Abstract:

Nonlinear phenomena are known to be significant after the wave of moderate amplitude passes a long distance through a weakly dissipative medium. Such ``accumulative'' effects are studied exhaustively by nonlinear wave physics. In contrast, the ``local'' nonlinearities are studied incompletely. Such nonlinear behavior can be demonstrated by a piston immersed in liquid and vibrating with high amplitude. This piston subjected to a harmonic load can radiate not only the fundamental frequency but high-order harmonics as well. Moreover, reaction to high-power radiation can create an additional nonlinear resistance to a piston motion. Local nonlinear phenomena are expessed clearly at vibration velocities comparable with the sound speed of the surrounding medium. Such a case can be realized using liquids containing gas bubbles where sound velocity is much less than one in a pure liquid. This work is devoted to the theoretical calculation of the temporal and spectral characteristics of a nonlinear wave radiated by a piston subjected to a harmonic external force. Two different problems are discussed corresponding to the piston considered as a linear and as a nonlinear vibrating system. [Work supported by RFFI and CRDF.]