Interaction Of Acoustic Waves Research Articles

Coherent surface acoustic wave–spin wave interactions detected by micro-focused Brillouin light scattering spectroscopy

We investigated the interaction of surface acoustic waves and spin waves with spatial resolution by micro-focused Brillouin light scattering spectroscopy in a Co40Fe40B20(10 nm) ferromagnetic layer on a LiNbO3-piezoelectric substrate. We experimentally demonstrate that the magnetoelastic excitation of magnons by phonons is coherent by studying the interference of light scattered off generated magnons and annihilated phonons. We find a pronounced spatial dependence of the phonon annihilation and magnon excitation, which we map as a function of the magnetic field. The coupling efficiency of the surface acoustic waves (SAWs) and the spin waves is characterized by a magnetic field-dependent decay of the SAWs amplitude.

Near-field wave interactions with defects and their implications on sub-wavelength acoustic imaging

Acoustic metamaterial concepts, such as metalenses and hyperlenses, have been studied with much interest for super-resolution imaging. However, the physics of wave scattering by sub-wavelength sized defects is still not very well understood. Here, we present studies on acoustic wave interactions with circular defects of sizes varying from over a wavelength to sub-wavelength scale. Near- and far-field scattering patterns of single circular defects are presented, connecting them to analytical frameworks. Scattering field signatures produced by two identical circular defects of different sizes placed side by side are then discussed. The separation distance between the defects is among the parameters varied to understand the effects of geometric features in successful imaging. Experimental results are presented to support the predictions reported in the paper. The insights have important implications for sub-wavelength imaging using acoustic metamaterials.

Effect of entropy waves on the thermoacoustic instability of choked outlet combustion chambers

Thermoacoustic instability is a major issue in aero-engine and gas turbine combustion chambers, especially for the case of lean premixed combustion. The instability is caused by the interaction of acoustic waves with unsteady heat release. As considering the accelerated entropy waves in the system, the entropy effect on the acoustic waves cannot be ignored, which will further modify the thermoacoustic instability. Recent researches have shown that the entropy waves can be generated by the steady heat sources or temperature gradients, which can exclude the interference of unsteady heat release factors in instability analysis. In this study, the effect of entropy waves on the thermoacoustic instability of the combustion chamber model with choked outlets is investigated by constructing a low-order acoustic network model. New modes introduced by entropy waves, called as the entropy acoustic modes (EA modes), are investigated by a steady heat source. Then the unsteady heat release is considered, and the effect of entropy waves on different modes and the coupling behavior of these modes are analyzed comprehensively. It is found that some modes are jointly affected by the flame, entropy waves as well as the acoustic waves, which are called as the entropy thermoacoustic modes (ETA modes). Moreover, the modal frequencies of the intrinsic thermoacoustic instabilities modes (ITA modes) are changed remarkably due to the introduction of entropy waves. In addition, the entropy wave dispersion and dissipation show a non-negligible effect on the thermoacoustic instability.

Contribution of the Magnetic Subsystem to the Generation of Longitudinal Acoustic Waves during Domain Wall Motion in Yttrium Orthoferrite

Purpose. Modern technologies in their development are increasingly in need of increasing the speed of processing and recording information. An alternative to semiconductor methods is magnetic memory based on changing magnetic moments. The speed of magnetization reversal is determined by the speed of motion of domain walls. The speed is maximum in weak ferromagnets. The purpose of this work is to study the effect of a magnetic wave generated by a moving domain wall on a longitudinal acoustic wave, taking into account the absorption of a magnetic wave in yttrium orthoferrite.Methods. The equation describing the effect of a magnetic wave generated by a moving domain wall on a longitudinal acoustic wave is solved using the following methods: the slowly varying amplitude method, the perturbation theory method, and the Lagrange method.Results. For an orthoferrite crystal, the contribution of the magnetic wave accompanying the motion of the domain wall in yttrium orthoferrite to the deformation of the amplitude of the longitudinal acoustic wave is calculated. This contribution in a bounded crystal, without taking into account the absorption of magnetic waves in the absence of the influence of acoustic waves on them, is of the order of 10-6 cm. In an unbounded crystal, the corresponding contribution, taking into account the absorption of magnetic waves, into the generation of longitudinal acoustic waves is of the order of magnitude 10-10 cm with a theoretical thickness of the domain wall D3 ≈ 10-6 cm.Conclusion. To study the mechanisms of the influence of a magnetic wave generated by a moving DW on a longitudinal acoustic wave, yttrium orthoferrite was taken. Since a weak ferromagnet is characterized by a significant increase in the magnetoelastic coupling when it overcomes the sound barrier. It is this circumstance that made it possible to experimentally observe the generation of elastic displacements by a moving domain wall. To develop devices for recording and processing information based on weak ferromagnets, it is necessary to fully investigate the mechanisms that affect the dynamics of a domain wall during its motion. Such a factor is the interaction of magnetic and acoustic waves with the domain wall, which can affect the quality of information processing. The evaluation of the contributions of these mechanisms can be used to develop the element base of devices for recording and processing information based on the magnetic memory of weak ferromagnets.

A novel model of nonlocal photoacoustic and plasmaelastic heated by laser pulsed excitation of nanoscale semiconductor medium

The study takes into account the diffusion of photo-excited carriers in the presence of a laser pulse and theoretically investigates photoacoustic wave propagation in the thermoelastic domain. In a nonlocality medium, the phenomena of thermomechanical and acoustic wave interaction are considered. Thermoelasticity, photothermal, and photoacoustic theories provide the controlling formulas. Photoacoustic waves are not dependent on electron–phonon or electron–hole thermalization processes; rather, they are produced by thermoelastic stress resulting from the temperature increase induced by the laser. The optical, elastic, and thermoelastic characteristics of nanoscale semiconductor materials are taken into account and photoacoustic signals are predicted by solving a thermal diffusion issue and a thermoelastic problem in combination. The mathematical model can be solved using the harmonic wave approach. By obtaining numerical solutions, all the physical fields of the physical domain, such as thermal, acoustic, mechanical, and carrier density diffusion, as well as displacements and temperatures, can be derived. The influences of nonlocal parameters, thermal delay, and laser pulse effect are investigated and compared using two- and three-dimensional visual representations, corresponding to two-dimensions and three-dimensions domains, respectively.

Modeling and Simulation of Parametric Nonlinear Focused Ultrasound in Three-Dimensional Bubbly Liquids with Axial Symmetry by a Finite-Element Model

This paper presents the development of a numerical model able to track in time the behavior of nonlinear focused ultrasound when interacting with tiny gas bubbles in a liquid. Our goal here is to analyze the frequency components of the waves by developing a model that can easily be adapted to the geometrical restrictions and complexities that come out in several application frameworks (sonochemistry, medicine, and engineering). We thus model the behavior of nonlinear focused ultrasound propagating in a liquid with gas bubbles by means of the finite-element method in an axisymmetric three-dimensional domain and the generalized-α method in the time domain. The model solves a differential system derived for the nonlinear interaction of acoustic waves and gas bubble oscillations. The high nonlinearity and dispersion of the bubbly medium hugely affect the behavior of the finite-amplitude waves. These characteristics are used here to generate frequency components of the signals that do not exist at the source through nonlinear mixing (parametric antenna). The ability of the model to work with complex geometries, which is the main advantage of the method, is illustrated through the simulation of nonlinear focused ultrasound in a medium excited from two spherical sources in opposite directions.

A domain decomposition technique for acoustic wave interactions and scattering

In this work, a two-dimensional domain decomposition technique (DDT) is developed based on an overset method that couples a nonlinear Euler solver with a linearized Euler solver. The nonlinear domain accounts for complex physics in the near field, such as acoustic wave interaction with shock waves and acoustic wave scattering from solid bodies. The linear domain allows the small perturbation waves induced by the nonlinear effects to propagate with minimal numerical dissipation and dispersion while also significantly reducing computational resources. To this end, two scenarios have been considered: (i) wave amplification and modulation in a converging-diverging duct with a standing shock wave and (ii) wave scattering from an incident acoustic wave over a supercritical airfoil. With DDT, these cases show a reduction in computational time by more than 70% compared to their respective fully-nonlinear simulations. The accuracy of the simulations with DDT is found to depend on the extent of overlap between the linear and nonlinear zones. In general, an overlap ratio of at least two is necessary to maintain high order of convergence rate, though still limited by the nonlinear scheme. Furthermore, the implementation of DDT in the external flow case can eliminate numerical noise observed at the far field of the fully-nonlinear counterpart, which do not have any effective non-reflecting boundary treatment.

Surface acoustic waves interaction with confined acoustic phonons in a coupled nanoridges dimer set atop of a multilayer design

We present a comprehensive study using finite element numerical analysis of the acoustic localized phonons supported by a gold nanoridges dimer-based multilayer design. The latter consists in a SiO2-substrate over which a gold film covered with a thin polymer is deposited. We investigate first the mechanical eigen-modes analysis of a single monomer ridge, where we find flexural and compressional type modes in the sub-GHz frequency range. This is realized by either setting the ridge in a periodic structure, which enables to get the dispersion curve of the modes, or by considering an isolated system bounded by perfect matched layers, where we use the equivalent of the local density of states to track the modes. A good agreement is obtained between the two methods. Similarly, we find in case of the coupled dimer ridges hybridized modes, namely the flexural and compressional modes of a monomer split-up into in- and -out-of-phase type modes. We demonstrate efficient coupling between the monomer/dimer localized phonons with surface acoustic waves (SAWs) as the simulated transmission spectra show dips at the frequencies of the monomer/dimer eigenmodes. For symmetry reasons, some of the dimer modes are expected to be optomechanically active. The proposed SAW-based device is meant to help design acousto-optic modulators or ultrasensitive sensors.

Real-time imaging of acoustic waves in bulk materials with X-ray microscopy

The dynamics of lattice vibrations govern many material processes, such as acoustic wave propagation, displacive phase transitions, and ballistic thermal transport. The maximum velocity of these processes and their effects is determined by the speed of sound, which therefore defines the temporal resolution (picoseconds) needed to resolve these phenomena on their characteristic length scales (nanometers). Here, we present an X-ray microscope capable of imaging acoustic waves with subpicosecond resolution within mm-sized crystals. We directly visualize the generation, propagation, branching, and energy dissipation of longitudinal and transverse acoustic waves in diamond, demonstrating how mechanical energy thermalizes from picosecond to microsecond timescales. Bulk characterization techniques capable of resolving this level of structural detail have previously been available on millisecond time scales-orders of magnitude too slow to capture these fundamental phenomena in solid-state physics and geoscience. As such, the reported results provide broad insights into the interaction of acoustic waves with the structure of materials, and the availability of ultrafast time-resolved dark-field X-ray microscopy opens a vista of new opportunities for 3D imaging of materials dynamics on their intrinsic submicrosecond time scales.

Surface Acoustic Wave Interaction with a Mixture of Oxygen and Nitrogen

Parameters of surface acoustic waves (SAW) are very sensible to change of physical conditions of a propagation medium. In the classical theory formulation, the waves are guided along the boundary of semi-infinity solid state and free space. A real situation is more complex and a medium commonly consists of two physical components: a solid substrate and a gaseous or liquid environment. In the case of stress-free substrate, the strongest impact on SAW properties have surface electrical and mechanical conditions determined by solids or liquids adhering to the boundary. This impact is utilised for constructing sensors for different gases and vapours e.g. (Jakubik et al., 2007; Hejczyk et al., 2011; Jasek et al., 2012). The influence of gaseous environment on the SAW properties is usually very weak and ignored. However, in certain condition it can be significant enough to be applied to sensor construction. In general, it concerns Rayleigh wave devices where energy leakage phenomenon is perceptible, especially when the gas being detected considerably changes the density of environment. The paper presents the results of experiments with oxygen-nitrogen mixture. Their primary aim was focused on finding the dependence of resonant frequency and attenuation in SAW resonator on parameters and concentrations of the gas in the environment.

Acoustic resonance effects and cavitation in SAW aerosol generation

The interaction of surface acoustic waves (SAWs) with liquids enables the production of aerosols with adjustable droplet sizes in the micrometer range expelled from a very compact source. Understanding the nonlinear acousto-hydrodynamics of SAWs with a regulated micro-scale liquid film is essential for acousto-microfluidics platforms, particularly aerosol generators. In this study, we demonstrate the presence of micro-cavitation in a MHz-frequency SAW aerosol generation platform, which is touted as a leap in aerosol technology with versatile application fields including biomolecule inhalation therapy, micro-chromatography and spectroscopy, olfactory displays, and material deposition. Using analysis methods with high temporal and spatial resolution, we demonstrate that SAWs stabilize spatially arranged liquid micro-domes atop the generator's surface. Our experiments show that these liquid domes become acoustic resonators with highly fluctuating pressure amplitudes that can even nucleate cavitation bubbles, as supported by analytical modeling. The observed fragmentation of liquid domes indicates the participation of three droplet generation mechanisms, including cavitation and capillary-wave instabilities. During aerosol generation, the cavitation bubbles contribute to the ejection of droplets from the liquid domes and also explain observed microstructural damage patterns on the chip surface eventually caused by cavitation-based erosion.

Sonochemistry of Liquid-Metal Galinstan toward the Synthesis of Two-Dimensional and Multilayered Gallium-Based Metal-Oxide Photonic Semiconductors.

The scientific field of two-dimensional (2D) nanostructures has witnessed tremendous development during the last decade. To date, different synthesis approaches have been developed; therefore, various exceptional properties of this family of advanced materials have been discovered. It has recently been found that the natural surface oxide films of room-temperature liquid metals is an emerging platform for the synthesis of novel types of 2D nanostructures with numerous functional applications. However, most of the developed synthesis techniques for these materials are based on the direct mechanical exfoliation of 2D materials as research targets. This paper reports a facile and functional sonochemical-assisted approach for the synthesis of 2D hybrid and complex multilayered nanostructures with tunable characteristics. In this method, the intense interaction of acoustic waves with microfluidic gallium-based room-temperature liquid galinstan alloy provides the activation energy for synthesis of hybrid 2D nanostructures. The microstructural characterizations reveal the impact of sonochemical synthesis parameters, including the processing time and composition of the ionic synthesis environment, on the growth of GaxOy/Se 2D hybrid structures and InGaxOy/Se multilayered crystalline structures with tunable photonic characteristics. This technique shows promising potential for synthesis of various types of 2D and layered semiconductor nanostructures with tunable photonic characteristics.

Interaction of two soliton waves in plasma including electrons with Kappa-Cairns distribution function

• The nonlinear propagation of soliton waves can be expressed by different equations. • KdV equation includes the equilibrium between nonlinearity and dispersion sentences, which gives information about the soliton waves. • One of the distribution functions that has been utilized in the last few years is the C-T distribution function. • The results demonstrated that the parameters and have a great impact on phase. velocity, nonlinear and dispersive coefficients, Sagdeev potential, maximum amplitude, and width of IASWs. a q The interaction of positron acoustic soliton waves (PASWs) with the arbitrary collision angle in plasma including cold fluid positrons, stationary ions and electrons with Kappa-Cairns (K-C) distribution function have been studied. The equations of Korteweg-de Vries (KdV) and the phase shifts are obtained by employing the extended Poincaré–Lighthill–Kuo (PLK) method for the two colliding waves. The influences of parameters of the K-C distribution function ( κ and α ), the collision angle θ and the proportion of the ion (electron) and positron unperturbed densities ( β i ( β e )) on the phase shifts are investigated.

Interaction of acoustic and electromagnetic waves for thermoacoustic imaging and vibration sensing

Acoustic wave and electromagnetic wave can interact and lead to rich physical phenomenon to be used for applications such as medical diagnosis, non-destructive material characterization, and remote sensing. In this talk, I will present our research studies on two ways acoustic and electromagnetic waves interact with each other: (1) When pulsed microwave is absorbed by tissue, thermoacoustic waves are generated through thermal expansion. We explored the sensing and processing of thermoacoustic waves generated by a pulsed microwave ablation antenna as a potential way for monitoring the ablation process in real time. (2) Electromagnetic waves such as Wi-Fi signals and light can be modulated by acoustic/mechanical vibrations in the environment. We developed non-contact vibration sensing systems based on such modulations, and also developed a metamaterial-based vibration amplification device that can enhance the vibration magnitude sensitivity over a broad range of vibration frequencies.

Acoustic energy harvesting of ambient noise urban environment

In this work, the efficiency of engineered materials for converting ambient acoustic noise into electrical power is investigated. Of particular interest are 3D-printed acoustic metamaterials. Initial investigation will focus on sonic crystals acoustic metamaterials. Numerical simulations of the acoustic wave and sonic crystals interaction will be conducted. Of particular interests are the strong scattering interactions. 3D-printed samples will be measured and tested. The simulation and measurement results will be presented and discussed.

Acoustic shock waves emitted from two interacting laser generated plasmas in air.

We present an acoustic detection technique to study the interaction of two shock waves emitted by two nearby, simultaneous, laser-induced air-breakdown events that resembles the phenomenon of interaction of fluids. A microphone is employed to detect the acoustic shock wave (ASW) from the interaction zone. The experiments were done at various separation distances between the two plasma sources. The incident laser energy of the sources is varied from 25 to 100 mJ in ratios from 1:1 to 1:4. The peak sound pressure of the ASW was compared between the single and dual plasma sources, showing that the pressures are higher for the dual plasma source than that of the single plasma. The evolution of peak sound pressures is observed to depend on (a) the pulse energy of the sources and (b) the plasma separation distance, d. For the equal energy sources, the peak sound pressures increased linearly up to a certain plasma separation distance d, beyond which the pressures saturated and decayed. For the case of unequal energy sources, the peak sound pressures showed an interesting response of increase, saturation, decay, and further increase with plasma separation distance d. These observations indicate the dynamics of acoustic wave interactions across the interaction zone of the two sources depend on the input laser pulse energy as well as the plasma separation distance d.

Dynamics and head-on collisions of multidimensional dust acoustic shock waves in a self-gravitating magnetized electron-depleted dusty plasma

The dynamics and collisions of dust acoustic (DA) shock excitations traveling in opposite directions are theoretically investigated in a three-dimensional self-gravitating magnetized electron-depleted dusty plasma whose ingredients are extremely warm positively and negatively charged massive dust grains as well as ions that follow the q-nonextensive distribution. A linear analysis and the extended Poincare–Lighthill–Kuo method are used to derive the dispersion relation, the two-sided Korteweg–de Vries Burgers equations, and the phase shift that occurs due to the wave interaction. It is found that gravitation introduces Jeans-like instability, reduces the wave damping rate, decays the aperiodic oscillatory structure of DA excitations, and strongly affects the amplitude, steepness, and occurrence of monotonic compressive and rarefactive shocks. Numerical simulations also highlighted the stabilizing role of the magnetic field and the singularities of the collision process of monotonic shock fronts as well as the undeniable influence of viscosity, ion nonextensivity, and obliqueness between counter-traveling waves on the phase shift and collision profiles. The present results may be useful to better understand interactions of dust acoustic shock waves in the laboratory and astrophysical scenarios, such as dust clouds in the galactic disk, photo-association regions separating H II regions from dense molecular clouds, Saturn's planetary ring, and Halley Comet.

High-speed non-contact measurement of elasto-optic coefficient via laser-induced phonons

The elasto-optic coefficient, which describes the interaction of acoustic waves and light in a medium, allows a contrast mechanism in optomechanics. However, the non-contact measurement is a challenge, limiting the study of some materials such as liquids. We present a high-speed non-contact method based on laser-induced phonons. The elasto-optic coefficients of common liquids are measured with only 10 ms and an averaged relative standard deviation of 1.52%, complementing the rare liquid data. By deciphering Brillouin spectra, the elasto-optic coefficient and viscoelastic parameters can be obtained simultaneously, and the introduction of the elasto-optic coefficient makes the characterization more sensitive. Benefiting from spatially resolved measurement, the elasto-optic coefficient is mapped to provide another contrast mechanism for mechanical imaging and may prove useful to characterize biological cells and tissues.

A triboelectric nanogenerator attached to a thermoacoustic heat engine for power generation

Thermoacoustics is a promising field that uses the phenomena of acoustic wave interaction with neighboring solid boundaries to build engines for power generation. A typical thermoacoustic heat engine (THE) converts heat from an input source to acoustic energy, which is then collected by an alternator to generate electricity. Moving parts are present in an alternator, rendering it expensive and less reliable. A viable alternative is the use of Triboelectric nanogenerators (TENG) as a conversion system. Thus, a thermoacoustic heat engine integrated with a TENG is modeled and analyzed in this paper. A three-tier methodology including analytical, FEM, and an electrical analogy approach is adopted to simulate and optimize the performance of a TENG-attached-THE. The simulation results show that a voltage and current of 11.2 V and 0.028μA, respectively, are produced, differing by + 1.2 V and + 0.013μA with the experimental results.

Terahertz resonance frequency through ethylene glycol phononic multichannel sensing via 2D MoS2/PtSe2 structure

Artificial periodic structures drew a lot of attention because of their ability to be built with novel acoustic features. A novel nanostructured phononic superlattice (NPhS) based two-dimensional multilayer structure as a high-sensitive multichannel liquid sensor that provided bright multichannel band gap windows has been introduced. Theoretically, the designed structure is composed of [(MoS2/PtSe2)4] NPhS with a cavity filled with different concentrations of Ethylene Glycol at room temperature toward acoustic bandgap engineering multichannel sensor. We examined the interaction of acoustic waves with nano and bulk phononic superlattice (PhS) structures. In addition, we studied the effect of using different analyte layer thicknesses on the resonance peaks that appeared inside the band gaps. Many sharp resonance peaks appeared in multi-band gaps, which introduced high sensitivity, Q-factor, and figure of merit (FOM) values for each concentration of Ethylene Glycol. Furthermore, the effect of resonance peaks' full width at half maximum (FWHM) on the Q-factor of the NPhS multichannel sensor has been studied. From our results, the relation between the sensitivity of our multichannel sensor and the resonance frequency of each concentration shows a linear behavior. The highest sensitivity was obtained for a 1.00 m% concentration of 0.21 (GHz/(kg/m3)) at a resonance frequency value of 0.21 THz. In addition, the NPhS multichannel sensor recorded the highest Q-factor for 0.8069 m% with a value of 1744 and the highest FOM for 0.3819 m% with a value of 0.05988 (m3/kg). Moreover, we studied the effect of temperature on the sensitivity of the NPhS multichannel sensor. We showed the highest sensitivity value of 1.79 (GHz/o C) at 10 °C towards Ethylene Glycol. Further, the dispersion relation of an acoustic wave propagating inside perfect and defected nano and bulk PhS structures has been introduced. Our proposed multichannel liquid sensor can introduce a novel sensitivity at Terahertz frequency ranges.