Shear-Layer Instabilities of a Pulsed Stack-Issued Transverse Jet

Shear-layer instabilities of a pulsed stack-issued transverse jet were studied experimentally in a wind tunnel. Jet pulsations were induced by means of acoustic excitation. Streak pictures of the smoke-flow patterns illuminated by the laser-light sheet in the median plane were recorded with a high-speed digital camera. Instantaneous velocities of the shear-layer instabilities in the flow were digitized by a hot-wire anemometer. By analyzing the streak pictures of the smoke-flow visualization, three characteristic flow modes, synchronized flapping jet, transition, and synchronized shear-layer vortices, are identified in the shear layer of the pulsed stack-issued transverse jet at various excitation Strouhal numbers. The shear-layer instabilities of the pulsed stack-issued transverse jet are synchronized by acoustic excitation except for transition mode. In transition flow mode, the shear-layer vortices would exhibit a frequency that would be twice as great as the acoustic excitation frequency.

Authors:

• Ching M. Hsu
• Rong F. Huang
• Michael E. Loretero

Keywords:

• Acoustic excitation
• jet in crossflow
• shear-layer instability.

References:

[1] Y. Kamotani, and I. Greber, "Experiments on a turbulent jet in a
crossflow," AIAA Journal, vol. 10, 1972, pp. 1425 - 1429.
[2] T. F. Fric, and A. Roshko, "Vortical structure in the wake of a transverse
jet," Journal of Fluid Mechanics, vol. 279, 1994, pp. 1-47.
[3] R. M. Kelso, T. T. Lim, and A. E. Perry, "An experimental study of round
jets in cross-flow," Journal of Fluid Mechanics, vol. 306, 1996, pp.
111-144.
[4] O.S. Eiff, and J.F. Keffer, "On the structures in the near-wake region of
an elevated turbulent jet in a crossflow," Journal of Fluid Mechanics, vol.
333, 1997, pp.161-195.
[5] R.F. Huang, and J. Lan, "Characteristic modes and evolution processes of
shear-layer vortices in an elevated transverse jet," Physics of Fluids, vol.
17, No. 3, 2005, pp. 1-13.
[6] M. S. Adaramola, D. Sumner, and D. J. Bergstrom, "Turbulent wake and
vortex shedding for stack partially immersed in a turbulent boundary
layer," Journal of Fluids and Structures, vol. 23, 2007, pp. 1189-1206.
[7] S. Gogineni, L. Goss, and M. Roquemore, "Manipulation of a jet in
crossflow," Experimental Thermal and Fluid Science, vol. 16, 1998, pp.
209-219.
[8] H. Johari, M. Pacheco-Tougas, J.C. Hermanson, "Penetration and mixing
of fully modulated turbulent jets in crossflow," AIAA Journal, vol. 37,
1999, pp. 842-850.
[9] A. Eroglu, R.E. Breidenthal, "Structure, penetration, and mixing of
pulsed jets in crossflow," AIAA Journal, vol. 39, 2001, pp. 417-423.
[10] H. Johari, "Scaling of fully pulsed jets in crossflow," AIAA Journal, vol.
44, 2006, pp. 2719-2725.
[11] R.T. M-Closkey, J.M. King, L. Cortelezzi, A.R. Karagozian, "The
actively controlled jet in crossflow," Journal of Fluid Mechanics, vol.
452, 2002, pp. 325-335.
[12] S.R. Shapiro, J.M. King, R.T. M-Closkey, A.R. Karagozian,
"Optimization of controlled jets in crossflow," AIAA Journal, vol. 44,
2006, pp. 1292-1298.
[13] R. C. Flagan, and J. H. Seinfield, Fundamentals of Air Pollution
Engineering, Prentice Hall, Englewood Cliffs, New Jersey, 1988, pp.
290-357.