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1
Content available Magnetoacoustic heating and streaming in a plasma with finite electrical conductivity
Perelomova Anna
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2019
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Vol. 23, No 1
49--60
EN
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.
2
Content available Nonlinear Interaction of Modes in a Planar Flow of a Gas with Viscous and Thermal Attenuation
Perelomova Anna
Archives of Acoustics
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2019
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Vol. 44, No. 3
551--559
EN
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.
3
Content available Impact of Boundary Conditions on Acoustic Excitation of Entropy Perturbations in a Bounded Volume of Newtonian Gas
Perelomova Anna
Archives of Acoustics
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2019
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Vol. 44, No. 2
321--328
EN
Excitation of the entropy mode in the field of intense sound, that is, acoustic heating, is theoretically considered in this work. The dynamic equation for an excess density which specifies the entropy mode, has been obtained by means of the method of projections. It takes the form of the diffusion equation with an acoustic driving force which is quadratically nonlinear in the leading order. The diffusion coefficient is proportional to the thermal conduction, and the acoustic force is proportional to the total attenuation. Theoretical description of instantaneous heating allows to take into account aperiodic and impulsie sounds. Acoustic heating in a half-space and in a planar resonator is discussed. The aim of this study is to evaluate acoustic heating and determine the contribution of thermal conduction and mechanical viscosity in different boundary problems. The conclusions are drawn for the Dirichlet and Neumann boundary conditions. The instantaneous dynamic equation for variations in temperature, which specifies the entropy mode, is solved analytically for some types of acoustic exciters. The results show variation in temperature as a function of time and distance from the boundary for different boundary conditions.
4
Content available Nonlinear Excitation of the Non-Wave Perturbations by the Magnetoacoustic Waves in the Non-Isentropic Plasma
Perelomova A.
Archives of Acoustics
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2018
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Vol. 43, No. 1
21--29
EN
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.
5
Content available Nonlinear phenomena of small-scale sound in a gas with exponential stratification
Perelomova A.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2017
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Vol. 21, No 2
135--147
EN
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.
6
Content available Curves of thermodynamic states in some fluids with dispersion
Perelomova A.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2017
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Vol. 21, No 1
53--64
EN
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.
7
Content available Structural damage detection using non-classical vibro-acoustic approaches
Dziedziech K., Pieczonka Ł., Dao P. B., Klepka A., Uhl T., Staszewski W. J.
Vibrations in Physical Systems
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2016
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Vol. 27
13--24
EN
The paper demonstrates how non-classical approaches can be used for structural health monitoring. Wavelet-based modal analysis, various non-classical nonlinear acoustic techniques and cointegration are used for damage detection. These approaches are illustrated using various examples of damage detection in metallic and composites structures.
8
Content available Features of Nonlinear Sound Propagation in Vibrationally Excited Gases
Perelomova A., Kusmirek M.
Archives of Acoustics
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2013
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Vol. 38, No. 3
357--362
EN
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.
9
Content available Badanie struktury dna Zatoki Gdańskiej metodą akustyki nieliniowej
Kozaczka S.
Zeszyty Naukowe Akademii Marynarki Wojennej
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2012
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R. 53 nr 1 (188)
97-106
PL
W pracy przedstawiono wyniki badań doświadczalnych i symulacyjnych, których celem jest wyznaczenie parametrów warstwowej struktury dna morskiego. W badaniach empirycznych zastosowano nieinwazyjną metodę sondowania wykorzystującą echosondę parametryczną SES-2000 Standard. Badania te przeprowadzono na akwenie Zatoki Gdańskiej. Wyniki sondowania porównano z danymi otrzymanymi z analizy odwiertów dokonanych przez wyspecjalizowane instytucje. Zwrócono uwagę na czynniki decydujące o dokładności pomiarów, a w szczególności na różne prędkości rozchodzenia się fali sondującej w zależności od rodzaju osadów dennych. Otrzymane wyniki są wstępem do opracowania pełnej procedury badania górnej warstwy dna morskiego wykorzystującej metody akustyki nieliniowej.
EN
The paper presents the results of experimental and simulation investigations, whose aim are to determine parameters of the sea bottom layered structure. The non-invasive sounding method employing SES-2000 parametric echo sounder was used to conduct empirical investigation. The investigations were conducted in the bay of Gdańsk. The results of the sounding were compared with the data obtained from the analyses of bore-holes made by specialized firms. Attention was paid to the factors responsible for the accuracy of measurement, especially to different speed values of propagation of the sounding wave dependent on the kind of bottom sediments.
10
Content available Theoretical Studies of Nonlinear Generation Efficiency in a Bubble Layer
Baranowska A.
Archives of Acoustics
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2012
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Vol. 37, No. 3
287-294
EN
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.
11
Content available Studies of Nonlinear Sound Dynamics in Fluids Based on the Caloric Equation of State
Perelomova A., Wojda P.
Archives of Acoustics
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2010
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Vol. 35, No. 4
619-633
EN
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.
12
Content available remote Modelling of acoustic heating induced by different types of sound
Perelomova A.
Archives of Acoustics
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2008
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Vol. 33, No. 2
209-219
EN
Dynamic equation governing acoustic heating is derived by splitting of the conservation laws into acoustic and non-acoustic parts. Numerical simulations result in the general conclusions about efficiency of acoustic heating produced by pulses of different polarity and shape. Efficiency of heating induced by stochastic and regular periodic sound of the identical intensity is numerically investigated.
13
Content available remote Influence of vortices on a progressive quasi-plane acoustic wave
Perelomova A.
Archives of Acoustics
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2006
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Vol. 31, No. 4
489-501
EN
The projecting of the quasi-plane flow into specific modes yields in a set of coupled equations accounting for all possible interactions of the basic types of motion. A particular case of interaction considers vortices affecting the character of sound propagation. The new dynamic equations describing the propagation of a progressive acoustic beam interacting with a vortex background are derived and discussed. Since two acoustic branches become separated, these equations include the first order derivative with respect to time. It is the main result of the present paper. Illustrations on the scattered acoustic pressure referring to the different types of vortex flow are presented.
14
Content available Contemporary aspects of the theory and application of nonlinear acoustics
Bjørnø L.
Archives of Acoustics
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2005
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Vol. 30, No. 1
73-85
EN
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.
15
Content available remote On numerical calculation of acoustic field of plane source
Leble S., Sukhov A.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2003
|
Vol. 7, No 2
185-198
EN
The harmonics of an acoustic beam have been evaluated numerically by means of an integral representation according to the perturbation theory. A method for evaluation of the integrals of a rapidly oscillating function has been applied. Special attention has been paid to the accuracy of calculations and an algorithm for error estimation has been proposed. A computer program has been realized, and the profiles of the first and the second harmonics have been plotted. The used methods can be applied for the problem with dissipation or dispersion.
16
Content available remote Analiza nieliniowości wybranych zagadnień wibroakustyki
Wernerowski K.
Vibrations in Physical Systems
|
2000
|
Vol. 19
289--290
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