Resonant Radiation of Boundary with a Travelling Distribution of the Field

Abstract

: The problem of acoustic monochromatic radiation by boundary with a traveling distribution of phases of normal vibrational velocities is considered. It is shown that when the spatial frequency of the traveling phase of normal velocities approaches the wave number in the medium, the energy transfer from boundary into a “sliding” (with respect to the boundary) sound wave can resonantly increase to a value many times greater than the energy transfer from of the in-phase boundary, correspondingly, into the normal one (with respect to the boundary) sound wave at the same modules of amplitudes of vibrational velocities of boundary. In addition, the resonant energy transfer of the boundary into a "sliding" wave is the greater, the larger the wave dimensions of the radiating pattern on boundary. It is shown that when a similar traveling distribution of sound pressure (instead normal velocity) is specified at the boundary, there is no resonance. The influence of the curvature of the radiating boundary on the above phenomenon of resonant radiation was studied. It is shown that the resonant radiation of the boundary with given running phases of normal velocities generates a tangential (with respect to the boundary) constant in time radiation reaction force. It is shown that for the case of a linear chain of equidistant monopoles (or pulsing spheres separated from each other by medium) with a traveling phase (a traveling wave antenna) of their oscillatory velocities, the resonance does not appear.