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Numerical Eduction of Active Multi-port Data for In-duct Obstructions
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.ORCID iD: 0000-0001-7898-8643
2016 (English)In: Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
2016.
Keywords [en]
multi-port, numerics, orifice, IDDES, LNSE
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-207474OAI: oai:DiVA.org:kth-207474DiVA, id: diva2:1096970
Projects
IdealVent
Note

QC 20170522

Available from: 2017-05-20 Created: 2017-05-20 Last updated: 2017-11-07Bibliographically approved
In thesis
1. Experimental and Numerical Multi-port Eduction for Duct Acoustics
Open this publication in new window or tab >>Experimental and Numerical Multi-port Eduction for Duct Acoustics
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sound generation and propagation in circular ducts for frequencies beyond the cut-on frequencies of several higher order acoustic modes is investigated. To achieve this, experimental and numerical set-ups are designed and used to research aeroacoustic interactions between in-duct components and to conceive noise mitigation strategies.

Describing in-duct sound for frequencies with a moderate number of propagating modes is important, for example, for improving the noise emission from mid-size ventilation systems. Challenges that are largely unacknowledged in the literature involve efficient test rig design, quantification of limits in the methods, numerical modelling, and development of effective noise mitigation strategies for higher order modes.

In this thesis, in-duct sound is mapped on a set of propagating pressure eigenmodes to describe aeroacoustic components as multi-ports with sound scattering (passive properties) and a source strength (active properties). The presented analysis includes genetic algorithms and Monte Carlo Methods for test rig enhancement and evaluation, multi-port network predictions to identify model limitations, and scale resolving (IDDES) and Linearized Navier Stokes computations for numerical multi-port eduction and the silencer design.

It is first shown that test rig optimization improves the quality of multi-port data significantly. Subsequently, measurements on orifice plates are used to test the network prediction model. The model works with high accuracy for two components that are sufficiently separated. For small separations, strong coupling effects are observed for the source strength but not for the scattering of sound. The measurements are used for numerical validation, which gives reliable results for coupled and uncoupled systems. The total acoustic power of tandem orifices is predicted with less than 2 dB deviation and the passive properties for most frequencies with less than 5 % difference from the measurement. The numerical (FEM) models are also used to design a completely integrated silencer for spinning modes that is based on micro-perforated plates and gives broadband attenuation of 3-6 dB per duct diameter silencer length.

The multi-port method is a powerful tool when describing aerodynamically decoupled in-duct components in the low- to mid-frequency range. Due to a robust passive network prediction, multi-port methods are particular interesting for the design of silencer stages. Furthermore, the demonstrated applicability to numerical data opens novel application areas.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. p. 55
Series
TRITA-AVE, ISSN 1651-7660 ; 30
Keywords
acoustics, aeroacoustics, flowacoustics, multi-ports, orifice, silencer, experiment, numeric, IDDES, LNSE, optimization, test rig, Monte Carlo
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-207475 (URN)978-91-7729-402-3 (ISBN)
Public defence
2017-05-29, F3, Lindstedtsvägen 26, Stockholm, 10:15 (English)
Opponent
Supervisors
Projects
IdealVent
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-20 Last updated: 2017-05-22Bibliographically approved

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