Simulation Of Propagation Research Articles

Rock fracture propagation in a damage zone by a constitutive model coupling volume and cohesive elements

AbstractThis paper presents a method to simulate fracture propagation in a damage zone in 2D, whereby Cohesive Zone (CZ) elements are assigned the same Continuum Damage Mechanics (CDM) model as their adjacent finite elements. Material hardening is a result of damage‐induced stiffness reduction in the finite and cohesive elements, while softening is modeled by cohesive debonding only. The damage components calculated at the numerical integration points of each finite element are averaged and that average is assigned to the nodes of the adjacent CZ elements. CZ element debonding triggers when a critical damage threshold is reached, beyond which, a linear softening law is used in both mode I and mode II. The proposed model is calibrated against published triaxial compression tests conducted on shale. Single‐CZ element simulations confirm that, below the critical damage threshold, elastic deformation energy is stored and energy is dissipated by damage propagation and irreversible deformation. Passed the critical damage threshold, stored elastic energy is released in the form of cohesive debonding energy. Borehole breakout simulations indicate that the proposed CDM‐based CZ model can predict the formation of spiral‐shaped fractures around a free circular cavity under biaxial stress. Simulations of fracture propagation in textured materials suggest that cohesive debonding within and between grains is triggered by the coalescence of localized zones of continuum damage, and that the grain size distribution affects both the fracture pattern and the softening behavior of the specimen considered.

2-D seismic wave propagation using the distributional finite-difference method: further developments and potential for global seismology

SUMMARY We present a time-domain distributional finite-difference scheme based on the Lebedev staggered grid for the numerical simulation of wave propagation in acoustic and elastic media. The central aspect of the proposed method is the representation of the stresses and displacements with different sets of B-splines functions organized according to the staggered grid. The distributional finite-difference approach allows domain-decomposition, heterogeneity of the medium, curvilinear mesh, anisotropy, non-conformal interfaces, discontinuous grid and fluid–solid interfaces. Numerical examples show that the proposed scheme is suitable to model wave propagation through the Earth, where sharp interfaces separate large, relatively homogeneous layers. A few domains or elements are sufficient to represent the Earth’s internal structure without relying on advanced meshing techniques. We compare seismograms obtained with the proposed scheme and the spectral element method, and we show that our approach offers superior accuracy, reduced memory usage, and comparable efficiency.

Design and low-velocity impact behavior of an origami-bellow foldcore honeycomb acoustic metastructure

The ancient art of origami has inspired the design and fabrication of numerous acoustic and energy-absorption mechanical metamaterials and metastructures. This study introduces an origami-inspired honeycomb acoustic metastructure designed for engineering applications that demand both high impact resistance and effective sound absorption. This acoustic metastructure is formed by bonding a panel containing periodically distributed perforated holes and a panel without perforations to a periodical array of trapezoidal origami-bellow units. Acoustic wave propagation and drop-weight impact simulations are conducted to investigate the acoustic performance and low-velocity impact behavior of the metastructure. The results show that the origami-bellow honeycomb structure exhibits superior sound absorption capacity over two frequency ranges, outperforming the conventional honeycomb-core sandwich structure. Furthermore, it is shown that, in comparison with both the conventional hexagonal honeycomb-core and the Miura-ori foldcore sandwich structures, the proposed acoustic metastructure demonstrates higher levels of impact resistance and energy absorption capacity. We also show that the mechanical performance of the introduced metastructure under low-velocity impact loads can be further enhanced by increasing the story height of the origami-bellow units. Besides, the matrix material of the origami foldcore can be tailored to suit various scenarios, providing noise control and collision robustness for a diverse range of engineering applications.

Numerical Simulation of integrated three-dimensional hydraulic fracture propagation and proppant transport in multi-well pad fracturing

Multi-well pad fracturing is an indispensable technology for the sustainable development of unconventional oil and gas reservoirs, but the integrated simulation of fracture propagation and proppant migration in massive fracturing treatments remains challenging, including complicated numerical implementations and computational bottlenecks due to its multi-physics, fracture front propagation, size differences between proppant particles and hydraulic fractures. In this work, an integrated model of fracture propagation and proppant migration in multi-well pad fracturing was established based on the three-dimensional discontinuous displacement method for fracturing deformation computations and the Eulerian-Eulerian framework for capturing proppant concentration. The proposed simulator not only accounts for key physical processes such as stress shadow, dynamic flow rate distribution in the wellbore, fluid leak-off, perforation erosion, fractures evolution, proppant bridging, and gravitational settling, but also couples the simulation of 3D planar propagating fractures and proppant transport at well-pad scale, and presents excellent computational efficiency and promising applications than conventional fracturing models. To explore the fracture geometries and proppant distribution in typically stacked layers, single-well, multi-lateral wells, and multi-well pad fracturing are simulated from simple to complex. The findings showed that fracture propagation is jointly affected by intra-stage, inter-stage, and inter-well stress interference mechanisms, and fracture geometries are characterized by unevenness, asymmetry, and heel bias. Proppant transport is controlled by the fracture width and geometries, and most of the proppant is concentrated near the wellbore area and bridging at the narrow fractures. Fracture geometries and proppant distribution are sensitive to the landing locations of horizontal wells because hydraulic fractures always grow in the path of least resistance. Although close lateral well-spacing is beneficial to improve the stimulation efficiency, there are some challenges such as overlapped SRV, enhanced inter-well interference, and severe fracturing hits. Compared with the layout of stacked wells, staggered wells are not only beneficial to reduce the vertical inter-well interference, but also improve reservoir stimulation efficiency. Overall, the stimulated area of the high in-situ stress layers is relatively low even with intentionally landed wells.

On the enriched mixed Galerkin method with θ scheme for the elastic wave equation

In this paper, we propose the application of an enriched Galerkin (EG) method to solve the elastic wave equation in the “displacement pseudo-pressure” mixed form, which is known for being locking-free. Unlike the continuous Galerkin (CG) method and the discontinuous Galerkin (DG) method, the EG method is based on the weak form of the DG method, and the enriched space combines a continuous piecewise linear vector-valued function space with some discontinuous piecewise linear functions. Specifically, we employ the enriched space to discretize the displacement, while the pseudo-pressure is discretized using the P0 element space. As a result, compared to the DG method, the EG method significantly reduces the number of degrees of freedom. Furthermore, we adopt a more general θ-scheme for time discretization, which behaves as an implicit scheme for 14≤θ≤1 and as an explicit scheme for 0≤θ<14. We establish error estimates for both the semi-discrete and fully-discrete schemes. The accuracy of the proposed method is validated through numerical examples, which not only confirm the theoretical analysis but also provide simulations of elastic wave propagation.

The impact and response of mini-haloes and the interhalo medium on cosmic reionization

ABSTRACT An ionization front (I-front) that propagates through an inhomogeneous medium is slowed down by self-shielding and recombinations. We perform cosmological radiation hydrodynamics simulations of the I-front propagation during the epoch of cosmic reionization. The simulations resolve gas in mini-haloes (halo mass 104 ≲ Mh[M⊙] ≲ 108) that could dominate recombinations, in a computational volume that is large enough to sample the abundance of such haloes. The numerical resolution is sufficient (gas-particle mass ∼20 M⊙ and spatial resolution &amp;lt;0.1 ckpc) to allow accurate modelling of the hydrodynamic response of gas to photoheating. We quantify the photoevaporation time of mini-haloes as a function of Mh and its dependence on the photoionization rate, Γ−12, and the redshift of reionization, zi. The recombination rate can be enhanced over that of a uniform medium by a factor ∼10−20 early on. The peak value increases with Γ−12 and decreases with zi, due to the enhanced contribution from mini-haloes. The clumping factor, cr, decreases to a factor of a few at ∼100 Myr after the passage of the I-front when the mini-haloes have been photoevaporated; this asymptotic value depends only weakly on Γ−12. Recombinations increase the required number of photons per baryon to reionize the Universe by 20 per cent–100 per cent, with the higher value occurring when Γ−12 is high and zi is low. We complement the numerical simulations with simple analytical models for the evaporation rate and the inverse Strömgren layer. The study also demonstrates the proficiency and potential of sph-m1rt to address astrophysical problems in high-resolution cosmological simulations.

Numerical and experimental study of ultrasonic seismic waves propagation and attenuation on high‐quality factor samples

AbstractWe propose an approach for measuring seismic attenuation at ultrasonic frequencies on laboratory‐scale samples. We use a Gaussian filter to select a bandwidth of frequencies to identify the attenuation in a small window and, by moving the window across the frequency content of the data, we determine the frequency‐dependent attenuation function. We assess the validity of the method with three‐dimensional numerical simulations of seismic wave propagation across different sample geometries, using free surface boundary conditions. We perform the simulations using viscoelastic media under various seismic attenuation models. Our numerical results indicate that we can successfully recover the representative viscoelastic attenuation parameters of the media, regardless of the sample geometry, by processing the seismic signal recorded either within the volume or at the boundaries. Due to the equipartition phenomenon, the energy of S‐waves is consistently higher in seismic records than that of P‐waves. Therefore, we systematically recover the attenuating properties of S‐waves in the medium. We also conduct experiments of seismic wave propagation on samples of aluminum and Fontainebleau sandstone to validate our approach with real data. The quality factor of the S‐wave in the aluminum medium increases from 300 to 7000 between 60 kHz and 1.2 MHz. The Fontainebleau sandstone, which is more attenuating, exhibits a that increases from 200 at 60 kHz to 1000 at 1.2 MHz. With our approach, we are not only able to recover the attenuation property but also identify the frequency‐dependent attenuation model of the samples. Our method allows for seismic attenuation recovery at ultrasonic frequencies in low‐attenuating media.

Numerical Simulation of Tsunami Generation and Propagation Due to Viscous Debris Flow Impact Using LS-DYNA

Numerical Simulation of Tsunami Generation and Propagation Due to Viscous Debris Flow Impact Using LS-DYNA

Propagation effects in polarization-gated attosecond soft-X-ray pulse generation.

Accurate estimation of the duration of soft-x-ray pulses from high-harmonic generation (HHG) remains challenging given their higher photon energies and broad spectral bandwidth. The carrier-envelope-phase (CEP) dependence of generated soft-x-ray spectra is indicative of attosecond pulse generation, but advanced simulations are needed to infer the pulse duration from such data. Here, we employ macroscopic propagation simulations to reproduce experimental polarization-gated CEP-dependent soft-x-ray spectra. The simulations indicate chirped pulses, which we theoretically find to be compressible in hydrogen plasmas, suggesting this as a viable compression scheme for broadband soft-x-rays from HHG.

Simulation of crack propagation in piping components using phase field approach

Understanding the fracture behaviour in pipelines transporting steam and other resources is vital for its longevity and structural integrity. The prediction of crack initiation and propagation, involving crack branching, and the nucleation of new cracks, etc. in fracture processes are challenging tasks. The phase field method (PFM), based on variational formulation, emerged as a competitive mathematical tool to address fracture mechanics problems. PFM does not require the presence of predefined cracks, handles the crack initiation and propagation within the same system. This feature provides an added advantage to PFM and overcomes the limitations of Griffith’s approach-based linear elastic fracture mechanics (LEFM). In the present work, simulation of the crack propagation in the piping components by employing phase field methodologies has been carried out. Two parameters namely; a phase field parameter (ϕ) that varies between 0 and 1 differentiating between broken and intact material, and a length scale parameter (l_0) that approximates the sharp crack into the diffused crack with exponential distribution are introduced in the mathematical modeling. Numerical modeling is solved using the staggered algorithm in three layered scheme defining the displacement field and phase field within a 3-D finite element framework and implemented in Abaqus via user-defined element (UEL) subroutine codes. PFM simulates the crack path and predicts the load-displacement response, which is validated with benchmark problems, and extended for piping components under monotonic loading. The proposed study accurately captures the crack growth behaviour as observed in experiments on SA312 Type 304LN stainless steel pipes and hence, demonstrated the robustness of the proposed formulation.

Direct numerical simulations of long-range infrasound propagation: Implications for source spectra estimation.

The evolution of observed dominant frequencies from a high-intensity infrasonic pulse with receiver range and stratospheric temperature is investigated using direct numerical simulations of the two-dimensional unsteady compressible Navier-Stokes equations. There is a high level of uncertainty in estimating source dominant frequencies based on received signals at sparse points on the ground. Nonlinear propagation effects in the ground-level thermospheric arrivals are found to significantly alter dominant frequency measurements compared to stratospheric arrivals with smaller amplitude sources. With a larger amplitude source, variations in observations are minimized as a result of nonlinear effects being ubiquitous across all atmospheric components of received signals but have a greater offset to the source dominant frequency. An approach to determine the source dominant frequency and minimize atmospheric variability is presented by calculating a source-to-receiver spectral transfer function averaged across the atmospheric states. This method reduces atmospheric variability in source frequency estimates within the pseudo-linear propagation regime and the average error to the known source frequency with a large amplitude source. The reduction of errors in source frequency estimates demonstrates the feasibility of using remote infrasound measurements as an indicator of source frequency and, in turn, the explosive yield of clandestine nuclear weapon test explosions.

Corrigendum to “The Conformal Finite‐Difference Time‐Domain Simulation of GPR Wave Propagation in Complex Geoelectric Structures”

Corrigendum to “The Conformal Finite‐Difference Time‐Domain Simulation of GPR Wave Propagation in Complex Geoelectric Structures”

Ion imaging of spatially inhomogeneous nanoplasmas in NaCl particles.

Studying photoemission from free, unsupported aerosol particles is a powerful method for gaining insight into light-matter interactions at the nanoscale. We used single-shot velocity map imaging to experimentally measure kinetic energy and angular distributions of ions emitted following interaction of sub-micrometer NaCl particles with femtosecond pulses of near infrared (NIR, 800 nm) and ultraviolet (UV, 266 nm) light. We combined this with time-dependent simulations of light propagation through the particles and a rate equation approach to computationally address the origin of the observed ion emission. For both NIR and UV pulses, ion emission is caused by the formation of an under-dense nanoplasma with similar densities, although using an order of magnitude weaker UV intensities. Such conditions result in remarkably similar ion fragments with similar kinetic energies, and no obvious influence of the plasma formation mechanism (photoionization or collisional ionization). Our data suggests that Coulomb explosion does not play a significant role for ion emission, and we discuss alternative mechanisms that can lead to material ablation from under-dense nanoplasma. Finally, we show how finite size effects play an important role in photoemission through generation of spatially inhomogeneous nanoplasmas, which result in asymmetric ion emission that depends on particle size and laser wavelength. By utilizing the single-particle information available from our experiments, we show how finite size effects and inhomogeneous nanoplasma formation can be exploited to retrieve the size and orientation of individual submicrometer aerosol particles.

Dynamic Simulation of the Probable Propagation of a Disaster in an Engineering System Using a Scenario-Based Hybrid Network Model

With the growing threat of worldwide natural disasters, the safety status of the engineering system is facing serious uncertainties. A small disturbance can cause unexpected serious losses through amplification effects of the fragile environment and unwanted interactions of system elements. The safety status of the disrupted engineering system is subject to profound uncertainty and cognitive ambiguity, which is an impediment to emergency simulation decision making. To analyze the likely future under profound uncertainty, this article develops a scenario-based method to simulate the dynamic evolution process of complex disasters for the engineering system. The complex chain of disasters is segmented into a set of correlated scenarios, and the cascading effects between these scenarios are modeled according to the risk&#x2212;propagation&#x2212;consequences process. We applied this method to a mega rail transportation project and established a disaster evolution network in an attempt to traverse all possible future scenarios during operation. The Monte Carlo simulations made it possible to assess the disastrous consequences of the various disturbances and to identify the most vulnerable nodes. This model is expected to reduce uncertainty and provide key information for emergency decision making within the engineering system project.

Molecular dynamics simulation of crack propagation in very small grain size nanocopper with different grain size gradients.

In this paper, we use molecular dynamics to simulate the crack propagation behavior of gradient nano-grained (GNG) copper models with different grain size gradients, compare the crack propagation rates of different models, and analyze the microstructural changes and the mechanism of crack propagation. The simulation results show that the increase of the grain size gradient of the GNG copper model can improve the fracture resistance of the material, and the crack propagation mode undergoes a transition from brittle propagation along the grain boundaries to the formation of pores at the grain boundaries, and then to ductile fracture along the inclined plastic shear zone. The number of dislocations increases with the grain size gradient, while the crack passivation is more serious, indicating that a larger grain size gradient is more effective in inhibiting crack propagation. The introduction of gradient grain size promotes crack propagation and weakens the plasticity of the material relative to the nano-grained (NG) copper model.

Neutrinos and Gamma Rays from Galaxy Clusters Constrained by the Upper Limits of IceCube

Clusters of galaxies possess the capability to accelerate cosmic rays (CRs) to very high energy up to ∼1018 eV due to their large size and magnetic field strength, which favor CR confinement for cosmological times. During their confinement, they can produce neutrinos and γ-rays out of interactions with the background gas and photon fields. In recent work, Hussain et al. have conducted three-dimensional cosmological magnetohydrodynamical simulations of the turbulent intracluster medium combined with multidimensional Monte Carlo simulations of CR propagation for redshifts ranging from z ∼ 5 to z = 0 to study the multimessenger emission from these sources. They found that when CRs with a spectral index in the range 1.5–2.5 and cutoff energy Emax=1016–1017 eV are injected into the system, they make significant contributions to the diffuse background emission of both neutrinos and γ-rays. In this work, we have revisited this model and undertaken further constraints on the parametric space. This was achieved by incorporating the recently established upper limits on neutrino emission from galaxy clusters, as obtained by the IceCube experiment. We find that for CRs injected with spectral indices in the range 2.0–2.5, cutoff energy Emax=1016–1017 eV, and power corresponding to (0.1–1)% of the cluster luminosity, our neutrino flux aligns with the upper limits estimated by IceCube. Additionally, the resulting contribution from clusters to the diffuse γ-ray background remains significant with values of the order of ∼10−5 MeV cm−2 s−1 sr−1 at energies above 500 GeV.

Transient Simulation of Electromagnetic Wave Propagation in Plasma Based on Dynamic Drude Model

Transient Simulation of Electromagnetic Wave Propagation in Plasma Based on Dynamic Drude Model

Mechanistic insights into the electron attachment process to guanosine in the presence of arginine.

The attachment of low-energy electrons (LEEs) to DNA biomolecules leads to irreversible damage. However, the behavior of this interaction can be influenced by the presence of amino acids. Herein, we have delved into the mechanism of electron attachment to the guanosine in the presence of arginine. This study used combined molecular dynamics (MD) simulations and quantum mechanics/molecular mechanics (QM/MM) approaches to collect and optimize the geometries having hydrogen-bonds (H-bonds) between guanosine and arginine, respectively, followed by atom centered density matrix propagation (ADMP) simulations to assess the electron attachment ability of guanine with and without arginine. The vertical detachment energy (VDE) and natural population analysis (NPA) suggest that the electron attached to guanosine occurs more readily due to the H-bonds between guanosine and arginine. The singly occupied molecular orbitals (SOMOs), VDE, and NPA from ADMP results corroborated the idea that in the presence of arginine, the electron effectively attached to the guanosine moiety while the auto detachment process becomes less probable in the case of arg-guanosine (two-H bonds). However, in the presence of arginine, the dissociative electron attachment (DEA) process for guanosine is exothermic, while in the absence of arginine, it is endothermic. This study provides new insight into the process of radiation damaging biological systems by elucidating the DEA to DNA subunits in the presence of amino acids, paving the way for a deeper understanding of radiation-induced damage in biological systems.

Comparative analysis and optimisation of hydrogen combustion mechanism for laminar burning velocity calculation in combustion engine modelling

Hydrogen stands out as a compelling alternative to fossil fuels for combustion engines. Predictive combustion models are instrumental in developing hydrogen-fuelled engines. A fundamental metric of these models is the laminar burning velocity (LBV), which can be precisely determined through laminar flame propagation simulations. In this context, the selection of an appropriate combustion mechanism is critical. This paper aims to propose the appropriate combustion mechanism for calculating LBV in predictive combustion models of hydrogen-fuelled engines. 15 state-of-the-art combustion mechanisms were applied to reproduce the LBV measurements in engine-like conditions, especially considering the application of lean combustion and water injection. The FFCM 1.0 mechanism was identified from them and further optimised to improve its prediction accuracy at elevated pressures for the lean mixture. The maximum deviation of LBV was reduced from 17.6 % to 8.7 % by this optimisation, in comparison to 10.5 % for its closest competitor mechanism, ELTE (Varga et al., 2015).

Methodology for numerical evaluation of fracture resistance under pinch loading of spent nuclear fuel cladding containing reoriented hydrides

It is important to maintain cladding integrity in spent nuclear fuel management. This study proposes a numerical analysis method to evaluate the fracture resistance of irradiated zirconium alloy cladding under pinch load known to cause Mode-III failure. The mechanical behavior and fracture of the cladding under pinch loading can be evaluated by a Ring Compression Test (RCT). To simulate the fracture of hydride precipitates, zirconium matrix, and Zr/hydride interfaces under the stress field generated by RCT, a micro-structure crack propagation simulation method based on Continuum Damage Mechanics (CDM) has been proposed. Our RCT simulation model was constructed from microscopic images of irradiated cladding. In this study, we developed an automated process to generate a pixel-based finite element model by separating the hydride precipitates, zirconium matrix, and interfaces using an image segmentation method. The appropriate element size was selected to ensure the efficiency and accuracy of a crack propagation simulation. The load-displacement curves and strain energies from RCT were compared and analyzed with the simulation results of different element sizes. The finalized RCT simulation model can be used to establish the failure criterion of fuel rods under pinch loading. The advantages and limitations of the proposed method are fully discussed here.