Abstract
Mixing of a jet stream with an ambient fluid depends on several factors. The importance of these factors can be expressed in form of dimensionless numbers, relating the time-scales of the different processes to each other. The different time-scales depend in the properties of the fluids in question (i.e. diffusivity), the geometrical set-up (e.g. nozzle shape, shear-layer thickness) and the operating conditions (laminar/turbulent and accelerating/decelerating or intermittent jet). Turbulence has enhanced mass and momentum transfer due to the generation of eddies of different scales. Similar effect can be attained by generating larger scale vortices by introducing intermittent injection. Intermittent injection enhances entrainment. The results show that the declaration phase contributes most to this process. The mechanism of vorticity generation for single phase and multi-phase jets, under different conditions, is discussed.
