The viscous strip approach to simplify the calculation of the surface acoustic wave generated streaming

In recent decades, the importance of surface acoustic waves, as a biocompatible tool to integrate with microfluidics, has been proven in various medical and biological applications. The numerical modeling of acoustic streaming caused by surface acoustic waves in microchannels requires the effect of viscosity to be considered in the equations which complicates the solution. In this paper, it is shown that the major contribution of viscosity and the horizontal component of actuation is concentrated in a narrow region alongside the actuation boundary. Since the inviscid equations are considerably easier to solve, a division into the viscous and inviscid domains would alleviate the computational load significantly. The particles' traces calculated by this approximation are excellently alongside their counterparts from the completely viscous model. It is also shown that the optimum thickness for the viscous strip is about 9-fold the acoustic boundary layer thickness for various flow patterns and amplitudes of actuation.