Acoustic Fields and Radiation Forces Induced by a Standing Surface Wave in Layered Viscous Media

Calculations are performed for the fields, amplitude, and dispersion characteristics of a surface acoustic wave in the “viscous fluid half-space–solid half-space” and “viscous fluid layer–elastic half-space” systems taken into account the shear components in the fluid. The resulting radiation pressure is calculated, which occurs in a viscous fluid layer under the impact of a standing surface wave and acts on the elementary fluid volume due to the nonlinearity of the equations of motion in single- and two-mode regimes. It is shown that viscosity results in a violation in the perfect periodicity and symmetry of the fields of the radiation forces and acoustic streaming. The shear components result in considerable radiation pressure forces localized in a narrow domain in the vicinity of the interface. The excitation of several wave modes in a system makes it possible to generate complex spatial distributions of radiation force fields. Then controlling the wave frequency and the layer thickness, one can reach either the predominance of the single-mode field or a comparable contribution of several modes. The fundamental mode is predominant in the vicinity of a wave resonance.