Authors: J. Packer, D. Attinger, Y. Ventikos
Affilation: University of Oxford, United Kingdom
Pages: 261 - 264
Keywords: acoustic streaming, CFD, lab-on-a-chip, microfluidic devices
Mixing, particle transport, and lysis of biological cells can be performed in microfluidic chips by actuators based on the controlled motion of a gas-liquid interface. There is strong motivation to develop practical and tractable computational tools geared towards the design of acoustic actuator-driven microfluidic chips. The second order streaming occurring in these situations is difficult to model with standard computational fluid dynamics techniques, due to the difference in time scales exhibited by the oscillation of the bubble or meniscus (O(kHz)) and the steady second order flow generated (O(10Hz) for the configurations considered). We present a novel technique for modelling the steady flow generated by viscous streaming in the vicinity of a bubble or meniscus, in which the high frequency motion of the bubble is replaced by a steady addition of momentum to the liquid. Using this technique we show that the viscous streaming from isolated gas-filled bubbles can be modelled satisfactorily, in a computationally tractable manner. We compare our findings with experimental results for a bubble in volume oscillation; furthermore, we extend this analysis to more complex configurations such as ultrasound-driven menisci in devices we have studied experimentally.