Multi-physics 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.

A new modeling method to evaluate effective forced-convective heat transfer rate of pipe flow with endothermic chemical reactions

Heat transfer correlation describes the relationship between heat transfer and factors such as fluid properties and flow conditions. The establishment of heat transfer correlations is of paramount importance in the design and calculation of heat exchangers and reactors in various chemical engineering fields as well as in certain aerospace applications. In this study, we present a theoretical derivation of a heat transfer correlation model for fully developed flow with gas-phase homogeneous chemical reactions. By means of theoretical derivations, the modeling of complex multi-physics coupling problems can be significantly simplified, and the impact of chemical reactions can be effectively demonstrated. The concept of effective specific heat and effective thermal conductivity are generalized to finite-rate chemically reacting flow. Modifications are proposed for Nusselt number correlation. It is shown by preliminary verification that evaluating error of new correlation has been significantly decreased by the modification. The enhancement factor can be evaluated by specific ratio cpr,x/cp*. To demonstrate the reliability of the derived correlation, we carry out numerical simulations and compare the results with derived formulations. The simulations show good agreement with the theoretical values, demonstrating that the derived correlation is both theoretically grounded and practically usable.

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 [...]

A system-level multi-field coupling algorithm for regenerative cooling thrust chamber of a LOX/methane rocket engine

A systematic and hierarchical multi-physics coupling simulation method is proposed to model the combustion, combustion-gas transonic flow, coolant transcritical flow, and transient heat transfer phenomena inside the regenerative cooling thrust chamber subsystem of a LOX/methane rocket engine. By combining this algorithm with a self-developed platform, two distributed parameter modules are developed. Based on the ground test conditions of a LOX/methane engine, a verification case is established, and transient simulation studies are conducted. Comparisons with steady-state test data show that the calculated errors for coolant temperature rise and pressure drop are not higher than 4%. The simulation results reveal the locations where the transition from liquid to supercritical state occurs within the cooling jacket and provide three peril points of wall temperature on the thrust chamber. This study comprehensively reveals the occurrence of transcritical transient processes inside the cooling channels during the regenerative cooling process, laying the foundation for future entire system simulation.

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 in exploitation and utilization of geo-energy: State-of-the-art and future perspectives

Multiphysics coupling in exploitation and utilization of geo-energy: State-of-the-art and future perspectives

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.

Freeze dehydration vs supercooling in tree stems: physical and physiological modelling.

Frost resistance is the major factor affecting the distribution of plant species at high latitude and elevation. The main effects of freeze-thaw cycles are damage to living cells and formation of gas embolism in tree xylem vessels. Lethal intracellular freezing can be prevented in living cells by two mechanisms, such as dehydration and deep supercooling. We developed a multiphysics numerical model coupling water flow, heat transfer and phase change, considering different cell types in plant tissues, to study the dynamics and extent of cell dehydration, xylem pressure changes and stem diameter changes in response to freezing and thawing. Results were validated using experimental data for stem diameter changes of walnut trees (Juglans regia). The effect of cell mechanical properties was found to be negligible as long as the intracellular tension developed during dehydration was sufficiently low compared with the ice-induced cryostatic suction. The model was finally used to explore the coupled effects of relevant physiological parameters (initial water and sugar content) and environmental conditions (air temperature variations) on the dynamics and extent of dehydration. It revealed configurations where cell dehydration could be sufficient to protect cells from intracellular freezing, and situations where supercooling was necessary. This model, freely available with this paper, could easily be extended to explore different anatomical structures, different species and more complex physical processes.

Research on the multi-physical coupling characteristics of the machine tool and milling process based on the systematically integrated model

Good machine tool precision and a stable milling process are important foundations for obtaining high-quality qualified parts. During the machining process, the machine tool and the milling process will impact each other, and further jointly affect the motion accuracy as well as part quality. This paper makes a deep analysis of the machine tool and milling process from a new perspective, which regards the machine tool and milling process as a coupled entirety, and studies the interaction between them from a systematic perspective. By establishing a systematically integrated model of the ball screw feed system and milling process, the multi-physical simulation of the whole system is realized with the consideration of multi-source harmonics. The electrical-magnetic-mechanical-kinematic coupling characteristics between the machine tool and the milling process are investigated based on the established model and experiments. The research results show that the servo system and the milling process are two major harmonic sources in the system that generate low-medium frequency and medium-high frequency harmonics, respectively. As the machining process progresses, these harmonics will be transmitted and coupled through the servo motor, mechanical structure, and feedback signals, leading to the fluctuation in the motion of the worktable and the influences on the surface quality of the final part. A type of part surface defect that can only be explained by integrated analysis of the whole system is also demonstrated. The research work indicates that the machine tool and milling process is an integrated system with strong coupling characteristics. It's of great significance to study them from a systematic perspective.

Multiphysics coupling in situ measurement method for laser repair of the Inconel 718 alloy structure

Multiphysics coupling in situ measurement method for laser repair of the Inconel 718 alloy structure

Advances in Tunable Bandgaps of Piezoelectric Phononic Crystals.

Bandgaps of traditional phononic crystals (PCs) are determined using structural geometric parameters and material properties, and they are difficult to tune in practical applications. Piezoelectric PCs with lead zirconium titanate piezoelectric ceramics (abbreviated to piezoelectric PCs) have multi-physics coupling effects and their bandgaps can be tuned through external circuits to expand the application range of the PCs. First, the typical structures of piezoelectric PCs are summarized and analyzed. According to the structure, common tunable piezoelectric PCs can be roughly divided into three categories: PCs that only contain piezoelectric materials (single piezoelectric PCs), PCs composed of embedded piezoelectric materials in elastic materials (composite piezoelectric PCs), and PCs that are composed of an elastic base structure and attached piezoelectric patches (patch-type piezoelectric PCs). Second, the tuning methods of bandgaps for piezoelectric PCs are summarized and analyzed. Then, the calculation methods of the bandgaps of piezoelectric PCs are reviewed and analyzed. Finally, conclusions are drawn on the research status of piezoelectric PCs, shortcomings of the existing research are discussed, and future development directions are proposed.

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.

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.

Numerical study on temperature field in the gob under different cooling control measures

The temperature and flow fields of the gob area are quantified in this paper. Firstly, a mathematical model for multi-physical coupling in the gob was established. The on-site test of Daqiang Coal Mine was conducted without injecting nitrogen, which verified the effectiveness of the model. The cooling effect of the nitrogen injection decreases as the distance between the air inlet side and the working surface increases. In addition, the hot air extraction was clearly evaluated and the movement of hot air was analyzed. Both nitrogen injection and hot air extraction in the mining area have a significant effect on reducing the airflow temperature at the coal mining face. The air flow temperature with nitrogen injection at each location was lower than that without nitrogen injection along the direction of the coal face. In contrast, the air temperature on the return air corner is greatly reduced after the hot air extraction measures are taken and it can improve the air thermal state near the return air corner. We can provide effective solutions to the problems of spontaneous combustion and thermal damage in high-temperature mines through theoretical research and practical exploration.

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 CFD-FEM analysis for Anaconda WEC with mooring lines

Anaconda wave energy converter (WEC) [1] is a typical flexible tube WEC design. In the past decade, the hydro-elastic performance of Anaconda model has been studied through experiments [2-3] and reduced-order numerical simulations [4-5]. However, to date, most of the undertaken research assumes that both ends of the tube are fixed, neglecting mooring lines that exist at designed conditions. The tube is allowed to move freely head to waves when mooring lines are considered. This is evident by an experiment conducted by Checkmate Flexible Engineering Ltd., where they observed a significant heave motion of Anaconda WEC, which may impact the dynamic response of WEC and further the energy conversion [6]. In our previous work [7], supported by the EPSRC project BASM-WEC (No. EP/V040553/1), a coupled numerical analysis tool using computational fluid dynamics (CFD) and finite element method (FEM) has been proposed to perform a numerical study for an Anaconda WEC model without considering mooring lines.In this paper, the coupled fluid-structure interaction (FSI) analysis tool [7] based on CFD-FEM method will be used to investigate Anaconda WEC with mooring lines. To account for the effects of free motion of WEC, we develop a sub-module to be embedded into the existing tool. The fluid and structure are solved by a two-phase CFD solver developed based on OpenFOAM and a three-dimensional FEM code CalculiX, respectively. The strong coupling between OpenFOAM and CalculiX is achieved by a multi-physics coupling tool preCICE.For the flexible tube, a commercial Natural Rubber material is studied. The hyper-elastic model YEOH is utilized to describe the nonlinear behaviour of material, and the model constants are calculated from the bi-axial tests. With the tool developed, numerical simulations are performed for different given regular waves. The flow details, velocity and pressure variation, structure deformation and stress distribution will be fully examined to better understand energy conversion performance of Anaconda WEC with mooring lines.
 References[1] Farley F J M D, Rainey R C T. Distensible tube wave energy converter: U.S. Patent 7,980,071[P]. 2011-7-19.[2] Chaplin J R, Heller V, Farley F J M, et al. Laboratory testing the Anaconda[J]. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2012, 370(1959): 403-424.[3] Heller V, Chaplin J R, Farley F J M, et al. Physical model tests of the anaconda wave energy converter[C]//Proc. 1st IAHR European Congress. 2000.[4] Farley F J M, Rainey R C T, Chaplin J R. Rubber tubes in the sea[J]. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2012, 370(1959): 381-402.[5] Babarit A, Singh J, Mélis C, et al. A linear numerical model for analysing the hydroelastic response of a flexible electroactive wave energy converter[J]. Journal of Fluids and Structures, 2017, 74: 356-384.[6] Checkmate Flexible Engineering, https://www.checkmateukseaenergy.com/, accessed 15th December 2022.[7] Huang Y, Xiao Q, Idarraga G, et al. Numerical analysis of flexible tube wave energy converter using CFD-FEA method[C]//International Conference on Offshore Mechanics and Arctic Engineering. American Society of Mechanical Engineers, 2023 (submitted).

Safety Performance and Failure Criteria of Lithium-Ion Batteries under Mechanical Abuse

With the increasing global focus on environmental issues, controlling carbon dioxide emissions has become an important global agenda. In this context, the development of new energy vehicles, such as electric vehicles, is flourishing. However, as a crucial power source for electric vehicles, the safety performance of lithium-ion batteries under mechanical abuse has drawn widespread attention. Evaluating the safety performance of lithium-ion batteries requires in-depth research. This paper provides a review of recent experimental and numerical simulation studies on the mechanical abuse of lithium-ion batteries. It showcases the main methods and conclusions of experimental research, compares different response forms under quasi-static and dynamic loading, discusses the causes of strain-rate dependence in lithium-ion batteries, and briefly describes the impact of the state of charge (SOC) on safety performance under mechanical abuse, as well as the influence of mechanical abuse on battery capacity and impedance characteristics. Furthermore, this paper summarizes the methods of numerical simulation research, analyzes the advantages and disadvantages of detailed modeling and homogenized modeling methods, summarizes the strain-based internal short circuit failure criteria, and reviews numerical predictive models based on multiphysics coupling. Finally, it presents the latest progress in studying the safety performance of battery packs through numerical simulations.