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Title: A statistical jet-noise model based on the acoustic analogy and a RANS solution
Author: Bassetti, Alessandro
ISNI:       0000 0001 3450 4483
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2009
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We introduce a hybrid model for the evaluation of jet noise. The model uses the information from a solution of the Reynolds-averaged Navier{Stokes equations (RANS). It evaluates the jet-noise power spectral density (PSD) in the quiescent region outside the turbulent jet. It includes the following components: 1. A propagation model based on the high- and low-frequency approximations of the Lilleyanalogy Green's function. The high-frequency approximation is determined by combining a moving-medium Lighthill analogy and ray acoustics. The low-frequency model is made by using a ow-factor approach on each component of the source two-point CPSD. We use available analytical expressions of ow factors evaluated in the low-frequency limit. 2. A xed-frame source model based on the source terms of the Goldstein (2001) expression for the Lilley analogy. Both the applied-stress and applied-force equivalent acoustic sources are retained. The used acoustic analogy allows for expressing the 2-point covariance of the applied-stress source by using 2-point velocimetry measurements in a turbulent jet. Specically the applied-stress source can be put in correspondence to the unit-density Reynolds-stress statistics. Available measurements of the unit-density Reynolds-stress 2-point statistics are here used to derive an analytical model for the applied-stress 2-point correlation coecient. Also the applied-force 2-point statistics, required for modelling noise source mechanisms at the presence of density inhomogeneities in the ow, is expressed on the basis of the unit-density Reynolds-stress 2-point statistics. Numerical methods are used to derive the frequency{wavenumber expression for a volumetric source-strength tensor. 3. A jet- ow prediction by using a commercial RANS solver and a set of connection relations expressing source-model parameters starting from the RANS solution. The RANS system includes Reynolds Stress modelling (RSM) closure equations. Turbulence anisotropy is then incorporated in the ow-statistics estimation. The proposed connection relations introduce a set of empirical parameters which are evaluated by matching model components to both velocimetry and acoustics measurements. Modelled far-eld jet-noise 1/3-octave spectra are compared to corresponding measurements for isothermal, unheated and hot jets.
Supervisor: Astley, Richard ; Morfey, Christopher Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TL Motor vehicles. Aeronautics. Astronautics ; QC Physics ; QA76 Computer software