Distribution Of Physical Fields Research Articles

Response of Moisture and Temperature Diffusivity on an Orthotropic Hygro-thermo-piezo-elastic Medium

This research explores the complex interaction between piezoelectric waves and heat-moisture diffusion within a semi-infinite piezoelectric material under hygro-thermal conditions. By employing a two-dimensional Cartesian framework, novel governing equations for a thermo-piezoelectrically orthotropic medium influenced by moisture effects are developed. Accurate representations for key parameters are obtained by utilizing normal mode analysis. The investigation examines the influence of critical factors like moisture content, diffusivity, and temperature diffusivity on the spatial distribution of various physical fields. Additionally, a particular scenario of significance is highlighted. These results have the potential to improve sensor, actuator, and energy-harvesting device performance and dependability.

Numerical Simulation of Airflow Velocity and Temperature Distribution in an Aircraft Cabin

In this work, a computational fluid dynamics (CFD) model is established to calculate the airflow distribution in the cabin of a single-channel Boeing 737-800 airplane. The RNG k-ε model, considering the calculation of turbulence kinetic energy and its rate of dissipation, is adopted to solve turbulence problems in physical field simulation. The proposed three-dimensional model is able to consider the particular physical factors and spatial structures, which can simulate the detailed distributions of complex physical fields, compared with the one-dimensional lumped parameter model. The velocity and temperature fields under different air supply velocities are then numerically investigated. The calculation results show that when the air velocity at the top air supply inlet is 1.4 m/s, the velocity and temperature distribution inside the cabin can both meet the comfort requirements of humans in the airworthiness standards. The results from this work can help to design an aircraft environmental control system.

Design and investigation of novel gradient flow fields for proton exchange membrane fuel cell

Ensuring sufficient gas supply and high distribution uniformity are crucial issues in the flow field design to improve the performance and durability of proton exchange membrane fuel cell (PEMFC). However, previous studies often ignore the gas-water distribution variations along the flow direction and adopt identical design for the entire flow field, resulting in unsatisfactory performance. To fill in this gap, this paper innovatively proposes two types of gradient flow field (gradient narrowing and gradient droplet) considering the gas-water distribution characteristics. The channel of the gradient narrowing flow field gradually decreases in all directions along the flow direction, and the gradient droplet flow field is composed of staggered droplet blocks, and the distribution density gradually decreases along the flow direction. The Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method is used for the comprehensive evaluation of flow fields. The results demonstrate that the gradient flow field can significantly improve the performance and physical field distribution. The gradient narrowing flow field has the best performance, with 11.39 % improvement in peak power density, 77.96 % increment in average oxygen mass fraction, and 43.11 % improvement in oxygen uniformity compared to parallel flow field. Further, the key geometric parameters sensitivity analysis of gradient narrowing flow field is carried out. This study contributes to understanding the underlying mechanism of mass transfer properties in the novel gradient flow field, and exploring its potential for high-performance flow fields design.

A Review of Polymer-Based Environment-Induced Nanogenerators: Power Generation Performance and Polymer Material Manipulations.

Natural environment hosts a considerable amount of accessible energy, comprising mechanical, thermal, and chemical potentials. Environment-induced nanogenerators are nanomaterial-based electronic chips that capture environmental energy and convert it into electricity in an environmentally friendly way. Polymers, characterized by their superior flexibility, lightweight, and ease of processing, are considered viable materials. In this paper, a thorough review and comparison of various polymer-based nanogenerators were provided, focusing on their power generation principles, key materials, power density and stability, and performance modulation methods. The latest developed nanogenerators mainly include triboelectric nanogenerators (TriboENG), piezoelectric nanogenerators (PENG), thermoelectric nanogenerators (ThermoENG), osmotic power nanogenerator (OPNG), and moist-electric generators (MENG). Potential practical applications of polymer-based nanogenerator were also summarized. The review found that polymer nanogenerators can harness a variety of energy sources, with the basic power generation mechanism centered on displacement/conduction currents induced by dipole/ion polarization, due to the non-uniform distribution of physical fields within the polymers. The performance enhancement should mainly start from strengthening the ion mobility and positive/negative ion separation in polymer materials. The development of ionic hydrogel and hydrogel matrix composites is promising for future nanogenerators and can also enable multi-energy collaborative power generation. In addition, enhancing the uneven distribution of temperature, concentration, and pressure induced by surrounding environment within polymer materials can also effectively improve output performance. Finally, the challenges faced by polymer-based nanogenerators and directions for future development were prospected.

Semiconductor elastic medium with electromagnetic porosity, photothermal excitation, and the Thomson effect

The Thomson influence on semiconductors can be studied by investigating the connection between the presence of thermoelectric and magnetic fields and porosity and the photothermal transport mechanism. Elastic waves, voids, magnetic fields, and thermoelectric effects in plasma are investigated. The governing equations were analyzed for a uniformly distributed and isotropic medium under two-dimensional [electronic and elastic (plasmaelastic)] deformations. The charge density is considered solely dependent on the induced electric current over time. The Laplace-Fourier transforms method in two dimensions is employed to obtain solutions for the primary variables. The recombination process results in the application of electro-mechanical loads and thermal effects on the free surface of a porous medium. The Laplace-Fourier transformations inversion operations help obtain comprehensive solutions in this study. The effects of porosity parameters and silicon (Si) on a semiconductor porous material are considered, and the resulting physical field distributions are analyzed and represented graphically.

Numerical and correlation analysis of conjugate heat transfer over the discrete braided composites plate

Braided composites, which have excellent mechanical and thermophysical performance, have been considered promising materials widely used in aerospace, renewable energy, and other fields. However, the conjugate heat transfer mechanism between working fluids and braided structures is still unclear. Due to the complicated structure and computational limitation, with a neglection of the structural discrete feature and velocity distortion, current pertinent research primarily relies on the equivalent method of homogenization. In this research, a detailed numerical investigation of conjugate heat transfer over a three-dimensional four-directional (3D4d) braided composite plate with anisotropic and discrete features is presented. The full-size geometric structure of the 3D4d braided plate is first established utilizing the representative volume element (RVE). For such periodic structures, a continuous Eulerian grid generation technique is developed. A local coordinate system approach for the heat conduction spindle based on discretization is subsequently proposed to address the anisotropy of heterogeneous materials. The accuracy of the proposed discrete model processing approaches is verified by comparison with homogenization techniques widely used and experimental data in the literature. It is discovered that the discrete structure with an interfacial thermal dispersion, has a unique physical field distribution in comparison to the homogenization cases. Moreover, a semi-theoretical heat transfer criterion for 3D4d composite is established based on the thermal correction of dispersed interface.

Research on Performance Optimization of Novel Sector-Shape All-Vanadium Flow Battery

The all-vanadium flow batteries have gained widespread use in the field of energy storage due to their long lifespan, high efficiency, and safety features. However, in order to further advance their application, it is crucial to uncover the internal energy and mass transfer mechanisms. Therefore, this paper aims to explore the performance optimization of all-vanadium flow batteries through numerical simulations. A mathematical and physical model, which couples electrochemical reactions and thermal mass transfer processes within a novel sector-shape all-vanadium flow battery, has been established. Subsequently, the impact of cell thickness and operating parameters on the distribution of various physical fields and performance parameters has been investigated. The results show that the potential and overpotential decrease as the electrode thickness increases, while the energy efficiency initially rises and then declines. As for operating parameters, higher electrolyte concentration demonstrates superior performance, while changes in electrolyte flow and current density have comprehensive effects on the battery. The cell performance can be adjusted based on the integrated mass transfer process and energy efficiency.

Photo-thermo-piezo-elastic waves in semiconductor medium subject to distinct two temperature models with higher order memory dependencies

PurposeThis study aims to examine the impacts of higher memory dependencies on a novel semiconductor material that exhibits generalized photo-piezo-thermo-elastic properties. Specifically, the research focuses on analyzing the behavior of the semiconductor under three distinct temperature models.Design/methodology/approachThe study assumes a homogeneous and orthotropic piezo-semiconductor medium during photo-thermal excitation. The field equations have been devised to encompass higher order parameters, temporal delays and a specifically tailored kernel function to address the problem. The eigenmode technique is used to solve these equations and derive analytical expressions.FindingsThe research presents graphical representations of the physical field distribution across different temperatures, higher order plasma heat conduction models and time. The results reveal that the amplitude of the distribution profile is markedly affected by factors such as the memory effect, time, conductive temperature and spatial coordinates. These factors cannot be overlooked in the analysis and design of the semiconductor.Research limitations/implicationsSpecific cases are also discussed in detail, offering the potential to advance the creation of precise models and facilitate future simulations.Practical implicationsThe research offers valuable information on the physical field distribution across various temperatures, allowing engineers and designers to optimize the design of semiconductor devices. Understanding the impact of memory effect, time, conductive temperature and spatial coordinates enables device performance and efficiency improvement.Originality/valueThis manuscript is the result of the joint efforts of the authors, who independently initiated and contributed equally to this study.

Fractional and MDD analysis of piezo-photo-thermo-elastic waves in semiconductor medium

This manuscript examines the effects of memory-dependent and fractional-order derivatives on a novel generalized piezo-thermo-elastic semiconductor model. The medium is homogenous and orthotropic, subjected to photo-thermal excitation. The governing equations include fractional-order parameters, relaxation time, time delay, and kernel function tailored to specific problem requirements. Normal mode method use to solve the equations, yielding analytical expressions. Graphical representations show physical field distribution across various fractional-order parameters, kernel functions, time delay, and frequency values. This study has the potential to advance precise model development and future simulations.

Design of computer-generated holograms based on semi-rigorous simulations of sub-wavelength structures.

Conventional design methods for computer-generated holograms often rely on the scalar diffraction theory because the calculation effort of rigorous simulations is too high. But for sub-wavelength lateral feature sizes or large deflection angles, the performance of realized elements will show distinct deviations from the expected scalar behavior. We propose a new design method that overcomes this issue by incorporating high-speed semi-rigorous simulation techniques that allow the modeling of light propagation at an accuracy close to the rigorous methods. This includes an approach to solve the inverse problem of calculating a geometric structure that is able to form a certain physical field distribution.

A novel method for aeroengine performance model reconstruction based on CDAE model

Aeroengine is a complex multi-module system. Due to the limitation of sensor cost and sensor installation conditions, it is usually impossible to install a large number of sensors to measure the physical parameters of the aeroengine modules to establish the accurate module characteristic models to achieve the purpose of module performance evaluation. To address this issue, the high-dimensional physical field reconstruction strategy base on limited measurement data is developed, which is of great significance to the modeling of module characteristics. A reconstruction framework of a high-dimensional physical field based on limited measurement data is built. The mapping relationship between limited measurement data and high-dimensional physical field data is established, and the relevant learning strategies based on the deep learning network are designed. To verify the effectiveness of the proposed method, the simulation dataset generated by the multi-component closed-loop simulation system and the aeroengine service dataset are used for experimental verification, and the mean and variance of mean square error are used as evaluation indexes. Experimental results show that the proposed method can obtain high-dimensional physical field distribution based on limited measurement data.

High Absorptivity and Ultra-Wideband Solar Absorber Based on Ti-Al2O3 Cross Elliptical Disk Arrays

Perfect metamaterial absorbers have attracted researchers’ attention in solar energy harvesting and utilization. An ideal solar absorber should provide high absorption, be ultra-wideband, and be insensitive to polarization and incident angles, which brings challenges to research. In this paper, we proposed and optimized an ultra-wideband solar absorber based on Ti-Al2O3 cross elliptical disk arrays to obtain the ultra-wideband absorption of solar energy. The addition of a cavity greatly improves the energy-absorbing effect in the operating band, which has research value. The absorption spectrum and field distribution were analyzed by the finite difference time domain method. For the physical mechanism, the electric and magnetic field distribution indicates that ultra-wideband absorption is caused by propagation surface plasmon resonance (SPR), localized SPR and Fabry–Perot (F-P) resonance excited between Ti and Al2O3 disks. The results demonstrate that the absorption bandwidth with the absorption rate beyond 90% reaches 1380 nm (385–1765 nm), and the average absorption reaches an astonishing 98.78%. The absorption bandwidth matches the main radiation bandwidth of the solar energy, which is approximately 295–2500 nm according to the data from the literature, and the total thickness of the structure is only 445 nm. Moreover, the ultra-wideband solar absorber is insensitive to the polarization angle and oblique incidence angle. The proposed ultra-wideband solar absorber has research and application value in solar energy harvesting, photothermal conversion and utilization.

Research on the Influence of Fault Arc on Polyimide Insulation Materials

In modern grid systems, electrical fires caused by faulty arcs occur more frequently. Arc protective clothing is the equipment that can effectively protect personal safety. Among them, polyimide insulation materials have the advantages of high-temperature resistance and high thermal resistance. Their performance in the field of arc protection is of high research value. In this paper, the effect of faulty arc on polyimide insulation material is studied by experimental and simulation control modes. The COMSOL software is used to simulate the process of electric arc affecting polyimide insulation material, and to simulate the physical field distribution of electric arc with different electrode spacing and different arc currents. An arc generation device is built, a copper calorimeter is designed to record the temperature rise of each experiment, a variety of arc parameters is changed, and the performance of polyimide insulation materials is analyzed to block the fault arc. A fault arc experimental platform was built, using a copper calorimeter to record the temperature rise of each experiment. Varying multiple arc parameters to analyze the performance of polyimide insulation materials in blocking fault arcs. The simulation and test results show that polyimide has an obvious barrier effect on the radiation temperature of the fault arc, and it can show good thermal insulation under different arc conditions, which proves that polyimide insulation materials have excellent protection performance against fault arcs in the energized operation environment.

Numerical solution and experimental study of Multi-field coupling for nickel-based coatings prepared by scanning electrodeposition at different currents

In this study, a dynamic grid mathematical model of scanning electrodeposition coupled with electric field, flow field, temperature field and concentration field was established. The transient distribution of multiple physical fields with different current densities (I was 0.075–0.275 A) and the growth of the coating were investigated. The preparation, morphology characterization and performance testing of nickel-based coatings were carried out. The results showed that the transient distribution of multiple physical fields reflected the deposition rule of the coating, and explains the deposition phenomenon of the coating with an “arch-shaped” distribution in the test. With the increase of current, the thickness of the coating and the degree of the arch increased. The numerical solution was consistent with the experimental law. The hardness, wear resistance and corrosion resistance of the coating increased first and then decreased. When I was 0.175 A (current densities was 700 A/m2), the maximum hardness of the nickel-based coating was 668.88 HV0.1, the minimum wear scar area was 1144.74 μm2, and the maximum equivalent resistance was 10,960 Ω. The temperature and concentration fields had little influence on the deposition process, and changes were only observed on the deposition surface. Electric and flow field distributions had greater influences on the deposition process, were the main reason for “arch-shaped” distribution.

Magnetic Field Influence of Photo-Mechanical-Thermal Waves for Optically Excited Microelongated Semiconductor

A theoretical novel model is investigated that describes the dynamic effects of the microelongation processes of an exciting semiconductor medium. The influence of the magnetic field for the optically excited medium is taken into consideration according to the photothermal transport characteristics. The governing equations were derived during the electronic (ED) and thermoelastic (TED) deformation processes when the microelongation parameters of the semiconductor medium were taken into account. The interference between thermal-magnetic-microelongat-plasma-mechanical waves is investigated. The dimensionless expressions are utilized to solve the main equations according to the harmonic wave technique in two-dimensional (2D) deformation. The complete solutions of the expressions of the physical field were obtained when some conditions were taken on the outer semiconductor surface. The theoretical microelongated semiconductor model in this investigation was checked by comparing it with some previous studies. The numerical simulation for the main physical field distributions is graphically displayed when the silicon (Si) material is used. The impact of various factors such as the magnetic field, thermal memory effect, and microelongation on the wave propagations for main fields was discussed.

Non-ideal characteristics in a micro packed-bed reactor: A coupled reaction-transport CFD analysis for propane dehydrogenation

Kinetic experiments can be significantly influenced by fluidic effects and transport limitations within reactors, particularly for strongly exo- and endo-thermic reactions. This paper describes the influence non-uniform physical fields, e.g. temperature, velcocity and species concentration, on the determination of kinetic parameters for endothermic systems with propane dehydrogenation (PDH) as a model process, which was analyzed using computational fluid dynamics (CFD) method based on the porous media model. Propane conversions calculated from 3-D porous media model at various conditions have discrepancies from the reported experimental data and 1-D numerical regression. This is due to the application of kinetic parameters obtained from 1-D plug flow assumption to the 3-D model with inhomogeneous temperature distributions. In the kinetic analysis, it is found that the low space velocity may lead to backward diffusion but can be a preference to minimize the temperature gradients within the catalyst bed. On the other hand, the commonly used higher space velocity may enlarge the temperature inhomogeneity. The sensitivity of temperature distribution with various reaction conditions is further analyzed. In addition, with respect to the packed bed properties, a high thermal conductivity and low loading of catalysts can reduce the non-uniformity of temperature distribution. Therefore, it is proposed that a mixed packing scheme with lower catalyst concentration and higher thermal conductivity could effectively suppress temperature gradients in kinetic analysis. This study exemplifies the necessity to consider the non-ideal distribution of physical fields for the kinetic study of reactions with strong thermal effects.

Effect of Variable Thermal Conductivity and Magnetic Field for the Generated Photo-Thermal Waves on Microelongated Semiconductor

A theoretical analysis of the dynamic impacts of a novel model in the microelongated-stimulated semiconductor medium is investigated. The influence of the magnetic field of the optically excited medium is taken into consideration according to the photothermal transport processes. The governing equations were created during the electronic (ED) and thermoelastic (TED) deformation processes. Thermal conductivity of the semiconductor microelongation medium is taken as temperature dependent. The interaction of thermal, microelongate, plasma, and mechanical waves is examined. Dimensionless formulae are used to solve the main equations in two dimensions (2D) using the harmonic wave method. The physical field equations have complete solutions when some conditions are applied to the semiconductor surface. The theoretical microelongated semiconductor model employed in this experiment was confirmed by comparing it to certain earlier studies. The numerical simulation for the principal physical field distributions is graphically displayed when silicon (Si) material is employed. The topic of the discussion was the impact of several factors, such as the magnetic field, thermal memory, and microelongation, on the propagation of waves for major fields.

Evaluation of the thermal and mechanical waves in anisotropic fiber-reinforced magnetic viscoelastic solid with temperature-dependent properties using the MGT thermoelastic model

The main objective of the current paper is to provide a modified thermo-viscoelastic mathematical model based on the Moore-Gibson-Thompson (MGT) equation to study the behavior of fiber-reinforced viscoelastic media. To describe the viscoelastic behavior of the fiber-reinforced material, the Kelvin-Voigt type is used. The relaxation time coefficient is included in the Green and Naghdi type III model (GN-III) to solve the problem of the infinite velocity propagation of heat waves. For an infinite viscosity-reinforced elastic solid with a cylindrical cavity, the proposed model was applied to investigate the effects of thermo-mechanical coupling and thermal relaxation coefficients on the studied fields. The cavity surface is considered to be traction-free and subject to temperature changes that fluctuate harmoniously. The Laplace transform tool was used to find analytical solutions for the distributions of different physical fields. The inverse Laplace transforms were calculated numerically using the Fourier series approximation approach. The effect of viscosity and the frequency of heat pulses on the fields under study are shown graphically. A comparison was made between several related models to confirm the effectiveness of the proposed system by presenting the numerical results in tables.

Generalized Thermoelastic Interaction in a Half-Space under a Nonlocal Thermoelastic Model

In the current article, the nonlocal thermoelastic theory is used to discuss the wave propagation in unbounded thermoelastic materials. Due to the inclusion of relaxation time in thermal conduction formulation and the equations of motion, this model was developed using Lord and Shulman’s generalized thermoelastic model. The theory of the nonlocal continuum proposed by Eringen is used to obtain this model. The integral transforms of the Laplace transform methods used to generate an analytical solution for physical variables are utilized to produce the analytical solutions for the thermal stress, displacement, and temperature distribution. The effects of nonlocal parameters and relaxation time on the wave propagation distributions of physical fields for material are visually shown and explored.

Performance prediction and design optimization of turbine blade profile with deep learning method

Aerodynamic design optimization of the blade profile is a critical approach to improve performance of turbomachinery. This paper aims to achieve the performance prediction with deep learning method and realize fast design optimization of a turbine blade. Two parameterization methods based on geometric relationships (PGR) and neural network (PNN) are proposed, which can generate smooth and complete blade profiles. A dual convolutional neural network (DCNN) is constructed to predict the physical fields and aerodynamic performance. The implementations of DCNN are accomplished based on the datasets generated by the two parameterization methods respectively, which are called PGR-DCNN and PNN-DCNN model. Results show that the prediction accuracy increases and then keeps stable as train size increases. The two models can offer the detailed physical field distribution within 3 ms and accurately predict the aerodynamic performance. The prediction errors of performance parameters for 99% samples in validation set are less than 0.5% with PGR-DCNN model, which are significantly better than conventional machine learning methods. Finally, based on the accurate predictive models, the gradient-based design optimization for rotor blade profile is completed in 38 s. The efficiency of the two optimal blades reaches 89.29% and 88.92% respectively, which verifies the feasibility of our method.