Attenuation Of Wave Propagation Research Articles

Power-law frequency-dependent Q simulations in viscoacoustic media using decoupled fractional Laplacians

Quantifying the seismic attenuation of wave propagation in the earth’s interior is essential for studying subsurface structures. Previous approaches for attenuation simulations (e.g., the standard linear solid and the fractional derivative model) are mainly based on the frequency-independent quality factor Q assumption. However, seismic attenuation in high-temperature and high-pressure regions usually exhibits power-law frequency-dependent Q characteristics. To simulate this Q effect in attenuative media, we derive a new viscoacoustic wave equation with decoupled fractional Laplacians in the time domain. Unlike the existing methods using relaxation functions to fit the power-law relationship in a specific frequency band, our equation is directly derived from the approximated complex modulus, which explicitly involves the reference quality factor and fractional exponent parameters. Furthermore, this equation contains two fractional Laplacians, which can easily simulate decoupled amplitude dissipation and phase distortion effects, making it amenable to Q-compensated reverse time migration. In the implementation, a Taylor-series expansion and a pseudospectral method are introduced to solve the fractional Laplacians with variable fractional exponents. Numerical experiments demonstrate the effectiveness of our method for power-law frequency-dependent Q simulations. As a forward-modeling engine, our derived viscoacoustic wave equation is a good supplement to the current Q simulation methods and it could be applied in many seismic applications, such as Q-compensated reverse time migration and full-waveform inversion.

Attenuation of electromagnetic wave propagation in Martian dust storms

Attenuation of electromagnetic wave propagation in Martian dust storms

Acoustic field simulation-based ultrasonic water immersion non-destructive testing for titanium alloy plate

ABSTRACT Titanium alloy plate is widely used in automotive, aerospace, medical and other fields. Ultrasonic testing is a highly efficient non-destructive testing method for the inspection of titanium alloy components. However, there are strong distortion and attenuation of sound wave propagation in titanium alloys due to the presence of anisotropy and inhomogeneities, making it difficult to detect tiny defects in such components. In addition, some configuration parameters, such as the water path depth also affect the distribution of the acoustic field in the detected components. It is necessary to predict the acoustic field distribution to achieve a better testing accuracy. An acoustic field simulation method based on a multi-Gaussian beam is proposed, which can model the focused acoustic field in a multilayer anisotropy medium. The relationship between the acoustic focused area and the water path depth was explored and optimised comprehensively. C-scan imaging of specimen with flat bottom holes was performed at different water path depths. The results show that the proposed method can optimise the configuration parameters to improve the accuracy of the flaw sizing. This study provides an effective method for testing titanium alloy plate.

Wave propagation and vibration attenuation in spiral ABH metamaterial beams

Metamaterials with low-frequency and broadband bandgaps have great potential for manipulating elastic/acoustic waves. Inspired by the frame structures that are widely used in engineering and the acoustic black hole (ABH) structure with extraordinary properties of wave manipulation and energy focalization, a novel metamaterial beam with spiral ABH resonators is proposed, which can cover nearly 63 % of the frequency range of 0–1100 Hz based on local resonance mechanism without degrading the strength and stiffness of the main structure. The dispersion relation and eigenmodes of low-frequency bandgap boundary are analytically derived, which provides explicit guidance for the adjustment of the bandgap characteristics. Compared with the metamaterial beam with rod mass resonators, the spiral ABH resonators have a larger energy proportion and better capacity for energy concentration. Furthermore, the results show that decreasing the base thickness of spiral ABHs can form the bandgap in the low-frequency range of 39–53 Hz. Increasing the tip thickness or base thickness of the spiral ABHs allows the tuning of the bandgaps to enlarge the bandgaps, which can exceed 50 % of the frequency range of 0–400 Hz. Due to the strong designability of the distribution and the number of spiral ABH resonators, the structure with ABH in the corners of the frame can cover 71.3 % of the 0–1100 Hz. Experimental results show that with only three cells, the proposed metamaterial beam allows considerable vibration attenuation within a broad frequency range, especially in the low-frequency range (167–235 Hz), and it can transfer and dissipate the vibration energy from the main beam to avoid large deformations in the frame, which conventional frame beam can hardly reach. This study provides new guidance for structural design and engineering applications of metamaterial beams.

Modeling and numerical simulation of a type of pure-viscoacoustic-wave equation in attenuated TI media

The anisotropy and attenuation features of subsurface media significantly affect seismic data processing. Ignoring anisotropy and attenuation in seismic wave propagation may result in inaccurate reflector positions, dimming amplitudes, and reduced spatial resolution in the imaging results. Therefore, accurate seismic wave modeling of anisotropy and attenuation is essential for understanding wave propagation in the Earth’s interior. This article derives three pure-viscoacoustic-wave equations from characterizing the Earth’s frequency-independent Q behavior in transversely isotropic (TI) media. Firstly, we propose three time-space domain pure-qP-wave equations in TI media based on different approximation methods, whose coefficients can be determined by different approximation methods and Thomsen’s anisotropic parameters ε, δ. Subsequently, we introduce the Kelvin-Voigt attenuation model into our derived three time-space domain pure-qP-wave equations and then obtain three pure-viscoacoustic-wave equations. To further demonstrate the effectiveness and accuracy of our methods, we give some 2D and 3D numerical tests. The numerical results indicate that the wavefield generated by pure-qP-wave equations and pure-viscoacoustic-wave equations have accurate kinematic characteristics of qP-wave in TI media and attenuated TI media and are free of S- wave artifacts while remaining stable under Thomsen’s anisotropic parameters ε< δ, so our methods have broader applicability compared with some existing methods. At the same time, simulation results of pure-viscoacoustic-wave equations also reflect the absorption and attenuation characteristics of qP-waves in attenuated TI media.

Experimental and theoretical analysis of pulsatile flow in elastic tubes: Wave propagation and attenuation

The objective of this study was to comprehensively examine the pulsatile flow behavior within an elastic tube using experimental and theoretical approaches. This work is an extension of our earlier report [Roknujjaman et al., Phys. Fluids, 34, 123612 (2022)]. In this paper, we adapted a quasi-one-dimensional model to elucidate the wave propagation and pulse attenuation phenomena in an elastic tube and compared with experimental findings. According to our investigation, the key findings were as follows: the experimental and predicted flow wave propagation trend agreed well. Additionally, because of the silicon tubes greater deformation than the urethane tubes, the pulsation was decreased farther in the silicon tubes than in the urethane ones. Furthermore, because of the reflected wave near the tube exit, the pulsations amplitude significantly increased, but it did not enlarge when the resistance was installed at the exit. Finally, we infer that the quasi-one-dimensional model is a better fit for experimental results compared to the two-dimensional model.

Viscoacoustic reverse time migration with stable and effective two-way attenuation compensation

Intrinsic attenuation in seismic wave propagation leads to amplitude dissipation and phase dispersion in seismic data. The attenuation (∼1/ Q) effect is a common cause for inaccurate image locations and dimmed image energy in reverse time migration (RTM). Conventional viscoacoustic or viscoelastic RTM methods implement attenuation compensation by reversing the sign of the amplitude loss term and keeping the dispersion term unchanged for forward and backward wavefield extrapolation, which requires the decoupled viscoacoustic wave equation and gives rise to the numerical instability issue. To address these problems, we develop a stable and effective two-way attenuation-compensated viscoacoustic RTM method. Our method uses a new two-way normalized crosscorrelation imaging condition to compensate the attenuation effect. In the new imaging condition, only the attenuated forward wavefield of sources and the viscoacoustic Green’s functions of receivers are required, which eliminates the instability source arising from the operation of reversing the sign of the dissipation term in the viscoacoustic wave equation. Because no modifications are made to the viscoacoustic wave equation, the new imaging condition can be calculated without any additional computational cost and can be applied to decoupled and coupled viscoacoustic wave equation-based RTMs, which is more flexible than other attenuation compensation strategies. Two synthetic tests and one field data example are presented to demonstrate the stability and effectiveness of our method.

Adding a low frequency limit to fractional wave propagation models

Power-law attenuation in elastic wave propagation of both compressional and shear waves can be described with multiple relaxation processes. It may be less physical to describe it with fractional calculus medium models, but this approach is useful for simulation and for parameterization where the underlying relaxation structure is very complex. It is easy to enforce a low-frequency limit on a relaxation distribution and this gives frequency squared characteristics for low frequencies which seems to fit some media in practice. Here the goal is to change the low-frequency behavior of fractional models also. This is done by tempering the relaxation moduli of the fractional Kelvin-Voigt and diffusion models with an exponential function and the effect is that the low-frequency attenuation will increase with frequency squared and the square root of frequency respectively. The time-space wave equations for the tempered models have also been found, and for this purpose the concept of the fractional pseudo-differential operator borrowed from the field of Cole-Davidson dielectrics is useful. The tempering does not remove the singularity in the relaxation moduli of the models, but this has only a minor effect on the solutions.

Evaluating the Reactions of Bridge Foundations to Combined Wave–Flow Dynamics

As the ongoing development of national infrastructure progresses, we see an increase in the construction of deep-water bridges, specifically cross-sea bridges. This paper uses Stokes’s wave theory to simulate and analyze how a bridge foundation dynamically responds to wave–fluid interactions. Firstly, the governing equations, boundary conditions and initial conditions of fluid motion are derived, expanded and solved via Stokes’s wave theory, and a spectral model is simulated and plotted. Based on the P-M spectrum and equal frequency method, a method of wave height attenuation during wave propagation is proposed. Using an SSTK-ω turbulence model, a numerical wave flume is established considering the fluid model, the selection of element type and the boundary conditions set, and the influencing factors of wave propagation (attenuation) are analyzed. Waves with different wave parameters (period, depth and height) are numerically simulated and compared with the theoretical values. Finally, we perform an analysis of the dynamic response under wave–current coupling conditions. We establish different operational scenarios and obtain the following results: under a load duration of 200 s, the peak transverse displacements for spans 1, 2 and 3 measure at 0.84 m, 0.63 m and 0.62 m, respectively. The peak transverse displacements under operational scenarios 2 and 3 show reductions of 25.0% and 25.7%, respectively, when compared to scenario 1. However, large transverse displacements remain. This suggests that the influence of waves and water flow on the transverse displacement of the main span should not be overlooked.

Reverse time migration imaging method for tunnel seismic forward‐prospecting in viscoacoustic media

AbstractThe imaging of geological structure in front of a tunnel face is conducive to the safe construction of tunnels. The reverse time migration (RTM) method is popular for its high imaging accuracy. However, most of the current tunnel seismic RTM methods assume complete elasticity, ignoring the nature of wave propagation attenuation, resulting in a poor imaging outcome, especially when tunnelling in the shallow subsurface. Thus, it is necessary to study tunnel RTM suitable for attenuating strata. First, considering the frequency of tunnel seismic forward‐prospecting is usually higher than that of ground surface seismic exploration, we established a corresponding tunnel viscous media model to enable viscoacoustic forward modelling of seismic wavefield. Then, a simultaneous compensation approach for its amplitude and phase velocity is proposed based on the combination of the real and imaginary parts of the complex modulus. After the compensation of seismic wavefields, the tunnel Q‐RTM imaging method in viscoacoustic media is formed, and its effectiveness is verified by numerical examples. Compared with RTM without attenuation compensation, tunnel Q‐RTM effectively enhances the imaging energy and has higher positioning accuracy, improving the imaging effect of complex structures (especially at larger distances from the tunnel face). In the end, a detailed case study is presented to demonstrat the potential of the proposed method for field application.

In situ switchable local resonance in elastic metamaterials through bistable topological transformation

We report a topology-transformable resonator with two distinct stable states, one kinematically determinate and endowed with nearly rigid-body motion at low-frequencies, and the other accompanied by a floppy pseudo zero-energy mode capable of showing low-frequency local resonance. Through a combination of numerical simulations and experiments, we unveil the role of contact-induced topological transformation, a phenomenon that empowers the resonator with negative dynamic effective mass. We demonstrate that the bistable resonator can be embedded into elastic metamaterials to enable in situ switch of local resonance, allowing on-demand augmentation and attenuation of elastic wave propagation within a prescribed regime of frequency.

Study of the attenuation of ultrasonic oscilliations in 3D-orthogonal woven composite

The particularities of 3D-woven composite’s defects are observed. Automated ultrasonic immersion through-transmission technique for their non-destructive testing is offered. X-ray computed tomography (X-ray CT) application for the definition of the reasons of ultrasonic waves high attenuation in 3D-orthogonal woven composite sample is described. The analysis of defects detected with X-ray CT is shown. The suggestion about connection between quantity of projection of defects total area at the plane which is perpendicular to ultrasonic wave propagation and ultrasonic wave attenuation has been made.

Metamaterial beam with dual-action absorbers for tunable and multi-band vibration absorption

This paper presents a new class of metamaterial beams of tunable and multi-band vibration absorption. The metamaterial beam is composed of uniform and periodic beam cells with locally resonant substructure called dual-action vibration absorber, DA. A DA vibration absorber comprising of three locally resonant subsystems, 3-DOF spring-mass-damper subsystems, is utilized to generate frequency stopbands to stop elastic wave propagation. The governing equations of motion for a periodic beam cell are derived. Several distinct mass and stiffness configurations for the metamaterial beam with DA vibration absorber are proposed. The dispersion relations and presence of three frequency stopbands are studied. A finite element method based on Timoshenko beam theory is used to model and analyze the introduced metamaterial beam with DA vibration absorber. The frequency response simulations agree well with the projected stopbands of the developed dispersion relations of the mass and stiffness configurations. The concept of the presented metamaterial beam with tunable and multi-stopbands is promising for wave propagation attenuation and control applications.

Thermal cycling effects on the seismic wave propagation coefficients of granite

The seismic wave propagation properties of granite after thermal cycles were experimentally investigated. The granite specimens were subjected to a series of thermal cycles with different thermal cycling temperatures and numbers. Ultrasonic and pendulum impact tests were performed on the granite after thermal cycles. Subsequently, a theoretical study was introduced to explore the wave propagation coefficients of granite after thermal cycles. The effects of the thermal cycling number on the wave attenuation rate, wave velocity, attenuation coefficient, and wavenumber were discussed. The results indicate that the wave velocity and dynamic elastic modulus decrease as the number of thermal cycles increases and that the damage factor increases as the number of thermal cycles increases. However, the variations in wave velocity, dynamic elastic modulus, and damage factor are concentrated mainly in the first thermal cycle. The results further indicate that the wave propagation coefficients, attenuation coefficient, and wavenumber increase as the number of thermal cycles increases. However, they are not significantly influenced by the amplitude and wavelength of impact loading.

Stress wave propagation attenuation law and energy dissipation characteristics of rock-barrier-coal composite specimen under dynamic load

Stress wave propagation attenuation law and energy dissipation characteristics of rock-barrier-coal composite specimen under dynamic load

Effect of Rain Attenuation on Millimeter Wave over Polarization

Millimeter wave has been used in radar applications for a long time, and is increasingly used in new fields, among which high data rate telecommunications is the most prominent. Short wavelength and unique propagation characteristics provide challenges and opportunities for design engineers working in these fields. Millimeter wave has become an indispensable part of 5G mobile communication field due to its excellent spectrum characteristics. In order to help the development of millimeter wave equipment, this paper mainly studies the millimeter wave rain attenuation phenomenon through the combination of theory and simulation. The effects of rainfall rate and polarization mode on millimeter wave propagation attenuation are compared and summarized. In addition, the total attenuation of millimeter wave communication path under different polarization rainfall characteristics is compared. Finally, the total loss of different frequency millimeter wave rainfall links is compared and analyzed. It provides a theoretical basis for the follow-up design and practical application of millimeter wave communication system.

Numerical analysis of wave propagation and vibration attenuation effects of periodic scattering piles in unsaturated poroviscoelastic ground

ABSTRACT The elastic wave propagation and vibration attenuation zones for periodically scattering piles in unsaturated ground were investigated using Finite-Element Method (FEM) and Bloch periodic theory. The unsaturated ground was modelled by unsaturated poroviscoelastic medium with the weak form governing equations derived from the mass and momentum conservative equations using Galerkin method and Fourier transform. The quadratic polynomial eigenvalue equations for the unsaturated medium were obtained using the Bloch periodic theory, and solved by FEM for the complex eigenvalues to evaluate the band gaps of the pile-soil system. The eigenvalue bands combined with the frequency response function were used to analyse the mitigation effects of piles in unsaturated ground with different soil properties and piles parameters. This research found that the pile-soil system has three propagational waves, in which the shear wave and the slow longitudinal wave carry low-frequency vibrations that undermine the attenuation effects of the piles barrier. The increasing soil saturation degree affects the attenuation effects by reducing the soil modulus and increasing the fluid content. And both of those two mechanisms reduce the frequency of the attenuation zones (AZ), which improves the low-frequency vibration attenuation, and reduces the width of AZ that could reduce the vibration mitigation effects.

Investigation on the Seismic Wave Propagation Characteristics Excited by Explosion Source in High-Steep Rock Slope Site Using Discrete Element Method

The influence of seismic waves induced by explosion sources on the dynamic response characteristics of rock slope sites is one of the most important problems affecting engineering construction. To investigate the wave propagation characteristics and attenuation law of seismic waves induced by explosive sources in rock sites from the perspective of time and frequency domains, the high-performance matrix discrete element method (MatDEM) is used to carry out numerical simulation tests on a granite rock medium site. The discrete element model of the high-steep rock slope is established by MatDEM, and the dynamic analysis of the rock medium site is conducted by loading blasting vibration load to generate seismic waves. The results show that the seismic waves in the rock site present characteristics of arc propagation attenuation. The maximum attenuation rate of the dynamic response is the fastest within 0.3 s and 25 m from the explosion source. The slope region can weaken the dynamic response of seismic waves generated by the explosion source. In particular, the high-frequency band (>20 Hz) has an obvious filtering effect. The dynamic response of the P-wave induced by the explosive source is greater than that of the S-wave in the bedrock and surface region. The dynamic amplification effect of the P-wave is greater than that of the S-wave in the slope region. The seismic waves in the slope region show an attenuation effect along the slope surface and have a typical elevation amplification effect inside the slope.

Identification of corrosion formation in CORTEN steel using acousto-ultrasonic approach and deep learning

PurposeThe acousto-ultrasonic approach is used for propagating stress waves through different configurations of CORTEN steel specimens. The propagated waves are recorded and analysed by piezoelectric sensors. The purpose of the study is to study the characteristics of the CORTEN steel by analysing the propagated waves.Design/methodology/approachTo investigate the attenuation in acoustic wave propagation due to the corrosion formation in CORTEN steel specimens and to train a neural network model to classify the attenuated acoustic waves automatically.FindingsDue to the corrosion formation in CORTEN steel specimens, attenuation is observed in amplitude, energy, counts and duration of the propagated waves. When the waves are analysed in their time-frequency characteristics, attenuation is observed in their frequency and spectral energy.Originality/valueThe corrosion formation in CORTEN steel can automatically be analysed by using the acousto-ultrasonic approach and the trained deep learning neural network.

Metamaterials with Reprogrammable Reciprocity

Metamaterials composed of asymmetric elements have been shown to break reciprocity; permitting the propagation of waves in one direction. The configuration of these metamaterials typically limits the propagation of the wave to a single direction, speed, or occurrence with little or no tunability. Here we present---theoretically, numerically, and experimentally---a simple design approach for reprogrammable metamaterials, which allows for all of these parameters to be tuned, enabled, disabled, or reset. We present a map of different geometries that allow for reciprocal and nonreciprocal wave propagation and attenuation. We show how a single design can be programmed on demand to support wave propagation and attenuation in both directions (reciprocal) or wave propagation in only one direction (nonreciprocal). In addition, we demonstrate real-time control of the wave velocity, both in amplitude and direction, as it propagates through the metamaterial. We show speeding up, slowing down, or complete reversal of the propagating wave direction. Furthermore, we show that the waves maintain a constant velocity regardless of the impulse magnitude, and even along a curved path. Our metamaterial could open exciting possibilities for designing nonlinear materials with exotic topological properties.