Mon June 23rd 2014
16:00 – 17:00
HR W121
Seminar Streaming due to acoustically excited bubbles in microchannels
Bhargav Rallabandi


Ultrasound excitation of bubbles produces powerful secondary flows, which have been employed in several microfluidic applications. While bubble-driven flows in bulk fluid have been studied extensively, the relevant situation in microfluidics, which typically involves a cylindrical bubble sessile on a wall of the device, is poorly understood. In particular, the analysis is complicated by the complex frequency response of the bubble and the attachment to rigid walls via contact lines. We develop here a theory that properly accounts for both volume and shape oscillations of the bubble, providing a complete description of the streaming as a function of only the driving frequency, the bubble size and the physical properties of the fluid. We show that despite the strong frequency dependence of the oscillation shape of the bubble, the streaming remains robust over a wide range of frequencies, due to a specific interaction between neighbouring surface modes. At very large frequencies, a striking reversal of the flow occurs due to the dominance of the volume mode over the more strongly damped surface modes. The theory allows us to study the transport of fluid in these flows and guides the design of applications such as micromixers and particle sorting devices.
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The 10th Complex Motion in Fluids 2021
Max Planck Gesellschaft
Centre for Scientific Computing