An improved exhaust system including a lobed mixer and an improved exhaust centerbody is provided. The improved exhaust centerbody includes means for cooperating with the lobed mixer to increase mixing effectiveness of the exhaust system without substantially increasing pressure losses attributable thereto. In a preferred embodiment of the invention, the cooperating means include a plurality of circumferentially spaced elongated deformations, such as grooves and ridges, which deformations extend radially with respect to a reference surface of the exhaust centerbody and which deformations are aligned in an axial direction substantially parallel to a longitudinal axis of the centerbody
