An apparatus (10) is presented for controlling a boundary layer (30) in a diffusing flow path (14) of a power generating machine (16). The apparatus includes a passage (18) in the power generating machine with an inlet (20) and an outlet (22). The apparatus also includes a fluid source (24) coupled to the inlet to transmit fluid into the passage. The apparatus also includes a vortex generator (26) within the passage effective to generate a vortex fluid (12) at the outlet. The outlet is positioned to inject the vortex fluid into the diffusing flow path of the power generating machine in order to control the boundary layer of the diffusing flow path. An apparatus is also provided to enhance the diffusion of a flow path within a power generating machine.