Propagation Of Compressional Waves Research Articles

Theoretical and experimental study of a two-dimensional circular stealth acoustic lens

The detection of underwater acoustic signals is a key focus in ocean development, and acoustic metamaterials play a crucial role in achieving this goal. Pentamode metamaterials exhibit fluid-like properties, allowing for the propagation of compressional waves without shear waves. In this study, a two-dimensional circular stealth acoustic lens based on pentamode metamaterials was proposed. By applying the transformation acoustics theory, the theoretical properties of circular stealth acoustic lenses were calculated, and they were verified with Finite Element Method (FEM). A practical model was designed with pentamode metamaterials and silicone oil, and its performance was verified with FEM software. A half-model was fabricated, and underwater experiments demonstrate that it does not effectively affect the propagation state of acoustic waves. The consistency between theoretical results and experimental findings highlights practical significance and broad application prospects for the circular stealth acoustic lens in the field of acoustic detection.

Propagation Characteristics of Initial Compression Wave Induced by 400 km/h High-Speed Trains Passing through Very Long Tunnels

When high-speed trains enter tunnels, an initial compression wave is generated. As the compression wave propagates at the local speed of sound to the tunnel exit, it radiates into the surrounding environment, forming micro-pressure waves (MPWs). MPWs create sonic booms, resulting in significant environmental issues. The magnitude of the micro-pressure waves is directly proportional to the pressure gradient of the compression wave at the tunnel exit. The nonlinear effects of the initial compression wave during propagation lead to a significant increase in pressure gradient. Therefore, the propagation characteristics of the initial compression wave during the tunnel are the crucial factor affecting the amplitude of MPWs. Based on the one-dimensional compressible unsteady non-isentropic flow model and the improved generalized Riemann variable characteristic method, this paper researched the propagation and evolution characteristics of an initial compression wave generated when 400 km/h high-speed trains enter tunnels with three portal shapes: (no tunnel entrance hood (no hood), an oblique, enlarged tunnel entrance hood (type A), an enlarged equal-section non-uniform opening hole tunnel entrance hood (type B)). The results show that when the initial compression wave propagates inside very long tunnels, the pressure gradient of the compression wave exhibits a trend of initially increasing and then decreasing with the increase in propagation distance. When the pressure gradient of the compression wave reaches its maximum value, the corresponding propagation distance is the steepening critical distance. For no tunnel entrance hoods, type A tunnel entrance hoods, and type B tunnel entrance hoods, the steepening critical distances are 5 km, 6 km, and 16 km, respectively. The steepening critical distance shortens with increasing train speed. Steady friction and unsteady friction effects mainly affect the pressure amplitude and pressure gradient during compression wave propagation, respectively. At lower ambient temperatures, the nonlinear effects in compression wave propagation are significantly enhanced. The mitigation effects of type A tunnel entrance hoods and type B tunnel entrance hoods on pressure gradient reduction are mainly concentrated within 4 km and 12 km, respectively. It is necessary to determine the optimal matching relationship between the tunnel entrance hood and tunnel length based on the characteristics of compression wave propagation to ensure their mitigating performance is maximized.

Influence of Foundation Stiffness on the Fragility Curves of a Concrete Gravity Dam Subjected to Near-Field Ground Motions Using Finite Element Method

A concrete gravity dam is being investigated to determine the fragility curves during near-field ground motions under various foundation stiffness conditions. This is accomplished using the finite element method for modeling the Latyan dam and its dam-reservoir-bed complex interaction system. The nonlinear constitutive model of concrete, plastic damage, is used to simulate the cyclic behavior of tensile and compressive failures in concrete. An acoustic element is used to model the propagation of compressive waves in the reservoir to account for the hydrodynamic effects of the lake reservoir. A total of 100 real and scaled accelerograms are used to simulate near-filed seismic loading in eight different concrete-to-foundation stiffness ratios. Based on the peak ground acceleration (PGA) of the earthquake, numerical models are applied to obtain the probability density function (PDF) and cumulative distribution function (CDF) for lognormal distributions and to determine and analyze the fragility curves of the dam. According to the findings, the seismic performance of the dam is improved for stiffness ratios of 0.75, 1, and 1.5, and the best seismic performance is determined for stiffness ratios of 1. Concrete dams with stiffness ratios of 0.75, however, perform better when the peak ground acceleration is greater than 0.74g compared to those with stiffness ratios of 1. DOI: https://doi.org/10.52783/pst.502

Wave propagation in three-dimensional fractional viscoelastic infinite solid body

In order to analyze the wave propagation in three-dimensional isotropic and viscoelastic body, the Cauchy initial value problem on unbounded domain is considered for the wave equation written as a system of fractional partial differential equations consisting of equation of motion of three-dimensional solid body, equation of strain, as well as of the constitutive equation, obtained by generalizing the classical Hooke’s law of three-dimensional isotropic and elastic body by replacing Lamé coefficients with the relaxation moduli to account for different memory kernels corresponding to the propagation of compressive and shear waves. By the use of the method of integral transforms, namely Laplace and Fourier transforms, the displacement field, as a solution of the Cauchy initial value problem, is expressed through Green’s functions corresponding to both compressive and shear wave propagation. Two approaches are adopted in solving the Cauchy problem: in the first one the displacement field is expressed through the scalar and vector fields, obtained as solutions of wave equations which are consequences of decoupling the wave equation for displacement field, while in the second approach the displacement field is obtained by the action of the resolvent tensor on the initial conditions. Fractional anti-Zener and Zener model I+ID.ID, as well as fractional Burgers model VII, as representatives of models yielding infinite and finite wave propagation speed, are used in numerical calculations and graphical representations of Green’s functions and its short and large time asymptotic behavior.

Bandgap structure of tensegrity mass–spring chains equipped with internal resonators

This work studies the dispersion relation of a Maxwell type mass–spring chain formed by lumped masses and the parallel arrangement of two different types of tensegrity prisms. Use is made of the Bloch–Floquet theory of discrete systems in association with a linearized model of the response of the tensegrity units under compression loading. Such a modeling is aimed at studying the propagation of compression waves under small perturbations of the initial equilibrium state of the system. For a given value of the cable’s prestress, the tensegrity systems connecting the lumped masses react as elastic springs, which exhibit axial deformations accompanied by relative twisting rotations of the terminal bases. The twisting motion of the chain affects the expression of the kinetic energy, and is accounted for by introducing a suitable definition of equivalent masses. The bandgap structure of the analyzed system is analytically determined and numerical results are obtained for a chain formed by physical models tensegrity θ=1 prisms aligned in parallel with minimal tensegrity prisms. The given results highlight the highly tunable frequency bandgap properties of tensegrity mass–spring chains exhibiting internal resonance capabilities.

Alleviation of micro-pressure waves radiated from tunnel hoods

When a train enters a tunnel, an impulsive pressure wave, called a micro-pressure wave (MPW), radiates from the tunnel exit. The MPW causes infrasound and audible noise near the tunnel portals; therefore, it should be reduced for environmental reasons. A typical countermeasure is the installation of a hood at the tunnel entrance portal. In a previous study, we proposed a new type of hood that combined two hoods with constant and different cross-sectional areas (a two-step hood). The two-step hood was more effective than the existing hoods. However, because the cross-sectional area of the portal of the two-step hood was larger than that of the existing hoods, the MPW radiated by a train entering the opposite tunnel portal increased in a double-track tunnel. This study developed a new concept for a tunnel hood that reduces the radiated MPW (performance at the MPW radiation stage) while maintaining the performance in terms of reducing the maximum pressure gradient of the compression wave (CW) generated by a train entering a tunnel (performance at the CW generation stage). The desired specifications for satisfying both performances were determined through calculations based on acoustic theory, and their performances were investigated through model experiments using a train model launcher. As the results, the desired specifications were lh3/lw>0.6, lh1≈lh2>lwMt/1-Mt, σh1=1.4, and σh2=2.5, where lh1, lh2, and lh3 are lengths of first hood, second hood, and added lateral wall, respectively, lw is wavefront thickness, Mt is the train’s Mach number, and σh1 and σh2 are the cross-sectional area ratio of the first and second hoods to tunnel, respectively. The developed hood is expected to provide more effective performance in mitigating MPW than existing hoods.

Passive sea ice thickness inference using cryophones.

Mechanical properties of Arctic sea ice can be inferred by observations of in-ice propagation of compressional, shear, and flexural waves. During the 1980s, impulsive signals were generated by a lead ball or sledgehammer dropped onto the sea ice, and the inference required observation of wave speeds. During ICEX20 and ARCEX23, passive cryophone observations were made of naturally occurring compressional wave resonances. Average first-year ice thicknesses during ICEX20 and ARCEX23 were inferred to be 1.3 and 1.6 m, respectively; these are consistent with independent observations and indicate the potential for remote, autonomous monitoring of sea ice thickness.

On the Assessment of Actual Compressive Strength of Concrete in Reinforced Columns: Influence of Core Diameter and Slenderness Ratio

Abstract This paper studies the influence of core diameters and slenderness ratio on the assessment of the actual compressive strength of concrete on reinforced-concrete elements. The experiment consists of the preparation of three reinforced concrete columns and the extraction of cores to carry out both destructive (core diameter of 64 mm, 79 mm, and 103 mm) and non-destructive tests. The non-destructive test deals with the propagation of elastic and compressive waves by deriving the ultrasound pulse velocities. The results show that the assessment of the compressive strength of concrete depends strongly on the diameter of cores and the extraction zones. Furthermore, the derivation of the actual compressive strength by referring to the compressive strengths of the cores with a diameter of 64 mm shows a stringent appearance of a size effect. More interestingly, valuable details about the correlation between the concrete compressive strength assessment based on destructive and non-destructive tests are also presented.

Recent developments in MHz radioscopy: Towards the ultimate temporal resolution using storage ring-based light sources

Hard X-ray imaging with ultra-high speed acquisition rates using synchrotron-based sources or free-electron lasers has recently gained significant attention: commercially available CMOS-based cameras as basis for indirect detection allow for the use of radioscopy with MHz acquisition rates in a routine manner. Hence, an increasing number of experiments are reported in the literature studying with ultra-high speed radioscopy phenomena ranging from materials research (additive manufacturing), astrophysics (meteorite formation) to dynamic compression (propagation of shock and compression waves). By using the high flux beamline BL40XU of the SPring-8 synchrotron light source this MHz radioscopy approach has been developed further: the outstanding high photon flux density at narrow bandwidth of beamline BL40XU allowed for reaching unprecedented temporal resolution at high X-ray imaging sensitivity. Furthermore, a proto-type of a new ultra-high speed framing camera was integrated, demonstrating that frame rates close to the native radio frequency of the storage ring should become feasible in the future, i.e. an approach towards GHz radioscopy.

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.

Effects of a filled discontinuity in a rock mass on transmission losses of compressional and shear wave of full-waveform sonic log data

The presence of discontinuities in a rock mass affects the propagation of compressional (P) and shear (S) waves recorded by an acoustic borehole logger. The purpose of this study is to develop a new approach for characterizing such discontinuities using the full-waveform (FW) sonic tool. The approach focuses on evaluating the sensitivity of P-wave and S-wave transmission losses to the mechanical and geometrical properties of the discontinuities intersecting the borehole. Numerical simulations enabled us to quantify the impact of a discontinuity on full-waveform sonic log data using two transmission loss factors—velocity variation and amplitude attenuation—associated with P- and S-waves. These factors were determined by comparing the arrival times and amplitudes of waves propagating across discontinuous and intact media. We performed a sensitivity analysis for a wide range of discontinuity widths, lengths, P- and S-wave velocity, and density of the infilling material, and for different mechanical properties of the embedded rock. S-waves were found to be generally more sensitive to the presence of a discontinuity than P-waves. The discontinuity length influences both the compressional and shear wave responses depending on their relation to the prevailing wavelength. We demonstrate that velocity variation is more indicative of the discontinuity width than amplitude attenuation. Overall, the analysis of our dataset indicates that the P- and S-wave transmission loss factors provide complementary information, as they tend to be more sensitive to a different discontinuity property. This finding, in turn, may lead to the development of integrated algorithms for robustly characterizing discontinuities.

Physical mechanisms of the Soret effect in binary Lennard-Jones liquids elucidated with thermal-response calculations.

The Soret effect is the tendency of fluid mixtures to exhibit concentration gradients in the presence of a temperature gradient. Using molecular-dynamics simulation of two-component Lennard-Jones liquids, it is demonstrated that spatially sinusoidal heat pulses generate both temperature and pressure gradients. Over short timescales, the dominant effect is the generation of compressional waves, which dissipate over time as the system approaches mechanical equilibrium. The approach to mechanical equilibrium is also characterized by a decrease in particle density in the high-temperature region and an increase in particle density in the low-temperature region. It is demonstrated that concentration gradients develop rapidly during the propagation of compressional waves through the liquid. Over longer timescales, heat conduction occurs to return the system to thermal equilibrium, with the particle current acting to restore a more uniform particle density. It is shown that the Soret effect arises due to the fact that the two components of the fluid exhibit different responses to pressure gradients. First, the so-called isotope effect occurs because light atoms tend to respond more rapidly to evolving conditions. In this case, there appears to be a connection to previous observations of "fast sound" in binary fluids. Second, it is shown that the partial pressures of the two components in equilibrium, and more directly, the relative magnitudes of their derivatives with respect to temperature and density, determine which species accumulate in the high- and low-temperature regions. In the conditions simulated here, the dependence of the partial pressure on density gradients is larger than the dependence on temperature gradients. This is directly connected to the accumulation of the species with the largest partial pressure in the high-temperature region and the accumulation of the species with the smallest partial pressure in the low-temperature region. The results suggest that further development of theoretical descriptions of the Soret effect might begin with hydrodynamical equations in two-component liquids. Finally, it is suggested that the recently proposed concept of "thermophobicity" may be related to the sensitivity of partial pressures in a multicomponent fluid to changes in temperature and density.

Impact of a dry granular flow against a rigid wall: MPM simulations with a new constitutive approach

The dynamic interaction between granular flowing masses and obstacles is a very complex phenomenon involving large displacements and high strain rates. To simulate the event in a continuum-based framework both advanced numerical tools and constitutive relationships are required. In this work, the impact of a dry granular mass against a rigid wall is numerically simulated using the open-source Material Point Method code ANURA3D, while the constitutive model proposed by Marveggio et al., 2021 is adopted for the granular mass. The model accounts for rate and grain packing dependence, which have been shown to be crucial to reproduce the propagation of compression and rarefaction waves inside the mass. The model is capable of reproducing “solidification” and “liquefaction” phenomena observed in the DEM impact tests results already available in the literature.

Compressive solitary waves in black phosphorene

Compressive solitons arise in crystals as a result of shock loading, and they can transfer energy over long distances, exhibiting weak damping. Propagation of compressive solitons in two-dimensional (2D) materials is studied much less than in 3D crystals. Here, molecular dynamics is used to analyze the dynamics of compressive solitons in single-layer phosphorene. The mechanisms of energy dissipation by the lattice are analyzed. The results obtained are compared with those obtained earlier for graphene and boron nitride. The damping of compressive solitons in phosphorene is stronger than in graphene and boron nitride, since it has a puckered structure and, therefore, more channels for energy dissipation. Overall, our results contribute to understanding the nonlinear dynamics of localized excitations in 2D materials. • Inducing features of compressive soliton wave are studied in black phosphorene. • Dynamics of compressive soliton wave propagation is discovered. • General channels of dissipation of the wave energy are detected.

The Effect of Mortar Mixture Variations on the Compressive Strength and Ultrasonic Pulse Velocity

This paper examines the correlation between compressive strength, porosity, and ultrasonic wave propagation in mortar. The research was conducted at the Yogyakarta State University Building Materials Laboratory. The study used an experimental method, mortar was made with variations in the ratio of cement and fine aggregate 1:3, 1:4, 1:5, 1:6, and 1:7 with a phase of 0.48. The manufacture of test objects in the form of a cube measuring 5x5x5 cm refers to SNI 03-6825-2002. Tests were carried out at the age of 3, 7, 14, 21, and 28 days with three samples per test age. The data was processed by quantitative descriptive method to determine the relationship between the variables, especially the relationship between wave propagation speed and compressive strength, as well as its relationship with the porosity value. The results of compressive strength and wave propagation speed are directly proportional to the age of the test. With the results of the compressive strength at 1:3, 1:4, 1:5, 1:6, and 1:7 variants, respectively 31.12 MPa, 19.83 MPa, 12.25 MPa, 5.38 MPa, and 3.89 MPa and wave propagation speed of 3827.67 m/s, 3641.7 m/s, 3561.3 m/s, 2019,0 m/s, and 1691.0 m/s. Then the porosity values are 11.12%, 12.88%, 16.36%, 17.60%, and 22.06%. The compressive strength has a correlation that is directly proportional to the logarithmic speed of wave propagation, the higher the value of the compressive strength, the higher the UPV value, and inversely proportional to the porosity value as well as the speed of the wave propagation which is inversely proportional to the porosity value. The higher the porosity value, the lower the compressive strength value and the UPV value.

Walking on snow-covered Arctic sea ice to infer ice thickness.

The ice-covered Arctic Ocean constitutes a unique underwater acoustic waveguide; it is a half-channel, upward refracting environment possessing a rough upper boundary consisting of sea ice of varying thickness. The sea ice itself is an acoustic waveguide, capable of supporting the propagation of compressional and shear waves. In particular, the ice supports compressional wave resonances created by impulsive forces on the upper surface of the ice. During ICEX20 and ICEX22, observations were made of compressional wave resonances excited by hammer drops, as well as by near-impulsive signals generated from the compression of dry snow underfoot while walking on the ice. Results demonstrate that ice thickness can be inferred from compressional wave resonances in the sea ice waveguide using signals generated by walking on the snow-covered ice. Inferred ice thickness estimates were consistent with observations made by magnetic induction and physical measurements in holes drilled through the ice. Average first- and multi-year ice thicknesses were inferred to be 1.1-1.3 m and 2.4-2.5 m, respectively.

Three-dimensional structure of freely-propagating flame prior to deflagration-to-detonation transition

The paper analyzes numerically the development of the freely expanding flame before the transition to detonation in three-dimensional space. The risks related to the transition to detonation in unconfined space arise at launch places and near-Earth space during rocket engine accidents. Clear and adequate models for such scenarios are in demand for the elaboration of safety measures. Here it is shown that the process of transition to detonation involves multidimensional effects related to the generation of compression waves and their amplification when interacting with the developing flame. The necessary conditions for deflagration-to-detonation transition are flame acceleration up to near-sonic speed and generation of transversal compression waves (propagating along the flame front). So, while the subsonic stage of flame acceleration can be successfully described by the quasi one-dimensional model supplemented by a known self-similar law of the flame area growth (folding factor), the model for the pre-detonation stage should take into account considered multidimensional effects. The presented results imply that there is no unambiguous relation between the transition to detonation and the folding factor.

Multi-frame, ultrafast, x-ray microscope for imaging shockwave dynamics.

Inertial confinement fusion (ICF) holds increasing promise as a potential source of abundant, clean energy, but has been impeded by defects such as micro-voids in the ablator layer of the fuel capsules. It is critical to understand how these micro-voids interact with the laser-driven shock waves that compress the fuel pellet. At the Matter in Extreme Conditions (MEC) instrument at the Linac Coherent Light Source (LCLS), we utilized an x-ray pulse train with ns separation, an x-ray microscope, and an ultrafast x-ray imaging (UXI) detector to image shock wave interactions with micro-voids. To minimize the high- and low-frequency variations of the captured images, we incorporated principal component analysis (PCA) and image alignment for flat-field correction. After applying these techniques we generated phase and attenuation maps from a 2D hydrodynamic radiation code (xRAGE), which were used to simulate XPCI images that we qualitatively compare with experimental images, providing a one-to-one comparison for benchmarking material performance. Moreover, we implement a transport-of-intensity (TIE) based method to obtain the average projected mass density (areal density) of our experimental images, yielding insight into how defect-bearing ablator materials alter microstructural feature evolution, material compression, and shock wave propagation on ICF-relevant time scales.

Adaptation of the SonReb method to the mea-surement of the compressive strength of a two-layers concrete structure

The three most common building materials which most structures are built from are: timber, steel and Reinforcement Concrete (RC). Estimating the in-situ compressive strength is an imperative issue to evaluate the performance of in-situ concrete structures during their service life. Most codes and technical recommendations indicate that in-situ concrete strength should be estimated by means of cores, possibly supplemented by Non-Destructive tests. In this study a series of ultrasonic refraction measurements on a two layers slabs (mortar over concrete) are carried out in order to recover the velocity of the compression waves of each layer in view of combining the results with the rebound method in order to estimate the compressive strength of the mortar layer. Accuracy of measurements of compression wave propagation velocities and errors on the estimation of the compressive strength are investigated.

Vertical vibration of end-bearing single piles in poroelastic soil considering three-dimensional soil and pile wave effects

This paper presents an analytical solution developed to describe the dynamic interaction between a single end-bearing pile subjected to a dynamic axial load on its head, and its surrounding poroelastic soil. The main feature of the solution is that both the two-phase soil and the pile are treated as three-dimensional continua. This allows capturing the propagation of compressional and shear waves in three dimensions, and their effect on pile response. The soil surrounding the pile is treated as porous medium and its response is described with Biot’s poroelastic theory, while the pile is treated as linear elastic solid, considering explicitly both vertical and radial pile displacements. The solution yields expressions for the displacement and velocity admittance at the pile head in the frequency domain, and allows computing pile head velocity time histories. These are applied to study the effects of wave propagation in three dimensions on pile response in the frequency- and in the time-domain, and identify the conditions under which these effects may be important for the analysis of piles in practice.