Multi-physics Coupling Analysis Research Articles

Comparative Study of Simulation of Temperature Rise in Ring Main Unit.

The Ring Main Unit (RMU) is a critical device in power distribution systems used for connecting and distributing electricity. However, due to its compact internal structure and high current load, heat dissipation issues are particularly prominent. To address this problem, this study innovatively proposes a simplified RMU model, employing finite element simulation methods to accurately solve for the ohmic losses of conductors under actual operating conditions and obtain ohmic loss data for various components. This is the first in-depth investigation of the RMU's temperature rise problem using such a comprehensive approach. Subsequently, the temperature field was solved using two different temperature field analysis modules, with a detailed comparison and analysis of the simulation results to identify similarities, differences, and trends in temperature distribution. The results indicate that the temperature field solution model, which considers convective heat transfer, is more accurate and aligns with actual operating conditions. This research provides an innovative approach and practical solutions for the design and optimization of RMUs. Future research can further explore multiphysics coupling analysis methods to address structural design and mandatory validation issues for high and ultra-high voltage RMUs and other electrical equipment, thereby providing important insights for engineering design.

Research on Improved Crystallization Properties and Underlying Mechanism of the Sb2Te3 Phase-Change Thin Film by Inserting Sn15Sb85 Layers.

As a non-volatile semiconductor memory technology, phase-change memory has a wide range of application prospects as a result of the excellent comprehensive performance. In this paper, multilayer thin films based on Sb2Te3 material were designed and prepared by inserting the Sn15Sb85 layer. The thermal and electrical properties of superlattice-like Sb2Te3/Sn15Sb85 phase-change films can be adjusted by controlling the thickness ratio of Sb2Te3/Sn15Sb85. In comparison to the monolayer Sb2Te3 film, the multilayer layer Sb2Te3/Sn15Sb85 materials have a higher crystallization temperature, larger crystallization activation energy, and longer data lifetime, indicating the great improvement of thermal stability. The changes in the phase structure and vibrational modes of multilayer Sb2Te3/Sn15Sb85 films were characterized by X-ray diffraction and Raman spectroscopy, respectively. The presence of Sn15Sb85 layers restrains grain growth and refines the grain size. The multilayer Sb2Te3/Sn15Sb85 films exhibit better surface flatness, smaller surface potential undulation, and lower thickness variations than single-layer Sb2Te3. Phase-change memory cells based on the [Sb2Te3 (1 nm)/Sn15Sb85 (9 nm)]5 thin film has a lower threshold voltage (1.9 V) and threshold current (3.1 μA) compared to the Ge2Sb2Te5 film. Meanwhile, the electrical heating model of a phase-change memory cell based on a [Sb2Te3 (1 nm)/Sn15Sb85 (9 nm)]5 multilayer structure was established by multiphysics coupling analysis, proving the great improvement in heat transfer performance and efficiency. The experimental and theoretical studies confirm that the insertion of the Sn15Sb85 layer can significantly improve the crystallization properties of Sb2Te3 films, paving the way for optimizing the phase-change materials by regulating the microstructural parameters.

Nonlinear coupled multi-physics field analysis of permanent magnet synchronous motor combining finite element analysis with optimized meshless method

Aiming at significant disadvantages of finite element analysis (FEA) performed in coupled multiphysics field calculation, including high computing cost and strong dependency on meshing quality. Taking a high-speed permanent magnet synchronous motor (P MSM) as an example, an approach combining FEA with optimized meshless method is proposed to solve the heat transfer problem. Firstly, electromagnetic losses under rated and 1.2 times overloaded operation conditions are calculated using FEA respectively. Secondly, three-dimensional FEA flow models considering the influence of viscosity varying with temperature are established. Thirdly, convective heat transfer coefficients are calculated as the boundary condition, after which the electromagnetic losses as heat sources are mapped to the threedimensional steady-state temperature field calculations using FEA and conventional meshless method respectively. Applying the above two methods, a singular boundary method (SBM) is employed to replace the temporal derivative term of the transient calculation equation. Finally, to mitigate the illconditioned matrix appearing in the conventional meshless method coupled with FEA, an optimized meshless method is proposed to recalculate the heat transfer equation. After that, the calculation results of the above methods are compared with experimental results. This research is beneficial for the multiphysical coupling analysis of electrical equipment with complex structures considering nonlinear factors.

Enhancing external quantum efficiency of deep ultraviolet micro-leds through geometry design and multi-physics field coupling analysis

Abstract High-efficiency deep-ultraviolet (DUV) micro light-emitting diodes (LEDs) are explored for inspiring development in numerous fields, such as non-line-of-sight solar-blind communication, optical pumping, and maskless lithography. In this study, we performed FDTD and SimuLED calculations to investigate the optimized DUV micro-LED structure geometry for high light extraction efficiency (LEE) by designing different mesa structures, including square, hexagonal, and circular geometries of micro-LEDs emitted at a wavelength of 275 nm. The results showed that a circular mesa of 5 μm diameter achieved a LEE of 27% from the bottom and sidewall emissions of as-prepared DUV micro-LED. And both the near- and far-field transverse magnetic polarized light intensities were enhanced by a factor of 1.5 over the square and hexagonal mesas. Meanwhile, the transverse electric (TE) polarized light of the circular mesa structure was enhanced and concentrated along the normal direction. Moreover, the internal quantum efficiency (IQE) of circular mesas with varied sizes was comprehensively investigated in the interactions of the thermal and electric fields. An AlGaN-based DUV micro-LED with a diameter of 5 μm was found to obtain the highest IQE owing to a high current-density distribution and its self-heating properties, thereby achieving a sufficiently high external quantum efficiency of 26.75%. This study provides a comprehensive technical report, including electrical, thermal, and optical analyses, and a new perspective for developing high-efficiency, high-performance DUV micro-LEDs in practical applications.

Research on multi-physical field analysis and assessment technique of virtual connection defects in cluster cable joints based on digital twin technology

As the “blood vessels” and “nerves” of the power grid, cables are important carriers for transmitting electric energy, and their failures will affect the safe and stable operation of the power grid. In this paper, a digital twin model of thermal characteristics is constructed for 10 kV YJV×400 cluster cable and its joint model. Based on the multi-physical field coupling analysis method, the fluid field, temperature field and current-carrying capacity of the cluster cable are analyzed. The temperature rise and airflow distribution characteristics of the joint and its external insulation when the defect of joint false connection occurs are analyzed. Based on the fuzzy analytic hierarchy process (FAHP), weights are assigned to the locations of multiple measurement points of the cable external insulation, and the temperature distribution of each measurement point is combined with the digital twin technology to calculate the hot spot temperature of the cable, so as to assess the defects of the joints of the cables. The digital twin platform is used for real-time monitoring of cable status and assessment of defects. The temperature rise experiments of cables under different carrying capacity and joint defects show that this method can accurately and efficiently calculate hot spot temperatures and assess defects of joints in cluster cables.

Electromagnetic–thermal field coupling in tissue ablation: The EAES design and optimization

The coupling control of multi-physics fields has become a focal issue in the engineering domain, especially for achieving a more precise simulation and prediction of physical phenomena. This approach plays a crucial role in enhancing design efficiency and optimizing material selection. Focusing primarily on the controllability between microwave and temperature fields, the Emission Area Extension Structure (EAES) is a novel structure in response to the demand for high circularity in microwave ablation. Finite element analysis was employed to examine the distribution characteristics of electromagnetic and temperature fields in liver tissue under varying power and time conditions. Comparative analyses were conducted to evaluate the impact and performance of the EAES vs traditional structures in ablation. Incorporating the EAES into conventional ablation needles allows for a more concentrated distribution of the electromagnetic field without altering the needle diameter. In the simulation of tissue ablation, the circularity of ablation increased by 10%, while water-cooling efficiency increased by 11%. The introduction of EAES, while maintaining its minimally invasive characteristics, effectively enhanced the controllability of conformal ablation. Furthermore, a mathematical model was developed to serve as a theoretical basis for selecting optimal preoperative parameters, incorporating conditions such as ablation time, power, range, and circularity. Overall, by conducting a multi-physics field coupling analysis on microwave ablation needles and proposing the EAES solution, this study aims to enhance the predictability, controllability, and safety of conformal ablation.

A multi-physics coupling analysis to predict stress corrosion characteristics of wires in rope under wear damage

To study the stress corrosion characteristics of wire with different wear conditions, namely depth, cross angle and length, Finite Element (FE) models of worn wires are developed based on multi-physics coupling analysis. The electromechanical parameters required for the FE simulations are determined from experimental testing. Then, the stress corrosion characteristics, i.e. stress, corrosion voltage, and corrosion current density, of the wear surface under different tensile displacements are obtained. The results show that the stress increases uniformly under different tensile displacements. However, different wear states present different stress corrosion characteristics. When the tensile displacement or wear state is sufficient to cause plastic deformation of worn wire, the corrosion characteristics changes dramatically.

The investigation of shrinkage cracking of paste and mortar based on the eccentric ring test and multiphysics simulation

The eccentric ring test presents a novel approach to evaluating the occurrence of shrinkage cracking in cementitious materials. The eccentric ring test has been confirmed to induce cracks on the thin sides of the specimen. However, the underlying mechanism behind this cracking phenomenon remains inadequately explored. In this study, the eccentric ring test is used to examine cement paste with different water-cement (w/c) ratios and mortar with varying aggregate volume fractions. The examination focuses on the influence of surface sealing and immersion curing on shrinkage cracking. The integrated shrinkage model, which is applicable to both autogenous shrinkage and drying shrinkage, is introduced to simulate the shrinkage of cementitious materials. The shrinkage cracking of eccentric specimens is further investigated through a multiphysics coupling analysis that considers shrinkage, humidity field, and stress field. The simulation results show that the humidity decreases more rapidly on the thinner sides during the shrinkage of the eccentric ring. The circumferential stress in the specimen is much greater than the radial stress. Additionally, the tensile stress in the circumferential direction exceeds 4 MPa on the outer ring. As the drying time increases, the circumferential tensile stress on the thin sides of the eccentric ring develops more rapidly, resulting in cracking on the thin side. The eccentric ring test is practicable in ordinary concrete and high-strength concrete, and the simulation is of significance in examining the cracking risk of concrete pipes and some thin wall components since these components are sensitive to the shrinkage cracking.

Multi-physics coupling analysis of test heat pipe reactor KRUSTY based on MOOSE framework

The heat pipe reactor utilizes heat pipes for passive heat transfer, eliminating the need for any moving parts. This feature significantly enhances its safety characteristics. Given the intricate nature of the heat pipe reactor system, a comprehensive multi-physics coupling simulation is necessary to study its safety features. In this study, a high-fidelity multi-physics coupling analysis incorporating a neutronic-thermal–mechanical-heat pipe coupling model is conducted. The work is based on the multi-physics coupling framework MOOSE, which integrates the Monte Carlo code OpenMC for neutronic analysis and built-in modules for 3-dimensional thermal–mechanical analysis. Furthermore, a heat pipe simulation method called the Thermal Resistance Grid Method is implemented within the MOOSE framework and employed in the multi-physics coupling analysis. To facilitate transient analysis, the Point Kinetics method is also integrated into the MOOSE framework to account for the time-varying power factor during reactor transients. The various modules and physical fields are coupled together using either loose or tight coupling strategies. These coupling strategies are applied to assess a test heat pipe reactor known as KRUSTY. Steady-state simulations are conducted for both normal operation and single heat pipe failure conditions, enabling the calculation of fission power distribution, temperature distribution, stress and strain profiles, as well as power and temperature redistribution following a heat pipe failure. Moreover, a load-following transient of KRUSTY is simulated, demonstrating its capability for load following without reactivity control. The aforementioned calculations validate the feasibility of the coupling framework utilized in this study and highlight its ability to accurately capture local phenomena within the reactor core.

Steady-state multi-physics coupling analysis of heat pipe cooled reactor core

The employment of heat pipe reactors is gaining significant traction due to their exceptional advantages in terms of mobility, safety, and applicability across a wide range of scenarios, including strategic defense locations, remote communities, and situations of power shortage. Importantly, most of the heat pipe reactors are designed as solid-state reactors, which avoids the challenges associated with two-phase flow problems that commonly arise from coolant transformation and makes it possible to analyze the reactor through the integration of multiple physical field coupling. In this paper, we conduct a 3D neutronic-thermal-mechanical coupled performance analysis of a heat pipe reactor operating under steady-state conditions. This analysis employs a combination of the Monte Carlo code and finite element analysis software, facilitating in-depth insights into the behavior of reactor. Coupling calculation results show that under normal operation, the maximum temperature and thermal expansion of core is 1338.94 K and 2.53 mm. In the steady-state coupling process, the influence of temperature parameters on neutronic calculation is mainly reflected in keff and its power level, the maximum temperature drops from 1347.26 K to 1338.94 K, but it has little influence on power distribution. By coupling calculations, the maximum stress of the reactor is reduced by 5.78 MPa. The research results will support the subsequent development of multi-physics coupled transient analysis code for heat pipe reactors.

Multiphysics coupling analysis of heat pipe reactor based on OpenMC and COMSOL Multiphysics

The heat pipe reactor is considered one of the most promising reactor power systems for deep space exploration due to its simplicity, modularity, and reliability. However, a significant challenge lies in the high temperature of the fuel, which can result in severe thermal expansion, thereby impacting the reactor's performance. In this study, we propose a new multiphysics coupling method based on OpenMC and COMSOL Multiphysics to address this issue. We validate this method through steady-state analysis of the heat pipe reactor KRUSTY. The results demonstrate that thermal expansion is the primary contributor to negative reactivity feedback. It has been noted that thermal expansion causes slight displacements of the fuel in the radial and axial directions, which must be considered during reactor system operation. Fortunately, the maximum thermal stress observed is approximately 51.0 MPa, well within the yield limit.

An equivalent winding thermal model considering fill factor and void ratio for multiphysics coupling analysis of permanent magnet linear motors

Accurately clarifying thermal characteristics and acquiring thermal limits of permanent magnet linear motors (PMLMs) is significant for system safety, which is often evaluated by computational thermal analysis. However, conventional thermal analysis methods are faced with the contradiction between the complexity of modeling and the accuracy of computation. To fix the problem, a new two-way multiphysics coupling method is developed by proposing an improved equivalent homogeneous winding thermal model. The energy consumption distribution is used as the heat source for thermal field calculation, and the material properties are determined by temperature in the electromagnetic field. To further reduce the complexity of winding region modeling and ensure the accuracy of calculation, an improved equivalent homogeneous winding thermal model is established by considering the fill factor and void ratio. The new coupling method is verified by temperature rise experiments on a single winding sample and a PMLM prototype. The error between the simulation and experiment of the single winding sample is less than 3 %, which indicates the high accuracy of the improved equivalent model. Meanwhile, the low error (less than 6 %) on the PMLM case indicates the high accuracy of the new multiphysics coupling method. Then, the temperature distribution of PMLM is analyzed, and the effect of the fill factor and void ratio on the temperature rise of PMLM is studied with the effect of the void ratio on the limiting temperature and continuous working time of PMLM discussed. It is demonstrated that both fill factor and void ratio affect the temperature rise of winding, and thus impact the temperature rise of the PMLM. The continuous working time decreases rapidly with the increase of the void ratio, and this effect will be more significant with a higher effective current. The results can provide references for improving the precision of temperature estimation and selecting a reasonable current density. This also demonstrates the high accuracy and efficiency of the new coupling method.

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.

Platform development for multi-physics coupling and uncertainty analysis based on a unified framework

The multi-physics coupled methodologies that have been widely used to analyze the complex process occurring in nuclear reactors have also been used to the R&D of numerical reactors. The advancement in the field of computer technology has helped in the development of these methodologies. Herein, we report the integration of ADPRES code and RELAP5 code into the SALOME-ICoCo framework to form a multi-physics coupling platform. The platform exploits the supervisor architecture, serial mode, mesh one-to-one correspondence and explicit coupling methods during analysis, and the uncertainty analysis tool URANIE was used. The correctness of the platform was verified through the NEACRP-L-335 benchmark. The results obtained were in accordance with the reference values. The platform could be used to accurately determine the power peak. In addition, design margins could be gained post uncertainty analysis. The initial power, inlet coolant temperature and the mass flow of assembly property significantly influence reactor safety during the rod ejections accident (REA).

Transfer learning and direct probability integral method based reliability analysis for offshore wind turbine blades under multi-physics coupling

Reliability of blades has a profound impact on both serviceability and safety of offshore wind turbines. Reliability estimation of wind turbine blade is a complex and time-consuming problem with multi-physics coupling and multi-failure modes correlation. Developing physics-of-failure modeling and reliability analysis methods with high efficiency and accuracy is a long-term challenge. In this work, a high availability and cost-effectiveness reliability estimation framework for offshore wind turbine blade by combining transfer learning (TL) and direct probability integral method (DPIM) is proposed. Extensive performance simulation of offshore wind turbine blade is a complex and necessary task, this paper develops a new adaptive sampling strategy to improve the validity of sample selection in the design space; On this basis, a physics-of-failure surrogate modeling approach is proposed by introducing TL method to fuse two kinds of multi-physics coupling analysis data, then the performance of all critical loads can be predicted efficiently in advance to provide a reliable design; Further, this paper provides an efficient reliability estimation method for offshore wind turbine blades by combining DPIM and surrogate model. Finally, the validity of the proposed approach is illustrated by numerical example and offshore wind turbine blade reliability estimation. The proposed framework provides a cost-effective alternative to higher loads simulation efforts and safety factors selection.

Numerical study on power battery thermal management system based on heat pipe technology

In the present work, a power battery pack and a novel thermal management system (TMS) based on the tubular heat pipe (THP) technology are designed according to the parameters of a pure electric light truck and battery. The TMS consists of THPs, power batteries, cooling plates, fins, and equivalent thermal conductivity is used to characterize the excellent thermal conductivity of THP. The heat generation rate of the battery at different discharge rates is obtained by establishing a multi-scale electrochemical–thermal coupling model, which accuracy is verified by the experiment. A multi-physics field coupling model is built to the thermal management system designed for the study. The results show that the battery temperature is higher when the battery is far from the THP in the cooling plate, and the maximum temperature reaches 35.6 °C at 1 C. Furthermore, the temperature difference between batteries is proportional to the discharge rate, and the maximum temperature difference reaches 7 °C at 2 C. The change in inlet temperature and wind speed can only restrain the temperature rise, while the temperature difference of the battery module is always 3.2 °C. When a fin spacing of 3 mm is chosen, the best temperature uniformity of the battery module is achieved at this time. The use of the multi-scale multi-physics field coupling analysis method in BTMS with heat pipes can be used as a reference for future numerical simulations of the same type.

Research of the Quenched Crankshaft Fatigue Property Based on the Multi-physics Coupling Analysis and the Theory of Critical Distance

Nowadays the electromagnetic induction quenching approach has been widely applied in the surface treatment process, especially for the parts made by metal materials such as the crankshafts. In this paper, quantitative study was adopted in researching the strengthening effect of this technique. First the multi-physics simulation was achieved to carry out the key information caused by this approach such as the temperature and residual stress distribution property. Then the fatigue limit load prediction was conducted based on the simulation results and the theory of critical distance. Finally corresponding experimental verification was performed to check the accuracy of the predictions. The results showed that the combination of the critical point method and the Goodmen mean stress model can provide highest accuracy in the prediction. While for the critical line method, the Gerbera mean stress model is the most suitable choice.

Dynamic performance of linear electromagnetic actuators in a stray magnetic field: theoretical analysis and experimental verification

Linear electromagnetic actuators (LEAs) are widely used in tokamaks, but they are extremely sensitive to and are prone to fail in a high-strength stray magnetic field (SMF), which is usually a concomitant with tokamaks. In this paper, a multi-physics coupling analysis model of LEA, including magnetic field, electric circuit and mechanical motion, is proposed, and the dynamic characteristics of LEAs in SMFs are studied in detail based on the proposed model. The failure mechanism of LEAs in SMFs is revealed, and the influence of SMFs on the dynamic performance of LEAs is studied and quantified. It is shown that the failure threshold of the LEA selected in this work under the rated condition is 27 mT and 14 mT in the positive and negative direction, respectively. Under a typical SMF of 10 mT in the negative direction, the closing time of the LEA will be extended by 40%, while its opening time will be shortened by about 10%. Experimental tests are also conducted, which verify the validity of the proposed model and the analysis results. This paper provides a basis for the diamagnetic optimization design of LEA, and it is of great significance to ensure the reliable operation of the tokamak.

Multi-physics coupling analysis on neutronics, thermal hydraulic and mechanics characteristics of a nuclear thermal propulsion reactor

As a highly developmental potential propulsion technology, nuclear thermal propulsion (NTP) technology has characteristics of high power and high specific impulse. A large number of relevant studies for NTP reactor have been carried out, but most studies only focused on the overall reactor performance parameters, ignoring the core reactivity safety and local assembly behavior safety. In this study, a cross-scale neutronics, thermal hydraulic and mechanics coupling model of the core-assembly is established by using three-dimensional Monte Carlo code and commercial CFD program to analyze three aspects: reactor control response security characteristics, heat release homogeneity of reactor and thermal hydraulic parameters. By means of value comparison of control system, three-dimensional power flattening and sensitivity analysis of single variable thermal–hydraulic parameter, the thermal hydraulic temperature safety and mechanical thermal stress safety of assemblies are significantly improved under control safety and inherent safety, which proves the importance of the neutronics, thermal hydraulic and mechanics characteristic balance.This paper can provide a theoretical basis for study on the assembly multi-physics behavior and safety characteristics of NTP reactors.

On-demand preparation of calcium alginate microspheres via piezoelectric microfluidics

Calcium alginate microspheres (CAMs) have attracted extensive attention as a novel drug carrier due to their cheapness, biodegradability, biocompatibility and nontoxicity. The existing preparation technologies of CAMs require complex process steps and involve multiple types of equipment, which are difficult to achieve the real-time and on-demand supply of microspheres in micro-reaction experiments. In this work, CAMs for prolonged drug release are prepared by the designed piezoelectric microfluidic devices using sodium alginate (NaAlg) and calcium chloride (CaCl 2 ). Specifically, the on-demand CAMs are synthesized timely by piezoelectric micro-jet followed by the transportation of piezoelectric micro-pump. Furthermore, various solution concentrations, main parameters of excitation signal and different nozzle diameters are evaluated in terms of size, morphology and drug release rate. The control method of CAMs’ size is obtained based on the multi-physics coupling analysis. Experimental results show that the doxorubicin hydrochloride loaded CAMs (DOX-CAMs) which can be prepared on demand, have excellent uniformity and dispersion, and the minimum average particle size is about 81.9 µm. The controlled drug release rate of DOX-CAMs reaches 83.2 % after 24 h. Moreover, the piezoelectric microfluidic devices and corresponding control methods may have potentials to be adapted for synthesizing other inorganic composite microspheres. • Piezoelectric microfluidics realize the timely supply of microspheres on demand. • The control strategy of microspheres was obtained by simulation analysis. • Preparation of high-quality microspheres with uniformity and dispersion. • Microspheres have excellent drug release performance.