Evaluation of Mixing Characteristics of Supersonic Jet - S. Manigandan - Bog

A free jet defined as a rapid stream driven by pressure issuing from the nozzle exit which exhibits excellent characteristics of flow field along the width to axial distance (X/D). Where X is the axial distance and D is the diameter of the nozzle exit. The extensive understanding of flow and mixing characteristics of supersonic jet has been gaining the importance in recent years owing to its vast application in many areas like rockets, aircraft engines, and nozzle for different application etc. Over few decades the fundamentals understanding of jets and the factors affecting jet spread had been studied extensively using techniques like analytical, experimental and numerical. The effectiveness and efficiency of the jet is determined using parameters like jet spread rate, potential core length and jet decay In addition to the above shear layer also defines the efficiency of free jet. Free jet is pressure driven rapid stream which issuing either from nozzle or orifice into a quiescent ambience without any obstruction, it can also be defined using the shear layer. Shear layer is the boundary layer where the interaction between the jet and atmosphere takes place due to the exchange of momentum. The magnitude of the shear layer not only depends on the shape of exit but also the mach number of the jet]. The value of the shear layer increases with respect to the jet Mach number. Hence understanding the physics of shear layer during the evolution of jet is important.

On the other hand, the characteristics of jet are also influenced by the shape of nozzle, exit profile, thickness, velocity profile and orientation of jet. Due to the velocity difference between the entraining flow and ambient boundary layer is formed at jet periphery. This boundary layer is called as shear layer. Usually shear layer is a highly unstable due to the jet spread in downstream direction. Which lead to formation of vortices. Secondly, these vortices enhance the mixing characteristics of free jet.

The jet is classified into free jet, confined jet, isothermal and non-isothermal jet. A free jet is a rapid stream which discharges into ambient fluid. If the jet is influenced with reverse flow then it is called confined jet. If the jet is attached to the surface called attached jet. Based on the effect of temperature the jet is categorized as isothermal and non-isothermal.