Effects of geometric configuration and velocity ratio on the near field flow characteristics of coaxial jets an experimental study

Abstract

Jet flow has several potential engineering applications, and turbulent newlinejet flow into still air or secondary stream has been extensively studied. Due to newlinethe complexity involved in the analysis of turbulent jet, the phenomenon newlineremains studied only experimentally. Previously, the structure, dynamism and newlinephysiochemical characteristics of jet flow have been well demonstrated, and newlineyet the flow field of a coaxial jet, which involves the interaction between two newlineco-flowing streams (inner and outer) as well as that between annular streams newlinewith the surrounding fluid medium, is a complex phenomenon that remains newlinemuch less explored. The near-field region of the flow field of a coaxial jet newlineconfiguration is the subject of present investigation. An experimental study newlinewas designed in that the jet was discharged freely from contoured profiled jets newlineinto still ambient air and the flow field studied. The velocity ratio ( ) between newlineinner and outer streams of the jet varied for fixed upstream conditions. newlineFurther, a relatively wide interface was introduced between the two streams. This interface affected the flow characteristics and also influenced the newlinestructure of coaxial jets. newlineIn addition, a non-circular jet was effectively used in a passive method newlineto enhance the mixing process between two co-flowing streams in the nearfield newlineflow of coaxial jet. A comparison between flows emanating from newlineequivalent geometries of axisymmetric (circular) and asymmetric (hexagon and cruciform) coaxial jets was done and presented through figures and tables. newlineThe fluid dynamics of equivalent coaxial circular and non-circular jets were newlinesuccessively measured at various in-flow conditions and presented in terms of newlineuniform velocity profile at jet exit point. newlineThe present study aimed to study for free stream jet the influence of newlinedesign geometry on the jet and injected flow parameters, i.e. velocity ratio of newlineinner to outer core. With respect to the geometry of the jet, it concentrated both on circular newlineand non-circular shapes (such as hexagon and cruciform).