I saw an error message when defining grid interfaces in sliding mesh with "periodic" type checked, which follows here: "Node(s) on face thread 13 has multiple shadows" What does it mean? How do I model the periodic type grid interface in fluent 6.0?

try using the "repair periodic" function --- text command grid/modify zones/repair periodic

also, the periodic sliding mesh model only works if both sides of the interface are the same size.