3-DIMENSIONAL SIMULATIONS OF JETS

We present three-dimensional direct numerical simulations of an hydrod ynamical supersonic jet, comparing them to analogous results obtained in two dimensions. The differences seen between three-dimensional and two-dimensional jet evolution including faster evolution, enhanced mix ing and larger jet momentum depletion, are interpreted in terms of spe cific physical differences between these two cases. We have identified two main physical differences: The first is the faster development of small-scale structures in three dimensions, through either the growth of linearly unstable non-axisymmetric (three-dimensional) modes or th e non-linear cascade of energy to smaller scales; the second is the di fferent scaling of volumes in the two cases. Based on our 2-D and 3-D results, we discuss the limitations of using two-dimensional simulatio ns to capture the evolution of three-dimensional jets.