Active Noise Control in Supersonic Impinging Jets

In recent years it has been demonstrated that direct
microjet injection into the shear layer of the main
jet disrupts the feedback loop inherent in high
speed impinging jet flows, thereby significantly
reducing the adverse effects. The amount of noise
reduced by microjet actuation is known to be
dependent on nozzle operating conditions. In this
book, two active control strategies using microjets
are suggested to maintain a uniform, reliable, and
optimal reduction of these tones over the entire
range of operating conditions.
In order to obtain an optimal performance of the
actuator, a two-mode feedback model that captures
both the low and high-frequency Rossiter mode was
suggested to investigate the role of pulsed microjet
in the feedback loop. Due to the fact that a low
frequency pulsing brought about additional reduction
compared to high frequency pulsing, the presence of
low frequency mode is identified. In the context of
the analytic model, the effect of pulsing is modeled
using a input-shaping controller that accomplishes
noise-reduction through a suitable redistribution of
the acoustic excitation over the high and low
frequencies.

Autorentext
Jae Jeen Choi received his Ph.D. in Mechanical Engineering from Massachusetts Institute of Technology. At M.I.T. he conducted research on active noise control of STOVL aircraft sponsored by Air Force Office of Scientific Research (AFOSR). Dr. Choi is currently involved in aircraft engine developement program at Generla Electric company.

Klappentext
In recent years it has been demonstrated that direct microjet injection into the shear layer of the main jet disrupts the feedback loop inherent in high speed impinging jet flows, thereby significantly reducing the adverse effects. The amount of noise reduced by microjet actuation is known to be dependent on nozzle operating conditions. In this book, two active control strategies using microjets are suggested to maintain a uniform, reliable, and optimal reduction of these tones over the entire range of operating conditions. In order to obtain an optimal performance of the actuator, a two-mode feedback model that captures both the low and high-frequency Rossiter mode was suggested to investigate the role of pulsed microjet in the feedback loop. Due to the fact that a low frequency pulsing brought about additional reduction compared to high frequency pulsing, the presence of low frequency mode is identified. In the context of the analytic model, the effect of pulsing is modeled using a input-shaping controller that accomplishes noise-reduction through a suitable redistribution of the acoustic excitation over the high and low frequencies.