Microstreaming generated by two acoustically induced gas bubbles

Abstract

A theory is developed that describes microstreaming generated by two interacting gas bubbles in an acoustic field. The theory is used in numerical simulations to compare the characteristics of acoustic microstreaming at different frequencies, separation distances between the bubbles and bubble sizes. It is shown that the interaction of the bubbles leads to a considerable increase in the intensity of the velocity and stress fields of acoustic microstreaming if the bubbles are driven near the resonance frequencies that they have in the presence of each other. Patterns of streamlines for different situations are presented.

Streaming flow by oscillating bubbles: quantitative diagnostics via particle tracking velocimetry

“…This is an expected result since both single-and double-bubble systems are driven in the same way and under the same experimental parameters. Therefore, although higher velocities are obtained in the double-bubble system, the flow strength is not increased, contrary to the theoretical result obtained by Doinikov & Bouakaz (2016). Consequently, no 544 R. Bolaños-Jiménez and others significant flow enhancement has been observed in this particular configuration of two bubbles.…”

“…The reason for the flow enhancement is due to a better coupling between the volume and translational oscillation modes, reflected through a change in the phase shift of each of the bubbles. However, note that the configuration studied by Doinikov & Bouakaz (2016) is very different to ours: first, in their work, bubbles are freely suspended in the liquid (not attached to a wall). Secondly, bubbles respond to a plane travelling acoustic wave aligned with the bubbles' axis, so that the translational modes are also aligned with it.…”

“…Particularly complex is the case of high-amplitude and nonlinear oscillations regime (high-power driving), where the bubble might eventually pinch off and emit smaller bubbles (Pelekasis et al 1999;Fernandez Rivas et al 2013b;Stricker et al 2013). The case of two bubbles driven in the low-amplitude oscillations regime has been recently studied numerically by Doinikov & Bouakaz (2016), revealing that larger velocities (and therefore larger wall shear stresses) should be expected as the bubbles are located closer to each other. The reason for the flow enhancement is due to a better coupling between the volume and translational oscillation modes, reflected through a change in the phase shift of each of the bubbles.…”

“…Consequently, no 544 R. Bolaños-Jiménez and others significant flow enhancement has been observed in this particular configuration of two bubbles. Unfortunately, reproducing experimentally the configuration proposed by Doinikov & Bouakaz (2016) is not straightforward and would require some type of optical bubble trap (Garbin et al 2007). This is however far from the scope of the current paper.…”

Acoustic microstreaming near a plane wall due to a pulsating free or coated bubble: velocity, vorticity and closed streamlines

“…They also developed a theory for streaming near a bubble in the presence of a distant wall showing that presence of wall gives rise to higher acoustic streaming around the bubble (Doinikov and Bouakaz 2014). Doinikov and Bouakaz described the microstreaming generated by two interacting bubbles and showed that driving the bubbles at near resonance frequencies gives rise to higher microstreaming velocity and stresses (Doinikov and Bouakaz 2016). In addition to theoretical works to study the microstreaming flow field, there are experimental studies showing the flow field around a single and two oscillating bubbles resting on a solid surface (Collis, et al 2010, Thameem, et al 2016, Tho, et al 2007).…”