Error Message—Found +r and –r coordinates in an axisymmetric model

Issue

An axisymmetric coordinate system is selected for a 2D geometry. Upon start-up, the following error is issued:

Error: Found +r and -r coordinates in axisymmetric model

Solution

The axisymmetric coordinate system allows for a 2D simulation of a 3D geometry. This is because the 3D geometry is centered about an axis, and is uniform at all angular positions. The geometry can vary radially, but because of the uniformity in the angular direction, a 2D slice can be used to accurately simulate the 3D flow in the device.

The key to modeling axisymmetric geometry is the center axis. To be uniform in the angular direction, the geometry is a body of revolution about the center axis, which is either the X or Y coordinate axis.

This error means that some part of the model crossed the center axis, which means that it does not represent a body of revolution.

To resolve this error:

1. Ensure that the correct axis was selected (under the Coordinate System branch of the Feature Tree). If the model is supposed to be axisymmetric about the X axis, selecting the Y axis may lead to this error.
2. Ensure that no part of the geometry crosses the axis. If the model is axisymmetric about the X, then the entire model should be above or below the X axis. It can touch the axis, but it can't cross it. Likewise for the Y axis, the entire model should be to the left or to the right of the Y axis, and can't cross it. Fix the geometry in the CAD system to ensure its correct placement.
3. For axisymmetric analysis, the geometry must be constructed in the XY plane. If it is in the XZ or YZ plane, this error will be issued. Make the correction in the CAD system.