Simulation of Homogeneous Particle Nucleation in a Free Turbulent Jet

The homogeneous particle nucleation in a free turbulent jet is simulated at Reynolds numbers of 3400 and 34,000 by using large eddy simulation (LES) coupled with our newly developed equivalent mean nucleation method (EMNM) for the present study. The simulated velocity field, passive scalar concentration, and nucleated particle concentration are compared with various available measurements in the literature. Both the simulated mean velocity and mean scalar concentration show self-similarity properties and agree well with the experimental measurements quantitatively in the literature. Using the EMNM, it is found that the nucleation primarily occurs in a very narrow region around the jet center-line. It is also found that the position of maximum nucleation is a function of the vapor temperature and concentration at the jet exit and its surrounding background (i.e., T-0, T-infinity, c(0), and c(infinity)), and the function varies monotonically with respect to these four parameters. Present numerical simulation and analysis also show that the group, (N) over baru(0)/d (where (N) over bar is the mean particle number concentration, u(0) is the jet velocity, and d is the jet exit diameter), is constant along the axial direction of the jet, which was first observed in the experiment of Lesniewski, T. K., and Friedlander, S. K. (1998). Particle Nucleation and Growth in a Free Turbulent Jet. Proc. R. Soc. Lond. A, 454: 2477-2504. However, a different physical explanation of the fact is provided. In this study, it is found that the maximum nucleation occurs around 20d away from the jet exit, other than in the shear layer (less than 5d), which was supposed by Lesniewski, T. K., and Friedlander, S. K. (1998). On the basis of the additional simulated results, more comprehensive and reasonable explanations of their measurement data are provided. In this study, an efficient and rigorous numerical method is presented to simulate the homogeneous particle nucleation in a free turbulent jet, and this has provided a deeper and thorough understanding of the process.