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Experimental and numerical acoustic characterization of ultrasonically absorptive porous materials

Wagner, Alexander and Martinez Schramm, Jan and Dittert, Christian and Sousa, Victor C. B. and Patel, Danish and Scalo, Carlo (2018) Experimental and numerical acoustic characterization of ultrasonically absorptive porous materials. 2018 AIAA AVIATION Forum, 25.-29. Juni 2018, Atlanta, USA.

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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 builds upon previous efforts by the authors, improving and extending the established experimental method, complemented by a numerical analysis based on linear acoustics. The latter includes a blind-hole porosity approximation, only accounting for the larger cracks in the C/C with complex acoustic impedance given by the inverse Helmholtz Solver approach, and a highly parametrized homogeneous acoustic Absorber model, accounting for the complete volumetric structure of the porous absorber albeit with lower fidelity. 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. It is found that neglecting the smaller pores and only accounting for the surface porosity, as done in the blind-hole porosity approximation, leads to the underestimation of the acoustic energy absorption coefficient. Phase shifts were found to be experimentally assessable, but remain to be corroborated by a numerical analysis. The comparisons carried out in this paper will pave the way for accurate determination of impedance boundary conditions to be applied in direct numerical simulations of hypersonic transition delay over C/C. 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.

Item URL in elib:https://elib.dlr.de/120018/
Document Type:Conference or Workshop Item (Speech)
Title:Experimental and numerical acoustic characterization of ultrasonically absorptive porous materials
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Wagner, AlexanderDLRhttps://orcid.org/0000-0002-9700-1522
Martinez Schramm, JanDLRUNSPECIFIED
Dittert, ChristianDLRUNSPECIFIED
Sousa, Victor C. B.vsousa (at) purdue.eduUNSPECIFIED
Patel, Danishpatel472 (at) purdue.eduUNSPECIFIED
Scalo, Carloscalo (at) purdue.eduUNSPECIFIED
Date:25 June 2018
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:ultrasonically absorptive porous materials, acoustic characterization, HEG, CC, CC-SiC
Event Title:2018 AIAA AVIATION Forum
Event Location:Atlanta, USA
Event Type:international Conference
Event Dates:25.-29. Juni 2018
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Transportation
DLR - Research area:Raumfahrt
DLR - Program:R RP - Space Transportation
DLR - Research theme (Project):R - Wiederverwendbare Raumfahrtsysteme (old)
Location: Göttingen , Stuttgart
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Spacecraft, GO
Institute of Structures and Design > Space System Integration
Deposited By: Wagner, Alexander
Deposited On:06 Jul 2018 10:17
Last Modified:31 Jul 2019 20:17

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