Simulation Of Propagation Research Articles

Simulation of light propagation in medium with an ultrasonically induced refractive index gradient

Modulation of the refractive index in a medium by external stimuli enables fast and reversible control of light propagation. This technology for controlling light has led to new discoveries in a wide range of research fields from physics to life sciences and has played a major role in the development of photonics devices. In this article, we focus on ultrasound as an external stimulus and have devised a method to control the refractive index of a medium using ultrasound. Our research group has previously discovered that a giant refractive-index gradient (Δn on the order of 10−2) was induced when water was irradiated with high-frequency (100 MHz range), high-intensity (on the order of MPa) ultrasound. Here, we report ray-tracing simulations in a medium with a refractive-index gradient induced by ultrasonic radiation. A numerical model of the refractive-index gradient was developed based on the experimental data, and ray-tracing simulations were performed using the Euler–Lagrange equation. The ray-tracing simulation results were close numerically to the profiles of the laser beam observed in the experiment when the laser beam was incident on the refractive-index-gradient medium.

Interfacial stress and crack propagation experimental study in mini-LED chip debonding

The ultra-miniaturization trend of chips presents new challenges for non-destructive peeling-off techniques. This study models the mini-LED chip-UV film adhesive system as a micro laminated structure and conducts the interfacial stresses and crack propagation analysis of the structure using theoretical, finite element and experimental methods. The innovations of this paper are the illustration of the negligible effect of size effect on 125 μm x 75 μm x 60 μm chips, and the determination of the technology parameter tuning method to promote chip peeling-off. Firstly, applying the first-order shear deformation theory, and considering the UV-curable acrylic adhesive layer and the UV film as elastic materials, Lamé coefficients are introduced to explore the free vibration of the micro laminated structure. The analyses indicate that the scale effect has an extremely small impact, within 0.5%, on natural frequencies of the 100-micron scale laminated structure with a small length-to-thickness ratio. Thereafter, a three parameter elastic foundation (3-PEF) model of the chip-UV film adhesive structure is established and the interfacial stresses distributions are parametrically analyzed. Additionally, an experimental platform for needle-ejecting chip peeling-off is designed and constructed. Finite element simulation, experimental observations, and image recognition of crack generation and propagation during the peeling process were performed. Results show that cracks are generated at both free ends of the adhesive layer and progressively extended inwards. This is consistent with the 3-PEF analytical solution, in which the stress concentration also occurs at free ends of the adhesive layer. The agreement between theoretical, simulation and experimental results regarding interfacial stresses provides a solid foundation for further analysis of chip peeling-off mechanism.

A 2.5D hybrid SBM-MFS methodology for elastic wave propagation problems

This paper proposes a novel hybrid methodology that combines the singular boundary method (SBM) and the method of fundamental solutions (MFS) for the computational simulation of elastic wave propagation. Particularly, the methodology aims to address radiation or scattering problems of longitudinally invariant systems in the wavenumber–frequency domain involving boundaries with intricate geometries. The approach uses the SBM to deal with the complex parts of these geometries and the MFS for the smooth ones. The method is studied in the framework of three case studies involving longitudinally infinite cavities in a homogeneous full-space with circular, square-shaped and five-cusped hypocycloid cross-sections. These three examples are selected to assess the accuracy and robustness of the hybrid SBM-MFS approach in comparison with alternative modelling strategies. The comparisons show that the proposed method inherits the accuracy of the MFS while keeping the robustness of the SBM when dealing with complex geometries. The method is found to be computationally more efficient than the SBM or the boundary element method (BEM). Moreover, the hybrid approach naturally mitigates the effect of fictitious eigenfrequencies, a feature that neither conventional versions of the SBM nor the BEM have.

Multiple hydraulic fracture propagation simulation in deep shale gas reservoir considering thermal effects

Deep and ultra-deep shale gas will gradually become the focus of unconventional oil and gas resources in the petroleum industry. In the development of shallow shale reservoirs, the multi-cluster hydraulic fracturing of horizontal wells is the commonly applied technique to create a network of fractures and achieve reservoir stimulation. However, for deep shale reservoirs, the behavior of multiple hydraulic fracture propagation is affected by stress interference between fractures. On the other hand, it is also influenced by the temperature disturbances caused by the injection of low-temperature fracturing fluids into high-temperature formations and the resulting thermal effects. Currently, most research on multiple hydraulic fracture propagation in shale only considers the interaction between fluids and solids while neglecting thermal effects. Therefore, based on the displacement discontinuity method, finite volume method, and finite difference method, this study established a numerical model for the non-planar propagation of multi-cluster hydraulic fractures in deep shale, considering the thermal effects. And the model was validated through numerical solutions of the temperature field and double-fracture propagation. Moreover, the number of fracture clusters, pumping rate, and formation temperature were selected as influencing factors, and the differences in multiple hydraulic fracture propagation with and without considering thermal effects were analyzed. The results show that as the formation temperature increases, the thermal effects become more significant, leading to greater differences in the morphology of multi-cluster fractures. Moreover, the thermal effects are more significant when the formation temperature exceeds 90 °C. Additionally, appropriately reducing the number of fracture clusters or increasing the pumping rate can to some extent mitigate stress interference between fractures and promote uniform fracture propagation. The findings of this study contribute to understanding the influence of thermal effects on multiple hydraulic fracture propagation and provide theoretical basis for the efficient development of deep shale gas.

Crack propagation simulation and overload fatigue life prediction via enhanced physics-informed neural networks

The fatigue crack growth simulation and life prediction of structures are implemented in this paper based on the physics-informed neural networks (PINNs). Firstly, the enhanced PINNs are proposed by introducing the crack tip asymptotic displacement fields, so that the crack tip stress intensity factors can be calculated accurately even when the number of collocation points is small and the distribution grid is regular. The enhanced PINNs essentially transform the solution of elastic body containing crack into the optimization of minimizing the constructed loss functions, and can invert the fracture parameters. Then, an automatic crack propagation simulation method is developed based on the enhanced PINNs. The network architecture and the overall node distribution can be unchanged during the crack propagation process, and only new crack surfaces need to be processed and corresponding loss functions need to be modified. Because the nodal refinement around crack-tip is not required, this simulation method is convenient and can accurately predict the mixed-mode crack propagation path. Finally, the fatigue crack growth life algorithm considering overload is developed, where the effect of each overload can be captured by the cycle-by-cycle method. Based on this algorithm, the retardation behavior can be characterized and the fatigue life of structure under the load spectrum with periodic overloads can be accurately predicted. The sufficient examples are given to verify the feasibility and accuracy of the method proposed in this paper.

Development of a fast-running method for prediction of blast propagation in partially confined spaces

In this contribution, a series of findings from Computational Fluid Dynamics (CFD) simulations of blast propagation within fully confined spaces are presented. These numerical works have been carried out as part of an ongoing in-house development towards a fast-running method to predict overpressures and impulses arising from detonations within the various configurations of carparks in Singapore. In land-scarce cities like Singapore, carparks are typically located within the same structural footprints and are integrated with other functions of the building to facilitate convenient access. Design of carparks are required to meet statutory provisions with regards to the layout, headroom clearance and safety. To this end, the present research study has adopted a three-stage approach. First, different representative configurations of carparks are determined by making reference to and rationalising based on the prevailing statutory provisions in Singapore. This is then followed by a series of parametric CFD simulations to obtain essential numerical data in order to characterise the blast propagation within the respective partially confined spaces. Finally, several regression models are employed to derive relationships between the critical parameters and the blast data, with the aim of achieving a fast-running predictive method. This paper seeks to provide detailed descriptions of the first and the second stages, as well as to present the comparisons of numerically converged solutions, which are obtained from preliminary CFD simulations using two mesh sizes, against semi-analytical solutions which are calculated based on guidance from UFC 3-340-02 for fully confined detonation as initial reference cases.

Advancing electromagnetic field modeling in axially anisotropic media with conformal method in 3D cylindrical coordinate systems

A conformal methodology for solving electromagnetic fields in axially anisotropic media in 3D cylindrical coordinate systems is proposed for the investigation of high-power microwave devices filled with such media. This method leverages the material properties of axially anisotropic media and employs the finite integral technique for solution. A simplified conformal algorithm is utilized for the boundaries of the computational region, extending the traditional conformal method for axially anisotropic media in 3D cylindrical coordinates. The proposed methodology is validated through simulations of TM01 and TE01 mode propagation in a circular waveguide filled with the medium. Subsequently, the method is integrated into particle-in-cell simulations, and an X-band relativistic backward wave oscillator filled with an axially anisotropic medium exhibiting azimuthal conductivity is numerically modeled. The results demonstrate that the medium with azimuthal conductivity effectively mitigates asymmetric modes in the relativistic backward wave oscillator, aligning with published literature. This study offers technical insights for research on high-power microwave devices incorporating axially anisotropic media, potentially facilitating the development of innovative microwave devices with enhanced performance characteristics.

Earthquake source impacts on the generation and propagation of seismic infrasound to the upper atmosphere

SUMMARY Earthquakes with moment magnitude (Mw) ranging from 6.5 to 7.0 have been observed to generate sufficiently strong acoustic waves (AWs) in the upper atmosphere. These AWs are detectable in Global Navigation Satellite System satellite signals-based total electron content (TEC) observations in the ionosphere at altitudes ∼250–300 km. However, the specific earthquake source parameters that influence the detectability and characteristics of AWs are not comprehensively understood. Here, we extend our approach of coupled earthquake-atmosphere dynamics modelling by combing dynamic rupture and seismic wave propagation simulations with 2-D and 3-D atmospheric numerical models, to investigate how the characteristics of earthquakes impact the generation and propagation of AWs. We developed a set of idealized dynamic rupture models varying faulting types and fault sizes, hypocentral depths and stress drops. We focus on earthquakes of Mw 6.0–6.5, which are considered the smallest detectable with TEC, and find that the resulting AWs undergo non-linear evolution and form acoustic shock N waves reaching thermosphere at ∼90–140 km. The results reveal that the magnitude of the earthquakes is not the sole or primary factor determining the amplitudes of AWs in the upper atmosphere. Instead, various earthquake source characteristics, including the direction of rupture propagation, the polarity of seismic wave imprints on the surface, earthquake mechanism, stress drop and radiated energy, significantly influence the amplitudes and periods of AWs. The simulation results are also compared with observed TEC fluctuations from AWs generated by the 2023 Mw 6.2 Suzu (Japan) earthquake, finding preliminary agreement in terms of model-predicted signal periods and amplitudes. Understanding these nuanced relationships between earthquake source parameters and AW characteristics is essential for refining our ability to detect and interpret AW signals in the ionosphere.

X-ray lensless optics and ptychography

One of the problems of modern optics is accurate and full description of the object and light fields. Thus, the optical properties of the materials should be characterized not only by their absorption, but also by the refraction, and the light fields near the object and detector — not only by the intensity, but also by the phase. The 1972 the work of Gershberg and Saxton was the first attempt to solve this problem in free space without optical elements, relying only on a quadratic detector and a computer simulation of the wave propagation. Today, such lensless imaging is used at different wavelengths, from terahertz to hard X-rays. The purpose of this work is to give a brief introduction to the theory of lensless imaging which can be applied to the X-ray region. The results of the corresponding experiments in invisible light using He-Ne laser and testing objects are also presented.

Voronoi-based 3D phase field model and numerical simulations of granite crack propagation

The distribution of mineral grains within underground rocks and materials is crucial for understanding geological processes and the stability of engineering structures. However, numerical simulation methods that consider 3D mineral particles are still immature. This study presents a 3D phase-field fracture model of mineral grains based on Voronoi polygons, making some beneficial attempts in this regard. The phase-field method does not rely on mesh reconstruction or crack path tracking and can simulate complex crack propagation behavior. Meanwhile, the Voronoi polygon can better describe the microscopic structure of rock with grain boundaries. Rooted in Voronoi polygons, this model efficiently captures the complex geometric shapes of mineral grains and accurately characterizes their positions, shapes, and sizes. Therefore, this study combines Voronoi polygons to establish a 3D phase-field model. Through two numerical simulation cases, the model demonstrates its effectiveness in simulating the impact of three-dimensional mineral grains on crack propagation behavior, showing that cracks tend to propagate at the boundaries or inside softer mineral grains. The modeling approach proposed in this paper has good reference value for numerical simulation studies considering the microscopic structure of rocks.

Accelerating simulations of Li-ion battery thermal runaway using modified Patankar–Runge–Kutta approach

Reliable and accurate simulations of the thermal runaway of Li-ion batteries are crucial for designing thermal management system. However, the stiff nature of thermal abuse kinetics makes it computationally challenging to obtain numerical solutions. To address this, we employed modified Patankar–Runge–Kutta (MPRK) methods for thermal runaway simulations. The explicit nature of these methods leads to computationally efficient simulations, while their ability to maintain positive physical quantities ensures robust integrations. We first investigated the performance of the second- and third-order MPRK methods, along with the well-known fourth-order Runge–Kutta method, for zero-dimensional thermal runaway simulations. Numerical tests revealed the superiority of the third-order MPRK method in terms of robustness and accuracy. To further improve its accuracy during a rapid temperature rise, we introduced an adaptive time-stepping method. This adaptive third-order MPRK method was then implemented in Ansys Fluent for three-dimensional simulations of thermal runaway propagation. Benchmark tests demonstrated an increase of 10 times in the computational speed compared with Fluent’s built-in solver, which was achieved by allowing significantly larger thermal time steps without compromising accuracy. The robust and efficient computational method proposed in this study will pave the way for future studies on multiphysics simulations of thermal runaway phenomena.

On the equivalence of scalar-pressure and vector-based acoustic dosage measures as derived from time-limited signal waveformsa).

The dynamic (acoustic pressure) and kinematic (acoustic acceleration and velocity) properties of time-limited signals are studied in terms of acoustic dose metrics as might be used to assess the impact of underwater noise on marine life. The work is relevant for the study of anthropogenic transient acoustic signals, such as airguns, pile driving, and underwater explosive sources, as well as more generic transient signals from sonar systems. Dose metrics are first derived from numerical simulations of sound propagation from a seismic airgun source as specified in a Joint Industry Programme benchmark problem. Similar analyses are carried out based on at-sea acoustic measurements on the continental shelf, made with a vector sensor positioned 1.45 m off the seabed. These measurements are on transient time-limited signals from multiple underwater explosive sources at differing ranges, and from a towed, sonar source. The study demonstrates, both numerically and experimentally, that under many realistic scenarios, kinematic based acoustic dosage metrics within the water column can be evaluated using acoustic pressure measurements.

Quantification and mitigation of the effect of resynchronization errors in ultrasound sensor network for passive imaging in elastic plates.

The problem of signal desynchronization in passive imaging based on noise correlation for defect detection in elastic plates is investigated. Although a post-processing resynchronization process relying on the symmetry of noise correlation functions can be applied prior to the imaging algorithm, perfect synchronization might not be achieved experimentally. Effect of such residual synchronization errors on the defect detection performance is quantified as a function of their probability density function. A mathematical regularization process is then proposed to reduce the standard deviation of the resynchronization errors by a factor of N-1/N (N is the number of sensors), which results in a significant improvement in the detection performance. Finally, these theoretical results are validated through a simple flexural-wave propagation simulation.

Evaluation of the X-ray/EUV Nanolithography Facility at AS through wavefront propagation simulations.

Synchrotron light sources can provide the required spatial coherence, stability and control to support the development of advanced lithography at the extreme ultraviolet and soft X-ray wavelengths that are relevant to current and future fabricating technologies. Here an evaluation of the optical performance of thesoft X-ray (SXR) beamline of the Australian Synchrotron (AS) and its suitability for developing interference lithography using radiation in the 91.8 eV (13.5 nm) to 300 eV (4.13 nm) range are presented. A comprehensive physical optics model of the APPLE-II undulator source and SXR beamline was constructed to simulate the properties of the illumination at the proposed location of a photomask, as a function of photon energy, collimation and monochromator parameters. The model is validated using a combination of experimental measurements of the photon intensity distribution of the undulator harmonics. It is shown that the undulator harmonics intensity ratio can be accurately measured using an imaging detector and controlled using beamline optics. Finally, the photomask geometric constraints and achievable performance for the limiting case of fully spatially coherent illumination are evaluated.

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.

Sound propagation simulation in the Strait of Hormuz using ROMS and RAMGEO models

Sound propagation simulation in the Strait of Hormuz using ROMS and RAMGEO models

Stratospheric Gravity Waves Impact on Infrasound Transmission Losses Across the International Monitoring System

AbstractThe international monitoring system (IMS) has been put in place to monitor compliance with the comprehensive nuclear-test-ban treaty (CTBT). Its infrasound component, dedicated to the monitoring of atmospheric events, gives also room to civil applications (e.g. monitoring of volcanic eruptions, meteorites, severe weather). Infrasound detection capabilities are largely determined by the state of the middle atmosphere. This requires an accurate knowledge of the atmospheric processes at play. More particularly internal gravity waves (GW) pose a challenge to atmospheric modelling because of unresolved processes. Using high-resolution simulation outputs over winter 2020 (20 January–1 March) we present a method to assess the impact of GW on infrasound surface transmission losses across the IMS. We validate the method by comparing simulated GW perturbations to GW lidar observations at Observatoire de Haute-Provence in France, and satellite-based GW energy estimations globally. We perform propagation simulations using atmospheric specifications where GW are filtered out and kept in, respectively. We demonstrate that the largest impact of GW across the IMS is not where GW activity is the largest, but rather where GW activity combines with infrasound waveguides not firmly set in a given direction. In northern winter, the largest variations of transmission losses at 1 Hz due to GW occur in the southern (summer) hemisphere in the direction of the main guide (westward propagation), with average values ranging between 10 and 25 dB in the first shadow zone. It corresponds to an average signal amplification of at least a factor 5 to 15, while this amplification is around 2 to 5 for the main guide in the northern winter hemisphere (eastward propagation).

Вплив детонаційної хвилі на перерозширений надзвуковий потік газу в со-плі

This paper proposes to use the detonation process to solve the problem of controlling highly maneuverable flying vehicles. The goal of the work is to study a new way of the thrust vector control of a rocket engine using the effect of a detonation shock wave on the gas flow in the nozzle. It is known that the method of thrust vector control by gas injection into the supersonic nozzle area of a rocket engine features one of the lowest losses of specific momentum and a high response speed and produces a significant lateral force. However, for the current level of rocket technology, there is a need to improve these characteristics. Detonation is considered as a method to intensify processes that affect the main gas flow and produce a lateral force. Its features make it possible to develop a system for pulse trajectory correction. In order to study the features of such a system, experimental studies of the detonation wave effect on a supersonic nozzle flow were conducted. A nozzle model and a gas generator for initiating a detonation wave interacting with the main supersonic air flow were developed and made. In the course of experiments, the effect of separation of the main flow from the nozzle wall by the detonation wave during the nozzle operation in the overexpansion mode was revealed. The duration of this effect was much longer than that of the detonation product effect on the main air flow in the nozzle, thus allowing it to be used in the development of a new thrust vector control method. To better understand the experimental results, a numerical simulation of the detonation wave propagation in a supersonic flow was carried out for the test conditions. The simulation was carried out in a non-stationary 2D formulation using the Solid Works software package. The goal of the simulation was to estimate the flow structure and the value of the relative lateral force produced by the change of this structure during detonation product injection into the supersonic nozzle area. The time evolution of the pressure field was obtained. The relative lateral force produced by detonation product injection into the supersonic air flow in the nozzle was determined. The presented features and method of jet engine thrust vector control may be used in unmanned systems operating in a wide range of speeds.

Simulation and optimization of unstable dynamic propagation of multiple fractures in the shale formation

Multi-cluster hydraulic fracturing of horizontal wells is a well-adopted technique with high efficiency to increase the production of tight and shale formations. However, the stress shadows among clusters pose challenges to the synchronous propagation of hydraulic fractures during multi-cluster fracturing. In order to explore the fracture propagation mechanism and characteristics under the influence of stress shadow in low-spacing staged multi-cluster fracturing, a three-dimensional hydraulic fracturing model was generated using a lattice-based method. This model considered the impact of geological and engineering parameters on the propagation behavior of multiple fractures in shale formation. A variable pumping approach is adopted, where the fracturing fluid is initially injected at a high rate and then transitioned to a lower rate. Afterward, a method was proposed to quantitatively assess the extent of fracturing in a specific area (i.e., the stimulated area), considering the impact of stress shadow within a single stage. The simulation results demonstrated significant differences in the fracture stimulation area due to the influence of each parameter in the case of uncontrollable geological factors and controllable engineering factors. An increase in both Young’s modulus and stress anisotropy of the reservoir results led to a corresponding increase in the total fracture stimulation area. As the principal stress orientation increased, the fracture stimulation area gradually decreased. In terms of operational parameters, the stimulated area of hydraulic fractures gradually decreased as the fracture spacing increased. With increasing injection rate, the stimulated area initially expanded and then decreased, peaking at an injection rate of 0.04 m3/s. These findings can provide valuable insights into the propagation behavior of multi-cluster hydraulic fractures under uncertain parameters, with significant implications for future engineering applications.

Numerical Simulation of Fracture Propagation during Temporary Plugging Staged Fracturing in Tight-Oil Horizontal Wells.

Fracture propagation with temporary plugging hydraulic fracturing in tight-oil reservoirs is simulated in this study. The research considers dynamic fluid redistribution, with stress differences among multiple fractures. The fracture morphology during temporary plugging staged fracturing (TPSF) is investigated by using a user-defined perforation element combined with a pore-pressure finite-element model. The precision of the integrated model is verified by using the standard finite-element approach. Then, case studies are presented to investigate the influence of cluster spacing, horizontal stress difference coefficients (SDC), injection rates, and barrier tensile strengths. The simulation results show that central cluster fractures are hampered by side-cluster fractures, while TPSF can alleviate the effect and lead to a more uniform propagation of all fractures. Stress interference weakens as cluster spacing increases, and propagation patterns are minimally influenced once spacing reaches 40 m. Higher injection rates can improve the injection pressure, enlarging fracture width, and potentially increasing the risk of fracture penetration. Barrier tensile strength and horizontal SDC can modify fracture geometries and determine the penetration behavior of multiple fractures.