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Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets

Heeb, Nicholas S.
http://orcid.org/0000-0002-8582-5807
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1445342666

Abstract Details

2015, PhD, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
An experimental investigation into the effect of azimuthal variance of chevrons and fluidically enhanced chevrons applied to supersonic jets is presented. Flow field measurements of streamwise and cross-stream particle imaging velocimetry were employed to determine the causes of noise reduction, which was demonstrated through acoustic measurements. Results were obtained in the over- and under- expanded regimes, and at the design condition, though emphasis was placed on the overexpanded regime due to practical application. Surveys of chevron geometry, number, and arrangement were undertaken in an effort to reduce noise and/or incurred performance penalties. Penetration was found to be positively correlated with noise reduction in the overexpanded regime, and negatively correlated in underexpanded operation due to increased effective penetration and high frequency penalty, respectively. The effect of arrangement indicated the beveled configuration achieved optimal abatement in the ideally and underexpanded regimes due to superior BSAN reduction. The symmetric configuration achieved optimal overexpanded noise reduction due to LSS suppression from improved vortex persistence. Increases in chevron number generally improved reduction of all noise components for lower penetration configurations. Higher penetration configurations reached levels of saturation in the four chevron range, with the potential to introduce secondary shock structures and generate additional noise with higher number. Alternation of penetration generated limited benefit, with slight reduction of the high frequency penalty caused by increased shock spacing. The combination of alternating penetration with beveled and clustered configurations achieved comparable noise reduction to the standard counterparts. Analysis of the entire data set indicated initial improvements with projected area that saturated after a given level and either plateaued or degraded with additional increases. Optimal reductions were 3-7dB depending on operating condition and observation angle. The fluidic enhancement of the low penetration chevrons indicated significant improvement in the overexpanded regime, with detrimental effect at higher conditions. Improvements were generally due to shock noise and turbulent mixing noise reductions caused by decreased shock strength and LSS growth inhibition. Investigation of azimuthal configurations indicated further improvements were achieved by the clustered configuration due to additional BSAN reductions caused by drastic modification of the shock cell structure due to elliptification of the jet cross section.
Ephraim Gutmark, Ph.D. D.Sc. (Committee Chair)
James Bridges, Ph.D. (Committee Member)
Kailas Kailasanmath, Ph.D. (Committee Member)
Steve Martens, Ph.D. (Committee Member)
Shaaban Abdallah, Ph.D. (Committee Member)
Paul Orkwis, Ph.D. (Committee Member)
258 p.
Aerospace Materials
Supersonic Jet; Aeroacoustics; Jet Noise; Chevrons; Fluidic Injection; Compressible Flow

Recommended Citations

Citations

  • Heeb, N. S. (2015). Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1445342666

    APA Style (7th edition)

  • Heeb, Nicholas. Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets. 2015. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1445342666.

    MLA Style (8th edition)

  • Heeb, Nicholas. "Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets." Doctoral dissertation, University of Cincinnati, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1445342666

    Chicago Manual of Style (17th edition)

ucin1445342666
310
© 2015, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.