The Potential of Ultrasonically Absorptive TPS Materials for Hypersonic Vehicles

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.

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confidence: 90%

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

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“…Such a material is for instance C/C-SiC which has been used successfully as TPS on hypersonic vehicles, [10,11], and which can be manufactured with a comparable porosity and microstructure as found on C/C. [12] To assess the potential of such a material with respect to transition control the requirement arises to determine the ultrasonic absorption characteristic at the surface. For this purpose a test rig was set up at DLR Göttingen to measure the reflection coefficient at varying static pressures as reported in Wagner et al [13].…”

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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

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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.

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Octra ‐ Optimized Ceramic for Hypersonic Application with Transpiration Cooling

Dittert

Kütemeyer

2017

Ceramic Transactions Series

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The Potential of Ultrasonically Absorptive TPS Materials for Hypersonic Vehicles

Cited by 11 publications

References 28 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

Octra ‐ Optimized Ceramic for Hypersonic Application with Transpiration Cooling

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