Charge Simulation Research Articles

A proposed method for calculating the voltage and current distributions of grounded and isolated networks subjected to line‐to‐ground faults

AbstractOne crucial objective of this article is to present simplified and accurate approaches to study the current distribution and ground surface potential around the area surrounding an earthed and isolated system in case of a line‐to‐earth fault. The present study is done in the case of uniform and two‐layer soils. Suggested models for calculating the distribution of the earth's surface current density, step, and touch voltages in grounded and isolated systems are presented, discussed, and adapted. The contact and arc resistances of line to ground faulty conductors are considered. Rods and/or grounding grids usually do grounded systems. The impact of both step and touch potentials and current density are investigated in this article. The methods of the calculations are based on the electrical concepts, the charge simulation method, and the imaging procedure for the grounding system. The suggested method can be considered a novel and simple technique for calculating the current distributions of the ground surface during line to ground fault. The results agree with those obtained by others, with the advantage of the proposed algorithm for its ease of application and simplicity. 3‐D dimensions’ contours of the current density and the electric potential on the earth surface around the faulty point are presented in case of homogeneous and two layers’ soil. Finally, this article's novelty is to devise a method for calculating the step and touch potentials and current density around the point of contact of the conductor carrying the electric voltages in the event of faults occurring in the electrical network, whether the network is grounded or isolated. Such faults of electrical networks may cause human hazards.

Effects of pellet-sinter interaction parameters on component segregation and bed porosity considering flow velocity and mixture composition: A DEM study

Bed permeability is a crucial factor in blast furnace performance which depends on the material distribution achieved through charging. Since a homogeneous bed of pellet and sinter is recommended, it is crucial to understand whether segregation of the pellet-sinter mixture occurs during charging. The Discrete Element Method is useful in this regard; however, simulations of pellet-sinter mixture charging currently lack credibility since pellet-sinter interaction parameters have not yet been calibrated and validated. Determining pellet-sinter interaction parameters will require significant efforts, so it is useful to know whether mixture segregation and the resulting bed permeability are sensitive to these parameters. In this work, we investigate to what extent the restitution coefficient, sliding friction coefficient and rolling friction coefficient between pellet and sinter affect segregation during bed formation and the resulting permeability in terms of porosity using a simplified charging setup. The investigation is done for different mixture compositions and flow velocities, and analysis settings including sample size and sampling directions. We conclude that all parameters affect segregation and porosity, regardless of the composition and velocity. Hence, all mixture parameters including the interaction parameters between the components must be carefully calibrated when developing a model for predicting permeability.

DFT study on adsorption properties of TM(Ni, Co)Nx -doped graphene for high-temperature sensing of SF6 decomposed gases

Gas sensing is the key to online monitoring SF6 decomposition gases in gas-insulated switchgear (GIS) fault diagnosis. However, the gas sensors for high-temperature sensing of SF6 decomposed gases are still lacking. In this paper, the adsorption performance of TM(Co, Ni)Nx-doped graphene as gas-sensing materials for the SF6 decomposed gases of SO2, SOF2, and SO2F2 were studied by DFT calculations, especially for the case at high temperatures. The adsorption energy (Eads), adsorption distance (D), transferred charge (Qt), and molecular dynamics simulations were performed to study the gas adsorption ability of TMN2-doped graphene. The electronic structures were clarified by analysis of the density of states (DOS), the partial density of states (PDOS), electron density difference, and molecular orbitals. The molecular dynamics simulations at 873 K indicated the high thermodynamic stability of TM(Co, Ni)Nx-doped graphene, which promised their superior gas sensing performance to detect SF6 decomposed gases at high temperatures.

A spatiotemporal evolution model of a short-circuit arc to a secondary arc based on the improved charge simulation method

The initial shape of the secondary arc considerably influences its subsequent shape. To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence, theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical. In this study, an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc. The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc. A secondary arc evolution model was developed based on this model. Moreover, the accuracy of the model was evaluated by comparison with physical experimental results. When the secondary arc current increased, the arcing time and dispersion increased. There is an overall trend of increasing arc length with increasing arcing time. Nevertheless, there is a reduction in arc length during arc ignition due to short circuits between the arc columns. Furthermore, the arcing time decreased in the range of 0°–90° as the angle between the wind direction and the x-axis increased. This work investigated the method by which short-circuit arcs evolve into secondary arcs. The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.

Multiscale Modelling of Battery Systems at Low Temperatures: Impact of Microscale on Performance

Lithium-ion batteries (LIB) are currently the most widely spread all-purpose energy storage technology. Although improved energy and power densities continue to widen and foster their adoption in multiple application domains, such as electric mobility, LIBs operating temperatures continue to be typically in a range of 15-35 °C. Particularly, at temperatures around and below 0 °C, the performance of LIBs is dramatically reduced, which prohibits deployment of LIBs in cold climates, high latitudes, mountainous regions, or aerospace applications. Low temperatures impact the cycling performance, safety and, most dramatically, decrease the battery capacity. This degradation in performance is a result of several microscale physical mechanisms affecting both electron and Li-ion transport, as well as reaction rates at electrodes and in electrolyte of batteries. In particular, at low temperatures, the charge transfer at the electrode/electrolyte, lithium diffusion in the solid material and Li-ion transport in electrolyte are diminished when compared to room temperature, yielding a reduction in capacity or even battery inoperability in some applications.To improve the low temperature performance, it becomes important to trace down the microscale mechanisms and identify dominant limiting phenomena to address them individually. Despite the fact that vast literature exists for many cathode and anode materials at low temperatures [1-2], identifying the dominant limiting physical mechanisms is still a topic of debate [3]. Different works attribute the low-temperature performance limitations to different aspects of the battery system, such as sluggish transport in the electrolyte [1], slow solid diffusion processes in the active materials [2], charge transfer disruption in electrode or electrolyte composite media or at the solid-electrolyte interface [4], leaving a multitude of possibilities for a particular battery system. Additionally, the complexity of the microscale phenomena in battery systems makes it difficult to trace the root causes from the macro to the microscale, and thus to tackle this problem effectively.In this context, modelling and simulation of the microscale charge and mass transport phenomena is a useful tool in providing insight into the microscale aspects dictating the macroscale operation. Typically, the Doyle-Fuller-Newman (DFN) multiscale model is applied to predict macroscale performance from microscale properties of the battery system [5]. In this model charge and mass conservation equations are solved for the input physical parameters describing the battery system such as geometry and parameters describing the battery materials comprising electronic conductivities of the electrodes, ionic diffusivities and conductivity of the electrolyte and electrochemical reaction rates at the electrode’s active particles. The balancing between these parameters with respect to each other will influence (and limit) the response of the LIB. Each of these parameters is typically considered to follow an Arrhenius relationship with temperature, where an activation energy controls the coefficients for the transport and reaction processes, such that at lower temperatures an exponential decrease in electronic and ionic transport as well as reaction rates leads to strongly reduced performance. However, the particular effects of low temperatures on these coefficients describing the battery microstructure phenomena and its impact on the macroscale performance remain poorly explored.In this paper, we report low temperature effects on microscale parameters and their influence on the macroscale performance with particular examples targeting low temperature effects in LiFePO4 (LFP) and LiNi1/3Mn1/3Co1/3O2 (NMC) based batteries. By implementing a multiscale DFN model in the finite element modeling software COMSOL Multiphysics®, we perform numerical simulations of these battery systems within a range of temperatures and operating conditions and compare them with experimental data. Our results allow to assess the effect of temperature based on microstructural parameters of the system and corresponding macroscale output. Figure 1 exemplifies typical simulation results of the temperature effect on discharge curves for LFP/Graphite (Figure 1a) and NMC/Graphite cells (Figure 1b). These results hold great potential for understanding battery’s microstructure impact on the overall performance at low temperatures and to inform electrode choice, battery design and manufacturing processes for low temperature battery systems. Acknowledgement This research has received funding from the European Union’s Horizon Europe research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 101062008.

Simscape Framework for Digital Lithium-Ion Battery Twins: Electrode & Electrolyte Domains

To speed up the development of novel batteries, time-consuming experimental work can be supported or partially replaced with simulations of physical batteries. Since the demand for laboratory research is growing rapidly, the same can be applied to mathematical models.So far, there is a huge variety of tools used to mimic the processes occurring in different scales: from a single active material particle up to a whole battery cell.1-4 Existing battery modeling software suites such as COMSOL, Siemens Simcenter, Python, or Matlab, require the user to hold a high degree of competence in informatics, computer science, and modeling.5-7 This may limit the use of simple battery models for laboratory workers in development and research.With all the above in mind, in our work, we want to present the concept of an easy-in-use battery twin model. In our project, new domains (mass/electrode and electrolyte) have been developed in Simscape – a library provided by Simulink which is part of the Matlab suite (Mathworks TM). With an intuitive, drag-and-drop interface and clear error and warning communication, Simscape is a promising tool that can be applied to simulate battery performance and other electrochemical systems. Our first implementation follows the nomenclature from Xia et al.8 The very first digital twin proposed here is represented by Newman’s P2D model where the battery as well as the particles in each electrode are discretized (i.e., divided into layers or shells, respectively). A set of non-linear partial derivative equations8 is solved with the application of the Butler-Volmer equation used to define the electrochemical reaction rate occurring on the surface of the particle in each layer. A schematic representation of such a battery setup with 5 layers of the separator, cathode, anode electrodes, and 10 shells describing the active material particles is depicted in Figure 1. The ionic concentration gradients in the electrolyte are shown for an exemplary charge simulation with a C-rate of 1/h.The current model will be extended by modeling the thermal properties occurring inside the battery during (dis)charging after in-depth numerical validation has confirmed its validity. In future work, parameters will be determined in the laboratory, and experiments will be conducted to compare with the results obtained in the digital twin.

Electrode microstructure design based on a CA-FD hybrid computation framework to alleviate the concentration polarization

The fast charging capability of lithium-ion batteries is considered as a critical requirement for the widespread replacement of fuel vehicles by electric ones. The high current applied in the fast charging process always causes concentration polarization due to the velocity difference between ionic diffusion and electron transport, which could lead to a low charging efficiency. The ionic diffusion velocities in both solid phase and liquid phase are strongly related to the microstructure of electrode particles. Based on the understanding of the reaction-diffusion mechanism, numerical simulation method is feasible to investigate the effect of microstructure on charging performance more economically. However, a two-dimensional model with the consideration of electrode microstructure consists of a set of highly coupled partial differential equations (PDEs), which is hard to be solved and inefficient with the irregular solid-liquid boundaries. Compared with PDEs, cellular automata (CA) is focused on the interaction between the adjacent discrete elements rather than solving the continuous variables across the whole region. According to this characteristic, mass transfer with complex solid-liquid boundaries can be simulated more conveniently by CA, but on the other hand, the restriction of applied current on the total reaction flux is hard to be considered in the CA model. Therefore, the diffusion part and the reaction part are processed by CA and finite difference (FD) method respectively. A CA-FD hybrid computation framework is proposed to consider the effect of microstructure on charging performances and visualize the concentration evolution inside the electrode particles. Based on this framework, the electrodes with uniform structure, porosity-layered structure and particle size-layered structure are constructed and applied in the charging simulations. According to the simulation results, the layered structures are beneficial for alleviating the concentration polarization in batteries, so that the charging efficiency of the electrodes can be improved without energy density loss by adopting these non-uniform structures in certain scenarios.

Hybrid random batch idea and nonlinear conjugate gradient method for accelerating charged polymer dynamics simulation

Hybrid random batch idea and nonlinear conjugate gradient method for accelerating charged polymer dynamics simulation

Modeling, analysis, and shielding of the electric field between extra-high-voltage AC transmission lines and oil pipelines

The static charges and induced voltages from extra-high-voltage alternating current transmission lines (EHVACTLs) on parallel oil pipelines (POPLs) raise the risk levels for people and animals. Thus, the objective of this paper was to reduce and/or mitigate the electric field which is concentrated on POPLs by using grounded shield wires under EHVACTLs. Three techniques are employed to reduce the electric field effects on POPLs of two distinct types of transmission lines (TLs), 500 kV and 220 kV. The first technique involves raising the tower’s height to improve the clearance space between the POPLs and the TL conductors. The second technique is increasing the horizontal distance between the POPLs and the nearest stressed conductors of the TL. The third technique involves placing shield wires beneath the stressed conductors of the EHVACTLs. The electric field under the EHVACTLs is calculated with and without the grounded shield wires using charge simulation method. The results of the first technique revealed that with increasing the tower height from 10 m to 15, 20, 25, and 30 m, the electric field decreased by 43.75%, 62.5%, 68.75%, and 75%, respectively. Herein, employing the second technique, the electric field intensity is reduced by 20% and 21% depending on the POPL placed at a distance from the right stressed conductor equal to the horizontal clearance between conductors of 500 kV and 220 kV, respectively. Besides, the results of the third technique proved that the shield wires under the EHVACTLs reduced the electric field intensity on the POPLs by 17.65% and 24.71% for 500-kV and 220-kV TLs, respectively.

Spacecraft Charging Simulations of Probe B1 of Comet Interceptor during the Cometary Flyby

Comet Interceptor will be the first mission to make a flyby of a long-period or interstellar comet. After launch, the spacecraft will wait at the Sun–Earth Lagrange point L2 for a yet-to-be-discovered comet to appear. The mission comprises three spacecraft: One main spacecraft, A, developed by ESA, and two subprobes, B1 and B2, developed by JAXA and ESA, respectively. All spacecraft will carry plasma instruments for a three-dimensional sampling of the cometary plasma environment. The plasma measurements will likely be affected by the spacecraft potential and by particles emitted from the spacecraft surface. In this work, we use the Spacecraft Plasma Interaction Software and the ElectroMagnetic Spacecraft Environment Simulator to make particle-in-cell simulations of the spacecraft–plasma interactions of probe B1 in different environments during the cometary flyby. This is done for two production rates of the target comet and two relative flyby velocities of the probe. At low flyby velocities, the spacecraft potential varies from 9 V in the solar wind to −5 V in the inner coma for a comet similar to comet 67P/Churyumov–Gerasimenko. For a comet similar to 1P/Halley, the potential is slightly less negative in the inner coma due to the more effective collisional cooling of the electrons in the environment. At high flyby velocities, secondary electron emissions from neutral gas impacts dominate the currents, charging the probe to positive potentials in most of the studied environments.

Calculation of Transmission Line Worker Electric Field Induced Current Using Fourier-Enhanced Charge Simulation

Exposure to quasi-electrostatic field induced currents is a hazard of live-line transmission work. These steady-state induced currents are typically less than 1 mA, and their sensory effects range from imperceptible to painful depending on the person and conditions such as contact area and duration. Permanent injury from these currents is unlikely but they can distract workers, increasing the risk of injury from falls or other dangers. Identifying contact current severity and training workers can help reduce the risk of accidents. Measuring induced currents along a climbing route is time-consuming and simulation is challenging because of the geometric complexity of the worker, the transmission structure, conductor bundles, and electric fields in the climbing space. This research explores the suitability of a recently published adaptation of the charge simulation method for calculating worker-induced currents. The method uses Fourier principles to improve computational efficiency while explicitly modeling all bundle subconductors. The research also examines simplifications for modeling lattice structures and human geometry. Calculated currents compare well to measurements for a worker climbing a 400 kV lattice structure. This indicates the method is a practical option for calculating steady-state contact current severity. A simple calculation is suggested for estimating these currents.

A cell-centred Eulerian volume-of-fluid method for compressible multi-material flows

We present a practical cell-centred volume-of-fluid method developed within a pure Eulerian setting for the simulation of compressible solid-fluid problems. The method builds on a previously published diffuse-interface Godunov-type scheme through the addition of a specialised mixed-cell update that is capable of maintaining sharp interfaces indefinitely. The mixed-cell update is local and may be viewed as an interface-sharpening extension to the underlying diffuse-interface scheme serving the same purpose as other techniques such as Tangent of Hyperbola INterface Capturing (THINC), and hence the method can be straightforwardly extended to include other coupled physics. We validate the method on a range of challenging test problems including a collapsing metal shell, cylinder impacts and the three-dimensional simulation of a buried explosive charge. Finally we demonstrate the robustness of the method, and its use in a multi-physics context, by modelling the BRL 105 mm unconfined shaped charge with reactive high-explosive burn and rate-sensitive plasticity.

Distributed Platform for Offline and Online EV Charging Simulation

Efforts to enhance electric vehicle (EV) charging processes have spurred the emergence of smart charging algorithms. However, these studies are intricate and costly, necessitating preliminary simulations to assess EV integration into power grids. Existing solutions to this issue tend to be limited to academia and proprietary systems. To address this, we propose a user-friendly and intuitive simulation tool employing a decoupled and flexible architecture. This architecture, achieved through open design and containerized microservices, streamlines maintenance, extension, and scalability. We substantiated the validity of our solution by simulating the charging infrastructure from an H2020 Research Project. Furthermore, we integrated our solution with an external system that executes smart charging algorithms. The proposed system yielded the desired results, enabling the project team to evaluate both the integration and algorithms, even amidst the COVID-19 lockdown.

Development and analysis of magnet-engaged piezoelectric energy generator under friction-induced vibration

Piezoelectric energy transducers, which can be an efficient solution for the power supply of wireless devices, have been widely researched. This study investigated the characteristics of a magnet-engaged nonlinear piezoelectric energy generator stimulated by friction-induced vibration (FIV), in two distinct design configurations (in-parallel and in-series). A mathematical model was developed, and the dynamic response of the mechanical system and voltage output from the piezoelectric shear deformation were solved using an iterative method. A friction model considering the Stribeck effect was introduced to describe the friction motion. The emergence of a stick-slip motion induced limit cycle and its vanishing delineates the unstable and stable regions of the system, respectively. A critical sliding velocity vc splits the regions. When the sliding velocity exceeds vc, the system remains in stable region with exclusive slip friction behavior. Parameter studies were conducted to explore the effect of decay factor β, dynamic friction coefficient μk, static friction coefficient μstatic, and normal force FN on vc. The results indicate that increasing β and μk can reduce the unstable region and generation of FIV, whereas, increasing FN and μstatic can promote the occurrence of FIV. The energy generation was evaluated by a transient charging simulation that has been experimentally validated in a previous study. The influence of β, μk, μstatic, and FN on the energy generation was also investigated relative to the operating velocity range (OVR) and sum of root mean square charging power (SRCP). The in-parallel systems exhibit a higher SRCP within the same OVR, whereas the in-series systems are more likely to excite FIV with a wider OVR. Additionally, the simulation results of fluctuating working conditions show that both fluctuating FN and v0 have negative effects on the energy generation. The nonlinear in-series system exhibits better robustness with the least affected SRCP and almost unchanged OVR under fluctuating FN and v0.

Numerical Simulations of Space Charge Waves Amplification Using Negative Differential Conductance in Strained Si/SiGe at 4.2 K

This paper introduces a two-dimensional (2D) numerical simulation of the amplification of space charge waves using negative differential conductance in a typical MOS silicon–germanium (SiGe)-based field-effect transistors (FET) and complementary metal oxide semiconductor (CMOS) technology at 4.2 K. The hydrodynamic model of electron transport was applied to describe the amplification of space charge waves in this nonlinear medium (i.e., the negative differential conductance). This phenomenon shows up in GaAs thin films at room temperature. However, this can be also observed in a strained Si/SiGe heterostructure at very low temperatures (T < 77 K) and at high electric fields (E > 10 KV/cm). The results show the amplification and non-linear interaction of space charge waves in a strained Si/SiGe heterostructure occurs for frequencies up to approximately 60 GHz at T = 1.3 K, 47 GHz at T = 4.2 K, and 40 GHz at T = 77 K. The variation of concentration and electric field in the Z and Y directions are calculated at 4.2 K. The electric field in the Z direction is greater than in the Y direction. This is due to the fact that this is the direction of electron motion. In addition to deep space applications, these types of devices have potential uses in terrestrial applications which include magnetic levitation transportation systems, medical diagnostics, cryogenic instrumentation, and superconducting magnetic energy storage systems.

Numerical prediction of the solidification and melting of encapsulated nano‐enhanced phase change materials

AbstractThe thermal properties of Octadecane vary due to the addition of copper oxide (CuO) nanoparticles. The synthesis of two nano‐enhanced phase change material (NEPCM) required the implementation of the two‐step method, using Octadecane as the base phase change material and CuO nanoparticles at 2.5 and 5.0 wt%. The experimental characterization determined the specific heat capacity, and thermal conductivity of the NEPCMs solid phase, including phase change enthalpy and temperature. These experimental results were then utilized for computational simulation of the thermal charging (solidification) and discharging (melting) processes of NEPCMs within a spherical enclosure, employing the ANSYS/Fluent software. The incorporation of CuO nanoparticles led to an increase in thermal conductivity while causing a decrease in specific heat capacity, enthalpy, and phase change temperature of Octadecane. The computational results revealed a reduction in the melting period and an improvement in the solidification of both NEPCMs. In terms of melting, the convective heat transfer coefficient increased by approximately 27.4% and 3.2% for the NEPCM at 2.5 and 5.0 wt% CuO, respectively. During the solidification process, the overall heat transfer coefficient experienced a significant increase of 43.8% and 59.8% for the NEPCM at 2.5 and 5.0 wt%, respectively.

Monte Carlo simulations of charged particle transport in plasmas: A fast single-scattering model

When simulating a charged particle trajectory in plasmas with Monte Carlo methods, the traditional single-scattering model is accurate but computationally expensive. The traditional multiple-scattering model reduces the computation cost but assumes an exponential distribution of the scattering angle, which overestimates the cumulative scattering angle. In this paper, we develop a new Monte Carlo method for the charged particle transport simulations. The scattering angle is naturally sampled from a modified screened Rutherford scattering cross section, in which a greatly amplified minimum deflection angle is used. With this model, the simulations give the same scattering angle distribution with the single-scattering model but only take a comparable computation cost with the multiple-scattering model when the small scattering angle and Markovian approximations can be fulfilled. This model would be especially useful for the study of inertial-confinement-fusion, which is sensitive to the alpha-particle energy deposition.

Origins and Influences of Voids in Composite Cathodes for All-Solid-State Batteries

With the exit from fossil-fuel energy becoming more and more urgent, advanced batteries are highly sought after and all-solid-state batteries (ASSBs) are seen as a promising technology potentially enabling lithium metal or reservoir-free anode designs which promote the energy density.Despite high research interest in the field, ASSBs still perform below expectations, the main challenges being elevated interfacial resistances, microstructure effects and processing, particularly at large scale. While the build-up of high resistances due to void formation upon lithium stripping at the anode side is increasingly understood, the void formation and its evolution in the composite cathode as well as the effects on the cell performance are widely unknown.Why consider voids in the cathode at all?In contrast to conventional, liquid electrolytes, solid ion conductors (such as thiophosphates) do not easily infiltrate voids and cracks in the cathode1. They possess a proper particle morphology and, depending on the solid electrolyte particle size distribution, its suitability to the active material particle sizes and morphologies the electrode structure that forms upon manufacturing can be quite different and influences the ion and electron transport as well as the charge transfer capabilities2-5. Experimentally determined void fractions in the composite typically range from 3 to 40 vol%6,7 and are therefore far away from being negligible.Apart from the void formation at manufacturing, scanning electron microscope (SEM) cross sections of cycled composites have also shown that the volume changes of LiNixCoyMn(1-x-y)O2 active material can lead to contact loss at the interface of the solid electrolyte and the active material8 which reinforces the importance of understanding the origins and the influences of voids on the cell performance.In this talk, we will discuss these, mainly from the modeling perspective including percolation network models4, flux-based simulations of the effective conductivity5 and electrochemical charge simulations based on the finite-element method9. Additionally, we use focused ion beam(FIB)-SEM tomography for the reconstruction of cathodes with different microstructures obtained by changing the particle size of the solid electrolyte. We investigate the influence of the solid electrolyte particle size distribution on the void space fraction and distribution and provide guidelines for further cathode optimization. Ruess, R.; Schweidler, S.; Hemmelmann, H.; Conforto, G.; Bielefeld, A.; Weber, D. A.; Sann, J.; Elm, M. T.; Janek, J., J. Electrochem. , 2020, 167, 100532.Minnmann, P.; Quillman, L.; Burkhardt, S.; Richter, F. H.; Janek, J., Electrochem. Soc., 2021 , 168, 040537.Jiang, W.; Zhu, X.; Huang, R.; Zhao, S.; Fan, X.; Ling, M.; Liang, C.; Wang, L., Energy Mater, 2022 , 12, 2103473.Bielefeld, A.; Weber, D. A.; Janek, J., Phys. Chem. C, 2019 , 123, 1626-1634.Bielefeld, A.; Weber, D. A.; Janek, J., ACS Appl. Interfaces, 2020 , 12, 12821-12833.Shi, T.; Zhang, Y.-Q.; Tu, Q.; Wang, Y.; Scott, M. C.; Ceder, G., Mater. Chem. A, 2020 , 8, 17399-17404.Ates, T.; Keller, M.; Kulisch, J.; Adermann, T.; Passerini, S. Energy Storage Mater., 2019 , 17, 204-210.Koerver, R.; Aygün, I.; Leichtweiß, T.; Dietrich, C.; Zhang, W.; Binder, J. O.; Hartmann, P.; Zeier, W. G.; Janek, J., Mater., 2017 , 29, 5574-5582.Bielefeld, A.; Weber, D. A.; Ruess, R.; Glavas, V.; Janek, J., Electrochem. Soc., 2022 , 169, 020539. Figure 1

Special finite elements with arbitrarily-shaped holes for heat conduction analysis of porous materials

Special finite elements are developed which adequately represent the state of heat conduction in the region around an arbitrarily-shaped hole. This is achieved with two assumed temperature fields. The frame field is defined along the element boundary while the intra-element field is independently approximated by using truncated T-complete solutions as trial functions for capturing hole effects. The geometrical irregularity of holes contribute to the difficulty in seeking T-complete solutions. By means of the charge simulation method and numerical conformal mapping technique, the systematic construction of T-complete solutions is shown which satisfy a priori the governing differential equation. Based on the modified variational principle, the two independent temperature fields are linked together at the element level, ensuring conformity across inter-element boundaries. The resultant element stiffness equation involves boundary integrals only, which provides a great flexibility in mesh generation with polygons. Numerical examples for the problems with a single, dual, and multiple holes are given to illustrate the efficiency and accuracy of the proposed method.

Numerical Solution of the Electric Field and Dielectrophoresis Force of Electrostatic Traveling Wave System.

Electrostatic traveling wave (ETW) methods have shown promising performance in dust mitigation of solar panels, particle transport and separation in in situ space resource utilization, cell manipulation, and separation in biology. The ETW field distribution is required to analyze the forces applied to particles and to evaluate ETW design parameters. This study presents the numerical results of the ETW field distribution generated by a parallel electrode array using both the charge simulation method (CSM) and the boundary element method (BEM). A low accumulated error of the CSM is achieved by properly arranging the positions and numbers of contour points and fictitious charges. The BEM can avoid the inconvenience of the charge position required in the CSM. The numerical results show extremely close agreement between the CSM and BEM. For simplification, the method of images is introduced in the implementation of the CSM and BEM. Moreover, analytical formulas are obtained for the integral of Green's function along boundary elements. For further validation, the results are cross-checked using the finite element method (FEM). It is found that discrepancies occur at the ends of the electrode array. Finally, analyses are provided of the electric field and dielectrophoretic (DEP) components. Emphasis is given to the regions close to the electrode surfaces. These results provide guidance for the fabrication of ETW systems for various applications.