Longitudinal Propagation Research Articles

Simulation and Control Strategies for Longitudinal Propagation of Acid Fracture in a Low-Permeability Reservoir Containing Bottom Water

The reservoir in the Anyue gas field, located in the Sichuan basin of China, belongs to the second member of the Dengying formation and has distinctive geological features. It is characterized by strong heterogeneity, low porosity, low permeability, and locally developed natural fractures. The reservoir space consists primarily of corrosion holes, natural fractures, and similar voids. Moreover, the lower reservoir exhibits high water saturation and a homogeneous bottom-water interface. Since it is a carbonate-based hydrocarbon reservoir with low porosity and permeability, deep acid fracturing has proven to be an efficient method for enhancing individual well production. However, the reconstruction of the second member of the Dengying formation reservoir poses significant challenges. The reservoir contains high-angle natural fractures, small vertical stress differences, and is located in close proximity to the gas–water interface. As a result, it becomes difficult to control the height of the acid break. Improper acid break treatment may easily result in water production affecting gas well production. To explore ways to control the longitudinal extension of acid fractures, 3D numerical models focusing on the initiation and expansion of acid fractures have been developed. This model takes into account geological and engineering factors such as stress differences, acid fracture displacements and scales, and their effects on the longitudinal extension of acid fractures. It was revealed that the pressure difference is the main controlling factor for the acid fracture height, followed by the reservoir thickness, the interlayer thickness, and the viscosity of the working fluid. Technical countermeasures for controlled fracture and high-acid fracturing tailored to different reservoir characteristics have been proposed, and design parameters for controlled fracture and high-acid fracturing can be optimized. By effectively controlling the vertical extension of the acid fracture, it is possible to maximize production from a single well while avoiding interference from the lower water layer. This study provides theoretical guidance for the application of deep-acid-fracturing techniques in low-permeability bottom-water gas reservoirs.

Stress wave attenuation in chocolate

The stress wave attenuation in five types of chocolate (extra dark, dark, milk, white, and ruby) was studied. The main acoustics properties of these chocolates were described in terms of longitudinal and transversal wave velocities. The attenuation of the stress waves was studied using the experimental technique known as the Split Hopkinson Pressure Bar (SHPB). The SHPB set-up consists of a specimen and linear elastic incident and transmission bar. Experimental data have been evaluated both in the time as well as frequency domain. Attenuation of the stress wave was described namely using the frequency dependence of the transmission coefficient of the stress wave. This damping increases with the plastic strain of the tested chocolate specimens. From a technological point of view, the fat content of the chocolate has the highest influence on the reduction of the longitudinal wave propagation velocity. The lowest attenuation was observed for the dark chocolate.

Evolving Phase Propagation in an Intermediate‐m ULF Wave Driven by Substorm‐Injected Particles

AbstractAn ultralow frequency (ULF) wave was simultaneously observed in the ionosphere by the Super Dual Auroral Radar Network (SuperDARN) radar at Hankasalmi, Finland and on the ground by the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometers with close proximity to the radar. The onset time of the wave event was around 03:00 magnetic local time. Fourier wave analysis of the event suggests a wave period of about 1,340 s with an equatorward latitudinal and eastward longitudinal wave phase propagation, and an effective azimuthal wave number of 17 ± 1, in the intermediate range of those observed in ULF waves. This wave has been interpreted as resulting from drifting electrons of energies of 13 ± 5 keV in a drift resonance condition linked to energetic particle populations during a magnetospheric substorm. The latitudinal phase characteristics of this wave experienced temporal evolution, believed to be caused by additional injected particle populations associated with the same substorm driving the wave, which resulted in an observed loss of HF backscatter. This observation of a unique type of temporal evolution in the phase propagation characteristics of ULF waves enhances current understanding about the structure, dynamics and source of these types of ULF waves.

Supersymmetric behavior of polarized electromagnetic waves in anisotropic media

A medium with specific anisotropic refractive indices can induce a supersymmetric behavior in the propagation of polarized electromagnetic waves, in an analog fashion to a quantum mechanical system. The polarizations of the wave are the ones which behave as superpartners from each other. For this to happen, the anisotropy of the medium must be transverse to the direction of propagation of the wave, with different refractive indices along the direction of each polarization, being in this way a biaxial medium. These refractive indices must be complex and follow a very specific relation in order to trigger the supersymetric response of the electromagnetic wave, each of them with spatial dependence on the longitudinal (propagation) direction of the wave. In this form, in these materials, different polarized light can be used to test supersymmetry in an optical fashion.

Exploring wave propagation and attenuation in a metamaterial bar using dual-action vibration absorber with multifrequency resonators

This paper introduces a method for attenuating longitudinal elastic waves in metamaterial bars through the utilization of Dual-Action (DA) vibration absorbers equipped with multifrequency resonators (MFRs). The metamaterial bar (Metabar) is composed of a linear arrangement of evenly distributed and enclosed DA vibration absorbers connected to an isotropic bar. The DA vibration absorber is constructed with multiple spring-mass resonators interconnected with each segment of the isotropic bar at two points. An analytical methodology is formulated employing Finite Element Modeling (FEM) and Bloch’s theorem to demonstrate the existence of multiple stopbands, leading to the generation of broad and configurable frequency stopbands. The article illustrates the design and modeling of the metabar’s DA vibration absorber, showcasing analytically that the vibration suppression and, consequently, wave attenuation within the metamaterial bar are grounded in the fundamental principles of basic mechanical vibration absorption. The DA absorber effectively prevents longitudinal wave propagation through the metabar by generating two internal forces to counteract any incoming wave within the stopband frequencies. Furthermore, these internal forces can be adjusted by optimizing the effective properties of the DA vibration absorber. A comprehensive parametric investigation is then conducted to analyze how the properties of the enclosed MFRs of the DA absorber, such as mass densities and stiffness coefficients, influence the locations and sizes of the frequency stopbands. The results from FEM simulations show a substantial alignment with dispersion curves across various prescribed configurations, offering strong validation for the proposed metamaterial design that integrates the DA vibration absorber with MFRs. The introduced mechanism for vibration absorption and suppression is of significance in applications involving the control and manipulation of wave propagation.

Symmetry analysis, optimal subalgebra, quasi-self-adjointness condition with conservation laws and analytical solutions for the ($$1+1$$)-dimensional Pochhammer–Chree model in longitudinal wave propagation

Symmetry analysis, optimal subalgebra, quasi-self-adjointness condition with conservation laws and analytical solutions for the ($$1+1$$)-dimensional Pochhammer–Chree model in longitudinal wave propagation

Spatial propagation characteristics of acoustic emission signals in parallel steel wire cables

Accurate spatial propagation characteristics facilitate damage spatial localization, which is crucial for assessing the condition of parallel steel wire cables (PSWC). Existing studies have focused on the longitudinal propagation of acoustic emission (AE) signals, limiting accurate spatial damage assessment. This study comprehensively explored the spatial propagation characteristics of AE signals in PSWC using finite elements and attenuation tests. AE signals propagate hexagonally on the transverse section, with different amplitude attenuation rates at different angles—8% at 0° and 60°, 5 % at 30° and 45°. Additionally, AE signals exhibit oscillatory propagation between different wires in the longitudinal direction. The longitudinal speed (5706 m/s) is approximately 4.2 times faster than the transverse speed (1371 m/s), and the propagation path can be simplified as longitudinal and then transverse, offering valuable guidance for damage localization. The optimum frequency is 150 kHz in the transverse direction and 30 kHz in the longitudinal direction.

Laser additive manufacturing of Miura-origami tube inspired quasi-zero stiffness metamaterial with prominent longitudinal wave propagation

ABSTRACT Origami metamaterials have become frontiers of research in many disciplines due to their infinite design space, simple size variation, and topologically variable properties. In this study, a novel metamaterial inspired by Miura-origami tubes with a complex quasi-zero-stiffness (QZS) structure was fabricated via laser powder bed fusion (LPBF). The unit of the QZS metamaterial consists of a two-layer quadrilateral frame and two vertical springs attached to its diagonal points. The geometric accuracy, densification level and mechanical properties of the QZS parts fabricated at various processing conditions were investigated and the optimised processing parameters were determined. The displacement response of the QZS parts was analysed by experiments in conjunction with simulation analysis. The results show that the LPBF-fabricated QZS metamaterials form four extra-wide longitudinal wave band gaps under low frequencies from 660 Hz to 2500 Hz. The proposed LPBF-fabricated QZS metamaterial shows great potential in impeding the longitudinal vibration of engineering structures.

Распространение магнитогидродинамических волн и гравитационная неустойчивость в астрофизической анизотропной и теплопроводной плазме

The hydrodynamic instability of a magnetised, self-gravitating rotating anisotropic plasma is analysed in the collisionless approximation and taking into account the heat flux vector on the basis of the modified Chew-Goldberger-Low equations. The dispersion relation is derived and simplified cases of propagation of small-amplitude perturbation waves are discussed, with modified analytical criteria for hydrodynamic instability obtained. In accordance with the general dispersion relation, three cases when the propagation of the perturbation wave passes across, along, and obliquely to the magnetic field vector are specifically considered. It is shown that anisotropic pressure and heat flux not only modify the classical Jeans instability criterion but also induce new unstable regions. It is found that the presence of uniform plasma rotation reduces the critical wave number and has a stabilising effect on the gravitational instability criterion for transverse propagation of the perturbation wave and has no effect in the case of its longitudinal propagation. The inclusion of thermal flows leads to the appearance of two additional wave modes. The results obtained are important for the construction of evolutionary magnetohydrodynamic models of collisionless astrophysical plasma.

Full-wave Image Reconstruction in Transcranial Photoacoustic Computed Tomography using a Finite Element Method.

Transcranial photoacoustic computed tomography presents challenges in human brain imaging due to skull-induced acoustic aberration. Existing full-wave image reconstruction methods rely on a unified elastic wave equation for skull shear and longitudinal wave propagation, therefore demanding substantial computational resources. We propose an efficient discrete imaging model based on finite element discretization. The elastic wave equation for solids is solely applied to the hard-tissue skull region, while the soft-tissue or coupling-medium region that dominates the simulation domain is modeled with the simpler acoustic wave equation for liquids. The solid-liquid interfaces are explicitly modeled with elastic-acoustic coupling. Furthermore, finite element discretization allows coarser, irregular meshes to conform to object geometry. These factors significantly reduce the linear system size by 20 times to facilitate accurate whole-brain simulations with improved speed. We derive a matched forward-adjoint operator pair based on the model to enable integration with various optimization algorithms. We validate the reconstruction framework through numerical simulations and phantom experiments.

Generation and characterization of a humanized ACE2 mouse model to study long-term impacts of SARS-CoV-2 infection.

Although the COVID-19 pandemic has officially ended, the persistent challenge of long-COVID or post-acute COVID sequelae (PASC) continues to impact societies globally, highlighting the urgent need for ongoing research into its mechanisms and therapeutic approaches. Our team has recently developed a novel humanized ACE2 mouse model (hACE2ki) designed explicitly for long-COVID/PASC research. This model exhibits human ACE2 expression in tissue and cell-specific patterns akin to mouse Ace2. When we exposed young adult hACE2ki mice (6 weeks old) to various SARS-CoV-2 lineages, including WA, Delta, and Omicron, at a dose of 5 × 105 PFU/mouse via nasal instillation, the mice demonstrated distinctive phenotypes characterized by differences in viral load in the lung, trachea, and nasal turbinate, weight loss, and changes in pro-inflammatory cytokines and immune cell profiles in bronchoalveolar lavage fluid. Notably, no mortality was observed in this age group. Further, to assess the model's relevance for long-COVID studies, we investigated tau protein pathologies, which are linked to Alzheimer's disease, in the brains of these mice post SARS-CoV-2 infection. Our findings revealed the accumulation and longitudinal propagation of tau, confirming the potential of our hACE2ki mouse model for preclinical studies of long-COVID.

Numerical and experimental investigations on quasi-static component generation of longitudinal wave propagation in isotropic pipes

In this paper, the quasi-static component (QSC) generation of longitudinal waves propagating in an isotropic pipe is investigated numerically and experimentally. The three-dimensional (3D) finite element (FE) simulations are first carried out to gain physical insights into the characteristics of QSC generation from longitudinal wave travelling in an isotropic pipe with weak material nonlinearity. By applying the axial displacement excitation in the FE model, L(0, 1) mode and L(0, 2) mode are excited simultaneously. Then, the generated QSC pulses are extracted using the phase reversal approach for analysis. It is found that the QSC pulses generated by L(0, 2) mode and L(0, 1) mode are L(0, 1) mode. Meanwhile, the shapes of QSC pulses at different locations are extracted and compared. In this study, a data pre-processing method is proposed to handle numerically calculated and subsequent experimentally measured displacement signals, and a nonlinear acoustic parameter is defined to evaluate the incipient damages. After that, an experiment is conducted to measure the QSCs induced by the propagation of longitudinal waves in an aluminum pipe. The experimental results indicate that the propagation of longitudinal waves in the aluminum pipe can induce the QSCs. Different levels of corrosion are created on the surface of the aluminum pipe and are assessed by the generated QSCs. The results show that the nonlinear acoustic parameter has a monotonically increasing trend with the growing severity of corrosion. The QSCs generated by longitudinal wave can be used to detect and evaluate the early-stage surface corrosion in the aluminum pipe.

Evolution of mechanical and corrosion properties of TiN/TiO2 nanocomposite multi-stage coating on AZ31 magnesium alloy using atomic layer deposition and in-situ oxidation

TiN/TiO2 nanocomposite film has been deposited on AZ31 magnesium alloy by two-step preparation involving atomic layer deposition and in-situ oxidation. The compact single and multi-stage coatings uniformly cover the surface. Mechanical property evaluation indicates that the resulting coating has good adhesion strength, well wear resistance and compressive residual stress. Furthermore, neutral salt spray test shows a uniform corrosion mode. Hydrogen evolution and electrochemical tests indicate excellent corrosion resistance. For example, compared to AZ31 magnesium alloy, the hydrogen evolution rate of the two-stage sample decreases by a farceur to 1/2, and corrosion current density drops by a farceur to 10-3. The single stage sample has a crystalline/amorphous interlayer structure and ∼ 20 nm thickness, which could lead to a compressive residual stress for the single stage sample and even for the multi-stage coating. The compressive residual stress delays the germination of tiny defects. Furthermore, the multi-stage structure presents more interfaces that can impede longitudinal crack propagation and limit corrosion media diffusion, which contribute to the corrosion resistance. The work not only proposes a good protective coating for magnesium alloy but also presents a strategy for corrosion resistant coating design.

Experimental evidence of nonreciprocal propagation in space-time modulated piezoelectric phononic crystals

A nonreciprocal system composed of a one-dimensional piezoelectric phononic crystal whose periodic electrical conditions are modulated in time is presented. One-way longitudinal wave propagation is studied experimentally and compared to finite element temporal simulations. The modulation is performed by prescribing grounded or floating potential conditions on a periodic set of electrodes through external circuits. This approach makes it possible to consider a wide range of modulation speeds, and the large number of unit cells of the phononic crystal allows us to characterize experimentally the full dispersion curves of the system. This permits to observe the presence of directional bandgaps and to follow the shift in frequencies of these bandgaps as a function of the modulation speed. The experiments show the linear evolution of the central position of the bandgaps with the increase in the modulation speed, as well as their progressive closure, over a wide range of frequencies. Experiments are also used to estimate the evolution of bandgaps in a dispersive system, a problem discussed in several theoretical works but never observed experimentally. This work may constitute the foundation for experimental analysis of Floquet acoustic metamaterials, accelerated-modulation space-time metamaterials, or acoustic analog of the event horizon.

Longitudinal wave propagation in an elastic cylinder embedded in a viscoelastic fluid

Abstract A novel analytical investigation of longitudinal wave propagation in an elastic cylinder embedded in a viscoelastic fluid is proposed. The Maxwell model is used to describe the viscoelastic fluid behavior. With appropriate boundary conditions, a complex dispersion equation of longitudinal wave has been established. The aim of this paper is to study the effect of the fluid rheological properties on the longitudinal wave characteristics (attenuation and velocity). It is shown that the attenuation is the sum of a viscous and non viscous component. The viscosity induced attenuation is predominant at low frequencies. On the other hand, the effect of the liquid amount and elastic cylinder radius on the attenuation and velocity are studied. A critical normalized liquid thickness is highlighted. Beyond this critical value, the influence of the outer boundary condition can be neglected. At last, among other interesting phenomena, it is highlighted that if the Deborah number increases, the attenuation decreases. This variation characterize a stiffening of the viscoelastic medium. In addition, the obtained results show that the viscosity measurement should be performed at low frequencies using small elastic cylinder radius. Accordingly, these investigations are novel and can be applied in geophysics, food industry, medicine, non-destructive testing of materials, design and development of fluid sensors.

Thermal behavior of aluminothermic thermite reaction for application in thermal sealing of oil wells

Motivated by a groundbreaking proposal to plug depleted oil wells using an exothermic reaction to melt the wellbore components, this work investigates the thermal behavior associated with the longitudinal propagation of a stoichiometric Fe2O3/Al thermite reaction. The primary objective of this study is to develop a reliable macroscopic numerical model capable of accurately estimating the heat generation and propagation during the reaction. A small-scale experiment is used to validate the numerical model, which approaches the experiment as a 2-D axisymmetric geometry within multiple regions. The reaction is modeled with a simplified zero-order kinetic model assuming a constant kinetic rate for all chemical species. A porous model assesses the impact of porosity on the overall heat diffusion, and a source-based phase change model is employed to evaluate the melting of the chemical species and the outer tube. Also, a disruptive model is included to consider the reaction between only condensed phases. The experimental validation demonstrated a good agreement between the numerical results with the disruptive model and transient temperature profiles measured experimentally. Varying the kinetic rate and porosity suggests that a slower reaction and denser mixture can enhance the heat transfer towards surrounding materials, potentially benefiting future applications in well sealing.

Light response uniformity of LuAG:Ce scintillating single crystal fiber grown by laser heated pedestal growth method

Own to its fine granularity and sub-millimeter position information, scintillating single crystal fibers (SSCFs) hold great potential for various applications such as electromagnetic calorimeters, positron emission tomography, and radiotherapy dosimetry. The light response uniformity of scintillating fibers is an important parameter for precise measurements of ionizing radiation. Three methods were designed to investigate the light response uniformity of the 184-mm-long LuAG:Ce SCCF. Relatively longitudinal-distributed uniformity of cerium element was obtained in this SSCF. The scintillation light attenuation coefficient of the SSCF is 0.27 cm−1 induced by X-ray photons with single-end readout mode and about 0.29 cm−1 induced by gamma rays with dual-end readout mode. The Ce3+ ions self-absorption along the longitudinal light propagation process is one of main reasons for the scintillation light attenuation. Weakening the Ce3+ ions’ self-absorption effect is a possible way to improve the light response uniformity of the LuAG:Ce SSCF.

Longitudinal wave propagation analysis in Entangled metallic wire materials using an improved wave and finite element method

This paper proposes a novel concept and methodology to study longitudinal wave propagation in entangled metallic wire material (EMWM), a porous structural network consisting of spatial helix wires. The numerical model of EMWM is constructed using representative volume elements (RVE) obtained through X-ray tomography and skeletonization of a standard specimen. By increasing the approximate periodic boundary, the improved wave and finite ele-ment method (WFE) is employed to model EMWM as approximately periodic structures, allowing for numerical simulations of wave propagation characteristics. Frequency bands and resonance modes of EMWM are calculated to analyze the characteristics of one-dimensional wave propagation. The numerical results show that EMWM exhibits unique frequency band characteristics compared to typical periodic porous materials. In the frequency range of 15 to n n 35 kHz, the first pass band corresponds to the tensile-compressive motion of the entire specimen, while the higher pass bands correspond to localized vibrations within the spatial wires. Additionally, the frequency bands can be adjusted across a wide range based on the relative density of EMWM specimens. The improved WFE method and obtained numerical data can facilitate the application of EMWM on high frequency vibration isolation.

Fully optic characterization of acoustic impedance implementable in conventional optical microscope

The intrinsic acoustic impedance (Z) changes with inflammation and canceration. This paper proposes an optically Z measurement method using a common optical microscope for simultaneous measurement of optical-acoustical observation. Photoacoustic (PA) waves were generated by the PA effect of the pulsed laser (a 527 nm nanosecond laser light) at the black ink and resin pasted area on the outside of the bottom of the petri dish (surface A). The generated PA waves propagated to the inner boundary of the petri dish and reflected, with a reflection coefficient of R. The reflected waves propagated to surface A and vibrated it. The surface vibration was measured with a self-built Sagnac interferometer using a contentious light laser and a 10x objective lens. Measurements were made air-filled and water-filled petri dishes. The observed times of echo signal corresponded to the sound speed of longitudinal and transverse propagation. The reflected wave amplitude of air was larger than in a water-filled petri dish. They related that R water and R air are 0.24 and 1.00, respectively. There corresponds to the Z ratio of the polystyrene petri dish and the water or air inside. Thus, this result showed that sample Z was measured optically.

Nonlocal Soft Plasmonics in Planar Homogeneous Multilayers

Plasmonics is the study of resonant oscillations of free electrons in metals caused by incident electromagnetic radiation. Surface plasmons can focus and steer light on the subwavelength scale. Apart from metals, plasmonic phenomena can be observed in soft matter systems such as electrolytes which we study here. Resonant charge oscillations can be induced for ions in solution, however, due to their larger mass, they are plasmon-active in a lower frequency regime and on a larger wavelength scale. Our investigation focuses on spatial confinement which allows increasingly strong charge interactions and gives rise to nonlocality or spatial dispersion effects. We derive and discuss the nonlocal optical response of ionic plasmons using a hydrodynamic two-fluid model in a planar homogeneous three-layer system with electrolyte-dielectric interfaces. As in metals, we observe the emergence of additional longitudinal propagation modes in electrolytes which causes plasmonic broadening. Studying such systems enables us to identify and understand plasmonic phenomena in biological and chemical systems.