Swirl and precession in submerged free and confined jets

The present thesis deals with an experimental investigation on swirl and precession in free and confined submerged jets in cold flow conditions by means of tomographic particle image velocimetry. Swirling and precessing jets are widely used to enhance the mixing performance in combustion applications. Therefore, the aim of the present research is devoted to elucidate insights on the 3D flow patterns of swirling flows characterized by either a periodic-stable precessing helical structures or intermittent bi-stable fluidic mechanism that produces a large scale precessing motion. To this purpose, a lean pre-vaporized premixed swirl injector is characterized through the study of its main flow features generated in free and confined configurations. Whereas, a fluidic precessing jet nozzle is undertaken to inspect the flow features characteristics of the precessing motion. Moreover, the precessing jet has been investigated for two inflow conditions using either a short-pipe nozzle, i.e., jet without grid, or placing a regular grid at the inlet. The flow features in swirling and precessing jets so generated are described in the thesis.