KNOWN ISSUE: Geometry-related objects doesn't always update when the expression that they depend on is changed
Geometry-related objects don't update when the expression they depend upon is changed in the Expression Editor.
If an expression is modified using the Expression Editor, the changes are not correctly propagated to geometry objects which depend on it, and no update will be performed until the geometry object is re-calculated for other reasons. However, if an expression is changed directly in the editor for that object, then changes are applied immediately.
An example of this problem is shown by the use of an expression to define the particle symbol scale (a beta feature).
Edit the expression directly on the appropriate editor (e.g. on the Particle Track Editor for the particle symbol scale).
ANSYS CFX Release 12.1.