Temat: nonlinear acoustics

Skocz do pozycji: 1.

Tytuł:: Magnetoacoustic heating and streaming in a plasma with finite electrical conductivity
Autorzy:: Perelomova, Anna
Tematy:: plasma
nonlinear acoustics
magnetoacoustic heating; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1954460.pdf Link otwiera się w nowym oknie
Opis:: Nonlinear effects of planar and quasi-planar magnetosound perturbations are discussed. Plasma is assumed to be an ideal gas with a finite electrical conductivity permeated by a magnetic field orthogonal to the trajectories of gas particles. The excitation of non-wavemodes in the field of intense magnetoacoustic perturbations,i.e., magnetoacoustic heating and streaming, is discussed. The analysis includes a derivation of instantaneous dynamic equations independent of the spectrum and periodicity of sound.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Curves of thermodynamic states in some fluids with dispersion
Autorzy:: Perelomova, A.
Tematy:: equation of state
nonlinear acoustics
hysteresis; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1940694.pdf Link otwiera się w nowym oknie
Opis:: Variations in the thermodynamic state of a dispersive medium, caused by sound, are studied. A bubbly liquid and a Maxwell fluid are considered as examples. Curves in the plane of thermodynamic states are plotted. They are in fact pictorial images of linear relations of excess pressure and excess density in the acoustic wave which reflect irreversible attenuation of the sound energy. The curves account for the nonlinear generation of the entropy mode in the field of sound. In the case of Maxwell fluids, loops may form under some conditions. Curves and loops for some kinds of stationary waveforms and impulse sound are discussed and compared.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Nonlinear phenomena of small-scale sound in a gas with exponential stratification
Autorzy:: Perelomova, A.
Tematy:: sound propagation
non-uniform media
nonlinear acoustics; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1940705.pdf Link otwiera się w nowym oknie
Opis:: The nonlinear dynamics of perturbations, quickly varying in space, with comparatively large characteristic wavenumbers k: k > 1/H, is considered. H is the scale of density and pressure reduction in unperturbed gas, as the coordinate increases (H is the so-called height of the uniform equilibrium gas). Coupling nonlinear equations which govern the sound and the entropy mode in a weakly nonlinear flow are derived. They describe the dynamics of the gas in the leading order, with an accuracy up to the terms k(H)-1. In the field of the dominative sound mode, other induced modes contain parts which propagate approximately with their own linear speeds and the speed of the dominative mode. The scheme of successive approximations of nonlinear links between perturbations in the progressive mode is established. The numerical calculations for some kinds of impulses confirm the theory.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Nonlinear Excitation of the Non-Wave Perturbations by the Magnetoacoustic Waves in the Non-Isentropic Plasma
Autorzy:: Perelomova, A.
Tematy:: magnetoacoustic waves
dynamics of plasma
nonlinear acoustics; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/177449.pdf Link otwiera się w nowym oknie
Opis:: Nonlinear excitation of slow modes by the planar magnetosonic perturbations in a plasma is discussed. Plasma is an open system due to radiation and external heating. This may stipulate enhancement of wave perturbations and hence the acoustical activity of plasma. Plasma is assumed to be a homogeneous ideal gas with infinite electrical conductivity. The straight magnetic field is orthogonal to the velocity of fluid’s elements. Nonlinear excitation of the non-wave modes (that is, the Alfvén and the entropy modes) by periodic and aperiodic planar magnetoacoustic perturbations, is discussed. The sawtooth wave and the small-magnitude harmonic wave are considered as examples of periodic in time perturbations. The conclusions concern acoustically active and thermally unstable flows as well.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Theoretical Studies of Nonlinear Generation Efficiency in a Bubble Layer
Autorzy:: Baranowska, A.
Tematy:: nonlinear acoustics
bubble layer
transmitted and reflected waves; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/176687.pdf Link otwiera się w nowym oknie
Opis:: The aim of the paper is a theoretical analysis of propagation of high-intensity acoustic waves throughout a bubble layer. A simple model in the form of a layer with uniformly distributed mono-size spherical bubbles is considered. The mathematical model of the pressure wave’s propagation in a bubbly liquid layer is constructed using the linear non-dissipative wave equation and assuming that oscillations of a single bubble satisfy the Rayleigh-Plesset equation. The models of the phase sound speed, changes of resonant frequency of bubbles and damping coefficients in a bubbly liquid are compared and discussed. The relations between transmitted and reflected waves and their second harmonic amplitudes are analyzed. A numerical analysis is carried out for different environmental parameters such as layer thicknesses and values of the volume fraction as well as for different parameters of generated signals. Examples of results of the numerical modeling are presented.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Searching for objects under the sea bed by the nonlinear acoustics methods
Autorzy:: Kozaczka, E.
Tematy:: sea exploration by acoustic methods – nonlinear acoustics
parametric sources; Pokaż więcej
Wydawca:: Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:: https://bibliotekanauki.pl/articles/258470.pdf Link otwiera się w nowym oknie
Opis:: Paper presents rules of producing sources of the parametric acoustic waves as an effect of the propagation of two parallel acoustic beams. Wave is generated in the mutual impact area, with a frequency equal to the difference of the frequencies of waves radiated from the original sources. This principle is a base of the construction of parametric sonars with very narrow directional characteristics and relatively low wave frequency. Moreover, the directional characteristics do not have side lobes - a drawback of the classic sonars. Parametric sonars are a good tool of detecting objects on the sea bed and particularly those buried in the sea bed. The use of parametric sonars in searches for objects such as mines or pieces of archeological value is a modern way of carrying out directed exploration of the sea bed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Nonlinear Interaction of Modes in a Planar Flow of a Gas with Viscous and Thermal Attenuation
Autorzy:: Perelomova, Anna
Tematy:: nonlinear wave theory
nonlinear acoustics
coupling dynamic equations
Burgers equation
diffusion equation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/177137.pdf Link otwiera się w nowym oknie
Opis:: The nonlinear interaction of wave and non-wave modes in a gas planar flow are considered. Attention is mainly paid to the case when one sound mode is dominant and excites the counter-propagating sound mode and the entropy mode. The modes are determined by links between perturbations of pressure, density, and fluid velocity. This definition follows from the linear conservation equations in the differentia form and thermodynamic equations of state. The leading order system of coupling equations for interacting modes is derived. It consists of diffusion inhomogeneous equations. The main aim of this study is to identify the principle features of the interaction and to establish individual contributions of attenuation (mechanical and thermal attenuation) in the solution to the system.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Studies of Nonlinear Sound Dynamics in Fluids Based on the Caloric Equation of State
Autorzy:: Perelomova, A.
Wojda, P.
Tematy:: nonlinear acoustics
parameters of nonlinearity
equations of state
Riemann wave; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/177850.pdf Link otwiera się w nowym oknie
Opis:: The sound speed and parameters of nonlinearity B/A, C/A in a fluid are expressed in terms of coefficients in the Taylor series expansion of an excess internal energy, in powers of excess pressure and density. That allows to conclude about features of the sound propagation in fluids, the internal energy of which is known as a function of pressure and density. The sound speed and parameters of nonlinearity in the mixture consisting of boiling water and its vapor under different temperatures, are evaluated as functions of mass concentration of the vapor. The relations analogous to that in the Riemann wave in an ideal gas are obtained in a fluid obeying an arbitrary equation of state. An example concerns the van der Waals gases. An excess pressure in the reflected wave, which appears when standard or nonlinear absorption in a fluid takes place, is evaluated in an arbitrary fluid.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Features of Nonlinear Sound Propagation in Vibrationally Excited Gases
Autorzy:: Perelomova, A.
Kusmirek, M.
Tematy:: nonlinear acoustics
parameter of nonlinearity
non-equilibrium media
vibrationally excited gas; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/176608.pdf Link otwiera się w nowym oknie
Opis:: Weakly nonlinear sound propagation in a gas where molecular vibrational relaxation takes place is studied. New equations which govern the sound in media where the irreversible relaxation may take place are derived and discussed. Their form depends on the regime of excitation of oscillatory degrees of freedom, equilibrium (reversible) or non-equilibrium (irreversible), and on the comparative frequency of the sound in relation to the inverse time of relaxation. Additional nonlinear terms increase standard nonlinearity of the high-frequency sound in the equilibrium regime of vibrational excitation and decrease otherwise. As for the nonlinearity of the low-frequency sound, the conclusions are opposite. Appearance of a non-oscillating additional part which is a linear function of the distance from the transducer is an unusual property of nonlinear distortions of harmonic at the transducer high-frequency sound.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Contemporary aspects of the theory and application of nonlinear acoustics
Autorzy:: Bjørnø, L.
Tematy:: nonlinear acoustics
absorption
diffraction
dispersion
focused fields
underwater applications
second-order nonlinearity parameter; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/176901.pdf Link otwiera się w nowym oknie
Opis:: The foundations of nonlinear acoustics may be traced nearly 250 years back in time, but only the last 50 years have shown an increasing number of attempts to exploit the research results in nonlinear acoustics. Based upon the fundamental equations of fluid dynamics, the second-order acoustic equations may be derived which can be reduced to a compound equation describing several of the most important and fast developing areas of research in nonlinear acoustics. The relations between this compound equation and Burgers' equation, Korteweg-DeVries equation, the K-Z-K equation, Westervelt's equation and the general second-order wave equation are discussed in depth. Finally, it is shown how the derivatives of the compound equation can be applied to nonlinear acoustic research related to materials characterisation by use of the B/A-ratio, to underwater acoustics by use of the parametric acoustic array and to focused, high-power ultrasonic fields.
Dostawca treści:: Biblioteka Nauki

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