A characterization of scattered acoustic intensity vector fields from simple spheres and cylinders in the resonance region.

摘要

In this study, the properties of the scattered acoustic vector fields generated by simple spheres and cylinders are investigated. Analytical solutions are derived from general acoustic pressure scattering models, and analyzed for wave numbers in the resonance region. The separable active and reactive components of the time-independent complex acoustic intensity are used to investigate the structural features of the scattered field components. Numerical results are presented for the near and transition regions. A method of mapping nulls in the active and reactive intensity field is described. The sphere analysis begins with a motionless, rigid model and is then extended to include a fluid-filled boundary, and finally the evacuated thin-walled shell. The cylinder study starts with the theoretical solution of a rigid, motionless, infinite-length cylinder, followed by a finite model with both rigid and elastic shell boundaries, developed using commercial finite element modeling software. Near field acoustic intensity structures are compared against mechanical material properties of vacuous shells. The ability to extract scattered field features is illustrated with measurements obtained from in-air experiments using an anechoic chamber and acoustic vector sensor probes to measure the scattered acoustic vector field from rigid spheres and cylinders. The vector properties of the time-independent complex intensity components and their relations to field energy density quantities are summarized. The far field extent of the scattered vector field properties from infinite and finite cylinders is discussed.