Field Simulation Research Articles

Investigations of the Impact of Geothermal Water Reinjection on Water-Rock Interaction through Laboratory Experiments and Numerical Simulations

In the quest for sustainable geothermal energy production, the adoption of geothermal reinjection technology has become a crucial element in the development of geothermal resources. However, the processes of injection and extraction can lead to interactions between water and rock within the geothermal reservoir, resulting in pore blockage. This study focuses on the Kaifeng Zhenyu Garden geothermal field as a case study to examine the water-rock interactions that occur during geothermal reinjection, as well as the subsequent changes in mineral composition and porosity within the reservoir. The findings reveal that the primary minerals undergoing dissolution are dolomite and feldspar, with the precipitation of calcite and clay minerals following suit. Additionally, results from field simulations corroborate that dolomite and feldspar are the main minerals dissolving, accompanied by the precipitation of calcite and illite. Notably, significant changes in mineral dissolution and precipitation near the geothermal well have led to a slight reduction in the reservoir's porosity. This investigation provides valuable insights into the water-rock interactions involved in geothermal reinjection processes across various geothermal fields.

Dynamic Ruptures on Bending Fault: Insights from Numerical Simulations of Transient Stress Field

ABSTRACT We delve into the spontaneous rupture propagation on bending faults by numerical simulations based on the boundary integral equation method with unstructured meshes. To study the effect of fault geometry on dynamic rupture propagation, special attention is paid to the role of the dynamic stress field. The numerical results demonstrate that the bending angle is a key geometrical factor influencing the rupture propagation because it affects both the initial stress distribution and the dynamic stress field on the bending branch. The rupture propagation on the bending branch can be separated into two distinct stages: first, the propagation from the main branch to the bending branch, which largely depends on the dynamic stress field near the bend; and second, a subsequent propagation stage primarily influenced by the initial stress state on the bending branch, with the influence of the dynamic stress field decreasing rapidly with distance from the bend. Geometrical smoothing of the bend can be regarded as a modification of the bending angle, which may significantly alter the behavior of rupture propagation near the bend. In theory, if the bending angle ranges between −120° and 60°, there is a potential for rupture to propagate onto the bending branch through the bend.

Magnetic fields in the outskirts of PSZ2 G096.88+24.18 from a depolarization analysis of radio relics

Context. Radio relics are diffuse, non-thermal radio sources present in a number of merging galaxy clusters. They are characterized by elongated arc-like shapes and highly polarized emission (up to ∼60%) at gigahertz frequencies, and are expected to trace shock waves in the cluster outskirts induced by galaxy cluster mergers. Their polarized emission can be used to study the magnetic field properties of the host cluster. Aims. In this paper, we investigate the polarization properties of the double radio relics in PSZ2 G096.88+24.18 using the rotation measure (RM) synthesis, and try to constrain the characteristics of the magnetic field that reproduce the observed depolarization as a function of resolution (beam depolarization). Our aim is to understand the nature of the low polarization fraction that characterizes the southern relic with respect to the northern relic. Methods. We present new 1–2 GHz Karl G. Jansky Very Large Array (VLA) observations in multiple configurations. We derived the RM and polarization of the two relics by applying the RM synthesis technique, and thus solved for bandwidth depolarization in the wide observing bandwidth. To study the effect of beam depolarization, we degraded the image resolution and studied the decreasing trend of polarization fraction with increasing beam size. Finally, we performed 3D magnetic field simulations using multiple models for the magnetic field power spectrum over a wide range of scales, in order to constrain the characteristics of the cluster magnetic field that can reproduce the observed beam depolarization trend. Results. Using RM synthesis, we obtained a polarization fraction of (18.6 ± 0.3)% for the northern relic and (14.6 ± 0.1)% for the southern one. Having corrected for bandwidth depolarization, and after noticing the absence of relevant complex Faraday spectrum, we inferred that the nature of the depolarization for the southern relic is external, and possibly related to the turbulent gas distribution within the cluster, or to the complex spatial structure of the relic. The best-fit magnetic field power spectrum, which reproduces the observed depolarization trend for the southern relic, was obtained for a turbulent magnetic field model, described by a power spectrum derived from cosmological simulations, and defined within the scales of Λmin = 35 kpc and Λmax = 400 kpc. This yields an average magnetic field of the cluster within 1 Mpc3 volume of ∼2 μG.

Optimization and Analysis of Flow Field Simulations Across Different Mach Regimes Using Discrete Numerical Methods

This article explores the development of flow field models in steady-state environments utilizing Euler equations and potential flow equations, with verification processes conducted using Python. The models demonstrate stability and high accuracy in low-velocity scenarios, capturing essential dynamics effectively. However, as the conditions transition to supersonic speeds, the models begin to exhibit increased errors. This discrepancy highlights the challenges faced in simulating high-speed aerodynamics accurately. The research underscores the importance of improving model fidelity in diverse Mach regimes, particularly in supersonic conditions where traditional methods struggle. Future research directions identified include the development of unsteady flow field models, which are crucial for dynamic analyses, optimization of grid structures for three-dimensional complex fields to improve computational efficiency, and the creation of extensive model libraries. These advancements aim to enhance the accuracy, reliability, and practicality of flow field simulations, extending their applicability in both academic studies and industry applications, particularly in aerospace engineering where precise flow modeling is critical.

Numerical Simulation of Resistance and Flow Field for Submarines near Ice Surface

When a submarine operates in polar regions, the polar environment inevitably impacts its resistance and flow field characteristics, especially when the submarine navigates near the ice surface. This paper investigates the hydrodynamic characteristics of a submarine sailing near the free water surface and the ice surface using computational fluid dynamics (CFD) methods. In order to quantify the impact of ice on the resistance and flow field characteristics of the submarine, the resistance coefficients are calculated for both near ice surface and free surface. The resistance, velocity field, and pressure distribution around the submarine at different depths and speeds are analyzed. The results indicate that the total resistance of the submarine sailing near the ice surface is lower than the free water surface. When the submarine is sailing near the ice surface, its total resistance coefficient decreases with increased submergence depth at a constant Froude number. At a fixed depth, the resistance coefficient also decreases as the Froude number increases. Additionally, when the dimensionless depth relative to the maximum hull diameter (D) exceeds 3.5, it has little effect on the resistance coefficient.

Performance and economic analysis of various geothermal power plant systems: Case study for the Chingshui geothermal field in Taiwan

Geothermal power plants are a source of sustainable energy. However, their performance is influenced by various factors, including production temperature and well locations, and few studies have investigated the relationships between these factors. To address this research gap, the present study developed integrated models of a geothermal reservoir and a variety of power plant systems. By using COMSOL and MATLAB, we conducted simulations for the Chingshui geothermal field in Taiwan to investigate the performance and economic feasibility of five common types of geothermal power plant systems over their operational lifetime under different well configurations. The key findings of this investigation are as follows. First, the locations of production wells are a primary factor influencing production temperature. Constructing wells in low-permeability zones results in considerable increases in the pressure differential in the injection pump; thus, wells should not be constructed in such zones. Second, as system flow rate and well depth decrease, production temperature remains relatively stable, net power output decreases, and system efficiency increases. This efficiency increase is caused by decreases in pumping power requirements at lower flow rates and shallower well depths. Finally, among the investigated systems, the organic Rankine cycle system had the lowest electricity production cost and shortest payback period within the enthalpy range of 500–1000 kJ/kg. Double-flash (DF) and DF–binary systems are also viable options when the mass flow rate is 10–20 kg/s and the enthalpy is 700–800 kJ/kg. Overall, the results of this study offer valuable insights for the design of geothermal power plants, thereby contributing to the optimization of renewable energy systems.

Study on the influence of high permeability magnetic iron on energy consumption reduction in high gradient magnetic separator

The green processing of weakly magnetic iron ore is inseparable from high-intensity and high-gradient magnetic separator (HGMS), which is one of the most energy-intensive magnetic separation equipment. Iron (Fe) armor serves as the key primary structure for enhancing magnetic field conduction efficiency within the magnetic system. The order of magnetic properties of commonly used magnetic yoke materials is: ordinary carbon structural steel < Q235 steel < DT4 electrical pure iron. But the utilization cost of DT4 electrical pure iron is the highest, especially the magnetic properties of DT4C super electrical pure iron are unstable and the yield is low. On the basis of ordinary pure iron materials, this article has developed a new type of 411 pure iron (411) upon controlling the levels of harmful elements, while increasing the concentration of beneficial elements.intensity Furthermore, through the utilization of magnetic field simulation software, the impact of 411 on the background magnetic field intensity of HGMS was analyzed. The results indicated that the newly developed 411 pure Fe exhibited a coercivity of 24.07 A/m, a saturation magnetization intensity of ∼ 1.69 T, a maximum relative magnetic permeability of 24.38 × 10-3H/m, demonstrating superior magnetic properties in comparison with Q235 and DT4C. When using 411 pure iron as the magnetic yoke material, the background magnetic field intensity of the HGMS can be increased by 6.85 % − 14.64 % compared with using DT4C super pure iron under the same excitation current conditions. The magnetic yoke with better magnetic conductivity will enhance the magnetic field utilization efficiency of the magnetic system, a reduce the excitation energy consumption, and improve the sorting performance of HGMS.

Using the reverse geometry method for warpage compensation on changing meshes with interpolation methods

AbstractIn the manufacturing process of injection molding, the geometric accuracy of the produced part is affected by shrinkage and warpage. To support efforts to compensate for these effects, this paper presents an extension of the numerical compensation approach known as the reverse geometry method. The reverse geometry method is based on the numerical forward simulation of the displacement field resulting from shrinkage and warpage. It is an iterative method that performs node‐based compensation in each step. The mention of node‐based compensation already indicates that the method is associated with a computational mesh. In particular, in its basic version, it is linked to a specific mesh that must be kept identical during all iteration steps. This requirement is not always compatible with commercial simulation tools for injection molding, which enforce automatic remeshing between simulations. We present an interpolation method that allows to handle changing meshes and illustrate the method with two practical examples.

Research on the Inner Surface Discharge of the Insulation Sheath of Electric Locomotive Cable Terminals

Adding an insulating sheath to the exposed metal part of the outer insulation of a roof cable terminal can extend the creepage distance of the leakage current and significantly reduce the probability of pollution flashover on the outer insulation of the equipment. However, during the actual operation of the locomotive, the inner surface of the insulating sheath is discharged, resulting in cable insulation breakdown, the mechanism of which is unclear. This paper establishes a cable terminal–sheath electric field simulation model and studies the interface air gap, the interface with wet pollution, and the distribution of damp pollution on the outer surface and other factors on the electric field distribution of the cable terminal–sheath structure and the interface discharge, revealing the mechanism of discharge on the inner surface of the cable terminal’s insulation sheath. A voltage of 25 kV rms is applied, and the simulation results show that when the outer surface of the cable terminal is clean and there are air gaps and wet dirt on the inner surface, the maximum distortion electric field at the inner surface is 0.8 × 105~3.4 × 105 V/m, and the value of the electric field at this time is not enough to cause a partial discharge; when there is a uniform layer of wet dirt on the outer surface of the cable terminal, the electric field on the inner surface averages 1.5 × 105 V/m, which is about 275% higher than the average electric field when the outer surface is clean; when there is wetting or an air gap on the inner surface at the same time, the maximum aberration electric field on the inner surface is 1.8 × 105~1.9 × 106 V/m. The wetting on the outer surface of the cable terminal strengthens the non-uniformity degree of the distribution of the electric field, and when there is wetting and an air gap on the inner surface, the over-voltage on the cable terminal inevitably leads to a discharge phenomenon in the air gap. This provides a theoretical basis for optimizing the insulation sheath structure to solve the discharge problem.

Influence of different vibration directions on the solder layer fatigue in IGBT modules

Insulated-gate bipolar transistor (IGBT) modules are extensively utilized in high-speed trains, ships, and electric vehicles. Compared to those used in power systems, IGBT modules in these applications are more susceptible to vibration effects on their reliability. This paper proposes a multi-physics field simulation method and a lifetime model for IGBT modules to assess the impact of different vibration directions on solder layer fatigue. Initially, a multi-physics field model of the IGBT module is developed, incorporating electrical, thermal, mechanical, and vibration coupling. The effectiveness of this multi-physics simulation model is verified by an experimental platform. Subsequently, the influence of different vibration directions on solder layer fatigue in the IGBT module is analysed, and a life model of the IGBT is proposed through simulation. Finally, a power cycling with a vibration environment experimental platform is established to validate the effect of vibration on solder layer fatigue in the IGBT module. The simulation and experimental results indicate that vertical vibration accelerates the solder layer fatigue of IGBT modules, and the lifetime of an IGBT module operating under vertical vibration at 30 Hz is about 15 % shorter than that of an IGBT module operating under power cycling alone. The error between the calculated results of the solder layer failure and the experimental result is <5 %.

A Green's Function Wind Turbine Induction Model That Incorporates Complex Inflow Conditions

ABSTRACTIn this work, we develop a new analytical turbine induction model that can incorporate complex inflow conditions including cases where the wind velocity and temperature profiles can vary as functions of height. This induction model is derived from the linearized Navier–Stokes and leads to a second‐order ODE that can be solved using a Green's function formulation. The corresponding Green's function for several configurations are found including the infinite domain, semi‐infinite domain with ground plane, and a power law velocity inflow profile. The results of this approach are then compared with simulations of the turbine induction field using the AMR‐Wind CFD solver with a uniformly loaded actuator disk model. These comparisons show that the Green's function approach captures the centerline blockage, three‐dimensional blockage flow field, and streamwise velocity slow down, with very good agreement for lower thrust conditions and at larger distances away from rotor disk. The effects of shear on the turbine blockage were also compared using a power law inflow profile, and we show that this approach matches the CFD predictions for the cases considered.

Comparisons of computer simulations and experimental data for capacitive hyperthermia using different split-phantoms

Introduction Several positive clinical trials have demonstrated that capacitive hyperthermia (CHT) improves the effectiveness of radiation therapy for the treatment of various cancer entities. However, the ability of CHT to induce significant heating throughout the body is under debate. Objectives To perform a pilot study involving comparisons of computer simulations and experimental data using different split-phantoms to validate hyperthermia treatment modeling for pre-planning for a clinical CHT system and to investigate the feasibility of split-phantom measurements in capacitive hyperthermia. Materials and methods The CHT system EHY-2030 (Oncotherm, Budapest, Hungary) was used. The system provides two electrode sizes, but only the smaller electrode, indicated as D200 electrode, was investigated in this pilot study. Horizontally and vertically splittable, different multi-slice phantoms with dielectric material properties simulating muscle and electrically low conductive fat were produced and heated. During the heating procedure, temperature-time curves were measured, and thermal images were captured. Specific absorption rate values were derived from the temperature rise (TR) values. Concomitantly, computer field simulations utilizing a detailed CAD-based model of the CHT system were performed using the simulation platform Sim4Life and compared with measurements. Results For the investigated electrode D200 the system power of 75 W was applied, which is half of the maximum power of 150 W and lies in the range of usual values for this electrode applied in patient treatments in our clinic. For 75 W, a heating of 3.6 °C in 6 min in a depth of 1 cm in an agar-based, muscle tissue-equivalent phantom was achieved. The addition of a 1 cm thick, synthetic, low dielectric fat layer reduced the TR up until a depth of 8.5 cm by on average around 38% (from 8.5 cm onwards the absolute local TR is similar, deviations are ≤0.1 °C). In terms of point-to-point absolute SAR comparison (without any normalization), up to a depth of 11 cm in the phantoms central vertical plot, the simulation differs from the measured TR points by on average 25% (ranging from 7% to 36%) for the homogeneous phantom and by on average 43% (ranging from 26% to 60%) for the inhomogeneous phantom. Conclusion Computer simulations and experimental data were compared for the CHT system EHY-2030 using the D200 electrode, applying a thermal imaging technique for different vertically splittable phantoms. This pilot study data can be used as a guidance regarding the expected heating for this commonly used electrode size but also to further elucidate the significance of non-thermal anticancer effects. Further studies are needed for different sizes and geometries of electrodes and phantoms.

Impact of Secondary‐Phase Particle Morphology on Grain Growth in Pure Copper Using a Phase Field Simulation Approach

Impact of Secondary‐Phase Particle Morphology on Grain Growth in Pure Copper Using a Phase Field Simulation Approach

Modeling and simulation of novel bio-emulated flow field with improved branch channels on PEMFC performance

The channel geometry of the bipolar plate in the proton exchange membrane fuel cell (PEMFC) significantly influences its performance. In this study, a bio-emulated flow field (BEFF) pattern in the bipolar plate was used based on the external carotid artery design with its branches. A comprehensive investigation was conducted using a three-dimensional (3-D) multiphase computational fluid dynamics (CFD) model on bio-emulated flow fields with branch channels of zero (BE-0), six (BE-6), and ten (BE-10). The results obtained were compared with traditional parallel flow fields (TPFF) and traditional serpentine flow fields (TSFF). The BE-10 results showed reduced pressure drop, uniform distribution of reactants, and higher power output compared with other configurations. The peak power density of BE-10 surpassed that of TPFF by approximately 45.07% and exceeded BE-0 by 10.39%. The novel BEFF structure with an increase in branch channels showed that the reactants, temperature, and static pressure distribution are more uniform with better water management.

Evaluation of a cross-border field simulation exercise on the response to outbreaks of infectious diseases in Namanga, Kenya and Tanzania.

Travel and trade, whilst playing a critical role in economic development, contribute to the spread of infectious diseases, including novel or emerging diseases, which can threaten health security locally, regionally and globally. The World Health Organization mandates preparedness through field simulation exercises to address infectious disease outbreaks, as highlighted by the COVID-19 pandemic. This study assessed the impact of the 2019 Namanga field simulation exercise, conducted in the border town shared by Kenya and Tanzania, on improving cross-border outbreak preparedness and response. It focused on participants' knowledge, skills acquisition and real-world application. An anonymous online survey was administered to participants 37 months post-field simulation exercise. In addition, key informant interviews and a focus group discussion with the Joint Border Management Committee in Namanga were conducted. The June 2019 field simulation exercise enhanced the skills, knowledge, and confidence of participants, including members of the border community, in preparing for and responding to outbreaks including COVID-19. The skills and knowledge gained were deemed valuable, relevant, and effective for use in future response activities. The analysis is limited by potential response bias, as only participants with positive experiences of the field simulation exercise may have responded more favourably. Addressing the limitations of design and implementation of the field simulation exercise and the challenges of cross-border response identified in this study are critical to optimising future responses.

Development of a Meander-Coil-Type Dual Magnetic Group Circumferential Magnetostrictive Guided Wave Transducer for Detecting Small Defects Hidden behind Support Structures.

In order to solve the problem that small defects hidden behind pipeline support parts are difficult to detect effectively in small spaces, such as offshore oil platforms, a meander-coil-type dual magnetic group circumferential magnetostrictive guided wave transducer is developed in this paper. The transducer, which consists of a coil, two sets of permanent magnets, and a magnetostrictive patch, can excite a high-frequency circumferential shear horizontal (CSH) guided wave. The energy conversion efficiency of the MPT is optimized through magnetic field simulation and experiment, and the amplitude of the defect signal is enhanced 1.9 times. The experimental results show that the MPT developed in this paper can effectively excite and receive CSH2 mode guided waves with a center frequency of 1.6 MHz. Compared with the traditional PPM EMAT transducer, the excitation energy of the transducer is significantly enhanced, and the defects of the 2 mm round hole at the back of the support can be effectively detected.

An investigation on energy-saving scheduling algorithm of wireless monitoring sensors in oil and gas pipeline networks

With the rapid development of the oil and gas industry, monitoring the safety and efficiency of pipeline networks has become particularly important. In this context, Wireless Sensor Networks (WSNs) are widely used for monitoring oil and gas pipelines due to their flexible deployment and cost-effectiveness. However, since sensor nodes typically rely on limited battery power, extending the network’s lifecycle and improving energy utilization efficiency have become focal points of research. Therefore, this paper proposes an energy-saving scheduling algorithm based on transformer networks, aimed at optimizing energy consumption and data transmission efficiency of wireless monitoring sensors in oil and gas pipelines. Firstly, this study designs a deep learning-based Transformer model that learns from historical data on energy consumption patterns and environmental variables to predict the energy and data transmission needs of each sensor node. Secondly, based on the prediction results, this algorithm employs a dynamic scheduling strategy that automatically adjusts the sensor’s operational mode and communication frequency according to the node’s energy status and task urgency. Additionally, we have validated the effectiveness of the proposed algorithm through field tests and simulation experiments. According to the experimental results, our model has higher efficiency in energy saving. Compared with Convolutional Neural Networks, Recurrent Neural Networks and Graph Neural Networks, the total energy consumption of sensor networks under the model scheduling in this paper was reduced by 6.7%, 33.4% and 26.3%, respectively. Our algorithms improve the energy efficiency and stability of the monitoring system and provide important technical support for future intelligent pipeline monitoring systems. We hope this paper will inspire future scientific research in this field.

Implementation of frozen density embedding in CP2K and OpenMolcas: CASSCF wavefunctions embedded in a Gaussian and plane wave DFT environment.

Most chemical processes happen at a local scale where only a subset of molecular orbitals is directly involved and only a subset of covalent bonds may be rearranged. To model such reactions, Density Functional Theory (DFT) is often inadequate, and the use of computationally more expensive correlated wavefunction (WF) methods is required for accurate results. Mixed-resolution approaches backed by quantum embedding theory have been used extensively to approach this imbalance. Based on the frozen density embedding freeze-and-thaw algorithm, we describe an approach to embed complete active space self-consistent field simulations run in the OpenMolcas code in a DFT environment calculated in CP2K without requiring any external tools. This makes it possible to study a local, active part of a chemical system in a larger and relatively static environment with a computational cost balanced between the accuracy of a WF method and the efficiency of DFT, which we test on environment-subsystem pairs. Finally, we apply the implementation to an oxygen molecule leaving an aluminum (111) surface and a ruthenium(IV) oxide (110) surface.

Strain-controlled switching of magnetic skyrmioniums in ultrathin nanodisks

Magnetic skyrmions and skyrmioniums have garnered significant attention due to their distinctive topologically nontrivial spin structures. Gaining a deep understanding of the magnetization dynamics of these structures and their interconversion processes is essential for fully leveraging their potential in magnetic storage technology. Here, the dynamics of strain-controlled generation and annihilation of skyrmions and skyrmioniums are investigated using phase field simulation methods. It is discovered that tensile strain can induce the transformation of a single domain into skyrmions and skyrmioniums, which can still exist stably after the strain is released. Notably, skyrmioniums demonstrate robust stability within a specific strain window of −0.2% to 0.5%. Beyond this, escalating the compressive strain magnitude induces a phase transition from skyrmioniums to skyrmions, culminating in a direct collapse to a single-domain state at a critical compressive strain of −0.8%. This study reveals that strain can effectively control a variety of topological magnetic domain structures and achieve their interconversion, providing guidance for the design of low-power, nonvolatile, multi-state spin storage devices.

Numerical assessments of geometry, proximity and multi-electrode effects on electroporation in mitochondria and the endoplasmic reticulum to nanosecond electric pulses

Most simulations of electric field driven bioeffects have considered spherical cellular geometries or probed symmetrical structures for simplicity. This work assesses cellular transmembrane potential build-up and electroporation in a Jurkat cell that includes the endoplasmic reticulum (ER) and mitochondria, both of which have complex shapes, in response to external nanosecond electric pulses. The simulations are based on a time-domain nodal analysis that incorporates membrane poration utilizing the Smoluchowski model with angular-dependent changes in membrane conductivity. Consistent with prior experimental reports, the simulations show that the ER requires the largest electric field for electroporation, while the inner mitochondrial membrane (IMM) is the easiest membrane to porate. Our results suggest that the experimentally observed increase in intracellular calcium could be due to a calcium induced calcium release (CICR) process that is initiated by outer cell membrane breakdown. Repeated pulsing and/or using multiple electrodes are shown to create a stronger poration. The role of mutual coupling, screening, and proximity effects in bringing about electric field modifications is also probed. Finally, while including greater geometric details might refine predictions, the qualitative trends are expected to remain.