Numerical exploration of acoustic dipole helical wave generation

Abstract

The focus of this talk is on acoustic helical waves, which are a type of wave that transmits phase information across a section of the plane linearly about the azimuth and can transfer angular momentum via the axial phase profile and have recently been applied to navigation and communications systems. A phased array of four crossed circular baffled transducers each producing a pressure field 90° out of phase adjacent to one another are used to create the pressure field. The far field pressure is determined utilizing a paraxial ray approximation for ideal sources but applied to the more complex conceptualization. The construction is effectively two perpendicular dipoles 90° out of phase and from superposition of the arrangement produce the helical wave. The mathematical model will be summarized and simulated. An interesting approximation of the total field is also given, relating the helical wave to a Bessel beam. Numerical examination of the arrangement is examined with visualizations of the pressure field, and discussion is given regarding transients created when the direction of helix changes.