A system includes a turbine casing assembly that includes an outer shell and an inner shell positioned substantially concentrically within the outer shell. The inner shell includes an inner surface facing away from the outer shell and an outer surface facing toward the outer shell, and the outer surface has one or more false flanges. At least one of the one or more false flanges includes a first surface protruding from the outer surface and facing the outer shell, and a flow diverting portion extending between the first surface and the outer surface of the inner shell. The flow diverting portion includes a first portion that diverges in a first circumferential direction between the first surface and the outer surface.