Theoretical and numerical studies of the streaming generated by a vortex beam

Abstract

Vortex beams are characterized by 3D fields with very interesting properties like the transmission of information, or the contactless manipulation of objects by acoustic tweezers. At high intensity, these beams can also induce flows due to a transfer of momentum to the fluid. The dynamics and structure of these flows are still poorly understood. In this work, we propose to study in details the coupling between the acoustic field and the hydrodynamic field by making the classical hypothesis of the separation of the scales between the acoustic waves and the flows. In this context, acoustics can be seen as a source term for the mechanical part of fluids via a term proportional to the divergence of an acoustic Reynolds tensor. In most existing studies, only plane waves are considered and this source term can be simplified, but this is not the case for an acoustic vortex. The acoustic field is calculated using a numerical software. From this computation, the various components of the source term are calculated and examined. They are then used at the input of a software in order to simulate the induced flow. The streaming also has a three-dimensional structure, whose main characteristics will be presented.