Experimental study on acoustic streaming in water containing microcapsules

Microbubbles strongly affect the sound field in a medium and various phenom ena are caused by this sound field. In particular, in this study, the influ ence of microbubbles on acoustic streaming in water is quantitatively inves tigated by an experimental method. In order to ensure a constant distributi on of microbubbles in water with time. and to appreciate the quantity of th e microbubbles, water containing a certain amount of microcapsules packed i n a cell is prepared. The streaming velocities are measured using a laser D oppler velocimeter (LDV). The observed results evidently show that the acou stic streaming velocity in water increases due to the microcapsules, and fl uid-dynamic nonlinearity affects both velocities with and without microcaps ules at a high sound pressure. This nonlinearity controls the velocity with microcapsules at a low sound pressure and also causes the dependence of th e ratio between the streaming velocities of the medium with microcapsules a nd that without microcapsules on the sound pressure.