: The layers used by a blade are required to not touch or intersect each other anywhere within the blade.

Note: When you change sketches that are used to define layers, the software will automatically attempt to maintain the association between the layers and the objects that refer to them. For example, if you add a curve near an existing curve, then delete the latter, the objects that originally referenced the deleted curve may be changed automatically to refer to the new curve. In cases where the software encounters difficulty maintaining assignments, a warning message may be issued.

If automatic reassignment is not applicable, manual reassignment can be carried out. For example, if you delete a curve that was being referenced by an object, and there is no other curve available for that object, then the object will be left in an invalid state. In that case, you could correct the problem by creating a new curve and manually reassigning that curve to the object. Note that for section definition objects, the manual reassignment must be done before regenerating the object.

You can create the FlowPath feature automatically via the Load BGD feature, or you can manually create the FlowPath feature. In either case, you can change the sketch selections once the feature has been created.

The FlowPath feature has optional hub cut and shroud cut properties to support trimming the flow path for a 'flow cut'. An example is if you have a base centrifugal compressor blade design that is used for a range of compressors. In this case, the FlowPath and Blade features would define the base blade geometry. You then want to use the same blade, but in a compressor of different size, so the blade height must be trimmed. The flow cut would be used to define the final flow path boundaries, and would trim the height of all blades in the flow path.

The flow cut affects all blades that reference the flow path. The flow cut properties take as input the sketch contours that define the flow cut. The additional feature properties are in a group below the Outlet Contour property.

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