Sound Radiation from the Boundary in a Circular Lined Duct with Flow

Alonso, Jose S.; Burdisso, Ricardo A.

doi:10.2514/6.2003-3144

Cited by 9 publications

(6 citation statements)

References 2 publications

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“…5 have proposed an 'exact' Green's function based on the numerical inversion of a matrix, which is being evaluated in the course of the present work…”

Section: Introductionmentioning

confidence: 99%

An Analytic Green's Function for a Lined Circular Duct Containing Uniform Mean Flow

Rienstra

Tester

2005

11th AIAA/CEAS Aeroacoustics Conference

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An analytic Green's function is derived for a lined circular duct, both hollow and annular, containing uniform mean flow, from first principles by Fourier transformation. The derived result takes the form of a common mode series. All modes are assumed to decay in their respective direction of propagation. A more comprehensive causality analysis suggests the possibility of upstream modes being really downstream instabilities. As their growth rates are usually exceptionally large, this possibility is not considered in the present study.We show that the analytic Green's function for a lined hollow circular duct, containing uniform mean flow, is essentially identical to that used by Tester e.a. in the Cargill splice scattering model. The Green's function for the annular duct is new.Comparisons between the numerically obtained modal amplitudes of Alonso e.a. and the present analytic results for a lined, hollow circular duct show good agreement without flow, irrespective of how many modes are included in the matrix inversion for the numerical mode amplitudes. With flow, the mode amplitudes do not agree but as the number of modes included in the matrix inversion is increased the numerically obtained modal amplitudes of Alonso e.a. appear to be converging to the present analytical result.In practical applications our closed form analytic Green's function will be computationally more efficient, especially at high frequencies of practical interest to aero-engine applications, and the analytic form for the mode amplitudes could permit future modelling advances not possible from the numerical equivalent.

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“…5 have proposed an 'exact' Green's function based on the numerical inversion of a matrix, which is being evaluated in the course of the present work…”

Section: Introductionmentioning

confidence: 99%

An Analytic Green's Function for a Lined Circular Duct Containing Uniform Mean Flow

Rienstra

Tester

2005

11th AIAA/CEAS Aeroacoustics Conference

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“…Although locally-reacting acoustic liners with uniform impedance are still commonly used to achieve significant noise reductions, the trend toward shorter and wider inlets is compelling liner designers to seek more efficient, advanced liner technologies. Whether these are uniform or nonuniform impedance liners, 1,2 it is increasingly crucial that the effects of grazing flow be accurately quantified. To that end, a number of impedance prediction models have been developed over the last five decades to predict the impedance of locally-reacting acoustic liners, both with and without grazing flow.…”

Section: Introductionmentioning

confidence: 99%

Design and Evaluation of Modifications to the NASA Langley Flow Impedance Tube

Jones

Watson

Parrott

et al. 2004

10th AIAA/CEAS Aeroacoustics Conference

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“…In addition to this example for annular ducts we have compared extensively our analytic Green's function for hollow ducts with the 'numerical' Green's function described by Alonso e.a.. 5 We consider two cases, one with no mean flow, M = 0, and one with a typical 'intake' Mach number of M = −0.45. A typical non-dimensional frequency is ω = 28 for the flow case and we choose ω = 31.354 for the zero flow case so that the cut-on ratio is about the same for both cases.…”

Section: Numerical Examplesmentioning

confidence: 99%

“…The upper figures refer to our analytical Green's function, the lower figures to our evaluation of the mode amplitudes from the numerical Green's function. 5 In Figure 5 we show the corresponding mode amplitude phase results.…”

Section: Numerical Examplesmentioning

confidence: 99%

“…Comparisons are presented with the 'numerical' Green's function of Alonso e.a.. 5,6 We will assume for now that all modes are decay in their respective direction of propagation. More comprehensive causality analyses, 3,7,8 suggests the possibility that one (or two in case of an annular duct) upstream-running modes are really downstream-running instabilities.…”

Section: Introductionmentioning

confidence: 99%

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