External Acoustic Waves Research Articles

Stress-strain state of the surface of a circular cylindrical shell under the action of acoustic waves

We present the results of an investigation of the stress-strains state of a mechanical system consisting of two coaxial circular cylinders connected by an elastic link under the action of external acoustic pressure waves. We establish regularities of the appearance of displacements of the elements of the surface of the circular cylinders and the characteristics of the state of the entire mechanical system under acoustic loading.

Resonant behavior of two eclipsed shells: Quasiharmonic study

The purpose of this paper is the presentation of temporal, frequential, and angular experimental studies of the acoustic scattering by two identical air‐filled elastic shells immersed in water. They are insonified by a quasiharmonic wave at normal incidence. The distance between the shells is about 1 to 3 diameters of one shell. The frequency range investigated corresponds to the whispering gallery wave resonances (l=2). The configuration considered is the eclipsed one: Emitter and shells are on the same axis. The complex structure of the backscattered temporal signal is analyzed and theoretically justified. According to the part of the temporal signal considered, different backscattering spectra are obtained and analyzed. The results are discussed in term of acoustic rays involving internal and external acoustic waves. In addition, a phenomenon of acoustic interference is clearly shown. At the resonance frequencies of one shell, the angular diagram shapes are justified and compared to those provided by an analytic model. In all cases, the results are compared to the well‐known results provided by the study of a single shell.

Ultrasonic jet in an external acoustic field

The interaction of supersonic jets with external acoustic waves is investigated in connection with the emission of sound of discrete frequency by the jets. A plausible physical scheme explaining the appearance and maintenance of the oscillations of supersonic jets with discrete frequency was proposed in [1]. A model problem of the effect of pressure perturbations of a given frequency, traveling along the surface of a two-dimensional jet is also investigated there. The results of the solution of this problem (in particular, the presence of critical frequencies at which the perturbations in the jet grow indefinitely in the direction of motion of the flow) substantiate the hypothesis that by virtue of its periodic (cellular) structure a supersonic jet has the properties of a resonator. In [1] the more general problem of interaction of a supersonic jet with an external acoustic field is also formulated, which is in complete correspondence with the physical scheme of the phenomena developed in that article. In the present work this problem is solved in its complete form for plane and cylindrical jets for symmetric and antisymmetric perturbations in an external acoustic field, and also in the presence of subsonic accompanying flow in the outer medium.