Named Selections of connected edges in Mechanical are transferred to ACP as Edge Sets. New Edge Sets can also be defined manually in ACP-Pre:
Edge Set Type: How the Edge Set is defined:
By Reference: Defined the Edge Set using an existing Element Set (activates the following options):
Element Set: The Element Set of which the Edge Set is part.
Limit Angle: The Edge Set is extended from the origin in both directions until the angle between two elements is bigger than the Limit Angle. If the Limit Angle is set to a negative value, the Edge Set is the whole boundary of the selected Element Set.
Origin: Origin to determine the closest boundary.
By Reference: An existing Element Set is used to define a new Edge Set through one boundary limited by an angle diffusion.
By Nodes: Manually select the nodes to define the Edge Set.