Investigation of Noise Reduction Methods on Supersonic Jets Exhausting from Scale Models of Military Style Nozzles

Open Access
Author:
Powers, Russell
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 04, 2012
Committee Members:
  • Dennis K Mc Laughlin, Thesis Advisor
Keywords:
  • Acoustics
  • Jet Noise
  • Noise Reduction
  • Corrugations
  • Corrugation
  • Bevel
  • Beveled
  • Experiment
  • Supersonic
  • Model
  • Military
  • Nozzle
Abstract:
Increasingly powerful and noisy military aircraft have generated the need for research leading to the development of supersonic jet noise reduction devices. The hot high speed supersonic jets exhausting from military aircraft during takeoff present a most challenging problem. Laboratory measurements are important so that noise reduction concepts can be evaluated early in the design process. Experimental research was conducted in the Penn State high speed jet noise facility on two separate methods of noise reduction of supersonic jet flows. The first noise reduction method was the beveled exit plane nozzle concept explored most recently by Viswanathan and the second was the internal nozzle corrugations pioneered by Seiner et al. The combination of the two methods was also explored. The jet plume from beveled nozzles was examined and shown to deflect less than 5 degrees for both over-expanded and under-expanded flows. A new method of rotating the exit plane about the centerline was used to create the beveled nozzles. This results in an extension of the bottom lip and a shortening of the top lip. Results show that for heated jets, noise in the peak emission direction was reduced by 3-4 dB on the long lip side of the nozzle. Similar magnitudes of noise reductions were still present with the forward flight capability being used. A novel research idea of creating fluidic corrugations similar to the nozzle corrugations has been started by Penn State. To further the understanding and analysis of the fluidic corrugations, the present study focused on the flow field and acoustic field of nozzles with two, three, and six nozzle corrugations. The effect of the combination of the internal corrugations with a beveled nozzle was explored. The results show that significant noise reductions of over 3 dB of both the mixing noise and the broad band shock associated noise can be achieved. Additionally, the combination nozzle was shown to reduce the noise over a wider range of polar angles and operating conditions than either the purely beveled nozzle or the nozzle with only hard walled nozzle corrugations.