### 2.9.5. Using r-Theta Profiles

Using r-theta profiles in ANSYS CFX is possible, but the following points should be noted to ensure that the profiles are set up as intended.

1. The r-theta coordinates specified in the profile are used to calculate X and Y positions in the Cartesian space. The local coordinate frame (selected on the Basic Settings tab for each boundary condition in CFX-Pre) is used to evaluate the X and Y directions. When the r-theta and X-Y coordinates are defined with respect to the same coordinate frame, the points (r=1, theta=0) correspond to (X=1, Y=0). For details, see Coordinate Frames.

2. When specifying cylindrical velocity components, a rotation axis is used on the Boundary Details tab to specify the velocity component directions. Note that this axis is independent of the axis used to evaluate the r-theta coordinate positions specified in the profile file.

3. Profiles specified using r-theta positions and U, V, W velocity components may not be usable unless:

   - The U and V velocity component directions correspond with the X-Y coordinate directions that will be mapped from your r-theta coordinates by CFX-Pre (outlined in point 1, above).

   - You understand that using a custom coordinate frame to achieve the correct X-Y mapping from your r-t theta positions will also change the U, V, W velocity component directions, which you enter on the Boundary Details tab (and this may not be what you intend).

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