Contribution
Microstreaming Induced by Acoustically Driven Oscillating Bubbles at a Solid Boundary
* Presenting author
Abstract:
Microstreaming is the net flow created by oscillating bubbles in the surrounding fluid through non-linear effects in the boundary layer of the bubble. This flow creates shear forces in the bulk and at surfaces. It has applications in mixing, transport of particles, or controlled action on objects or cells. Understanding this process quantitatively might help in biomedical applications or in sensitive cleaning without damage.We examine the streaming and the shear stress on a nearby solid wall induced by a bubble oscillating in an ultrasonic field of 24 kHz. High-speed recordings are compared to 3D numerical simulations, based on the Finite-Volume / Volume-of-Fluid method for two compressible fluids, including surface tension. The experimental results show that complicated surface mode oscillations occur that lead to a bubble break-up into a localized “chaotic” bubble cluster. Nevertheless, an averaged flow field persists far from the cluster, transporting away split-off microbubbles. Numerical results can reproduce the bubble’s surface oscillations until the breaking of axi-symmetry to a reasonable degree.