The Mixing Mechanism by Organised Turbulence Structures in a Plane Jet Excited by a Novel Method

  • M. A. Badri Narayanan
  • Max F. Platzer
Conference paper
Part of the International Union of Theoretical and Applied Mechanics book series (IUTAM)

Abstract

A plane subsonic turbulent jet was subjected to controlled periodic oscillations of high amplitude at the nozzle exit. The oscillations produced considerable jet spreading and entrainment. Vortex dynamics played a significant role in this process and the amplification of the applied periodic disturbances was associated with a fairly well defined Strouhal number. Three distinct phases in the flow could be observed during excitation, namely, (a) flapping motion near the exit region, (b) formation of vortices at a critical Strouhal number and their amplification, and (c) breakdown of large vortices into smaller components with the flow becoming fully turbulent. The jet when operated with a simple straight duct-diffuser ejector system increased the thrust augmentation ratio by a factor of 1.20.

Keywords

Vortex Platinum Smoke 

Symbols

H

Height of the nozzle at exit.

b

Width of the jet corresponding to Uo/2

L

Throw length, i.e., maximum movement of the reciprocating segments

P

Static pressure

Us

Mean velocity in the X direction

U

Exit velocity

Ue

Center line velocity

o

Entrainment ratio

R

Reynolds number HUe/V

Se

Strouhal number fb/Uo

ft

Excitation frequency

fe

Natural frequency of the steady jet

Tn

Thrust of the jet based on isentropic conditions

\({\mathop {\text{T}}\limits_{\text{e}} ^{\text{o}}} \)

Thrust of the ejector

øe

Thrust augmentation ratio (To + Te)/To

θ

Half angle of the diffuser

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References

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Copyright information

© Springer-Verlag Berlin Heidelberg 1988

Authors and Affiliations

  • M. A. Badri Narayanan
    • 1
  • Max F. Platzer
    • 1
  1. 1.Department of AeronauticsNaval Postgraduate SchoolMontereyUSA

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