On the Azimuthal Mode Propagation in Axisymmetric Duct FLows

Li, Xiaodong; Schemel, Christoph; Michel, U.; Thiele, Frank

doi:10.2514/6.2002-2521

Cited by 15 publications

(9 citation statements)

References 12 publications

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“…The multiple scales method also used within the referenced paper does not include reflected waves due to the area change and mean flow as well as mode scattering. These may be important effects for the considered generic aeroengine inlet geometry as it was shown by Li et al [26].…”

Section: B Generic Aeroengine Benchmark Comparisonmentioning

confidence: 85%

“…Apart from small roundoff and interpolation errors, the mean flow and modal shapes are exactly the same as used for the MS solution. This possible reason for a large difference [16,26] can therefore also be dropped. There is no explanation for the different directivity of the main lobe observed for one of the cases.…”

Section: B Generic Aeroengine Benchmark Comparisonmentioning

confidence: 99%

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Comparison of Time-Domain Impedance Boundary Conditions for Lined Duct Flows

Richter¹,

Thiele²,

et al. 2007

AIAA Journal

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Two time-domain impedance models developed recently have been examined and tested numerically. One is based on the three-parameter model of Tam and Auriault augmented by a method to evaluate the effective impedance under flow conditions for a harmonic source. The other is Rienstra's extended Helmholtz resonator model. Its timedomain representation is fully based on the idea of Özyörük and Long to use a z transformation for an impedance function with periodic frequency response. The implementation of the models in a numerical simulation tool with the dispersion relation preserving scheme is discussed in detail. A filtering approach guarantees the stability of the Myers boundary condition. The results from both of the two models agree notably well with each other. The validation and verification of both models are carried out for the latest NASA impedance tube experiment. The adaptability to realistic inlet configurations is shown using a generic aeroengine geometry with available numerical results. Overall, both models give a similar physical behavior if limitations are carefully considered. The extended Helmholtz resonator is used as termination impedance. A broadband impedance eduction is successfully carried out, resulting in an extended Helmholtz resonator representation for a ceramic tubular liner. Nomenclature A, B, C, D = coefficient matrices (LEE) F 0 = flux vector (LEE) i = imaginary unit, e i!t convention m = face reactance (EHR) n = radial mode number n = wall normal vector p = pressure amplitude p 0 = pressure perturbation p 0 = mean pressure R = face resistance (EHR) R 0 0 = effective resistance parameter (EFI) s p = auxiliary variable (EFI and EHR) T l = period time (EHR) u n = normal velocity amplitude u 0 = mean velocity vector u 0 n = normal velocity perturbation u 0 = velocity perturbation X 0 1 = effective reactance parameter (EFI) X 0 1 = effective reactance parameter (EFI) Z= complex impedance = cavity reactance (EHR) = ratio of the specific heats "= cavity resistance (EHR) = correction coefficient (EFI and EHR) t = Myers term (EHR) = azimuthal mode number x = damping coefficient 0 = perturbation state vector ! = angular frequency % 0 = mean density % 0 = density perturbation

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Section: B Generic Aeroengine Benchmark Comparisonmentioning

confidence: 85%

Section: B Generic Aeroengine Benchmark Comparisonmentioning

confidence: 99%

Comparison of Time-Domain Impedance Boundary Conditions for Lined Duct Flows

Richter¹,

Thiele²,

et al. 2007

AIAA Journal

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“…Entropy fluctuations are usually excited at higher amplitudes for low frequencies. Neglecting the heat transfer and the turbulent mixing processes, a CAA approach, as is established for interior noise propagation in aero-engines inlets, 3 is suitable for description of the propagation of entropy waves and their sound radiation.…”

Section: Methodsmentioning

confidence: 99%

Sound Generation in the Outlet Section of Gas Turbine Combustion Chambers

Schemel¹,

Thiele²,

Bake

et al. 2004

10th AIAA/CEAS Aeroacoustics Conference

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Indirect combustion noise is investigated experimentally and numerically. This noise is generated in the outlet nozzle of combustion chambers if the entropy of the medium is nonuniform, which is the case in the exhaust of combustors. The contribution to the total noise emission of aeroengine combustors is not known. A test rig for the experimental investigation of this noise emission in the presence of swirl is first described. The indirect noise is generated in an exchangeable convergent-divergent nozzle at the exit of the combustor. The noise radiation is studied in a circular exhaust pipe with probe microphones using a radial mode analysis of the microphone signals. First results of the measured sound fields are reported. The experimental situation will be studied numerically with a 4 th order accurate CAA-method, which is first validated with theoretical results of the literature for the cases of a compact nozzle or diffuser and incoming entropy and sound waves in a one-dimensional mean flow. The agreement with the results of sound generation due to incoming entropy waves and the sound reflection and transmission for incoming sound waves is very good. The method is then applied to the more realistic cases of non-compact nozzles and it is found that the amplitudes of the generated waves are substantially smaller in comparison to the one-dimensional theory. The sound generation of real cases like a swirling hot-spot and entropy waves in a one-dimensional flow through a convergent-divergent nozzle as well as plain entropy waves in the swirl flow of the experimental setup are finally studied and the noise emission is computed.

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“…The boundary conditions, flowfi eld and perturbed flow field are assumed to be constant in the azimuthal direction. Similar to the modal axisymmetric approach for fan tone problems [17], this assumption allows to reduce the dimension of the problem by one.…”

Section: Mathematical Modelmentioning

confidence: 99%

CAA Simulation and Intensity Based Evaluation of a Model Experiment for Indirect Combustion Noise

Richter¹,

Morgenweck²,

Thiele³

2009

Acta Acustica united with Acustica

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The efficient prediction of combustion noise by azonal approach is discussed. Forthe so called propagation zone an optimized finite difference method adopted from fantone noise propagation is applied together with alinear perturbation approach based on the Euler equations. Special attention is payed to the indirect noise generation in the propagation zone, where initially quiet perturbations of the fluid state radiate noise when accelerated or decelerated in av arying base flowregime. Anon-isentropic mathematical model is chosen. The approach is compared with apreviously published experiment for the assessment of indirect combustion noise. The numerical results showthe strong influence of reflections from the inflowboundary of the plenum on the resulting pressure response in the outlet duct. By assuming reasonable reflections from the plenum, the observed time signal of the pressure reaches ar easonable agreement between numerical simulation and experiment. Furthermore, the acoustic intensity is used to showthe good quality of the numerical solution. Finally,the intensity based source location identifies the nozzle as adominant source of sound, with large magnitudes of generation and annihilation of acoustic energy.The source power found in the heated volume is more than twoorders of magnitude smaller than in the nozzle. This result again underlines the importance of indirect combustion noise. PACS no. 43.20.Mv,43.28.Kt, 43.60.Jn ACTA ACUSTICA UNITED WITH ACUSTICA Richter et al.:M odel experiment forindirect combustion noise Vol. 95 (2009)

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On the Azimuthal Mode Propagation in Axisymmetric Duct FLows

Cited by 15 publications

References 12 publications

Comparison of Time-Domain Impedance Boundary Conditions for Lined Duct Flows

Comparison of Time-Domain Impedance Boundary Conditions for Lined Duct Flows

Sound Generation in the Outlet Section of Gas Turbine Combustion Chambers

CAA Simulation and Intensity Based Evaluation of a Model Experiment for Indirect Combustion Noise

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