Experimental Validation of the Two-port Impedance Eduction Method

Denayer, Hervé; Roeck, Wim De; Desmet, Wim

doi:10.2514/6.2019-2515

Cited by 1 publication

(1 citation statement)

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“…( 2). Furthermore, the availability of multiple microphones allows the use of the iterative plane wave decomposition procedure of reference [19] which solves the set of equations for additional environmental parameters (c 0 , M ... ), effectively reducing uncertainties on the measured pressure plane wave amplitudes.…”

Section: Measurement Proceduresmentioning

confidence: 99%

Experimental characterization of the impedance of (sub-)millimeter perforations with flow

Vandemaele,

Denayer,

De Roeck

et al. 2022

Proceedings of the 10th Convention of the European Acoustics Association Forum Acusticum 2023

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For the design of more compact acoustic wall treatments for flow duct applications, (sub-)millimeter perforations can be considered as promising component for acoustic (meta)liners. By decreasing the perforation dimensions, an increased acoustic resistance and low acoustic mass reactance can be achieved, enabling the potential for wideband absorption without jeopardizing the aerodynamic performance. The perforations' aero-acoustic properties are, however, significantly influenced by the flow conditions and configurations in which they are operating. In this paper, the flow-acoustic behavior of orifices with perforation diameters ranging from 0.5 to 3mm is characterized using a multi-microphone three-port measurement technique. Within this framework, small perforated samples are flush-mounted in the wall of a main measurement duct, covering a side-branch measurement duct. Measurements are conducted for different grazing flow rates and the effect on the perforate resistance and external end correction is studied. Generally, the perforate resistance increases and the external end correction decreases with increasing flow rate with both effects diminishing for larger diameters at higher frequencies. Correlating the results with skin friction velocity yields an acceptable estimate for the end correction for all diameters and flow rates. For the resistance, however, no significant trend is observed.

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Section: Measurement Proceduresmentioning

confidence: 99%