Measurement of density fluctuations using digital holographic interferometry in a standing wave thermoacoustic oscillator

Autor: Thibault Wassereau, Guillaume Penelet, Mathieu Leclercq, Pascal Picart
Přispěvatelé: Laboratoire d'Acoustique de l'Université du Mans (LAUM), Centre National de la Recherche Scientifique (CNRS)-Le Mans Université (UM)
Jazyk: angličtina
Rok vydání: 2016
Předmět:
Zdroj: Experimental Thermal and Fluid Science
Experimental Thermal and Fluid Science, Elsevier, 2016, 70, pp.176-184. ⟨10.1016/j.expthermflusci.2015.09.012⟩
ISSN: 0894-1777
Popis: International audience; This paper describes an optical setup for measuring density fluctuations associated to acoustic oscillations in a thermoacoustic prime-mover. A time-resolved, full-field holographic interferometry technique is used, which enables to measure the optical phase difference between a reference beam and a probe beam passing through the acoustic resonator. The paper first presents the experimental setup and the processing of holograms from which the instantaneous variations of the gas density along the line of sight of the probe beam are obtained. Then, the measurement technique is applied to the analysis of density fluctuations in the neighborhood of the heated side of a stack in a standing wave thermoacoustic prime mover during the transient regime of wave amplitude growth. The experimental results reveal that there exists very significant entrance effects, which lead to the generation of higher harmonics as well as mean (time-averaged) mass rarefaction in the vicinity of the stack termination. Finally, a short discussion is provided, based on a simplified modeling of higher harmonics generation in temperature associated to the oscillations of an inviscid gas through the stack, but the model fails in explaining the magnitude of the phenomena observed.
Databáze: OpenAIRE
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