Impedance Eduction of Acoustic Liners via the Inverse Helmholtz Solver (iHS) Approach

Patel, Danish; Gupta, Prateek; Scalo, Carlo

doi:10.2514/6.2018-3455

Cited by 2 publications

(3 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The inverse Helmholtz solver (iHS) 41,42 From a high resolution image of the C/C block (figure 3), the edges of large surface are autoand their volumes meshed to be provided as an input geometry to the iHS, which evaluates the broadband impedance of each individual surface cavity. These impedances are then combined, noting that the admittance of the surrounding hard surface is zero, to yield the effective surface averaged impedance for the C/C block in consideration.…”

Section: Computational Toolsmentioning

confidence: 99%

Numerical Investigation of Second Mode Attenuation over Carbon/Carbon Surfaces on a Sharp Slender Cone

Sousa

Patel

Chapelier

et al. 2018

2018 AIAA Aerospace Sciences Meeting

Self Cite

View full text Add to dashboard Cite

We have carried out axisymmetric numerical simulations of a spatially developing hypersonic boundary layer over a sharp 7• -half-angle cone at M∞ = 7.5 inspired by the experimental investigations by Wagner (2015). Simulations are first performed with impermeable (or solid) walls with a one-time broadband pulse excitation applied upstream to determine the most convectively-amplified frequencies resulting in the range 260kHz -400kHz, consistent with experimental observations of second-mode instability waves. Subsequently, we introduce harmonic disturbances via continuous periodic suction and blowing at 270kHz and 350kHz. For each of these forcing frequencies complex impedance boundary conditions (IBC), modeling the acoustic response of two different carbon/carbon (C/C) ultrasonically absorptive porous surfaces, are applied at the wall. The IBCs are derived as an output of a pore-scale aeroacoustic analysis -the inverse Helmholtz Solver (iHS) -which is able to return the broadband real and imaginary components of the surface-averaged impedance. The introduction of the IBCs in all cases leads to a significant attenuation of the harmonically-forced second-mode wave. In particular, we observe a higher attenuation rate of the introduced waves with frequency of 350kHz in comparison with 270kHz, and, along with the iHS impedance results, we establish that the C/C surfaces absorb acoustic energy more effectively at higher frequencies.

show abstract

Section: Computational Toolsmentioning

confidence: 99%

Numerical Investigation of Second Mode Attenuation over Carbon/Carbon Surfaces on a Sharp Slender Cone

Sousa

Patel

Chapelier

et al. 2018

2018 AIAA Aerospace Sciences Meeting

Self Cite

View full text Add to dashboard Cite

show abstract

“…A novel methodology to determine the spatial distribution of the complex acoustic impedance at the open surface of an arbitrarily shaped geometry, associated with an incident planar acoustic wave of assigned wavenumber vector and frequency was developed in the first inverse Helmholtz Solver (iHS) [14,15]. This code reconstructs, at a given detected and meshed to be fed as input to the iHS.…”

Section: B Numerical Setupmentioning

confidence: 99%

“…A brief discussion of the iHS methodology and its context in the current study is provided in section B. A detailed description and validation of the methodology can be found in Patel et al [15].…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical acoustic characterization of ultrasonically absorptive porous materials

Wagner

Schramm

Dittert

et al. 2018

2018 Joint Thermophysics and Heat Transfer Conference

Self Cite

View full text Add to dashboard Cite

The paper addresses the experimental and numerical acoustic characterization of ultrasonically absorptive porous materials with random microstructure such as carbon fiber reinforced carbon ceramic C/C or C/C-SiC. The present study carries on a preceding experimental study of the authors by improving and extending the established experimental method and by conducting complementary numerical studies. The latter uses a new inverse Helmholtz Solver associated with an incident planar acoustic wave to estimate the complex acoustic impedance at the open surface of an arbitrarily shaped cavity. The experimental approach is complemented by high speed schlieren visualization and Mach-Zehnder Interferometer measurements to qualitatively and quantitatively assess the interaction between an ultrasonic wave packet and a porous surface. The main emphasis of the paper is to assess the potential and the limitations of the experimental methods and the comparison of the experimental results to the numerically obtained absorption characteristics.

show abstract

Impedance Eduction of Acoustic Liners via the Inverse Helmholtz Solver (iHS) Approach

Cited by 2 publications

References 36 publications

Numerical Investigation of Second Mode Attenuation over Carbon/Carbon Surfaces on a Sharp Slender Cone

Numerical Investigation of Second Mode Attenuation over Carbon/Carbon Surfaces on a Sharp Slender Cone

Experimental and numerical acoustic characterization of ultrasonically absorptive porous materials

Contact Info

Product

Resources

About