Simulation of the mixing of a passive scalar in a round turbulent jet

In this paper we present the results of the direct numerical simulation (DN S) of mixing of a passive scalar in a spatially developing free round turbu lent jet. The Schmidt number used in the simulations is equal to 1.0 and th e Reynolds number, based on the orifice diameter and velocity is equal to 2 .0 x 10(3). The primary objective of this paper is to consider the self-sim ilarity of the jot in the far field. Having considered the self-similarity of the velocity in a previous publication, we concentrate here on the self- similarity of the concentration of the passive scalar. To this end we have considered the profiles of the mean concentration and its fluctuations, tog ether with the concentration probability density function distribution. The results have been compared with various experimental data that have been p ublished in the literature. In general, the results agree very well with th e experimental data. The conclusion is that the mean concentration is self- similar in the far field. The profiles of the root mean square of the conce ntration fluctuations are not self-similar. Furthermore, it is shown that t he turbulent Schmidt number is equal to 0.74, which agrees very well with e xperimental values. (C) 2001 Published by The Japan Society of Fluid Mechan ics and Elsevier Science B.V. All rights reserved.