Micro-fluidic based numerical simulations and experiments on streaming induced by oscillatory flows

Streaming effect induced in oscillatory viscous flows has been studied for more than a century. An intensive literature review is made first in this study, and the major applications related to streaming are discussed. In this study, the streaming problem is the fluid drifting phenomenon that occurs in a volume-cycled (tidal volume is fixed during oscillation) oscillatory flow in a channel with specified geometries (bifurcation networks and tapered shapes) Different from all the previous studies, this study extends the streaming effect down to the micro scale. Numerical approaches were carried out using Fluent (ANSYS, Inc., Canonsberg, PA), a commercial computational fluid dynamics (CFD) software. The resultant mass concentration fields, temperature fields and particle trajectories all showed streaming effect and agreed with literature. The effects of non-dimensional amplitude and frequency were investigated and several potential applications were discussed. It is found that oscillation amplitude has a dominant effect on streaming velocity in channel networks. Streaming velocity is directly proportional to the oscillation frequency. Oscillation streaming flow can be used as a cost-effective and reliable convective transport means when the thermal/mass diffusivity is less than the fluid kinematic viscosity (Schmidt numbers are greater than one). Experiments were also conducted and the streaming effect generated in the micro channels qualitatively agreed with the numerical simulation results. Different streaming flows are found in several geometries. Possible geometry combinations are presented for future work. Oscillation amplitude is found to play a critical role in oscillation induced streaming effect, especially for micro scale cases. Oscillatory flows are found to have great potential in micro-mixing applications