Some embodiments of the invention provide an electric machine module including a rotor assembly. The rotor assembly can include a rotor hub, a first set of rotor laminations which can include a portion having a first inner radius, and a second set of rotor laminations which can include a portion having a second inner radius larger than the first inner radius. At least one circumferential flow channel defined by the first set of rotor laminations, the second set of rotor laminations, and the rotor hub can at least partially circumscribe the rotor hub.