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.
On leave from Indian Institute of Science, Bangalore.
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Abbreviations
- 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
- ø e :
-
Thrust augmentation ratio (To + Te)/To
- θ :
-
Half angle of the diffuser
References
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© 1988 Springer-Verlag Berlin Heidelberg
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Badri Narayanan, M.A., Platzer, M.F. (1988). The Mixing Mechanism by Organised Turbulence Structures in a Plane Jet Excited by a Novel Method. In: Liepmann, H.W., Narasimha, R. (eds) Turbulence Management and Relaminarisation. International Union of Theoretical and Applied Mechanics. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-83281-9_32
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DOI: https://doi.org/10.1007/978-3-642-83281-9_32
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