Theory of a two source-location method for direct experimental evaluation of the four-pole parameters of an aeroacoustic element

Munjal, ML; Doige, A.G.

doi:10.1016/0022-460x(90)90843-o

Cited by 206 publications

(79 citation statements)

References 8 publications

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“…A general network element can be thought of as a black box to which acoustic waves enter and exit through the so-called ports. For a two-port element, the scattering-matrix formalism could be written as [33,34]:…”

Section: Scattering Matrixmentioning

confidence: 99%

Validation of a Discontinuous Galerkin Implementation of the Time-Domain Linearized Navier–Stokes Equations for Aeroacoustics

Arina¹

2016

Aerospace

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Abstract:The propagation of small perturbations in complex geometries can involve hydrodynamic-acoustic interactions, coupling acoustic waves and vortical modes. A propagation model, based on the linearized Navier-Stokes equations, is proposed. It includes the mechanism responsible for the generation of vorticity associated with the hydrodynamic modes. The linearized Navier-Stokes equations are discretized in space using a discontinuous Galerkin formulation for unstructured grids. Explicit time integration and non-reflecting boundary conditions are described. The linearized Navier-Stokes (LNS) model is applied to two test cases. The first one is the time-harmonic source line in an incompressible inviscid two-dimensional mean shear flow in an infinite domain. It is shown that the proposed model is able to capture the trailing vorticity field developing behind the mass source and to represent the redistribution of the vorticity. The second test case deals with the analysis of the acoustic propagation of an incoming perturbation inside a circular duct with a sudden area expansion in the presence of a mean flow and the evaluation of its scattering matrix. The computed coefficients of the scattering matrix are compared to experimental data for three different Mach numbers of the mean flow, M 0 = 0.08, 0.19 and 0.29. The good agreement with the experimental data shows that the proposed method is suitable for characterizing the acoustic behavior of this kind of network.

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Section: Scattering Matrixmentioning

confidence: 99%

Validation of a Discontinuous Galerkin Implementation of the Time-Domain Linearized Navier–Stokes Equations for Aeroacoustics

Arina¹

2016

Aerospace

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“…The mathematical description of transfer matrix is given by (1) Direct acoustic transfer matrix measurement: In 1-D acoustics the acoustic perturbations can in principle be obtained by only two microphones placed on either side of the element [16,5]. To minimize the impact of errors induced due to turbulent flow and combustion noise, methods were developed that incorporate a higher number of microphones on each side of the test element.…”

Section: Alternative Methodsmentioning

confidence: 99%

“…Because of their complexity often these functions are measured [4] or derived from more complex models which are based on experimental investigations. The fundamental method to obtain the flame transfer matrix (FTM) experimentally was proposed in [5], which was further developed into the multi microphone method (MMM) [6,7,8,9,10]. While this method allows the most general acoustical characterization of the combustor elements, e.g.…”

Section: Introductionmentioning

confidence: 99%

Determination and Scaling of Thermo Acoustic Characteristics of Premixed Flames

Alemela

Fanaca

Hirsch

et al. 2010

International Journal of Spray and Combustion Dynamics

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The paper investigates the determination and the scaling of thermo acoustical characteristics of lean premixed flames as used in gas turbine combustion systems. In the first part, alternative methods to characterize experimentally the flame dynamics are outlined and are compared on the example of a scaled model of an industrial gas turbine burner. Transfer matrix results from the most general direct method are contrasted with data obtained from the hybrid method, which is based on Rankine-Hugoniot relations and the experimental flame transfer function obtained from OH*-chemiluminescence measurements. Also the new network model based regression method is assessed, which is based on a n − τ − σ dynamic flame model. The results indicate very good consistency between the three techniques, providing a global check of the methods/tools used for analyzing the thermo acoustic mechanisms of flames. In the second part, scaling rules are developed that allow to calculate the dynamic flame characteristics at different operation points. Towards this a geometric flame length model is formulated. Together with the other operational data of the flame it provides the dynamic flame model parameters at these points. The comparison between the measured and modeled flame lengths as well as the n − τ − σ parameters shows an excellent agreement. NOMENCLATURE

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“…8 The real and imaginary part of the impedance was computed using Eqs. ( 15 ) and ( 16 ) (neglecting non-linear terms) for a plate with a thickness of tp=1mm, a slit width a=0.15mm, and a perforation ratio n=0.05, which represents typical plate dimensions used for this work. One observation from Figure 5 a) is the almost constant resistance, whereas the graph of the reactance has a linear slope.…”

Section: E Modal Filtermentioning

confidence: 99%

“…The scattering matrix is determined with the multiple source (or multiple excitation) method described in Ref. [12] corresponding to the two-source method for the plane wave range [13][14][15]. This procedure is independent of reflections from the boundaries of the test setup and eliminates the need for reflection free terminations.…”

Section: Introductionmentioning

confidence: 99%