Effect of exit conditions on the self-preservation states of round jets

Centerline velocity measurements are made in two round jet flows issuing with the same Reynolds number (86\,000) from a smooth contraction and a long straight pipe, respectively. The influence of exit flow conditions is investigated to induce the different self-preservation states in the far field of the two jets. The smooth contraction jet flow is found to approach more rapidly to self-preservation than the pipe jet. The study suggests that the observed self-preservation states may be related to the underlying turbulence structures in the near field of the two jets.