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## Aeroacoustic analysis of mixing noise generated by turbofan engines

#### Abstract

The topic of this thesis is aeroacoustic analysis of mixing noise generated by turbofan engines. In this work, both numerical methods and experimental data have been involved. The investigation of mixing noise generation in a fluid flow is performed for two different nozzles and the results obtained from relevant analyses are compared later on. The thesis is divided into six chapters. In the first chapter, the problem of noise generated aerodynamically and most influential noise sources inherent to modern aircraft are described. The need of noise reduction in civil aviation is thoroughly explained along with recently imposed regulations related to this matter. The emphasis is put on the jet noise phenomenon. The numerical methods which are commonly used for the identification of mixing noise are introduced and a practical hybrid approach to Computational Aeroacoustics (CAA) of conducting aeroacoustic analyses by means of Reynolds-Averaged Navier Stokes (RANS) methodology and Lighthill acoustic analogy is described. In chapter two, a theoretical background is provided. The RANS method is derived herein from governing equations of motion and k–ε turbulence model is presented. This chapter is also devoted for the presentation of aeroacoustics and, especially, Lighthill acoustic analogy which is based on both equations of motion and inhomogeneous wave equation. The validation of RANS approach for a short-cowl nozzle is conducted in chapter three. The adequate simulations are performed by means of ANSYS Fluent software. The model of the nozzle and computational domain are presented. This chapter contains also a comparison of the results obtained for three different kinds of meshes – unstructured triangular, refined unstructured triangular and structural quadrilateral which has been created using ICEM CFD package. In the next chapter, the impact of two different turbulence models is investigated. The analysis is performed for k-ε and k-ω SST turbulence models. The results of the analysis for structural quadrilateral mesh are presented there in more detail. The penultimate chapter presents the aeroacoustic analysis of two different nozzles – short-cowl, which has been described previously, and coplanar nozzle. Particular flow properties are described thoroughly. Further, the sound pressure levels measured at given points along nozzles’ axes are demonstrated and compared with each other. At the end of the chapter, the conclusions regarding the results of simulations are presented. The last chapter of the thesis contains the description of the entire conducted research and the conclusions drawn from the study. The proposal of further research in the field of Computational Aeroacoustics is also included in this chapter.
Diploma type
Engineer's / Bachelor of Science
Diploma type
Engineer's thesis
Author
Łukasz Adam Sobieraj (FPAE) Łukasz Adam Sobieraj,, Faculty of Power and Aeronautical Engineering (FPAE)
Title in Polish
Analizy aeroakustyczne hałasu generowanego przez strumienie wylotowe silników turbowentylatorowych
Supervisor
Zbigniew Rarata (FPAE/IAAM) Zbigniew Rarata,, The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)Faculty of Power and Aeronautical Engineering (FPAE)
Certifying unit
Faculty of Power and Aeronautical Engineering (FPAE)
Affiliation unit
The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)
Study subject / specialization
, Mechanika i Projektowanie Maszyn
Language
(en) English
Status
Finished
Defense Date
11-02-2019
Issue date (year)
2019
Pages
47
Internal identifier
MEL; PD-4991
Reviewers
Zbigniew Rarata (FPAE/IAAM) Zbigniew Rarata,, The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)Faculty of Power and Aeronautical Engineering (FPAE) Sławomir Kubacki (FPAE/IAAM) Sławomir Kubacki,, The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)Faculty of Power and Aeronautical Engineering (FPAE)
Keywords in Polish
aeroakustyka, hałas spowodowany mieszaniem, silnik turbowentylatorowy, aerodynamika, metody numeryczne, Aeroakustyka Obliczeniowa, Obliczeniowa Mechanika Płynów, Reynolds-Averaged Navier Stokes, analogia akustyczna Lighthill’a, mieszanie turbulentne
Keywords in English
aeroacoustics, mixing noise, turbofan engine, aerodynamics, numerical methods, Computational Aeroacoustics, Computational Fluid Dynamics, Reynolds-Averaged Navier Stokes, Lighthill acoustic analogy, turbulent mixing
Abstract in Polish
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Identyfikator pracy APD: 31392

Uniform Resource Identifier
https://repo.pw.edu.pl/info/bachelor/WUT76464aebc9f742d98011a0074d861348/
URN
urn:pw-repo:WUT76464aebc9f742d98011a0074d861348

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