Small scale isotropy and universality of axisymmetric jets

This paper addresses the long-standing debate about whether the asymptotic jet can be universal. It is argued that the ansatz of a universal spreading rate is inconsistent with more accurate and recent measurements where the scatter in the opening angle is found to exceed the experimental accuracy, implying a true lack of universality in these basic quantities. A universal scaling theory may still be proposed by including the spreading rate in the similarity transformations. We will show that this approach leads to a conflict with the presumed recovery of isotropy in the dissipative scales of the flow. The issue is addressed here by using direct numerical simulations of free-jets to finally show that a complete universality is also incompatible with the experimental data available in the literature. (C) 2007 American Institute of Physics.