Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets

Alghane, M., Chen, Baixin, Fu, Yong Qing, Li, Yifan, Desmulliez, Marc, Mohammed, M. I. and Walton, Anthony (2012) Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets. Physical Review E, 86 (5). 056304. ISSN 1539-3755

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Official URL: http://dx.doi.org/10.1103/PhysRevE.86.056304

Abstract

We report an experimental and numerical characterization of three-dimensional acoustic streaming behavior in small droplets of volumes (1–30 μl) induced by surface acoustic wave (SAW). We provide a quantitative evidence of the existence of strong nonlinear nature of the flow inertia in this SAW-driven flow over a range of the newly defined acoustic parameter F NA =Fλ / (σ/Rd) ≥0.01, which is a measure of the strength of the acoustic force to surface tension, where F is the acoustic body force, λ is the SAW wavelength, σ is the surface tension, and Rd is the droplet radius. In contrast to the widely used Stokes model of acoustic streaming, which generally ignores such a nonlinearity, we identify that the full Navier-Stokes equation must be applied to avoid errors up to 93% between the computed streaming velocities and those from experiments as in the nonlinear case. We suggest that the Stokes model is valid only for very small acoustic power of ≤1 μW (F NA <0.002). Furthermore, we demonstrate that the increase of F NA above 0.45 induces not only internal streaming, but also the deformation of droplets.

Item Type: Article
Subjects: F300 Physics
Department: Faculties > Engineering and Environment > Physics and Electrical Engineering
Depositing User: Yifan Li
Date Deposited: 26 Feb 2015 14:59
Last Modified: 02 Aug 2016 15:41
URI: http://nrl.northumbria.ac.uk/id/eprint/21239

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