### 10.6.4. Export to Vista TF (.geo)

The VistaTFExport feature defines the parameters necessary to write the flow path geometry data (.geo file) for Vista TF. The .geo file contains a 2D mesh of the flow path geometry, including the locations of the blade leading and trailing edges. The .geo data also includes the blade type, blade camber surface data, blade thickness data and blade count for each blade row.

To export a .geo file, create a VistaTFExport feature. Start by clicking the icon.

The feature properties are listed below.

Table 10.6: Details View for the VistaTFExport Feature

Details of [Feature Name]
Vista TF Export | [Feature Name]
Blade(s) | [Blade feature selection]
Export to file | [Yes | No]
(If “Export to file” = “Yes”) Geo File Name | [.geo filename]
Streamwise mesh count | [Integer Value > 2]
Spanwise mesh count | [Integer Value > 1]
Selected Blades: [number] [a]
Blade 1 | [Blade reference]
Blade 2 | [Blade reference]
Blade 3 | [Blade reference]
[a] Blade items are listed for all selected blades.

Note: The Vista TF solver expects the flow path (from inlet to outlet) to be oriented in the direction of the machine axis, which is the Z-axis.

The VistaTFExport feature requires you to select the Blade features that will be exported to the .geo file. The selected blades must all belong to the same flow path. Therefore, the VistaTFExport feature can only export the data for a single flow path. Only the selected blades in the flow path will be considered for export; all other blades in the flow path will be ignored.

Note: If you select blades that are in the same blade row, and if those blades have leading and/or trailing edges of the same shape (within round-off error), then those blades are required to use the same contour sketch to define the edges that have the same shape. If the edges that have the same shape are instead defined using different contour sketches (that have the same shape), then VistaTFExport feature generation will fail.

The ‘Export to file’ option specifies whether to explicitly save the data to a .geo file. When using the ANSYS Workbench Project Schematic view, exporting to a file is unnecessary because the data is transferred automatically. If the .geo file is explicitly written, then you need to specify the .geo file name.

The .geo file contains the geometry coordinates for the flow path in terms of quasi-orthogonal (q-o) ‘lines’ running from hub to shroud. The q-o lines are spaced approximately uniformly from inlet to outlet, based on the mid-span meridional length. The number of q-o lines is specified by the ‘Streamwise Mesh Count’ property, where the minimum count is determined based on the number of selected blades in the flow path. If the specified Streamwise Mesh Count is less than the calculated minimum, then the calculated minimum will be used.

The number of q-o lines has a direct impact on the throughflow calculation accuracy and computation time. Increasing the number can improve accuracy, but it will also increase computation time. Increasing the number beyond a certain maximum may cause instabilities in the convergence process. Typical radial impellers with an axial inducer should be calculated with around 15 q-o lines in the bladed region, which equates to approximately a q-o line every 5° of curvature.

The Spanwise Mesh Count property specifies the number of points used to define each quasi-orthogonal line; the points are uniformly spaced from hub to shroud. The minimum number is two. Increasing this parameter will improve the exported geometry representation for highly curved blades, but it should not be necessary to go beyond about 30. This parameter has no effect on the number of streamlines that are actually used in the throughflow calculation.

When the .geo file is generated, a warning will be given for the VistaTFExport feature if the streamwise to spanwise aspect ratio of any of the mesh elements is greater than 15 or less than 1/15. Depending on the aspect ratio, you will be suggested to increase or decrease the appropriate streamwise or spanwise mesh count.

If the ThroatArea feature (see Throat Area Feature) is used for a selected Blade, the throat information for that blade will be written to the .geo file. This information may improve the calculation of the choke mass flow rate in the Vista TF solver. Without this information, Vista TF will make its own estimate of the throat area.

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