Measured and calculated vertical structure of a sound field in the ocean

Results of measuring the monochromatic sound field with a dipping probe in the deep ocean are presented. The sound speed profile in the region of measurements had a minimum at a depth of 1600 m. The experiment was carried out in the Atlantic Ocean with the use of two vessels separated by a distance of approximately four ray cycles (～240 km). The experimental data are compared with the calculations based on a new concept of the Brillouin waves for describing the vertical structure of the sound field produced by rays. It is shown that a satisfactory agreement between experiment and calculation can be achieved by fitting the parameters of the experiment. Such a procedure allows one to refine or even to determine the experimental conditions, which not are always known. The proposed method of calculation offers an opportunity for solving inverse problems of ocean acoustics.     

The run-up of nonlinearly deformed sea waves on the coast of a bay with a parabolic cross-section

The run-up of long waves on the coast of a bay with a parabolic cross-section, where the region of constant depth along the principal axis of the bay is connected with the linearly inclined segment, is considered. The study is carried out analytically in the framework of the nonlinear shallow-water theory under the approximation that the height of the initial wave is small compared to the basin depth, and the reflection from the inflection point of the bottom is negligibly small. Three types of incident waves, viz., a sinusoidal wave and solitary waves of positive and negative polarities, are considered in detail. It is shown that a sinusoidal wave undergoes nonlinear deformation at a segment of constant depth faster than solitary waves of positive and negative polarities. Solitary waves of negative polarity steepen somewhat faster than solitary waves of positive polarity. Waves of positive polarity steepen at wave front, while waves of negative polarity steepen at wave rear. These differences in steepness may become crucial at the wave run-up stage, since the wave run-up height on the coast of a bay with a parabolic cross-section is directly proportional to the steepness of a wave that arrives at the slope and can lead to the anomalous run-up of waves on the coast.     

A Method for Detecting and Localizing Inhomogeneities in Plates Using Lamb Waves

Acoustical Physics - The paper presents the results from a study of the interaction of Lamb waves with inhomogeneities in composite plates. It was found that waves of this type are diffracted by...     

Nonlinear acoustics in Nizhni Novgorod (A review)

This article reviews the development of nonlinear acoustics in Nizhni Novgorod from the days when the idea of parametric transmission and reception was conceived until the present time.     

Nonlinear Acoustic Profiling of Liquid Flows

A means of nonlinear acoustic Doppler tomography is described and the results from its simulation are analyzed. The technique can be applied to the gas inclusions normally present in liquids. The distribution of the flow velocity can be reconstructed by making certain assumptions about the distribution of gas inclusions.     

Vitali $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l} $$ Anatol’evich Zverev (On his 80th birthday)

Chronicle

Vitali $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ Anatol’evich Zverev (On his 80th birthday)     

Acoustic diagnostics of bubble objects in a liquid

Passive and active linear and nonlinear acoustic methods intended for observation of hydrodynamic cavitation and for bubble object imaging are considered.     

A Piezoceramic Resonator for Sonoluminescence Analysis

Acoustical Physics - The results of the numerical simulation and experimental study of an entirely piezoceramic cylindrical resonator to generate sonoluminescence are presented. The data on the...     

Sound Propagation in a Particle Suspension with a Rotational Degree of Freedom

Acoustical Physics - Suspensions are often found in nature and in technological processes. Suspension particles can differ in density and compressibility from the parent medium and affect the speed...     

Numerical simulation of gas bubble motion in a flow-through resonator

The problem of gas bubble motion in an acoustic resonator with a fluid flow is solved using numerical methods. It is shown that the distribution of the bubble concentration, which is nonuniform over the resonator length, is formed upon homogeneous introduction of bubbles. The problem on the bubble concentration distribution the along the resonator axis (with fluctuations of the bubble introduction period taken into account) is considered, and the fluctuation parameters are determined at which the periodic structure of the concentration distribution is preserved. The distribution of bubbles with different sizes over the resonator length is determined. It is shown that a resonator with a fluid flow accomplishes bubble selection by size (the average bubble concentration in the resonator increases with an increase in bubble size). The field in the resonator was calculated taking into account the effect of bubbles on sound velocity and damping.