Abstract
The paper considers the features of the formation of an acoustic field by a spherical source with complicated properties in a regular plane-parallel waveguide, which is of practical importance in marine instrumentation and oceanographic research. The calculation algorithm is based on the use of the Helmholtz equation and the Fourier method for each partial region and the conjugation conditions on their boundaries. The presented calculation allows one to get rid of the idealized boundary conditions on the source surface, with the subsequent determination of the excitation coefficients of the waveguide modes within the framework of the Sturm-Liouville problem. In this case, the attraction of the boundary conditions on the surface and the bottom of the sea, as well as the Sommerfeld conditions, makes it possible to obtain the real distribution of the field in the vertical sections of the waveguide. The obtained frequency dependences of the pressure and vibrational velocity components show their amplitude-phase differences, which reach 90 degrees, which partially explains the appearance of singular points in the intensity field in a regular waveguide. It has been determined that multiple reflections of sound waves from the boundaries of the working space and the space of the waveguide cause oscillations of the pressure components with a change in the amplitude level up to 6 dB. It was found that with an increase in the size of the source, a kind of resonance is formed in the working space, the frequency of which depends on the depth of the sea and corresponds to the region kr=x=5.8. It was found that when the acoustic field is formed in the working space, the frequency response of the impedance components is represented as a multiresonant dependence formed on the basis of the frequency characteristics of the lower modes and their combinations. Experimental studies have shown that the results of calculations of the mode composition of the acoustic field of the emitter, obtained in the conditions of the pool, correspond to the spatial characteristics of the mode components of the acoustic field with an error of up to 3 dB
Highlights
An increase in problem areas in the field of ocean research makes it necessary to search for new and improve existing formulations and solutions of problems in underwater acoustics
The direction of wave acoustics, which has not been fully investigated, seems to be interesting and useful in terms of the problems of the formation of acoustic fields in shallow seas. This direction implies the approximation of model concepts of traditional formulations of radiation problems to real situations of operation of complicated sound sources under conditions of multiple reflections of sound waves from the surface and bottom of a shallow sea
It seems promising to study the features of the formation of the acoustic field in a regular plane-parallel liquid waveguide simulating a shallow sea
Summary
An increase in problem areas in the field of ocean research makes it necessary to search for new and improve existing formulations and solutions of problems in underwater acoustics. The direction of wave acoustics, which has not been fully investigated, seems to be interesting and useful in terms of the problems of the formation of acoustic fields in shallow seas This direction implies the approximation of model concepts of traditional formulations of radiation problems to real situations of operation of complicated sound sources under conditions of multiple reflections of sound waves from the surface and bottom of a shallow sea. In this regard, it seems promising to study the features of the formation of the acoustic field in a regular plane-parallel liquid waveguide simulating a shallow sea. At the same time, such complications should include: the presence of sound scattering by the emitters, the phenomenon of dispersion, the actual multimode and variability of its structure, as well as the conclusion and use of functional equations to determine the partial regions, boundary conditions and conjugation conditions
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