Sadhana

, Volume 12, Issue 1–2, pp 31–43 | Cite as

The behaviour of excited plane jets

  • M A Badri Narayanan
Flow Management
  • 17 Downloads

Abstract

A plane subsonic jet can be excited to entrain more fluid from its surroundings by subjecting it to antisymmetric periodic disturbances. The essential feature in this phenomenon is the rolling-up motion of an initially flapping jet to form large vortices which are responsible for greater entrainment. Several methods developed to impart oscillations to the flow at the nozzle, such as the acoustic pressure oscillator, the vibration of a single vane in the potential core region, the reciprocating lip system and the twin vane exciter, are described in this article. A minimum threshold in amplitude is necessary for exciting the flow. However, the frequency of oscillation is much less than that predicted by stability considerations.

Keywords

Jet unsteady flows vortex dynamics jet excitation 

List of symbols

a

maximum amplitude of vane oscillation

fe

oscillating frequency

H

height of the nozzle

Q0

mass flow at the nozzle exit

Q

mass flow in the jet at anyx station

St

Strouhal number =feδ/Um

T1,T2

thrust of the jet and ejector, respectively

U

mean velocity

Ue

exit velocity

Um

mean velocity along the centre line of the jet

xc

distance between the nozzle exit and the region of amplification

x

coordinate along the longitudinal axis

y

coordinate along the width of the jet

δ

width of the jet based on half the centre velocity (Um/2)

ɛ

entrainment ratio = (QQ0)/Q0

φ

thrust augmentation ratio = (T1 +T2)/T1

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References

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Copyright information

© Indian Academy of Sciences 1988

Authors and Affiliations

  • M A Badri Narayanan
    • 1
  1. 1.Department of Aerospace EngineeringIndian Institute of ScienceBangaloreIndia

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