Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice

Aeroacoustics damping performance of an in-duct perforated orifice with a bias flow in terms of acoustic power absorption Δ and reflection χ coefficients are evaluated in this work. For this, experimental measurements of a cold-flow pipe system with a diameter of 2b with an in-duct perforated plate...

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Main Authors: Zhao, Dan, Sun, Yuze, Ni, Siliang, Ji, Chenzhen, Sun, Dakun
Other Authors: School of Mechanical and Aerospace Engineering
Format: Article
Language:English
Published: 2021
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Online Access:https://hdl.handle.net/10356/150535
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-1505352021-06-07T02:02:17Z Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice Zhao, Dan Sun, Yuze Ni, Siliang Ji, Chenzhen Sun, Dakun School of Mechanical and Aerospace Engineering Engineering::Mechanical engineering Acoustic Damping Sound Absorption Aeroacoustics damping performance of an in-duct perforated orifice with a bias flow in terms of acoustic power absorption Δ and reflection χ coefficients are evaluated in this work. For this, experimental measurements of a cold-flow pipe system with a diameter of 2b with an in-duct perforated plate implemented are conducted over the frequency range of 100 to 1000 Hz first. The effects of (1) the downstream pipe length Ld, (2) porosity η, (3) bias flow Mach number Ma and (4) the orifice thickness lw are experimentally evaluated on affecting the noise damping performance of the in-duct perforated orifice. It is found that decreasing Ld leads to increased Δmax (maximum power absorption). However, the orifice thickness plays a negligible effect at lower frequency, and a non-negligible role at higher frequency range. The maximum power absorption Δmax and reflection coefficients χmax are found to be approximately 80% and 90% respectively. There is an optimum porosity or Mach number corresponding to Δmax. In addition, Δ and χ are periodically changed with the forcing frequency. To simulate the experiments and gain insights on the damping performance of the orifice with a diameter of 2a, an 1D theoretical model that embodies vorticity-involved noise absorption mechanism is developed. It is based on the modified form of the Cummings equation describing unsteady flow through an orifice and the Cargill equation describing acoustically open boundary condition at the end of the downstream duct. It is shown that Δ and χ are strongly related to (1) the bias flow Mach number Ma, (2) forcing frequency ω, (3) porosity η, (4) and the downstream pipe length Ld. Comparing with the experimental measurements reveals that good agreement is obtained. This confirms that the present experimental and theoretical study shed lights on the optimum design of in-duct orifices. National Research Foundation (NRF) This work is supported by the University of Canterbury, New Zealand with Grant No. 452STUPDZ, and National Research Foundation, Prime Minister’s Office, Singapore, with Grant No. NRF2016NRF-NSFC001-102 and National Natural Science Foundation of China with Grant No. 11661141020. This financial support is gratefully acknowledged. 2021-06-07T02:02:17Z 2021-06-07T02:02:17Z 2019 Journal Article Zhao, D., Sun, Y., Ni, S., Ji, C. & Sun, D. (2019). Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice. Applied Acoustics, 145, 328-338. https://dx.doi.org/10.1016/j.apacoust.2018.10.025 0003-682X 0000-0002-4484-6505 https://hdl.handle.net/10356/150535 10.1016/j.apacoust.2018.10.025 2-s2.0-85055625217 145 328 338 en NRF2016NRF-NSFC001-102 Applied Acoustics © 2018 Elsevier Ltd. All rights reserved.
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Mechanical engineering
Acoustic Damping
Sound Absorption
spellingShingle Engineering::Mechanical engineering
Acoustic Damping
Sound Absorption
Zhao, Dan
Sun, Yuze
Ni, Siliang
Ji, Chenzhen
Sun, Dakun
Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice
description Aeroacoustics damping performance of an in-duct perforated orifice with a bias flow in terms of acoustic power absorption Δ and reflection χ coefficients are evaluated in this work. For this, experimental measurements of a cold-flow pipe system with a diameter of 2b with an in-duct perforated plate implemented are conducted over the frequency range of 100 to 1000 Hz first. The effects of (1) the downstream pipe length Ld, (2) porosity η, (3) bias flow Mach number Ma and (4) the orifice thickness lw are experimentally evaluated on affecting the noise damping performance of the in-duct perforated orifice. It is found that decreasing Ld leads to increased Δmax (maximum power absorption). However, the orifice thickness plays a negligible effect at lower frequency, and a non-negligible role at higher frequency range. The maximum power absorption Δmax and reflection coefficients χmax are found to be approximately 80% and 90% respectively. There is an optimum porosity or Mach number corresponding to Δmax. In addition, Δ and χ are periodically changed with the forcing frequency. To simulate the experiments and gain insights on the damping performance of the orifice with a diameter of 2a, an 1D theoretical model that embodies vorticity-involved noise absorption mechanism is developed. It is based on the modified form of the Cummings equation describing unsteady flow through an orifice and the Cargill equation describing acoustically open boundary condition at the end of the downstream duct. It is shown that Δ and χ are strongly related to (1) the bias flow Mach number Ma, (2) forcing frequency ω, (3) porosity η, (4) and the downstream pipe length Ld. Comparing with the experimental measurements reveals that good agreement is obtained. This confirms that the present experimental and theoretical study shed lights on the optimum design of in-duct orifices.
author2 School of Mechanical and Aerospace Engineering
author_facet School of Mechanical and Aerospace Engineering
Zhao, Dan
Sun, Yuze
Ni, Siliang
Ji, Chenzhen
Sun, Dakun
format Article
author Zhao, Dan
Sun, Yuze
Ni, Siliang
Ji, Chenzhen
Sun, Dakun
author_sort Zhao, Dan
title Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice
title_short Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice
title_full Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice
title_fullStr Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice
title_full_unstemmed Experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice
title_sort experimental and theoretical studies of aeroacoustics damping performance of a bias-flow perforated orifice
publishDate 2021
url https://hdl.handle.net/10356/150535
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