Acoustic streaming induced by two orthogonal ultrasound standing waves in a microfluidic channel

•Theory for acoustic streaming in a microfluidic channel is developed.•The case of two orthogonal ultrasound standing waves is considered.•The standing waves are induced by leaky surface waves in the channel wall.•Trajectories of fluid particles involved in acoustic streaming are calculated.•Circula...

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Veröffentlicht in:Ultrasonics 2018-07, Vol.87, p.7-19
Hauptverfasser: Doinikov, Alexander A., Thibault, Pierre, Marmottant, Philippe
Format: Artikel
Sprache:eng
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Zusammenfassung:•Theory for acoustic streaming in a microfluidic channel is developed.•The case of two orthogonal ultrasound standing waves is considered.•The standing waves are induced by leaky surface waves in the channel wall.•Trajectories of fluid particles involved in acoustic streaming are calculated.•Circular fluid rotation in the plane of the wave propagation vectors is reported. A mathematical model is derived for acoustic streaming in a microfluidic channel confined between a solid wall and a rigid reflector. Acoustic streaming is produced by two orthogonal ultrasound standing waves of the same frequency that are created by two pairs of counter-propagating leaky surface waves induced in the solid wall. The magnitudes and phases of the standing waves are assumed to be different. Full analytical solutions are found for the equations of acoustic streaming. The obtained solutions are used in numerical simulations to reveal the structure of the acoustic streaming. It is shown that the interaction of two standing waves leads to the appearance of a cross term in the equations of acoustic streaming. If the phase lag between the standing waves is nonzero, the cross term brings about circular vortices with rotation axes perpendicular to the solid wall of the channel. The vortices make fluid particles rotate and move alternately up and down between the solid wall and the reflector. The obtained results are of immediate interest for acoustomicrofluidic applications such as the ultrasonic micromixing of fluids and the manipulation of microparticles.
ISSN:0041-624X
1874-9968
DOI:10.1016/j.ultras.2018.02.002