Attenuating Jet Installation Noise with a Lobed Nozzle

Master of Science Thesis

Master thesis (2021)

Authors

J.H. Mijjer Aerospace Engineering

Contributors

D. Fiscaletti Wind Energy - Aerospace Engineering (supervisor 1)
W.J. Baars Aerodynamics - Aerospace Engineering (supervisor 2)
Faculty
Aerospace Engineering
Copyright: © 2021 Jur Mijjer
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Published Date

13-10-2021

Language

English

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Faculty

Aerospace Engineering

Abstract

Over the last few decades, the bypass ratio and nacelle diameter of modern turbofans have been increasing to achieve higher efficiencies. This trend has forced the underwing-mounted engines to be coupled more closely to the wing surface and the flap system, which significantly enhances the low-frequency noise, known as jet installation noise (JIN).

In this project, lobed nozzles are proposed and tested as a passive flow control technique for the reduction of the JIN. Measurements were performed using hot-wire anemometry and a linear array of microphones to investigate the effects of lobed nozzles on the near-field structure of a jet. The lobed nozzles were found to alter the convection velocities of the pressure fluctuations and the transition to turbulence of the jet. Moreover, far-field pressure measurements were performed inside the anechoic wind tunnel to examine the effects of the near-field structure on the perceived far-field noise. These findings can be used to assess the effectiveness of lobed nozzles for the reduction of the JIN in specific jet installation configurations.