A turbomachine includes a combustor assembly, a cap assembly attached to the combustor assembly, a centerbody within the cap assembly, a wall of the centerbody having a first end, a second end and an intermediate portion, and an external turbulator member in operable communication with the cap assembly. The external turbulator member is spaced from the wall to form a passage defined by a gap between the wall of the centerbody and the external turbulator. The external turbulator member includes a step positioned at the second end of the centerbody. The step defines a radial distance about the second end of the centerbody. The external turbulator member is formed having a step-to-gap ratio relative to the centerbody in a range of about 0.8 to about 1.2.