Numerical and analytical investigation of aerosol acoustics through ducts

Date

2017

Author

Arslan, Ersen

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The aim of this thesis is to develop a numerical approach which can solve the sound propagation problem in air-filled circular duct containing water droplets (regarded as an aerosol) in order to obtain acoustic absorption and dispersion characteristics of the system. There exist several analytical approaches in literature for treatment of basic aerosol problems with certain limitations; however; in order to solve rather complex cases, these limitations must be handled and worked out. In this study, a coupled phase approach is chosen due to its superiority for aerosol acoustics among others. The developed codes in 1-D and 3-D (axisymmetric) forms are based on finite difference method in frequency domain. Perfectly Matched Layers (PML) equations are adopted for inlet and outlet boundaries. The codes have been validated with the corresponding analytical results, while existing analytical solutions are extended to cover the cases of mean flow and 3-D (axisymmetric) cases. Results of 1-D solutions have shown that the effect of finite mass loading on attenuation is not linearly proportional. Furthermore; the effect of mean flow has relatively different behavior on attenuation with respect to concentration level and flow direction. The dependency of dispersion on the mean flow and the concentration level is not similar for all frequencies. On the other hand, the 3-D solution has been analyzed for higher order duct modes and impedance wall conditions, emphasizing on the discrepancies between 1-D cases. Last but not the least, 3-D results show that aerosol parameters interestingly have significant effect on the cut-off frequencies of the duct.

Subject Keywords

Acoustical engineering., Air ducts

URI

http://etd.lib.metu.edu.tr/upload/12620996/index.pdf
https://hdl.handle.net/11511/26454

Collections

Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

E. Arslan, “Numerical and analytical investigation of aerosol acoustics through ducts,” Ph.D. - Doctoral Program, Middle East Technical University, 2017.