Acoustic radiation force acting on a small bubble in progressive waves

Based on Doinikov's theoretical report [J. Fluid Mech. 267, 1-21 (1994)] the acoustic radiation force acting on a small bubble in plane progressive waves is calculated including the viscosity of a fluid. The theory predicts that the bubble moves toward the sound source, although it always moves in the direction of the wave propagation in an inviscid fluid. The movement of hydrogen bubbles are experimentally observed in a 50 kHz progressive wave in water. It has been found that the bubbles are evidently pulled back to the source. The agreement between experiment and theory is good in a qualitative sense. However, there is seen some discrepancy for the estimated force by one order of magnitude.