Three-dimensional wave propagation through single crystal solid–liquid interfaces

The large difference in the ultrasonic velocity of solid and liquid semiconducting materials results in significant ray refraction and pulse time delays during propagation through solid–liquid interfaces. This has led to an interest in the use of ultrasonic time-of-flight (TOF) measurements for deducing the interfacial geometry. A ray-tracing analysis has been used to analyze two-dimensional wave propagation in the diametral plane of model cylindrical solid–liquid interfaces. Ray paths, wavefronts, and TOFs for rays that travel from a source to an arbitrarily positioned receiver on the diametral plane have been calculated and compared to experimentally measured TOF data obtained using a laser generated/optically detected ultrasonic system. Examinations of both the simulations and the experimental results reveals that the interfacial region can be identified from transmission TOF data. When the TOF data collected in the diametral plane were used in conjunction with a nonlinear least-squares reconstruction algorithm, the interface geometry (i.e., axial location and shape) were precisely recovered and the ultrasonic velocities of both solid and liquid phases were obtained with error of less than ∼3%.

A coupled three-dimensional fluid-elastic wave propagation mathematical model has been developed to handle environmental interactions in the ocean between a fluid medium and an elastic bottom. The existing model combines three-dimensional fluid and elastic wave propagation models with the incorporation of a set of horizontal fluid-elastic interface conditions. This paper extends the above model to consider an irregular fluid-elastic interface. The theoretical development of the irregular fluid-elastic interface equations is presented. Comparison of the fluid-elastic irregular interface to the horizontal case is one of the major objectives of this paper. Another major objective of this paper is the construction of a complete set of three-dimensional fluid-elastic wave equations, including the irregular interface, in a form suitable for stable numerical solution.

Percussive drilling, that uses rotary torque and axial impact simultaneously, is an established method of making holes in concrete. This paper deals with the development of a finite element model, based on three-dimensional wave propagation, which represents the impact process of percussive drilling in concrete. The solid model of the percussive drilling system consists of five separate components, viz. shank, fluted body, socket tip, carbide blade and concrete target. After integration and meshing, the finite element model is analysed using three-dimensional wave propagation techniques. The bias weight and the impact impulse were set up as inputs to the drilling system. A "surface to surface eroding" interface was selected for the drill tip-concrete contact surface while a "rigid wall" interface was chosen for the concrete-ground support contact surface. Simulation results showed the usefulness of the model in understanding how the three-dimensional wave, due to impact, propagates through the drilling system resulting in penetration of the drill bit into concrete. The accuracy of the model was successfully verified with prior-known one-dimensional analytical model and experimental penetration results. Finally, to illustrate the potential use of this model to design and analyse percussive drilling system, the effect of variation of rake angle, helix angle, point angle, and bias weight on the extent of penetration is presented. The results clearly showed the importance of simulating the impact process for designing new percussive drill bits.

This paper explores the utility of a unified method for solving Maxwell's equations. Two benchmark problems, waveguide mode analysis and three-dimensional wave propagation, are employed to demonstrate the present approach. Numerical results indicate that the unified method is very accurate for solving electromagnetic problems.

On the three-dimensional wave propagation through cascading screens having a periodic system of arbitrary openings

Gravity waves (GWs) are well known for their role in shaping large-scale dynamics of the atmosphere, but they also induce strong local variability in the vertical velocity, temperature, and other fields. Such variability is often omitted when it comes to global effects due to averaging and resolution limitations. However, small-scale dynamics, such as gravity waves, have a crucial role in cirrus microphysics and life cycle. Ice clouds, on the other hand, can have a pronounced effect on the Earth’s radiation budget and global moisture distribution, making their accurate representation in climate and numerical weather prediction (NWP) models particularly important.This work investigates the effects of gravity waves on cirrus cloud microphysics using the global ICON (Icosahedral Nonhydrostatic) model. A novel, self-consistent parameterization of GW-induced homogeneous ice nucleation developed by Dolaptchiev et al. (2023) is employed, and additional GW effects on depositional ice growth are considered. The local GW field is represented using the Multi-Scale Gravity Wave Model (MS-GWaM), which supports multiple GW source types and three-dimensional wave propagation, thereby enhancing the physical realism of the parameterized GW dynamics. The full coupling of GW forcing, along with feedback from the supplemented ice scheme into the overall microphysics and radiation schemes, has been implemented and assessed within the ICON model.The results of the global test runs reveal significant GW impacts on ice formation mechanisms, leading to enhanced homogeneous nucleation in the upper troposphere–lower stratosphere (UTLS) compared to the baseline ICON configuration. Furthermore, GW-induced temperature fluctuations obtained from MS-GWaM and coupled online to depositional growth substantially increase ice growth efficiency. It results in larger ice mixing ratios in the mid-latitudes and subtropical regions. Further analyses are planned to assess the sensitivity of the coupled version to different MS-GWaM configurations, the role of lateral GW propagation, and the relative contributions of different gravity wave sources.

This study aims to systematically investigate the wave propagation behavior in curved sandwich nanoplates incorporating zirconia–Ti6Al4V cores and graphene-enhanced foam layers, subjected to combined thermal and magnetic fields. To achieve this, a high-order shear deformation plate theory coupled with nonlocal strain gradient elasticity theory is employed. Three distinct foam distribution patterns—U-foam, S1-foam, and S2-foam—are considered to assess their influence on wave characteristics. The results reveal that phase and group velocities decrease with increasing foam content, thermal softening effects, and reduced curvature radius, whereas the presence of a magnetic field contributes to increased wave velocities. Interestingly, the impact of foam distribution varies significantly among configurations, with U-foam showing the most pronounced effect (40%), followed by S1-foam (10%) and S2-foam (3%). These findings underscore the potential applicability of such nanostructures in advanced engineering systems, particularly in radar-absorbing materials; high-temperature nanoelectromechanical systems; and lightweight, thermally responsive sensors for wearable healthcare technologies.

A technique similar to inverting Abel's equation is used to invert the descent of dimensions method between three-dimensional, cylindrically-symmetric and two-dimensional wave propagation. The end result is a very simple relationship between the two types of wave propagation. Apart from its intrinsic interest, the large number of two-dimensional studies reported in the literature could now be related to their three-dimensional counterparts.

Cerium distribution coefficient and its dependence on oxygen partial pressure in Nd 2−xCe xCuO 4 single crystal growth

In order to better understand bone conduction sound propagation across the skull, three-dimensional (3D) wave propagation on the skull surface was studied, along with its dependence on stimulation direction and location of a bone conduction hearing aid (BCHA) actuator. Experiments were conducted on five Thiel embalmed whole head cadaver specimens. Stimulation, in the 0.1-10 kHz range, was sequentially applied at the forehead and mastoid via electromagnetic actuators from commercial BCHAs, supported by a 5-N steel band. The head response was quantified by sequentially measuring the 3D motion of ∼200 points (∼15-20 mm pitch) across the ipsilateral, top, and contralateral skull surface via a 3D laser Doppler vibrometer (LDV) system, guided by a robotic positioner. Low-frequency stimulation (<1 kHz) resulted in a spatially complex rigid-body-like motion of the skull that depended on both the stimulation condition and head support. The predominant motion direction was only 5-10 dB higher than other components below 1 kHz, with no predominance at higher frequencies. Sound propagation direction across the parietal plates did not coincide with stimulation location, potentially due to the head base and forehead remaining rigid-like at higher frequencies and acting as a large source for the deformation patterns across the parietal sections.

In this paper we discuss the performance of second-order absorbing conditions prescribed on ellipsoidally-shaped truncation boundaries for the resolution of scalar wave phenomena in three dimensions. The second-order conditions employed herein belong to a larger class of arbitrarily-shaped convex absorbing boundaries developed earlier [21] for acoustic scattering and radiation problems in unbounded domains. In [21] we discussed their performance when used on spherical truncation boundaries for applications in both the time- and frequency-domains. Here, we extend their applicability to ellipsoidal geometries and demonstrate that significant computational savings are attainable due to the reduced computational domain afforded by the ellipsoid.

To identify the yielding phenomena often observed in tensile test at high strain rates even for the constitutive equation of material without any yielding phenomena, numerical simulations using the dynamic FEM analysis have been performed to study the effect of specimen geometry and loading configurations in the Split-Hopkinson Pressure Bar apparatus. Stress distributions in the specimens and the loading bars are clarified, and it is found that the three-dimensional stress wave propagation from the specimen to the loading bar dominates the yielding phenomena due to radial oscillations associated with, even though a slight effect of the specimen geometry is involved to some extent. It is also found that the relevant shape of loading bar end is served to suppress the yielding phenomena.

In this paper, a class of radiation boundary conditions for two-and three-dimensional elastic wave propagation is developed. The boundary conditions are based on compositions of simple first-order operators. Some recent empirical investigations have suggested that certain earlier radiation boundary conditions may be unstable if the ratio of P-wave velocity to S-wave velocity is sufficiently large. The boundary conditions developed in the present paper are stable for all values of the velocity ratio. The boundary operators used here are defined by relatively simple formulas that apply without modification to problems in both two and three dimensions. Given an arbitrary angle of incidence, some parameters in the boundary conditions can be adjusted to make the conditions perfectly absorbing for P- waves and/or S-waves traveling at that angle of incidence to the boundary.

A k-space method for moderately nonlinear wave propagation in absorptive media is presented. The Westervelt equation is first transferred into k-space via Fourier transformation, and is solved by a modified wave-vector time-domain scheme. The present approach is not limited to forward propagation or parabolic approximation. One- and two-dimensional problems are investigated to verify the method by comparing results to analytic solutions and finite-difference time-domain (FDTD) method. It is found that to obtain accurate results in homogeneous media, the grid size can be as little as two points per wavelength, and for a moderately nonlinear problem, the Courant-Friedrichs-Lewy number can be as large as 0.4. Through comparisons with the conventional FDTD method, the k-space method for nonlinear wave propagation is shown here to be computationally more efficient and accurate. The k-space method is then employed to study three-dimensional nonlinear wave propagation through the skull, which shows that a relatively accurate focusing can be achieved in the brain at a high frequency by sending a low frequency from the transducer. Finally, implementations of the k-space method using a single graphics processing unit shows that it required about one-seventh the computation time of a single-core CPU calculation.

It is an acquired result that, in order to enable realistic earthquake hazard assessment and reliable estimation of the ground motion response to an earthquake, three-dimensional velocity models have to be considered. In this paper we present a new analytical procedure for determining the seismic wavefield in a 3D anelastic model based on the combination of the ray theory with the modal summation method. The proposed procedure has been validated by considering the three-dimensional model of the Kanto basin (Japan) available in the literature. Three-dimensional simulations were performed for the 1990 Odawara earthquake. The results obtained were compared both with recorded signals and with simulations available in the literature for several stations located within the Kanto basin. Besides the advantage of being a useful tool for assessment of seismic hazard and seismic risk reduction, it is characterized by high efficiency, in fact, once the study region is identified and the 3D model is constructed, the computation, at each station, of the three components of the synthetic signal (displacement, velocity, and acceleration) takes less than 3 h on a 2 GHz CPU.