Identification of the acoustic response in the irrotational near-field of an excited subsonic jet

2016 ◽  
Vol 15 (4-5) ◽  
pp. 496-514 ◽  
Author(s):  
Michael Crawley ◽  
Ching-Wen Kuo ◽  
Mo Samimy
Keyword(s):  
Near Field ◽  
Acoustic Response ◽  
Subsonic Jet

Theoretical and Numerical Investigations of Acoustic Response of a Multiperforated Plate for Combustor Liners

2015 ◽  
Author(s):  
V. Popie ◽  
E. Piot ◽  
S. Tordeux ◽  
F. Vuillot
Keyword(s):  
Film Cooling ◽  
Near Field ◽  
Perforated Plate ◽  
Combustion Instabilities ◽  
Acoustic Response ◽  
Combustion Chambers ◽  
Perforated Plates ◽  
Numerical Investigations ◽  
Definition Of ◽  
Physical Quantities

Multiperforated plates are used in combustion chambers for film cooling purpose. As the knowledge of the acoustic response of the chamber is essential for preventing combustion instabilities, the acoustic behaviour of the perforated plates has to be modeled. This can be done either by considering the transmission impedance of the plates, or their Rayleigh conductivity. In this paper, the link between these two values is given in the frame of matched asymptotic expansions. Especially the far-field or near-field nature of the physical quantities used in the definition of the impedance and Rayleigh quantity is enlighted. Direct numerical simulations of the propagation of an acoustic plane wave through a perforated plate are performed and post-treated so that the assumptions underlying the definitions of impedance and Rayleigh conductivity are checked.

Dynamics of an impinging jet. Part 2. The noise generation

1982 ◽  
Vol 116 ◽  
pp. 379-391 ◽  
Author(s):  
Nagy S. Nosseir ◽  
Chih-Ming Ho
Keyword(s):  
Coherent Structures ◽  
Near Field ◽  
Pressure Fluctuations ◽  
Aerodynamic Noise ◽  
Far Field ◽  
Noise Generation ◽  
Physical Mechanisms ◽  
Field Noise ◽  
Subsonic Jet ◽  
Jet Axis

The aerodynamic noise generated by a subsonic jet impinging on a flat plate is studied from measurements of near-field and surface-pressure fluctuations. The far-field noise measured at 90° to the jet axis is found to be generated by two different physical mechanisms. One mechanism is the impinging of the large coherent structures on the plate, and the other is associated with the initial instability of the shear layer. These two sources of noise radiate to the far field via different acoustical paths.

scholarly journals Near-field Wavepackets and the Far-field Sound of a Subsonic Jet

2013 ◽  
Author(s):  
David E. Breakey ◽  
Peter Jordan ◽  
Andre Cavalieri ◽  
Olivier Léon
Keyword(s):  
Near Field ◽  
Far Field ◽  
Field Sound ◽  
Subsonic Jet

Nonlinear interaction model of subsonic jet noise

2008 ◽  
Vol 366 (1876) ◽  
pp. 2745-2760 ◽  
Author(s):  
Neil D Sandham ◽  
Adriana M Salgado
Keyword(s):  
Near Field ◽  
Sound Radiation ◽  
Jet Noise ◽  
Interaction Model ◽  
Simplified Model ◽  
Nonlinear Interactions ◽  
Radiation Characteristics ◽  
Instability Modes ◽  
Field Sound ◽  
Subsonic Jet

Noise generation in a subsonic round jet is studied by a simplified model, in which nonlinear interactions of spatially evolving instability modes lead to the radiation of sound. The spatial mode evolution is computed using linear parabolized stability equations. Nonlinear interactions are found on a mode-by-mode basis and the sound radiation characteristics are determined by solution of the Lilley–Goldstein equation. Since mode interactions are computed explicitly, it is possible to find their relative importance for sound radiation. The method is applied to a single stream jet for which experimental data are available. The model gives Strouhal numbers of 0.45 for the most amplified waves in the jet and 0.19 for the dominant sound radiation. While in near field axisymmetric and the first azimuthal modes are both important, far-field sound is predominantly axisymmetric. These results are in close correspondence with experiment, suggesting that the simplified model is capturing at least some of the important mechanisms of subsonic jet noise.

A Linearized Unsteady Aerodynamic Analysis for Real Blade Supersonic Cascades

1997 ◽  
Vol 119 (4) ◽  
pp. 686-694
Author(s):  
M. D. Montgomery ◽  
J. M. Verdon ◽  
S. Fleeter
Keyword(s):  
Flat Plate ◽  
Numerical Stability ◽  
Near Field ◽  
Axial Flow ◽  
Acoustic Response ◽  
Unsteady Aerodynamic ◽  
Field Solution ◽  
Blade Cascade ◽  
Impulsive Loads ◽  
Blade Row

The prediction capabilities of a linearized unsteady potential analysis have been extended to include supersonic cascades with subsonic axial flow. The numerical analysis of this type of flow presents several difficulties. First, complex oblique shock patterns exist within the cascade passage. Second, the acoustic response is discontinuous and propagates upstream and downstream of the blade row. Finally, a numerical scheme based on the domain of dependence is required for numerical stability. These difficulties are addressed by developing a discontinuity capturing scheme and matching the numerical near-field solution to an analytical far-field solution. Comparisons with semi-analytic results for flat plate cascades show that reasonable predictions of the unsteady aerodynamic response at the airfoil surfaces are possible, but aeroacoustic response calculations are difficult. Comparisons between flat plate and real blade cascade results show that one effect of real blades is the impulsive loads due to motion of finite strength shocks.

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