Mixing in non-circular single and coaxial jets with and without confinement

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This research program involves the experimental investigation of heated and unheated non-circular turbulent single and coaxial jets which may be confined or unconfined.  Jets are flows, such as the effluent from a chimney stack, the exhaust from an aircraft engine, flow into a combustion chamber, etc., which emanate from nozzles and orifices. When one of the nozzles or orifices surrounds the other, a coaxial jet is formed.  Unconfined jets are those which issue into practically unbounded surroundings, while confined jets are those which are surrounded by walls.  Jets are referred to as turbulent when the critical value of a flow parameter known as the Reynolds number, which is the ratio of the forces that drive the flow to those that retard it, is exceeded in them.  One differentiates, depending upon the nozzle or orifice exit shape, between circular and non-circular jets. The rate at which the jet fluid mixes with the surrounding fluid can have important effects on, for example, the dispersion of pollutant effluents from chimney stacks in the environment, the generation of noise by jet aircraft, and the mixing of fuel and air in an aircraft or automobile engine.  A clear understanding of the phenomenon of jet mixing will facilitate the control of the aforementioned technologically important processes and thus enable the performance improvement of the devices in which they occur.  Jet mixing can be enhanced either actively (i.e., through disturbances in time imposed on the flow) or passively (i.e., through changes in the nozzle or orifice geometry). Non-circular jets, both single and coaxial, show promise as an effective way of enhancing mixing passively. The present research is, therefore, focussed on studying the phenomenon of jet mixing in non-circular single and coaxial jet flows.  The program has two principal objectives: first, to contribute to the fundamental understanding of the phenomenon of jet mixing in non-circular jets, and second, to provide experimental data which can be used to facilitate turbulence modelling for the numerical computation of these flows.