Ultrasound transmission through monodisperse 2D microfoams

Area of Science:

• Acoustics
• Fluid Dynamics
• Materials Science

Background:

• Acoustic properties of solid foams are well-understood, but sound propagation in liquid foams remains largely unexplored.
• Previous research focused on 3D polydisperse liquid foams, necessitating studies on more controlled structures.

Purpose of the Study:

• To experimentally investigate ultrasound transmission through a single layer of monodisperse bubbles.
• To characterize the acoustic response of well-defined liquid foam structures.

Main Methods:

• Generation of a single layer of monodisperse bubbles using microfluidics.
• Experimental measurement of ultrasound transmission through the bubble monolayer.

Main Results:

• Sound velocity in the monolayer is found to be solely dependent on the gas phase.
• The liquid network structure influences sound propagation, described by a transfer parameter similar to porous materials.
• Observed sound attenuation is consistent with viscous dissipation within the gas pores, not solely thermal dissipation.

Conclusions:

• The gas phase is the primary determinant of sound velocity in monodisperse liquid foam monolayers.
• Liquid network architecture plays a role, quantifiable by a porous material analogy.
• Viscous dissipation in gas pores is the dominant mechanism for sound attenuation in these systems.