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Regensburg 2019 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 32: Complex Fluids and Soft Matter (joint session DY/CPP)

DY 32.5: Vortrag

Mittwoch, 3. April 2019, 16:15–16:30, H3

Shear-waves from cavitation in soft solids — •Julien Rapet1,2, Yoshiyuki Tagawa3, and Claus-Dieter Ohl1,21Nanyang Technological University, Singapore — 2Otto-Von-Guerricke Universität, Magdeburg, Germany — 3Tokyo University of Agriculture and Technology, Tokyo, Japan

While the fluid mechanics of cavitation is a mature research area, very little is known for bubbles undergoing large and non-spherical volume changes in a soft elastic solid. Here soft solids made from gelatin-water mixtures mimic tissue. Previous studies demonstrated that the collapse of a bubble entrapped in soft solids emits longitudinal waves at the speed of sound. Yet the elasticity of the medium supports also transversal waves propagating at a considerable lower speed. We show how cavitation in elastic solids may lead to the emission of such shear waves, particularly the collapse of bubbles near an air/solid interface. The cavitation bubbles are obtained by focusing a pulsed laser into the tissue mimicking material. The bubble dynamics and shear wave propagation are observed with high-speed imaging and photoelastic imaging, respectively. We show that similar to water the cavity moves during collapse away from the free surface accelerating a jet in the direction of the bubble's center of mass motion. During this process the volume between the air/solid interface and the bubble is sheared. Yet the dynamics is much faster than the shear wave speed and therefore the shear stress remains confined. For sufficiently strong and non-spherical collapses, the gelatin surface deforms and a crack starting from the interface propagating towards the bubble.

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