Experimental and modelling investigations of droplet dispersion in a turbulent jet
The turbulent dispersion of non-evaporating droplets in an axisymmetric round jet issuing from a nozzle is investigated both experimentally and theoretically. The experimental data set has a well-defined inlet boundary with low turbulence intensity at the nozzle exit, so that droplet dispersion is not affected by the transport of nozzle-generated fluctuating motion into the jet, and is influenced solely by gaseous turbulence produced in the shear layer of the jet. This data set is thus ideal for testing algebraic models of droplet fluctuating motion that assume local equilibrium with the gaseous turbulence. A two-fluid turbulence modelling approach is adopted, which uses such an algebraic model and the k - ε turbulence model to predict the droplet and fluid turbulent correlations, respectively. We have shown that the k - ε turbulence model lacks generality for predicting the spread of momentum in jets with and without a potential core. However, in general, the model predicts the radial dispersion of droplets in the considered turbulent jet with reasonable accuracy over a broad range of droplet sizes, once deficiencies in the k - ε turbulence model are taken into account.