, Volume 12, Issue 1, pp 31–43

The behaviour of excited plane jets


  • M A Badri Narayanan
    • Department of Aerospace EngineeringIndian Institute of Science
Flow Management

DOI: 10.1007/BF02745659

Cite this article as:
Narayanan, M.A.B. Sadhana (1988) 12: 31. doi:10.1007/BF02745659


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.


Jet unsteady flows vortex dynamics jet excitation

List of symbols


maximum amplitude of vane oscillation

f e

oscillating frequency


height of the nozzle

Q 0

mass flow at the nozzle exit


mass flow in the jet at anyx station


Strouhal number =f e δ/U m

T 1,T 2

thrust of the jet and ejector, respectively


mean velocity

U e

exit velocity

U m

mean velocity along the centre line of the jet

x c

distance between the nozzle exit and the region of amplification


coordinate along the longitudinal axis


coordinate along the width of the jet


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


entrainment ratio = (QQ 0)/Q 0


thrust augmentation ratio = (T 1 +T 2)/T 1

Copyright information

© Indian Academy of Sciences 1988