Acoustic Wave Propagation Research Articles

Acoustic wave propagation and scattering in visco-acoustic medium: Integral equation representation and De Wolf approximation

A visco-acoustic medium is an approximate representation of the absorption and attenuation characteristics of the actual earth medium, which will cause energy attenuation and velocity dispersion of seismic waves. The propagation law of scattered waves in viscoelastic media can be revealed through seismic wave forward simulation. However, the numerical simulation of scattered waves in a visco-acoustic medium using the De Wolf approximation method based on the Lippmann-Schwingr (L-S) equation has not been studied. Therefore, based on the Futterman dispersion relation, the mathematical expression of the integral equation of acoustic wave propagation and scattering in the visco-acoustic medium is derived. We combine the De Wolf approximation with the quality factor Q. The thin slab approximation and screen approximation methods are two realizations of the De Wolf approximation. The thin slab approximation and the screen approximation continuation operator in the viscous-acoustic medium are constructed and applied to the numerical simulation of the scattered wave field. The research results of the concave model and complex model indicate that due to the influence of medium viscosity, the energy of the deep reflected waves is weaker in the forward modeling records of the thin slab approximation method and screen approximation method, and the dominant frequency of seismic waves moves towards the low-frequency direction; Compared with the finite difference results, they only calculate one reflection, and there are no multiple wave signals in the seismic records. Finally, We discuss the thin slab approximation and the screen approximation method for detail around the division of the thickness of the thin slab, the selection of the reference frequency, and the non-uniformity of the medium.

Theoretical and numerical study on transient acoustic wave propagation across ice layers in the Arctic Ocean.

The study of transient acoustic wave propagation across the Arctic Ocean ice layer provides theoretical guidance for the design of trans-ice acoustic communication systems. In this study, the Arctic Ocean was modeled as an ice-water composite structure, where the ice and water are regarded as an elastic solid and liquid, respectively. An analytical transient solution for acoustic wave propagation in this structure was derived using the eigenfunction expansion method. Further, the numerical procedures were presented and used to analyze the acoustic wave propagation characteristics across the ice layer. The results show that waveforms corresponding to the radial displacements are more severely distorted than the axial displacements. The amplitudes of the radial and axial displacements decreased rapidly with increasing propagation distance. The ice thickness had a greater impact on the radial displacement than axial displacement; the thicker the ice, the greater the distortion for both radial and axial displacements.

Propagation of Acoustic Waves in a Moving Monodispersed Gas Suspension

Propagation of Acoustic Waves in a Moving Monodispersed Gas Suspension

Towards an understanding of the mechanisms of therapeutic ultrasound on biomimetic models of cancer

Therapeutic ultrasound is transforming the treatment of a range of malignancies in a non-invasive and non-systemic manner. Low-intensity ultrasound (LIUS) has been proposed to selectively eradicate cancer cells but the underlying biological mechanisms remains unknown. To gain an understanding of this phenomenon, 2D breast cancer monocultures were sonicated at varying acoustic intensities (0.1–0.5 W·cm−2) and excitation times (1–10 minutes). Additionally, 2D monocultures consisting of healthy cell lines were sonicated at varying acoustic intensities (0.1–0.5 W·cm−2) to determine any distinguishing biological responses. To begin recapitulating in vivo conditions, breast cancer cells were also seeded into 3D collagen hydrogels. At a 1 MHz frequency, 20% duty cycle, 100 Hz pulse repetition frequency, a significant drop in cancer cell viability is observed at a sonication intensity of 0.5 W·cm−2 and over 10 minute excitation time. Healthy counterparts subjected to the same parameters revealed no distinguishing effects. Sonication of breast cancer cells seeded in 3D collagen hydrogels revealed no effect in cell viability compared to non-sonicated controls. The acoustic wave propagation software OptimUS was used to determine the influence culturing plates have on ultrasound propagation, revealing these materials can significantly vary the acoustic field at frequencies relevant to LIUS.

Pseudomagnetic fields in bilayer phononic crystals

Pseudomagnetic field (PMF), as an artificial gauge field, has attracted widespread attention in the exploration of magnetic-like effects in artificial structural materials. It offers a novel mechanism for manipulating wave fields in classical wave systems where there is no or weak response to actual magnetic fields. In this work, we construct acoustic PMFs in bilayer phononic crystals by imposing uniaxial linear gradient strain on the scatterers of both layers. Under the PMFs, the linear nodal rings, occurring at around the K and points of the bilayer phononic crystals, split into acoustics Landau levels (LLs). Specifically, the n = 0 plateau of the LLs splits into two discrete ones due to the interlayer coupling. Furthermore, we construct two heterostructures by splicing two phononic crystals with opposite PMFs and observe unique in-plane snake-like propagations of the edge state as well as oscillations between the upper and lower layers. Bilayer structure provides additional degree of freedom to generate PMFs in various types of semimetals and enriches the manipulation of acoustic wave propagations. In addition, it can be extended to other classical wave systems, such as electromagnetic wave and mechanical systems.

Anti-scattering propagation in multiple-bend valley phononic crystals

Valley topological phononic crystals (PCs) have attracted wide attention due to the topological properties of their edge states. In general, valley interface states can exist in the interfaces that are constructed by opposite valley topological phases. Here we study the anti-scattering propagation properties of edge states in a single valley PC. We present that the edge states can exist in different boundary terminations with different band dispersions. The boundary transport behaviors of acoustic waves along the two designed PCs are demonstrated numerically. The results show that the chiral edge states are immune against additional scatterers that preserve the valley pseudospins, but the backscattering can happen when intervalley scattering is included. Nevertheless, the anti-scattering propagation in complex multiple-bend structures can be realized by the smooth transition between the edge states and the valley interface states. Similar to the designed frequency-selective device, more prospective applications can be anticipated in the manipulation of acoustic wave propagation.

A nonlocal photoacoustic effect with variable thermal conductivity of semiconductor material subjected to laser heat source

This study explores the behavior of laser-exposed photo-excited carriers, investigating the propagation of photoacoustic waves in the thermoelastic domain. It also delves into the theoretical generation of surface acoustic waves in semiconductors through photo-thermoelastic processes. The research considers the interaction between thermomechanical and acoustic waves in a nonlocal medium with temperature-dependent thermal conductivity. Unlike relying on electron–phonon or electron-hole thermalization processes, photoacoustic waves here result from thermoelastic stress induced by the laser-induced temperature increase. The investigation accounts for the optical, mechanical, and thermoelastic properties of nanoscale semiconductor materials. Predictions of photoacoustic signals are derived by solving a combined thermal diffusion issue and a thermoelastic problem, using Laplace and Fourier transforms in the mathematical model. Numerical solutions encompass various physical fields within the time domain using the inversion technique of Laplace and Fourier transforms, such as thermal, acoustic, mechanical, and carrier density diffusion. The study evaluates and compares the influences of thermal memory and thermal conductivity presenting visual representations.

Effect of Signal Features and Model Variables on Energy-Traced Arrival Time Picking of Acoustic Signals Used for Structural Damage Detection

To monitor damage developments in structures, various structural health monitoring methods based on different principles are used. The common aspect of elastic wave-based methods is to place appropriate sensors on the structure, to detect acoustic wave propagation and to analyze these signals the sensors transformed. The arrival time of these recorded signals to the sensors is the most significant parameter used to determine critical information such as the time and location of the damage. Therefore, the accurate calculation of the arrival time affects the accuracy of the damage detection. In this study, effects of the signal-to-noise ratio (SNR), sampling frequency, length of the signal, and length of the focal window on determining the arrival time of the signals to the sensors were investigated. For this purpose, an energy-traced arrival time picking approach (Akaike Information Criterion, AIC), which is the frequently used method in the literature, has been applied to a typical acoustic signal originated from a concrete cracking. The results of the study suggest the necessity of noise elimination, the optimum level of data logging and the ratios of focal window lengths for accurate time of arrival detection in the field monitoring of the structures using acoustic methods.

Analysis of propagation and resonance properties of longitudinal leaky surface acoustic wave on LiNbO3/SiC bonded structure

Abstract The propagation and resonance properties of longitudinal leaky surface acoustic waves (LLSAW) on a bonded structure comprising an X-cut LiNbO3 (LN) thin plate and a 4H-SiC support substrate are theoretically investigated. The strong LLSAW responses with high Q factors were obtained at the LN thin-plate thickness h where the LLSAW phase velocity was slower than the bulk shear wave of 4H-SiC of 7126 m/s, and a fractional bandwidth (FBW) of 9–10% was obtained for the normalized Al film thickness by wavelength h Al/λ = 0.06–0.07 and h/λ = 0.30–0.40. Moreover, even at h/λ with a faster phase velocity than the bulk shear wave of 4H-SiC, the strong LLSAW responses without spurious response owing to the LLSAW higher-order mode were obtained. Finally, h Al/λ = 0.031 and h/λ = 0.19 were extracted to obtain a phase velocity of 7800 m/s, high Q factors, and FBW of 7.6%.

Novel nonlinear quantum dust acoustic waves for modified variable coefficients Zakharove–Kusnetsov equation in dusty plasma

In this paper, the direct similarity reduction method is used to reduce the modified variable coefficient Zakharove–Kusnetsov equation (vcmZK), which represents the propagation of quantum dust acoustic waves (QDAWs) in an inhomogeneous magnetized dusty plasma field, into a nonlinear ordinary differential equation (NODE). Moreover, the Jacobi elliptic method is used to solve the NODE, where many novel double periodic, kink, and solitary wave solutions are obtained. Additionally, we have chosen to plot periodic, kink, and soliton QDAWs solutions according to some choices for the variable coefficients. According to the a chieved results, we can conclude that the choices of the functional forms of the variable coefficients can control the QDAWs propagation. Finally, the new discovered results may have many important applications in astrophysics, atmospheric science, nanotechnology, and industrial plasma physics.

Analyzing the impact of flexible shells and sound absorbent lining on acoustic wave behavior in ducts

This study focuses on investigating the propagation of acoustic waves in a cylindrical waveguide with higher‐order derivative‐based boundary conditions and a sound absorbent lining. The mode‐matching method is employed to solve the governing boundary value problem, utilizing continuity conditions for pressure and velocity at waveguide interfaces. The objective is to establish a theoretical framework for analyzing and optimizing the acoustic performance of the waveguide, considering the influence of crucial parameters. The study's findings hold significant practical implications in acoustic engineering and noise control, enabling accurate prediction of acoustic wave behavior and facilitating the design of effective noise reduction measures and optimized sound‐absorbing materials in various applications. Additionally, the numerical techniques developed here can be extended to address more complex waveguide geometries and boundary conditions.

A STUDY ON THE INVESTIGATION OF THE TRAVELING WAVE SOLUTIONS OF THE MATHEMATICAL MODELS IN PHYSICS VIA (m + (1/G))-EXPANSION METHOD

The Gardner equation models the propagation of dust ion acoustic waves. As a result, it has received extensive attention in the literature. For the first time, the (m + (1/G))-expansion method is used to establish novel exact wave solutions for the Gardner equation. Solutions can exhibit various types of behavior, which can be visualized using 3D and contour graphs. The results obtained demonstrate that the presented method is powerful, useful, practical, and suitable for examining the model.

Simulations and analysis of underwater acoustic wave propagation model based on Helmholtz equation

In this study, we explore the effectiveness of elliptic partial differential equations (PDEs) in two and three dimensional space based on Helmholtz equation for simulations of acoustic sound in a very complex environment of propagation. For this purpose, we use an advance and robust numerical technique by utilizing the properties of shifted Chebyshev spectral collocation method. This technique is an extension of the traditional Chebyshev polynomials, incorporating a shift in their argument to enhance flexibility across a wider domain, while retaining an extraordinary numerical characteristic such as orthogonality and spectral convergence making them exceptionally effective in finding the approximate solutions. The exponential order of convergence of the proposed approach is shown both through theoretical and numerical approaches. We provide a number of numerical experiments to verify the theoretical results. The spectral convergence has been substantially enhanced by these numerical examples. The exponential order is further validated by numerical error behaviour in both L 2 and L ∞ norms.

Exact ion acoustic N solitary waves with variable velocity in inhomogeneous plasma induced by charged space debris

We have considered the propagation of nonlinear ion acoustic waves in a weakly inhomogeneous, cold (T i =0), collisionless space plasma in presence of charged space debris objects. The (1+1) dimensional evolution equation for the nonlinear ion acoustic wave is shown to have the form of a forced KdV equation with variable coefficients. The forcing term comes from the orbiting charged space debris and the variable coefficients of the forced KdV equation arise due to the equilibrium plasma quantities that depend on the slowly varying spatial coordinate. We have derived the exact one solitary wave, two solitary wave and then exact N solitary wave solutions of the forced system for some given choices of pinned debris functions where the velocity of the solitary waves varies with the slowly varying spatial coordinate. To the best of our knowledge, these exact, debris induced N solitary wave solutions with variable velocity in inhomogeneous plasma are important and new; hence may generate new ideas on research in this field.

Acoustic emission source location for composite tubes using finite element simulation and machine learning

ABSTRACT Acoustic emission is widely used in engineering structural health monitoring, where damage location based on acoustic emission have great advantages. Currently, most of the acoustic emission location work requires extensive experimental studies. In this study, acoustic emission source location model was proposed based on BP neural network and acoustic emission wave propagation simulation, thus reduced the experiments required for acoustic emission localisation and improved the location accuracy. Initially, finite element simulation was conducted to study the propagation of acoustic emission waves in composite tubes. The calculated findings showed a high level of agreement with the experimental data. Additionally, the first arrival time of the signal was extracted according to the Akaike information criterion, and the neural network was trained and tested using the simulated data, while the trained network model was validated using the experimental data. The results show that the finite element method is a reliable alternative test method. More than 94% of the sound source location results have absolute location error within ± 3 mm, and the all points is less than ± 5 mm. The deviation of the location results showed significant improvement compared to the traditional time difference of arrival method, verifying the feasibility of the method.

КОМП'ЮТЕРНЕ МОДЕЛЮВАННЯ НЕСТАЦІОНАРНОГО ПРОЦЕСУ РОЗВИТКУ НАДЗВУКОВОГО ПЕРЕРОЗШИРЕНОГО СТРУМЕНЮ

Questions of numerical simulation of non-stationary process of the development of a supersonic overexpanded jet are considered. Unsteady Reynolds-averaged Navier-Stokes equations (URANS) of compressible flows, written in an arbitrary coordinate system, along with the Spalart-Allmaras one-equation differential turbulence model are applied. The calculations of non-stationary formation of an air cold supersonic jet during the blowing through a conical Laval nozzle (simulation of engine start-up) were made. The physical features of the shock and acoustic waves generation and propagation are discussed. In the stationary phase an overexpanded free supersonic turbulent jet is formed, which includes a Mach disc in its structure. The obtained results were compared with experimental data and calculations by other authors based on the ANSYS Fluent and FloEFD CFD tools.

Microbubble-enhanced transcranial MR-guided focused ultrasound brain hyperthermia: heating mechanism investigation using finite element method

Recently, our group developed a synergistic brain drug delivery method to achieve simultaneous transcranial hyperthermia and localized blood–brain barrier opening via MR-guided focused ultrasound (MRgFUS). In a rodent model, we demonstrated that the ultrasound power required for transcranial MRgFUS hyperthermia was significantly reduced by injecting microbubbles (MBs). However, the specific mechanisms underlying the power reduction caused by MBs remain unclear. The present study aims to elucidate the mechanisms of MB-enhanced transcranial MRgFUS hyperthermia through numerical studies using the finite element method. The microbubble acoustic emission (MAE) and the viscous dissipation (VD) were hypothesized to be the specific mechanisms. Acoustic wave propagation was used to model the FUS propagation in the brain tissue, and a bubble dynamics equation for describing the dynamics of MBs with small shell thickness was used to model the MB oscillation under FUS exposures. A modified bioheat transfer equation was used to model the temperature in the rodent brain with different heat sources. A theoretical model was used to estimate the bubble shell’s surface tension, elasticity, and viscosity losses. The simulation reveals that MAE and VD caused a 40.5% and 52.3% additional temperature rise, respectively. Compared with FUS only, MBs caused a 64.0% temperature increase, which is consistent with our previous animal experiments. Our investigation showed that MAE and VD are the main mechanisms of MB-enhanced transcranial MRgFUS hyperthermia.

Magnetoacoustic waves in a partially ionized astrophysical plasma with the thermal misbalance: A two-fluid approach

We consider the propagation of magnetoacoustic (MA) and acoustic waves of various frequency ranges in a partially ionized plasma at an arbitrary angle to the magnetic field, taking into account the influence of heating, radiative, and thermo-conductive cooling, as well as ion-neutral collisions. A dispersion equation that describes the evolution of nine modes was obtained in a compact mathematical form using the two-fluid model. The number and type of propagating waves (modified fast and slow MA waves, MA waves in the ion component, acoustic waves in the neutral component, as well as isothermal MA and isothermal acoustic waves) vary in different frequency ranges depending on the parameters of the medium. Analytical expressions are found for the speed and damping rates of all these propagating waves, and it is shown how dispersion and damping are formed by three processes: thermal misbalance, ion-neutral collisions, and thermal conductivity. Comparison of analytical calculations of the velocity and damping rates of MA waves with the numerical solution of the dispersion relation under conditions characteristic of the low solar atmosphere and prominences showed high accuracy of the obtained analytical expressions. The strong influence of thermal misbalance caused by gasdynamic perturbations on the speed and damping rate of modified magnetoacoustic waves in a strongly coupled region is shown as well.

Low frequency dust acoustic drift instability in the equatorial electrojet

The dust acoustic drift instability has been investigated at the lower electrojet region of the dusty ionosphere by considering a linearized fluid model. The effect of dust-neutral collisions, electron–ion recombination at the surface of the dust particles, and electron and ion inertia on the onset and growth of the instability have been explored in minutiae. The perturbed densities are gleaned from the electron, ion, and dust dynamics, which engendered generalized dispersion relations. The generalized dispersion relation delineates the propagation of low-frequency dust acoustic drift waves. The dispersion relation is solved numerically for various cases of interest at the two different altitudes(∼90km and ∼100km) of the lower electrojet region. It has been found that the instability is unlikely to develop due to recombination alone, similar as observed in the case of laboratory dusty plasma. A significant reduction of the growth rate has been observed in the low-frequency mode due to the dust-neutral collision both in the presence and absence of an equilibrium electron density gradient. However, the effect of dust-neutral collision is not discernible in the relatively higher frequency mode, which exists at an altitude of 100km. Moreover, the presence of electron and ion inertia has a stabilizing effect on the instability. The analysis presented here is germane to the lower ionospheric dusty electrojet region in which electrons are magnetized, but ions and dust particles are unmagnetized.

Dynamic Equations for the Propagation of Acoustic Waves in Pre-Deformed Materials

Dynamic Equations for the Propagation of Acoustic Waves in Pre-Deformed Materials