creator Ramachandran, Rakesh Chandran advisor Raman, Ganesh In the field of aero-acoustics, one of the primary areas of interest has always been centered around the resonant flows. The fluid structure interactions gives rise to a reverberant field, which results in high amplitude fluctuating pressures associated with the resonant tones that could lead to sonic fatigue failure of sensitive components in the vicinity of such flows. One such fluid structure interaction is the cavity flow problem. Several flow control technologies exist to suppress cavity tones but most of them lose efficacy at off-design conditions and particularly at higher subsonic and supersonic flows. It is due to this fact that there is a high demand for high control authority flow control actuators. In order for an actuator to have higher control authority, one must be able to use a mechanism that has sufficient energy to disrupt the cavity tone generation mechanism at higher subsonic Mach numbers. One such mechanism is the shock tube generating high strength shock waves. To the best of our knowledge, there does not appear to be any use of shock waves to suppress noise emitted by cavity in aircrafts. The main challenge lied in developing the miniature shock tubes that could produce high intensity shock waves. In the present work, we designed, developed and tested these miniature shock tube flow control actuators. The initial part of this work involved a detailed study of the theory behind producing shock waves using a shock tube. The designing and development part included a lot of trial and error adjustments to produce shock waves as predicted by the 1D shock wave theory. Two shock tube actuators were developed, one having a single shock tube and another with three shock tubes but with the same exit area as the previous one. We carried out various characterization experiments measuring the unsteady pressure at the exit of these shock tubes and also the walls of the shock tube. The experimental investigation of the shock tubes revealed that miniature version of the shock tubes indeed produced high intensity shock waves as predicted by the shock wave theory. Apart from the shock tube actuators, fast acting solenoid valves which does not produce any shock were also tested, to compare the efficacy of both types of actuators. The later part of the work focuses on the actual application of these actuators as flow control devices. First, we delve into the acoustic suppression results which show the amount of tonal noise suppression achieved by using these actuators. For the M = 0.6 case the valves produced very good suppression up to 20 dB but the mass flow rate of these valves were about 26% of the main jet mass flow rate. In the M = 0.8 flows the valves produced negligible suppression. The multiple shock tube performed better than the single shock tube in both cases with a tonal noise suppression of up to 12 dB and 10 dB for M = 0.6 and M = 0.8 flows, respectively. The effect of the shock wave on the cavity tone was evident from the results and had a memory effect on the cavity tone suppression. Due to this the mass flux and the momentum coefficient for the shock tube actuators were considerably low. In order to better understand the mechanism through which the actuators suppress cavity tones, mean velocity measurements and phase averaged pressure measurements were carried out. Based on these results, it was observed that the lifting of the shear layer was the dominant mechanism behind steady and pulsed mass injection. In addition to this beamforming, used for locating the noise sources, was also used to study the cavity tones. Detailed discussion of the results are presented in this report. Submitted by Dana Lamparello (dlampare@iit.edu) on 2012-02-29T16:46:09Z No. of bitstreams: 2 Rakesh_Ramachandran_MS.pdf: 4157411 bytes, checksum: dc4819a69fb207c0bfd899945d2a547f (MD5) First page.pdf: 451710 bytes, checksum: b4dbf7d5a9f948ff9c0cc3139cea7fef (MD5) Made available in DSpace on 2012-02-29T16:46:09Z (GMT). No. of bitstreams: 2 Rakesh_Ramachandran_MS.pdf: 4157411 bytes, checksum: dc4819a69fb207c0bfd899945d2a547f (MD5) First page.pdf: 451710 bytes, checksum: b4dbf7d5a9f948ff9c0cc3139cea7fef (MD5) Previous issue date: 2011-05 M.S. in Mechanical and Aerospace Engineering, May 2011 2011-04-11 2011-05 http://hdl.handle.net/10560/2527 en Thesis born digital application/pdf In Copyright http://rightsstatements.org/page/InC/1.0/ Restricted Access MMAE / Mechanical, Materials, and Aerospace Engineering Illinois Institute of Technology Affiliated department