7.2.1. Profile Data Expansion (Option = Expansion)

Given an existing profile data file that describes, in Cartesian coordinates, a section that possesses rotational periodicity around a rotation axis, you can use an Expansion transformation to obtain a new profile with multiple "copies" of the section, rotated around the axis, extending to as many passages as required (up to a full wheel). The input profile is "replicated" about the specified axis in the positive rotational direction (according to the right-hand rule). The number of replications required is either specified directly or, if Expansion Option is set to Expand to Full Circle, given by the ratio of the specified values for Passages in 360 and Passages in Profile.

In the expanded profile, a sector number is added to account for the number of passages that must be covered by the expansion. Sector numbering starts from 1. In the case of a single passage per sector, the sector number corresponds to the passage number. Note that sector numbers are not added to profiles that contain gaps within the part being expanded.

The procedure for expanding profile data involves the following steps:

  1. Set the profile transformation option to Expansion.

  2. If the original profile contains variables that require phase shifting during expansion (for example, Mode Shapes from Ansys Mechanical cyclic symmetry analysis), the Use Profile Instancing option is available (and selected by default). This option is available only for a profile that has been exported by Ansys Mechanical and that contains a complex mode shape, including the Harmonic Index parameter.

    Expanding the profile using instancing takes proper account of the phase shift between the blade passages.

  3. Specify the axis about which the profile must rotate during the expansion process.

    If you select the Rotation Axis option, enter two Cartesian points on the axis to indicate the axis origin and the direction of increasing axial coordinate. These points can be entered manually or selected in the viewer by clicking any coordinate box and then clicking in the viewer. The working units are assumed to apply to the point coordinates.

  4. Set Passages in Profile to the number of passages that are modeled by the original profile.

  5. Set Passages in 360 to the number of passages in a complete 360° revolution.

  6. By default, Expansion Option is set to Expand to Full Circle, causing the profile to expand such that it wraps completely around the machine axis. If this is not wanted, then set Expansion Option to Spec. Number of Passages and specify the required number of passages for the expansion (Pass. in Expansion).

  7. Specify a non-zero Theta Offset value to carry out the expansion starting from a rotated version of the original profile.

 

7.2.1.1. Notes and Limitations of Profile Data Expansion

Profile Expansion has the following limitations:

  • If a non-integer number of replications is needed to obtain a 360° profile, then the data for the last replicated portion is truncated and a gap is left. The gap is positioned to be as far away from the original profile as possible.

  • Only files that have spatial data consisting of three spatial Cartesian coordinates (X, Y, Z) are supported.

  • Variables in the profile file that are identified as vector components in cylindrical coordinates will be transformed so that their axial, circumferential, and radial components remain constant in each replication. It is assumed that vector variables in cylindrical coordinates (such as Velocity Axial, Velocity Radial, and Velocity Circumferential) are relative to the same axis of rotation as used for the profile expansion.

  • Variables are identified as components of Cartesian vectors if they are standard CFX Cartesian vector components or if they have named with a X, Y, or Z suffix (upper or lower case). If all three components of a vector are present, then the three components are treated as components of a Cartesian vector, and the vector is rotated appropriately when the profile is replicated. If not all three components of the vector are present, then the components are ignored and will not appear in the expanded profile file. It is assumed that all three components of a vector have consistent units.

  • Variables that are standard CFX tensor components (for example, components of Reynolds Stress) will be ignored and will not appear in the expanded profile file.

  • Variables from the profile file that are not identified as vector and tensor components will be assumed to be scalar variables and will take the same value in each replication, leading to a rotationally-periodic variable definition in the expanded profile.

  • It is advisable to check an expanded profile file by initializing it and then coloring the resulting User Function, to ensure that vector variables have been transformed as intended.

  • A new variable, Sector Tag, is written to the expanded profile file only if an integer number of replications is needed to obtain a 360° profile. This identifies each replication by a unique integer.