Stability of acoustic streaming flows in plane channels.

We study the stability of acoustic streaming flows of normal fluids induced by a small-amplitude surface acoustic wave propagating along the walls of a confined parallel-plane channel or slab in the incompressible flow regime. The secondary flows derived are of negligible effect to the stability characteristic after comparing with the primary flow. The governing equation which was derived by considering the weakly nonlinear coupling between the wavy wall and viscous fluid is obtained and then the eigenvalue problem is solved by a numerical code together with the associated dynamic and kinematic conditions. The value of the critical Reynolds number was found to be near 4873 which is smaller than the case 5772 for conventional pressure-driven flows.