From flying wheel to square flow: Dynamics of a flow driven by acoustic forcing

Abstract

Acoustic streaming designates the ability to drive quasisteady flows by acoustic propagation in dissipative fluids and results from an acoustohydrodynamics coupling. It is a noninvasive way of putting a fluid into motion using the volumetric acoustic force and can be used for different applications such as mixing purposes. We present an experimental investigation of a kind of square flow driven by acoustic streaming, with the use of beam reflections, in a water tank. Time-resolved experiments using particle image velocimetry have been performed to investigate the velocity field in the reference plane of the experiments for six powers: 0.5, 1, 2, 4, 6, and 8 W. The evolution of the flow regime from almost steady to strongly unsteady states is characterized using different tools: the plot of time-averaged and instantaneous velocity fields, the calculation of presence density maps for vortex positions and for the maximal velocity and vorticity crest lines, and the use of spatiotemporal maps of the waving observed on the jets created by acoustic streaming. A transition is observed between two regimes at moderate and high acoustic forcing.

Acoustic streaming enhanced mass transfer at a wall

“…No purely periodic regime has been observed with the considered values of the parameters; the flow variations appear rather as low frequency random variations. This type of dynamics has already been observed in some of our former works [16,35,36]. In [36] in particular, we have shown the very rich and sensitive dynamics in such acoustically driven flows, with a flow regime which could change from periodic to quasiperiodic and chaotic within a 15% wide acoustic power range.…”

Enhancement of heat transfer in forced convection by using dual low-high frequency ultrasound

“…It induces a pressure gradient within the fluid and thus fluid movement in the same direction as the acoustic field [14] . The ability of high-frequency ultrasound to generate intense Eckart’s acoustic streaming has been well-studied [15] and thus can increase turbulence within a flow and thereby enhancing heat transfer [16] , [17] .…”

Gold-implanted plasmonic quartz plate as a launch pad for laser-driven photoacoustic microfluidic pumps

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