Nonlinear and diffraction effects in acoustic beams of cylindrical symmetry

Nonlinear evolution of diffracted acoustic beams generated by sources of cy lindrical shape is studied. The theoretical model utilizes a modified parax ial technique developed previously for describing apodized axisymmetric bea ms of high power. A set of combined nonlinear equations for a wave profile near the beam axis is obtained, and exact solutions of the set of equations are derived in the frequency and time representations for an initially har monic wave. The following phenomena are analyzed: the nonlinear distortion of the wave profile, the influence of the diffraction effects and cylindric al divergence of the beam on the generation of harmonics at the beam axis, the directivity pattern of the radiation in linear and nonlinear modes, and the influence of the source rotation on the spatial structure of the acous tic field.