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Characteristic study of non-circular incompressible free jet

Manivannan Ponnambalam (Dept. of Aeronautical Engineering, Hindustan College of Engineering, Chennai, India)
Sridhar Banbla Tharaka Narendra (Department of Aerospace Engineering MIT, Anna University, Chennai, India)

This paper reports an experimental investigation of bulk properties of turbulent, which is three dimensional, incompressible, air jets issuing into still air surrounding from the nozzles. The jet orifices utilized included circular, hexagonal and cruciform geometries. Experimental results of pertinent mean flow properties such as axis velocity decay, half width growth, potential core and turbulence intensities are reported. Single Hotwire anemometer was used for measurements of the velocity field. The experiment for the three jets was conducted under the same nominal conditions with the exit Reynolds number of 15,400. Consistent with previous investigations of other non circular jets, the cruciform jet is found to have an overall superior mixing capability over the circular counter part. Immediately downstream of the nozzle exit, it entrains, and then mixes with, the surroundings at a higher rate. This jet has a shorter potential core with higher rates of decay and spread than the circular jet. This phenomenon of axis switching is also found to occur in this jet.

Keywords: noncircular jets, cruciform, hexagon, half width, turbulence intensity