Multi-physical Field Coupling Research Articles

Simulation Study of Transient Eddy Current Effect in 3T Animal Gradient Coil

In the process of high-field magnetic resonance imaging (MRI), the eddy current modeling and simulation of the cold screen and metal parts are not highly accurate. To solve this problem, this paper uses the target field method to design a 3T animal gradient coil model. To get more realistic simulation results, a complex model including a gradient system, cryogenic vessel, cold screen, epoxy resin, and temperature holes was constructed. The model was refined using the finite element method, and the effects of eddy currents induced by the gradient coil on the cylindrical cryogenic container and cold screen in the superconducting magnetic resonance instrument under the state of multi-physical field coupling were simulated. The model effectively reflects the transient eddy current distributions on the cold screen and cryogenic vessel in the MRI system and their time-dependent temperature rise effects.

Special Issue on the Geo-Environmental Problems Caused by Underground Construction

Geo-environmental disturbances refer to the significant changes in physical, mechanical, and even chemical properties of soils; are closely related to interrelated multi-physical field coupling systems of solid particles, water, and gas in the shallow stratum; and are caused by underground engineering construction [...]

Analysis and Optimization of Contact Material Ablation under the Cumulative Effect of the Number of Breakings of OLTC.

Vacuum on-load tap-changers (OLTC) for converter transformers have a much higher number of breakings than conventional circuit breakers. Contact ablation after several breakings will affect the stability and life of the device. This paper establishes the electromagnetic thermal multi-physical field coupling model of the vacuum interrupter for OLTC based on the finite element analysis method. The thermal field distribution of normal and ablative contact materials during the breaking process was analyzed. The key parameters affecting the contact temperature under the cumulative number of breakings are analyzed and the optimized design is completed. The simulation results show that the contact surface reaches a maximum temperature of 1390 K at 8 ms. There is a significant increase in the area of the high-temperature area on the contact surface. The possibility of re-ignition of the interrupter is increased. Based on the judgment matrix method, the key influencing parameters of the contact temperature rise are analyzed. The final parameters are selected as follows: contact material-CuCr8 alloy, contact seat thickness-2 mm, contact thickness-10 mm, and contact diameter-40 mm.

Optimized Design Method of Dry Type Air Core Reactor Based on Multi-Physical Field Coupling

A 3D simulation model of dry-type air core reactors is established through the multi-physical-field coupling method based on an electromagnetic-temperature-structural field, and the electromagnetic distribution characteristics, temperature, and structural deformation of the reactor are analyzed. The inductance, temperature rise, structural deformation, and amount of metal conductors of the reactor are the optimization parameters. Initially, the sample data was obtained through the orthogonal test method and multi-physical-field coupling simulation; then, the VIKOR (Vise Kriterijumski Optimizacioni Racun) method was used to equalize and control the electromagnetism, temperature rise, structural deformation, and metal conductor consumption of the reactor. Finally, multi-physical-field coupling technique is used to verify the correctness of the method. The results show that the inductance deviation of the optimized reactor is 4.51%, the highest temperature and the maximum deformation of the encapsulation coil are reduced by 13.5% and 0.52%, and the metal conductor mass of the coil increases by 7.57%, which meet the design requirements.

Coupling flow and electric fields to simulate migration and remediation of uranium in groundwater remediated by electroosmosis and a permeable reactive bio-barrier

Combined remediation technologies are increasingly being considered to uranium contaminated groundwater, such as the joint utilize of permeable reactive bio-barrier (Bio-PRB) and electrokinetic remediation (EKR). While the assessment of uranium plume evolution in the combined remediation system (CRS) have often been impeded by insufficient understanding of multi-physical field superposition. Therefore, advanced knowledge in multi-physical field coupling in groundwater flow will be crucial to the practical application of these techniques. A two-dimensional multi-physical field coupling model was constructed for predicting the uranium degradation in CRS. The study demonstrates that the coupling model is able to predict the uranium plume evolution and rapidly evaluate the performance of CRS components. The results show that field electric direction and flow field strength are the key factors that affect the retardation and remediation performance of CRS. The reverse electric field direction significantly affected the contact reaction time of uranium in the system. The uranium residence time in the reverse electric field was 3.8 d, which was significantly greater than the original electric field (2.0 d). Depending on the voltage, the reverse electric field direction was 16%–36% more efficient than the original direction. The strength of the flow field was about two orders of magnitude higher than that of the electric field, so the groundwater flow rate dominated remediation efficiency. Reducing the flow rate by 1/2 could improve the performance of the system by approximately 66%. In addition, the coupling model can be utilized to design standard CRS for real site of uranium contaminated groundwater. To meet the optimal performance, the direction of the electric field should be set opposite to the flow field. This work has successfully used a coupling model to predict uranium contaminant-plume evolution in CRS and estimate the performance of each component.

A Compact Microwave-Driven UV Lamp for Dental Light Curing

The size of current microwave-driven UV lamps limits their direct application in dental light curing. This article proposes a coaxial structure to miniaturize the UV lamp. First, the Drude model and the finite difference time domain algorithm were used to analyze the multi-physical field coupling and the complex field distribution within the lamp. Second, the dimensional parameters of the lamp were optimized, which enabled the lamp to be miniaturized and operate with high performance. Third, to analyze the sensitivity of the lamp, the effects of input power, gas pressure, and gas composition on its performance were investigated. It was found that an input power of 6 watts was enough to light the bulb with over 90% energy utilization. Finally, to verify the feasibility, an experimental system was set up. The lamp was successfully lit in the experiment, and its spectral output was tested. The results show that the microwave-driven UV lamp based on a coaxial structure is miniaturized and broad-spectrum, making it suitable for clinical dental light curing.

A Broadband, High-Power Resonant Piezoelectric Active-Valve Pump Driven By Sandwich Bending Transducers

A resonant piezoelectric active-valve pump driven by the serial connected there-chambers is proposed based on three sandwich bending transducers (SBTs). The pump possesses the superiorities of high bandwidth and high output power. The configuration and driving principle of the pump are designed and studied. The wet modal and frequency response analyses are performed to determine the resonant frequency and output displacement, and their consistencies are also evaluated. The multi-physical field coupling model of the pump is established by bi-directional fluid structure interaction. The influences of frequency and outlet pressure of the pump on flowrate characteristics at different voltages are revealed. A physical prototype of the pump is manufactured and the tested setup is constructed to measure the output performances. This work shows that the maximum flowrate of the pump is 345 mL/min at 1.95 kHz; the maximum pressure can reach up to 242 kPa at 2.05 kHz. Besides, the self-filling pressure is 78 kPa; and the maximum driving power is 432 mW with an outlet pressure of 125 kPa. The results show that the developed pump is expected to be used in the hydraulic drive system of UAV variable swept wing.

Multi-physics coupling analysis of high-power IGBT module bonding wires fault considering stray inductance of main circuit

The insulated gate bipolar transistor (IGBT) module is subjected to unbalanced electric-thermal stress for a long time due to its own turn-on and turn-off, the fluctuation of processing power and the change of external operating environment, resulting in fatigue failure. And there is a strong coupling effect between its electrical, temperature and mechanical properties. At the same time, the fatigue failure of IGBT module is also the result of multi-physical field coupling. This paper reveals the influence mechanism of main circuit stray inductance on the electric-thermal-stress coupling characteristics of high power IGBT module bonding wires fault in the context of mine-used inverter application. First, the inverter main circuit topology model considering stray inductance is constructed, and the loss value of the power chip is obtained based on extracting the busbar stray inductance and establishing the IGBT module behavior model, and the validity of the results is verified. Secondly, the package structure model of IGBT module is established and the failure analysis boundary conditions are determined, and then the joint circuit-finite element method is used to reveal the operation behavior characteristics of IGBT module under the combined action of multi-physical fields. Finally, the influence of main circuit stray inductance on the multi-physical field coupling characteristics of IGBT module and its change law are compared and analyzed under the bonding wires fault condition to study the causes of fatigue failure of IGBT module.

An internal ballistic model of electromagnetic railgun based on PFN coupled with multi-physical field and experimental validation

To accelerate the practicality of electromagnetic railguns, it is necessary to use a combination of three-dimensional numerical simulation and experiments to study the mechanism of bore damage. In this paper, a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun, and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network (PFN) is carried out. Various test methods such as spectrometer, fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity, transient magnetic field strength and stress-strain of rail. Combining the simulation results and experimental data, the damage condition of the contact surface is analyzed.

Thermal insulation performance and dynamic response of anti-freeze subgrade of high-speed railway in seasonally frozen regions

In order to counteract the adverse effects of seasonally frozen regions, measures need to be taken to insulate high-speed railway subgrades and implement anti-freeze structures. The present study delves into this topic by analyzing the thermal–mechanical behaviors of railway subgrade through on-site measured data. Then, using the hydrodynamic theory, a model of frozen soil with Multi-physical field coupling is built, on which the temperature field and frost heave development of six different subgrade structures are explored, and produces a vehicle-track-subgrade coupling dynamic model that is used to calculate the dynamic performance of vehicles and the dynamic response transfer between subgrade layers under the influence of different anti-freeze subgrade structures. The results show that the subgrade structure built using concrete insulation (asphalt concrete (AC) or cellular concrete (CC)) + cement stabilized crushed stone (CSCS) + polyurethane (PU) panel mitigates the impact of external air temperatures and internal cooling, helping to reduce the maximum frost heave while simultaneously achieving improved thermal insulation. Further, these anti-freeze subgrade structures also bolster the safety and stability of high-speed railway vehicle operations. Therefore, it is suggested that the “concrete insulation layer + CSCS layer + PU panel” structures be utilized as a reference during the design of subgrade structures in seasonally frozen regions.

Microstructural evolution of joints with and without Sb, Ni in Sn58Bi solder under electro-thermal-force coupling

Severe atomic migration occurs in the solder under the effect of multi-physics field coupling, leading to serious reliability problems. Under the influence of multi-physics field coupling, severe atomic migration occurs in solder, resulting in significant reliability issues. In Cu/Sn58Bi/Cu joints subjected to 0.5 × 104 A/cm2 current density and temperature cycling from −45 °C to 60 °C, the primary diffusing atom was Bi. However, when the temperature range was extended to −45 °C–90 °C, Cu atoms became the primary diffusing species. This led to rapid thickening of the interfacial intermetallic compound (IMC) and failure due to penetration cracks and excessive consumption of the Cu interconnect layer. The addition of Sb to Sn58Bi to form (Cu, Sb)6Sn5 IMC inhibited Cu atom migration and mitigated rapid dissolution of the Cu interconnect layer and overgrowth of the interfacial IMC. The formation of a biphasic structure adjacent to the interfacial IMC improved joint deformability and prevented premature joint failure. COMSOL analysis revealed that the highest current densities in the Cu/Sn58Bi/Cu interconnect layer and solder joint were 6.041 × 104 A/cm2 and 1.368 × 104 A/cm2, respectively, under the influence of 0.5 × 104 A/cm2 current. The current density in the Cu interconnect layer was 4–5 times higher than that inside the solder joint. However, the addition of Ni formed (Cu, Ni)6Sn5 IMC, promoting Cu atom diffusion and accelerating joint failure under multi-physics field coupling. This study provides key insights into how alloying elements modulate atomic migration in Sn–Bi-based solder joints.

Mechanism analysis using multi-physical field coupling: Silicon carbide-assisted microwave heating of UMT-coated soil

To immobilize radionuclides in the soil of uranium mill tailing (UMT), the microwave vitrification method is considered as a promising alternative. In order to examine how changing microwave power and sample size affects microwave heating, a numerical model is constructed here that considers electromagnetic and heat transmission. The simulation findings demonstrate that a silicon carbide (SiC) susceptor and microwave aid can be used to treat the soil in UMT using microwave power. Due to the economic advantages, a 400 W microwave input power adds significantly to thermal heterogeneity. The size of the soil samples is also important since it affects how microwaves heat the soil and how the heat is distributed. The 20 mm in diameter, 10 mm thick soil sample performed the best under the 400 W input power.

Numerical Simulation of Plasma Igniter Efflux Characteristics Based on Multi-Physical Field Coupling

To explore the chamber plasma jet ignition effect, the establishment of pre-chamber plasma jet ignition based on a 3D model using the method of numerical simulation was carried out on the working process of the plasma ignition numerical calculation. The analysis of firearms in the combustion chamber ignition characteristics provided a reference for the ignition performance boost. The results show that the jet velocity at the igniter outlet can reach 78 m/s and the jet temperature can reach 2300 K, which makes the hot jet spread far enough in the reflux area and ensures that the jet can achieve the effect of heating and igniting in a larger area. The mixture in the air reacts with the kerosene position along the border, ignition in the igniter fine channel before export, igniter speeding up the export position of flow velocity, the jet core region of the temperature of 2400 K, the igniter export position of kerosene component concentration was 45%, the concentration of O2 was 20%, the H2O concentration was 15%, and the CO2 concentration was 7%. The ratio of air to kerosene should be such that the two flow at similar speeds in the mixing area.

Multi-physical field coupling simulation and thermal design of 10 kV-KYN28A high-current switchgear

Switchgear is a key equipment in the power grid, which is widely put into operation in substations and distribution networks. The development trend of high voltage, high current, miniaturization, and long life has put forward higher requirements on the heat dissipation performance of switchgear, which is of great significance to the controllability, stability, and power expansion of the equipment. The current heat dissipation measures are single and not strongly targeted. This paper adopts the multi-physical field coupling simulation method and proposes relatively efficient and reliable solutions for the cooling of the whole switchgear and the contact overheating problem. The main conclusions are as follows: (1) At the same inlet velocity, the heat transfer coefficients of the upper three-phase busbar are higher for T1T2, S2T2, and B2T2. When the inlet velocity v = 2 m/s, its average value is 51.4% higher than that of the other three variants. The heat transfer coefficient of T1T2 (v = 2 m/s) reaches the maximum, hupper = 3.9 W/(m2∙K). (2) The fans should be placed on the top of the switchgear as a priority, and the heat dissipation effect and cooling efficiency of T1T2 (v = 2 m/s) are the best, with the maximum FOM = 5.4 and the minimum maximum temperature Tmax = 73.2 °C. (3) The radiator should be combined with the fan to achieve better heat dissipation. When the bending angle is θ = 180° and the inlet velocity is v = 1 m/s, the heat dissipation is 56.1% higher than natural convection, and the Tmax is reduced by 16.4 °C, which is 20.9% lower than that of natural convection.

Numerical study of the fracture propagation mechanism of staged methane deflagration fracturing for horizontal wells in shale gas reservoirs

The staged methane deflagration fracturing of horizontal wells is a new reservoir stimulation method serving the high-efficiency exploitation of shale gas reservoirs. To study the propagation mechanism of deflagration fracture, a multi-physics field coupling numerical model of deflagration fracturing considering the synergistic effects of stress impact and gas wedging is constructed based on the continuum-discontinuum element method (CDEM). The linear elastic constitutive and the tensile-shear composite constitutive models considering strain softening are applied to the block element and the interface element, respectively, and the cubic law is designated to describe the flow of explosion gas in the fracture element. The CDEM model is solved explicitly and iteratively by dynamic relaxation technology, and a calculation module of deflagration pressure is developed by programming. Then, numerical studies of staged methane deflagration fracturing in horizontal wells under different factors are performed. The results indicate that methane deflagration fracturing could overcome the stress concentration around the well, forming 5–8 main fractures of about 4.7 m in each section. Peak pressure has the most significant effect on the methane deflagration fracturing, with an influence degree of up to 2.72%. When the peak pressure increases from 150 MPa to 340 MPa, the reservoir fracture degree increases by 6.17% and the fracture half-length of σH direction increases by 0.99 m. When the in-situ stress difference increases from 0 to 30 MPa, the main fracture distribution of the staged deflagration fracturing is more crowded and the fracture half-length can increase by about 1.1 m. The increase in the deflagration section number and the deflagration section spacing is conducive to increasing the reservoir fracture degree and the deflagration fracture range. The maximum fracture length in the σH direction of each section is almost equal, which is useful for realizing the uniform extension of fractures in multistage fracturing.

Investigation of the Degradation Mechanism of SiC MOSFET Subjected to Multiple Stresses.

The performance requirements for power devices in airborne equipment are increasingly demanding, while environmental and working stresses are becoming more diverse. The degradation mechanisms of devices subjected to multiple stresses become more complex. Most proposed degradation mechanisms and models in current research only consider a single stress, making it difficult to describe the correlation between multiple stresses and the correlation of failures. Then, a multi-physical field coupling model based on COMSOL is proposed. The influence relationship between temperature, moisture, electrical load, and vibration during device operation is considered, and a three-dimensional finite element model is built to investigate the multi-stress degradation mechanism under multi-physical field coupling. The simulation results show that, compared with single-stress models, the proposed multi-stress coupled model can more accurately simulate the degradation process of SiC MOSFET. This provides references for improving the reliability design of power device packaging.

Intermittent injection of carbon dioxide to control the risk of coal spontaneous combustion and methane explosion: A case study in U-type ventilation

The compound risk of coal spontaneous combustion (CSC) and methane (CH4) explosion poses a serious threat to mining safety. Green resource utilization of carbon dioxide (CO2) can help achieve carbon neutrality. Therefore, CO2 is seen as a means to prevent compound risk of CSC and CH4 explosion. To address the situation at the 4209 working face, a multi-physical field coupling model was established to simulate the CSC and CH4 explosion in the gob of a U-type ventilation system. The accuracy of the model was verified against measured data from the gob. Following the injection of CO2 into the gob, the volume of the compound risk area was significantly reduced. The effects of intermittent CO2 injection were compared to those of continuous injection, and it was determined that intermittent injection was the preferred method, taking injection cost into account. Three injection frequencies were tested, with F= 1/2 d showing the optimal effect. When the injection frequency was set to F= 1/2 d, and three CO2 injection flow rates were tested, it was demonstrated that a flow rate of 141.3 m3/h provided the most effective risk reduction while meeting the required CO2 concentration in the working face.

Multi-Physical Analysis and Optimization in Integrated Lithium Niobate Modulator Using Micro-Structured Electrodes

With the increase in the modulation rate of thin-film lithium niobate (LiNbO3, LN) modulators, the multi-physical field coupling effect between microwaves, light, and heat becomes more significant. In this study, we developed a thin-film LN modulator model using undoped pure LN thin film and T-shaped slow-wave electrodes. Furthermore, we utilized this model to simulate the microwave heating and light heating situations of the modulator. The temperature of the LN modulator was analyzed over time and with different signal frequencies. We also studied the influence of temperature rise on microwave and light signals, and we analyzed the change of S parameters and the Phase Shift of the light signal caused by temperature rise. Finally, we improved the thermodynamic characteristics of the modulator by adding a diamond heat dissipation layer. The diamond was obtained through the Chemical Vapor Deposition (CVD) technique and was a polycrystalline diamond. After adding the diamond heat dissipation layer, the temperature rise of the modulator was significantly improved, and the adverse effects of temperature rise on microwave signals were also significantly reduced.

Design and optimization of superconducting CUSP electromagnetic field structure based on a COMSOL-GMDH-MOSO hybrid strategy

As the semiconductor industry gains momentum, there is a significant focus on producing high-quality silicon wafers with larger diameters. However, the preparation of major-diameter, high-quality silicon single-crystal has encountered challenges such as intense convection inside the melt and high oxygen impurity concentration at the interface between the fluid and solid phases. To tackle these problems, the external superconducting CUSP electromagnetic field structure was designed to optimize the crystal growth parameters. A hybrid strategy of the multiphysics field coupling method, Group Method of Data Handling (GMDH) type neural network identification, and the Multiple Objective Snake Optimizer (MOSO) algorithm was proposed to optimize the superconducting CUSP electromagnetic field structure. A two-dimensional axisymmetric model was established for 18-inch silicon single-crystal preparation using the Magnet system Applied Czochralski (MCZ) method. The amount of longitudinal plies of superconducting CUSP electromagnetic field coils, coil spacing, and the thickness of magnetic shields were selected as design variables, and the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume were used as dual objective functions. The required samples for GMDH training were provided by COMSOL Multiphysics (COMSOL) numerical calculations, and polynomial mathematical equations were established with the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume as the dual objective functions. Then the Pareto optimal solution for the electromagnetic field structure design variables was obtained using the dual objective function optimized by MOSO. With the hybrid strategy, numerical simulations and theoretical analysis of the crystal preparation process parameters under the effect of the superconducting electromagnetic field with the optimal structure were carried out. The results displayed that the added superconducting CUSP electromagnetic field reduced the crystal radial and axial thermal gradients and greatly suppressed the melt convection. As a result, the heat distribution inside the hot fused silicon was more even, the thermal gradient at the solid–liquid interface was reduced by 68.4%, and the oxygen impurity content was reduced by 82.1%, which effectively improved the crystal quality. The thermal field simulation results verified that the proposed hybrid strategy provided a new numerical calculation method for obtaining the optimal superconducting electromagnetic field structure.

Numerical Simulation Analysis of Three-phase Submerged Arc Furnace Using the Multi-field Method

To reveal the distribution law of the multi-physics field in the smelting of the submerged arc furnace, the temperature distribution in the furnace for a given electrode diameter was studied, and the multi-physics field coupling model of the submerged arc furnace was established, based on Maxwell’s equation, Ohm’s law, numerical analysis of fluid governing equations and heat transfer mechanism. The results show that the current density is mainly affected by the skin effect on the surface of the electrode, with a maximum value of 35000 A/m2; the Joule heat is mainly concentrated at the bottom of the electrode in the material layer; the maximum value of the magnetic flux density is at the electrode pole center circle, about 0.02 T; the flow of the fluid in the molten pool is affected by the Lorentz force and gravity, and the distribution of the Lorentz force in the slag layer is more obvious; the maximum temperature in the furnace reaches 2500°C and is located at the bottom of the electrode, which is gradually transferred from the material layer to the slag layer.