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Communication Dans Un Congrès Année : 2014

PROPAGATION OF ACOUSTIC WAVES IN A FOAM - PART I: EXPERIMENTS

Juliette Pierre
Benjamin Dollet
Jérôme Crassous
Wiebke Drenckhan
Caroline Derec
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Valentin Leroy
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Résumé

We present an experimental investigation of the acoustic properties of liquid foams. Velocity and attenuation of sound were measured in different foam samples, with a systematic study of the role of parameters such as the frequency, the liquid volume fraction, the bubble size, the nature of the gas, and the nature of the surfactants. Three experimental setups were used to cover a frequency range spanning three orders of magnitude (500 Hz to 600 kHz): an impedance tube [Pierre, 2013a], a pair of narrow-band 40 kHz transducers [Ben Salem, 2013], and a pair of broadband transducers [Pierre, 2013b]. Two main regimes of propagation were identified, with a limit at approximately fR=5 kHz.mm, where f is the frequency and R the average bubble size. At low frequencies (or for small bubbles), the velocity was found to follow the so called mixture law, i.e. depending only on the liquid volume fraction, with no clear influence neither on the bubble size, nor on the type of surfactant. A noticeable exception were Gillette foam samples, in which the velocity was higher than expected. The attenuation, on the other hand, was found to depend mainly on the nature of the gas and the bubble size. Three sources of attenuation were identified: thermal losses due to heat exchange during bubble oscillations, local viscous losses, and viscous losses along the wall of the tube (Kirchhoff losses). The latter term could be related to a macroscopic viscosity of the foam, whose order of magnitude and dependence on R were in good agreement with previous measurements at lower frequencies [Costa, 2013]. In the second regime, at high frequencies (or for large bubbles), the propagation of acoustic waves was dispersive, with a peak of attenuation and a velocity reaching values substantially higher than in the previous regime. The frequency of the maximum of attenuation was close to the Minnaert resonance of the individual bubbles of the foams, suggesting that foams might behave acoustically like (very concentrated) bubbly liquids.
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Dates et versions

hal-01079135 , version 1 (31-10-2014)

Identifiants

  • HAL Id : hal-01079135 , version 1

Citer

Juliette Pierre, Benjamin Dollet, Florence Elias, Jérôme Crassous, Reine-Marie Guillermic, et al.. PROPAGATION OF ACOUSTIC WAVES IN A FOAM - PART I: EXPERIMENTS. EUFOAM2014, Jul 2014, thessalonique, Greece. ⟨hal-01079135⟩
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