Mesh Grid Research Articles

Effect of external magnetic field and dust grains on the properties of ion-acoustic waves

An experimental study to investigate the effect of an external magnetic field on the propagation of ion-acoustic waves (IAWs) has been carried out in hydrogen plasma containing two-temperature electrons and dust grains. It is a first step in understanding the propagation properties of IAWs in such an environment. A low-pressure hot cathode discharge method is chosen for plasma production. The desired two-electron groups with distinct temperatures are achieved by inserting two magnetic cages with a cusp-shaped magnetic field of different surface field strengths in the same chamber. The dust grains are dropped into the plasma with the help of a dust dropper, which gain negative charges by interacting with the plasma. The IAWs are excited with the help of a mesh grid inserted into the plasma. A planar Langmuir probe is used as a detector to detect the IAWs. The time-of-flight technique has been applied to measure the phase velocity of the IAWs. The results suggest that in the presence of a magnetic field, the phase velocity of IAWs increases, whereas introducing the dust particles leads to the lower phase velocity. The magnetic field is believed to have a significant effect on the wave damping. This study will aid in utilising IAWs as a diagnostic tool to estimate plasma parameters in the presence of an external magnetic field.

GPU implementation of the discrete unified gas kinetic scheme for low-speed isothermal flows

In this paper, two GPU parallel algorithms are proposed for the discrete unified gas kinetic scheme (DUGKS) for simulating low-speed isothermal flows. Algorithm-I uses a two-level fine-grain technique for the parallelization of physical spatial space, while Algorithm-II adopts this technique for both physical spatial and particle velocity spaces. To evaluate the performance of the proposed algorithms, several typical benchmark problems are simulated, including the two-dimensional (2D) and three-dimensional (3D) lid-driven cavity flows, the micro channel and cavity flows. Numerical results show that our GPU algorithms can achieve satisfactory computational efficiency. For Algorithm-I, the speedup can reach 250 and 338 on a Tesla V100 GPU card for the 2D and 3D continuum cavity flows, respectively, and a hundredfold acceleration can be obtained for the rarefied cases. While for Algorithm-II, a speedup of about 70 can be attained for rarefied cases. However, it is not applied to continuum problems that only require a small number of velocity points. Moreover, comparisons between the two GPU algorithms are also conducted for the rarefied flows with various grid meshes and velocity directions. The results show that Algorithm-I performs better when physical mesh size is large, while Algorithm-II can provide higher efficiency for a coarser mesh with medium number of discrete velocities. Special attention is also paid to comparisons between Algorithm-I and MPI parallelization with 128 CPU cores based on physical space discretization approach, and it is found that Algorithm-I has a clear advantage on V100 GPU when dealing with sparse physical grids in both continuum and rarefied cases.

Optimization design of ground grid mesh of 69/13,8 KV substation using ETAP

Optimization design of ground grid mesh of 69/13,8 KV substation using ETAP

Matlab Implementation using Holtrop and Mennen Method of Bare Hull Resistance Prediction for Surface Combatant Ship Coupled with CFD

Holtop’s & Mennen’s method is one of the most widely used technique in resistance and powering prediction for tankers, general cargo ships, container ships and combatant surface ships. Holtrop’s Statistical Analysis method is utilized, as in comparison to the other options, more complete and closer to the actual results. The main purpose of this paper is to develop a Matlab application using Holtop’s & Mennen’s method for studying and research the total resistance of DTMB 5415 combatant ship. The solid modelling is developed using Maxsurf. The computational fluid dynamic (CFD) technique is applied to analyze the hydrodynamic behaviour of hull form and predict the total resistance (Rt) to provide a description of the other prediction methods. The simulation process was executed using ANSYS software based on fluid flow (STAR-CCM+) solver. The variation of computational grid used in computation is SST (Shear Stress Transport) coarse and fine mesh size for hull speed up to 32 kn. RT resulted from CFD computation is validated with results from Holtrop that has been developed by Matlab implementation. The larger the grid meshing size, the better the validation of the results. The CFD technique demonstrated good agreement with Holtrop formulae in predicting the (RT) of DTMB 5415

Coupled neutronics, thermal-hydraulics, and fuel performance analysis of dispersion plate-type fuel assembly in a cohesive way

The nuclear reactor is a multi-physics and multiscale coupling system. The conditions of high temperature and high neutron flux in the reactor pose a significant challenge to the thermodynamic performance of the fuel. To evaluate the plate-type fuel's performance, a coupling calculation of neutron physics code OpenMC, fuel performance analysis code BEEs-Plates, and nuclear reactor system analysis code NUSAC has been implemented based on the open-source MOOSE platform. A novel and efficient method for mesh grids generation and data mapping between external codes and MOOSE was proposed to ensure accurate data exchange. This method can simplify the mesh grids generation process of external codes and accurately transfer data across different mesh grids. Finally, the coupling calculation of the JRR-3 M research reactor fuel assembly was carried out based on the above coupling code, and the neutronics parameters, thermal–hydraulic parameters, and fuel performance-related parameters of the fuel assembly were analyzed. The calculation results show that the maximum fuel burnup will reach 16.91% FIMA after 240 days. With the increase of fuel burnup, the peak power of the fuel assembly is significantly shifted towards both ends of the height direction. The VonMises stress, volume stress, creep strain, and displacement of the fuel will be considerable. Finally, the impact of the coupling calculation on the accuracy of the computational efficiency is preliminarily investigated.

Evaluating uncertainties in CFD simulations of patient-specific aorta models using Grid Convergence Index method

Cardiovascular diseases are among the most important causes of global mortality. Computational Fluid Dynamics (CFD) is a powerful research tool that analyzes the hemodynamics of artery and blood flow patterns. In this study, CFD simulations are performed to assess the patient-specific healthy aorta, fusiform, and saccular aneurysm with various mesh types, including tetrahedral, polyhedral, and poly-hexacore. The aim of this study is to explore how different mesh types and grid densities impact the hemodynamic properties of physiological flows, with the goal of identifying the most cost-effective meshing approach. A mesh independence study is carried out to ensure the precision of the results, considering the wall shear stress distribution. For this, five different mesh resolutions are generated for each geometry. The uncertainties of the simulations associated with the discretization techniques and solutions are evaluated using the Grid Convergence Index (GCI) method. The findings showed that increasing the mesh density provides smaller uncertainty. GCI values for the wall shear stress are in the range of convergence, indicating that the results are reliable and accurate. Mesh type selection affects the accuracy and computational cost of our simulations. The polyhedral and poly-hexacore meshes lead to a good compromise between precision and computational cost, while the tetrahedral mesh style gives the most precise results with fluctuation. This work provides a systematic approach based on the Grid Convergence Index method in order to select the most appropriate mesh type for evaluating uncertainties in CFD simulations of patient-specific healthy aortas and aortas with abdominal aneurysms. According to the findings and GCI analysis, the polyhedral mesh type was chosen for all patient-specific aorta models. The study clearly demonstrated its superiority over other mesh types, considering uncertainties and computational costs associated with different mesh styles.

Optimal design analysis of substation ground grid mesh

Substations are grounded by means of earth-embedded electrodes in order to provide safety during normal or fault conditions. Electric substations are effectively grounded to guarantee the proper operation of electrical devices, minimize the likelihood of flash-over during transient conditions as well as dispel lightning strokes. A structure is termed grounded if it is electrically bonded to earth-embedded metallic frames. The earth-embedded metallic frames provide a conducting pathway of electricity to the earth and it is called a ground grid system. Substation ground grid mesh is comprised of vertical and horizontal conductors as well as vertical rods buried beneath the substation ground. Electric current flow through the human body is hazardous. Therefore, ground grid systems should be designed such that the likely electric body current in an operator or passer-by should not exceed the standard defined limits under any foreseeable harmful circumstances and as well provide protection of equipment. The objective of this study is to determine substation, safe ground grid system parameters as well as the cost-effectiveness of designing substation ground grids by comparing the IEEE Std. 80-2000/2013 and the Finite Element Method (FEM). ETAP 16.0 Power Tool is employed in carrying out this analysis. The substation expected maximum short circuit current is stated. The design analysis using both methods is presented separately and suggestions are made with reference to the most cost effective and safest method for the effective designing of the substation ground grid system.

A novel dc fault protection scheme based on intelligent network for meshed dc grids

This paper proposes a fault detection and classification scheme for multi-terminal high voltage direct current (MT-HVdc) lines by integrating discrete wavelet transform (DWT) multi-resolution analysis with artificial neural networks (ANNs). Previously, such intelligent protection schemes used manual approaches or arbitrary rules of thumb to optimize a set of hyperparameters of the neural networks without applying any optimization algorithm. In order to improve accuracy, this work proposes an efficient Bayesian Optimization (BO) approach for evaluating and establishing the regulated hyperparameters for ANNs. The DWT multi-resolution analysis (MRA) and Parseval’s theorem are used to extract energy variation for various faults. The energy variation of fault signals at different scales is fed into a multi-stage model to optimize the hyperparameters of neural networks with minimal training setup time and compute effort. After training, the data-based algorithm is implemented in a single-end main and coordinated secondary unit with control logic. The proposed scheme intends to detect internal short-circuit dc faults as quickly as possible and cover the failure of the main unit with expedited backup action. The findings of the study reveal that the proposed scheme can accurately detect internal faults in a variety of testing conditions and remain stable against external faults or disturbances with an average recognition accuracy of 99.38%.

Layout Dependence Stress Investigation in through Glass via Interposer Architecture Using a Submodeling Simulation Technique and a Factorial Design Approach.

The multi-chiplet technique is expected to be a promising solution to achieve high-density system integration with low power consumption and high usage ratio. This technique can be integrated with a glass interposer to accomplish a competitive low fabrication cost compared with the silicon-based interposer architecture. In this study, process-oriented stress simulation is performed by the element activation and deactivation technique in finite element analysis architecture. The submodeling technique is also utilized to mostly conquer the scale mismatch and difficulty in mesh gridding design. It is also used to analyze the thermomechanical responses of glass interposers with chiplet arrangements and capped epoxy molding compounds (EMC) during curing. A three-factor, three-level full factorial design is applied using the analysis of variance method to explore the significance of various structural design parameters for stress generation. Analytic results reveal that the maximum first principal stresses of 130.75 and 17.18 MPa are introduced on the sidewall of Cu-filled via and the bottom of the glass interposer, respectively. Moreover, the EMC thickness and through glass via pitch are the dominant factors in the adopted vehicle. They significantly influence the stress magnitude during heating and cooling.

Non-uniform Rectilinear Grid in the Waveguide Modeling of the Vocal Tract

For many years, a digital waveguide model is being used for sound propagation in the modeling of the vocal tract with the structured and uniform mesh of scattering junctions connected by same delay lines. There are many varieties in the formation and layouts of the mesh grid called topologies. Current novel work has been dedicated to the mesh of two-dimensional digital waveguide models of sound propagation in the vocal tract with the structured and non-uniform rectilinear grid in orientation. In this work, there are two types of delay lines: one is called a smaller-delay line and other is called a larger-delay line. The larger-delay lines are the double of the smaller delay lines. The scheme of using the combination of both smaller- and larger-delay lines generates the non-uniform rectilinear two-dimensional waveguide mesh. The advantage of this approach is the ability to get a transfer function without fractional delay. This eliminates the need to get interpolation for the approximation of fractional delay and give efficient simulation for sound wave propagation in the two-dimensional waveguide modeling of the vocal tract. The simulation has been performed by considering the vowels /ɔ/, /a/, /i/ and /u/ in this work. By keeping the same sampling frequency, the standard two-dimensional waveguide model with uniform mesh is considered as our benchmark model. The results and efficiency of the proposed model have compared with our benchmark model.

Data-driven boundary regression for equivalent identification of external parameters in steady-state models of power systems

External Network Modeling (ENM) is an important method to simplify and accelerate power system control, protection, and optimization. Traditional model-based methods obtain accurate external parameters by analyzing the physical properties of the whole system. In the case of incomplete physical information, the use of data-driven models has become an effective means to analyze the operating state of power systems. In this paper, a data-driven approach is used to propose an external equivalent parameter identification framework for steady-state models of power systems to accurately estimate the operating states of power systems of interest. Linear correction coefficients are used to deal with the challenges brought by the nonconvexities of the power flow equation to the regression. Based on the linearly mapped power flow equation, we derive the Multivariate Linear Regression (MLR) model of the external power system. The Box-Cox transformation (BCT) and ridge regression algorithm (RRA) algorithms are designed to address data normality, collinearity, and overfitting. The proposed framework is tested on a series of IEEE standard cases, which include both meshed transmission grids and radial distribution grids, with both Monte Carlo simulated data and public testing data. The results show that the proposed method can obtain a higher calculation accuracy than model-based methods can. The results also demonstrate that the proposed data-driven equivalent framework can obtain accurate regression parameter matrices under the condition of non-normal data, and accurately reflect the physical parameters of the external power system.

Mechanism of Au nanowire growth by Au evaporation on Si substrates irradiated with Ar ions

This study aims to clarify the mechanism of site-selective Au-nanowire (NW) growth on Si substrates irradiated with Ar ions. Au NWs are grown by Au evaporation at specific regions in the boundary zones between the ion-irradiated and unirradiated areas of Si substrates. The NW growth area are restricted by placing a grid mesh with a certain hole size within the boundary zone to limit the irradiation area. The length and diameter of the NWs can be controlled by controlling the hole size. Cross-sectional microscopic analyses reveal the presence of a thin Si-oxide layer as well as an Au–Si buried layer beneath the NWs. A site-selective Au NW growth model is developed by modifying the already-existence model. By fitting the Au NW length calculated using our model to the experimental data, the surface diffusion length of Au adatoms (λs) is estimated to be approximately 7 μm, close to the radius of the irradiated area Rw (6 μm). This validates our model that assumes that the NWs are grown at the bottom from the Au adatoms migrating onto the substrate. The Au-NW growth mechanism is discussed along with the role of the oxide layer and surface diffusion of Au adatoms.

Hybridizing FDM and FVM scheme of high-precision interface fast capture for mixed free-surface-pressurized flow in large cascade water delivery system

In recent years, China has been building several inter-basin water conveyance projects across mountains and deep valleys, leading to the extensive use of long tunnels and inverted siphons. The dynamics of mixed free-surface-pressurized flows are critical for tunnel design and operational safety. However, traditional numerical computation schemes cannot precisely and efficiently capture the pressure interface because the tunnel may be more than 70 km long. This study aims to develop a hybrid scheme that is as fast as the large-time-step Preissmann four-point scheme (FDM) and has the approximate interface accuracy of the finite volume method (FVM) by dynamic grid meshing. A dynamic mesh domain model (DM) is proposed by adopting an FVM mesh with a small time step to dynamically capture the interface and applying an FDM mesh with a large time step to improve computational efficiency. The results show that the method can simulate flow patterns, such as transcritical and pressurized flows, by ignoring the acceleration convection terms and capturing mixed free-surface-pressurized flows conveniently, accurately and efficiently. Furthermore, it can accelerate the computational speed of the transient mixed flow by a factor of approximately 100 when the target tunnel length exceeds 1200 m. The proposed scheme cannot capture the water hammer pressure because of the large time step. However, it can be effectively utilized in large cascade water delivery systems where the flow changes gradually.

Insights into an analytical simulation of a natural convection flow controlled by Arrhenius kinetics in a micro-channel

The focus of this paper is the investigation of an Arrhenius-driven chemical reaction in an upstanding micro-channel over an imposed transverse magnetic field with fully developed constant free convection flow. Subject to suitable boundary conditions, the temperature and velocity equations are resolved in non-dimensional form employing the homotopy perturbation method (HPM). the fundamental flow behaviors of temperature, velocity, and volumetric flow are explored as a consequence of regulating characteristics such as fluid-wall interaction parameter, rarefaction parameter, chemical reaction parameters, wall-ambient temperature difference ratio, and Hartman number. The findings are carefully investigated and graphically represented in several mesh grid graphs. It was established that increasing the values of the rarefaction parameters and chemical reaction results in an upsurge in the fluid velocity and volume flow rate, respectively, whereas increasing the Hartman number results in observable flow retardation. Additionally, when the chemical reactant parameter is ignored, the numerical comparison is in excellent agreement with the previously published results.

REVIEW ON VOLTAGE SAG STUDIES FOR DISTRIBUTION GRID INCLUDING RENEWABLE ENERGY SOURCES

Several types of power quality problems can be observed in power network. These power quality problems include voltage unbalance, voltage flicker, voltage sags and swells, interruptions, and voltage and current harmonics. Voltage sag is one of the vital power quality issues. This problem can cause a decrease in power grid voltage over a short time horizon. The aforementioned problem is caused by various types of short circuits and the widespread use of sensitive devices. These problems have a significant impact on power systems. In this review article, the different ways to prevent voltage sag have been presented by considering literature studies. Concerning voltage sags in radial and mesh grids, the equipment used, and methods have all been taken into account. In these studies, the articles about voltage sag-related problems have been put into groups based on certain criteria. These criteria include the consideration of uncertainties in electricity demand or renewable sources. The recommendations related to the voltage sag studies have been presented. These suggestions are based on the inclusion of electricity consumption and renewable energy source uncertainties. The future works have been mentioned by considering these load and renewable system uncertainties.

General Exact Schemes for Second-Order Linear Differential Equations Using the Concept of Local Green Functions

In this paper, we introduce a special system of linear equations with a symmetric, tridiagonal matrix, whose solution vector contains the values of the analytical solution of the original ordinary differential equation (ODE) in grid points. Further, we present the derivation of an exact scheme for an arbitrary mesh grid and prove that its application can completely avoid other errors in discretization and numerical methods. The presented method is constructed on the basis of special local green functions, whose special properties provide the possibility to invert the differential operator of the ODE. Thus, the newly obtained results provide a general, exact solution method for the second-order ODE, which is also effective for obtaining the arbitrary grid, Dirichlet, and/or Neumann boundary conditions. Both the results obtained and the short case study confirm that the use of the exact scheme is efficient and straightforward even for ODEs with discontinuity functions.

MIXED CONVECTIVE AND RADIATIVE HEAT TRANSFER IN A HORIZONTAL CONCENTRIC AND ECCENTRIC CYLINDRICAL ANNULI

A numerical investigation has been performed to study the effect of eccentricity on unsteady state, laminar aiding mixed convection in a horizontal concentric and eccentric cylindrical annulus. The outer cylinder was kept at a constant temperaturewhile the inner cylinder was heated with constant heat flux. The study involved numerical solution of transient momentum (Navier-Stokes) and energy equation using finite difference method (FDM), where the body fitted coordinate system (BFC) wasused to generate the grid mesh for computational plane. The governing equations were transformed to the vorticity-stream function formula as for momentum equations and to the temperature and stream function for energy equation.A computer program (Fortran 90) was built to calculate the bulk Nusselt number (Nub) after reaching steady state condition for fluid Prandtl number fixed at 0.7 (air) with radius ratio ( =2.6), Rayleigh number (Ra=200), Reynolds number (Re=50) for both concentric and eccentric cylindrical annulus with different eccentricity ratios (ε=0, 0.25, 0.50, 0.75) and angular positions (φo=0o, 45o , 90o , 135o , 180o ).The results show a reasonable representation to the relation between Nusselt number and (ε, φo). Generally, Nub decreased with the increase in (ε and φo). Also, results show that the best thermal performance for the inner cylinder was at the angularposition (φo=0o ) for eccentricity ratio (ε=0.25), while the maximum reduction in the rate of heat transfer for the inner cylinder was at the angular position (φo=180o) for eccentricity ratio (ε=0.75).Comparison of the result with the previous work shows a good agreement.

POPULATION FLUCTUATION OF SUCKING INSECTS IN IRRIGATED AND NON-IRRIGATED COTTON CROPS

In the cotton crop (Gossypium hirsutum L.), there is a complexity of pests that appear systematically, thus significantly reducing crop yield; and their population fluctuation is strongly influenced by meteorological conditions that result in a greater or lesser density of these insects. Thus, this work aimed to evaluate the population fluctuation of insect pests with sucking feeding behavior in an area with and without irrigation in the cotton plant under second-harvest conditions. The experiment was developed at the State University of Maringá - Campus of Umuarama. In the experimental area, grid meshes of 10 × 10 m were demarcated, forming plots of 100 m², resulting in a total of 64 points in the irrigated area and 42 points in the non-irrigated area. The sampling points were demarcated in the center of each grid where three randomly selected plants were sampled. Samplings were carried out weekly, from 37 to 122 days after the emergence (DAE) of cotton, examining the aerial part of the plant, to observe the presence of aphids (Aphis gossypii), thrips (Frankliniella schultzei), and whitefly (Bemisia tabaci). The non-irrigated area provided the highest population peaks of whiteflies and thrips. On the other hand, the irrigated area had a higher incidence of aphids. However, with the increase in the population of ladybugs, the incidence of pests reduced significantly, showing the efficiency and importance of the control carried out by natural predators.

Use of Infrared Thermometry to Observe Temperature Variation Associated with the Healing Process in Wounds and Ulcers: TIHUAP Cohort Study Protocol.

We are interested in observing how temperature differences between the wound bed and perilesional skin are related to the healing process in primary care patients with wounds. Multisite prospective cohort study with one-year follow-up in the Metropolitan North area of Barcelona. Recruitment of patients over 18 years with an open wound will take place from January 2023 to September 2023. Temperature checks will be conducted on a weekly basis at control visits and wound care. The following variables will be measured: Percentage reduction of wound area over time, thermal index, the Kundin Wound Gauge, and the Resvech 2.0 Scale. The temperature will be measured weekly using a handheld thermometer and mesh grid to frame the temperature points. The healing trajectory will also be monitored on a monthly basis via photographic imaging, the Resvech Scale, calculation of wound size, percentage reduction of wound area over time, and thermal index for one year of follow-up or until the wound is cured. This study may represent a turning point for its introduction into primary care. Early diagnosis of wound complications would facilitate treatment decision-making for healthcare professionals, thus improving the management of resources related to chronic wounds.

Distributed cooperative Kalman filter constrained by advection-diffusion equation for mobile sensor networks.

In this paper, a distributed cooperative filtering strategy for state estimation has been developed for mobile sensor networks in a spatial-temporal varying field modeled by the advection-diffusion equation. Sensors are organized into distributed cells that resemble a mesh grid covering a spatial area, and estimation of the field value and gradient information at each cell center is obtained by running a constrained cooperative Kalman filter while incorporating the sensor measurements and information from neighboring cells. Within each cell, the finite volume method is applied to discretize and approximate the advection-diffusion equation. These approximations build the weakly coupled relationships between neighboring cells and define the constraints that the cooperative Kalman filters are subjected to. With the estimated information, a gradient-based formation control law has been developed that enables the sensor network to adjust formation size by utilizing the estimated gradient information. Convergence analysis has been conducted for both the distributed constrained cooperative Kalman filter and the formation control. Simulation results with a 9-cell 12-sensor network validate the proposed distributed filtering method and control law.