a turbine engine exhaust diffuser assembly having a tuneable exhaust velocity profile is disclosed . the assembly includes structure that generates a desired , tunable velocity profile within working fluid exiting the exhaust diffuser assembly . the exhaust assembly includes an concentric boundary sleeves that extend along a central axis and form an exhaust flowpath between them . a flow deflecting member disposed within the flowpath longitudinally divides the flowpath into a first region and a second region . the first region is characterized by a first predetermined velocity profile , and the second region is characterized by a second predetermined velocity profile . the second velocity profile is determined by at least one pre - selected dimension of the flow deflecting member . methods of maximizing hrsg energy extraction capacity and extending hrsg lifespan are also disclosed .