Number Of Meshes Research Articles

The numerical simulation of particulate reinforced composites by using a two-dimensional VCFEM formulated with plastic, thermal, and creep strain

The working environment of industrial fields where the Particulate Reinforced Composites (PRCs) are commonly used is complex. In these harsh environments, PRCs produce some nonlinear strains, such as plastic, thermal, and creep strains, which affect the performance of PRCs to some extent. In addition, the actual structure of PRCs contains a massive amount of inclusions, and the number of inclusions could reach the magnitude of millions or even tens of millions. For the large-scale numerical simulation of PRCs, ordinary displacement finite element requires a large number of meshes, which increases their computational complexity and unsolvability. For real PRCs with random particle distribution, homogenisation theory does not accurately capture the true state of stress concentration in PRCs. The Voronoi cell finite element method (VCFEM) can be a good solution to the drawbacks of the above two numerical simulation methods. The subject of the present work explores a modified complementary energy generalized function that takes the constitutive relationship of nonlinear strain into account, proposing a two-dimensional VCFEM, formulated with plastic, thermal, and creep strain. The simulation results are compared with the computed results of a commercial finite element software Marc to verify the validity and accuracy of the VCFEM. Results of the comparison show that the VCFEM has the advantages of simple meshing and faster computation under the same precision. The VCFEM, considering plastic, thermal, and creep strains proposed in this paper, lays the foundation for future large-scale numerical simulations of PRCs containing a large quantity of inclusion structures and can realistically capture the stress concentration state of PRCs. At the end of the article, the impact of the order of stress function on the calculation results is discussed.

Applicability evaluation of innovative simplified methods of slatted floor in pig houses – A CFD study

The slatted floor system is often used in pig housing. Computational Fluid Dynamics (CFD) is a valuable technique for determining the airflow and gas dispersion within the pit headspace through the slatted floor. However, there is a practical issue related to modeling the thousands of small slot openings in real livestock buildings for CFD simulation. It is unpractical to simulate the slatted floor with geometry details due to the large mesh number and the limited computer capacity. In this study, several methods to simplify the model of the slatted floor were explored to reduce the computational cost. The study was based on CFD analysis supported by experimental validation. The slatted floor was modeled in four ways: direct geometry method (DGM), porous-region method (POM), and profiled-porous-region method (including PPOM-cell (PPOM-C) and PPOM-floor (PPOM-F)). To assess the feasibility of the simplification, the four modeling approaches were compared with the experimental data. The results showed that it’s feasible to model the slatted floor as POM or PPOM. The accuracy of POM was high, but it was greatly affected by the calculation of the resistance coefficient. PPOM-C has greatly reduced the amount of calculation, which could be used to simplify the large-scale pig house model whose flow fields and gas emissions below the slatted floor could be ignored. The simulation result of PPOM-F was the closest to DGM, however, due to the large number of meshes and complex setup, it was not suitable for practical simulation.

Experimental study of the influence factors of the droplet size of rotary nozzles during manned helicopter spraying operations

The droplet size significantly affects the performance of aerial spraying operations. Thus, it is crucial to develop rotary nozzles for helicopter spraying operations and analyze the influence of droplet size. We conducted a calibration test of the nozzle rotation speed to analyze the effects of air velocity, blade installation angle, hub diameter, and blade length on the rotation speed. The results showed that the rotation speed increased with an increase in air velocity and nozzle diameter and decreased with an increase in the blade angle. The rotation speed of three types of rotary nozzles was measured in the range of 576–15 358 r/min. A high-speed wind tunnel test was conducted to determine the droplet size of the rotary nozzles at different rotation speeds, spray flow rates, and hub mesh numbers. The influence degree of the three factors on the droplet size was rotation speed > spray flow rate > mesh number. The multiple linear regression equation of the volume median diameter (VMD) of the droplet size was obtained. The droplet size obtained from wind tunnel and flight tests at 5000 and 7000 r/min was compared. The droplet size was in the range of 148.56–259.39 μm and was slightly larger under wind tunnel conditions than during the flight test. The relative width of the droplet spectrum was small for both test methods, indicating that the droplet size distribution of the three rotary nozzles was uniform. Finally, the spray nozzles were used for insect control in forest areas and achieved a control efficiency of 94.6. This study provides a reference for optimizing the operating parameters of spraying nozzles and improving the performance of helicopter-based low-volume spraying operations.

A shape-stabilized phase change composite from biomass cork powder as a matrix for thermal energy storage and photothermal conversion

Cork powder (CP) is a natural biodegradable biomass material. In this work, a series of shape stable-phase change composites (SSPCCs) based on n-docosane (ND) and CP are fabricated to avoid waste of resources. Four different mesh numbers (80–600) of CP are utilized as supporting skeletons for ND. The honeycomb structure of the CP is gradually destroyed, and the folded construction of the cell wall is straightened with the increase of the CP mesh number. Among them, CP80 and CP160 have a complete honeycomb structure, which can better encapsulate ND inside the cell, and the encapsulation ratio of ND is about twice as high as that of CP400 and CP600. Due to the excellent hermeticity of CP160, the corresponding SSPCC has a maximum melting and freezing latent heat are 122.81 J/g and 121.31 J/g, respectively, and the mass retention after leakage experiments is still as high as 99.43 %. In heat recovery and photothermal experiments, CP-based SSPCCs can be in with good storage performance. Moreover, the melting and crystallization coefficients for ND/CP160 after cycling are only 1.72 % and 2.44 %, respectively, representing excellent thermal reliability and reusability. In summary, cheap and abundant CP can be applied to prepare SSPCC with favorable thermal energy storage and conversion performance.

The Content of Magnetic Material in Black Sand of Yeh Gangga Beach

Yeh Gangga Beach is one of the black sand beaches in the Tabanan district. The abundant black sand on this beach stretches along the shoreline with varying grain sizes. This black sand characterizes the specific surface composition as iron sand deposits with high magnetic mineral content. The very high need and use of magnetic minerals in various fields prompt a study of the magnetic mineral content in the black sand of Yeh Gangga beach.The magnetic material content was determined by the extraction method which was expressed in terms of mass fraction. The grain size distribution was determined by the sieve method using a sieve shaker consisting of six mesh numbers, namely 30, 100, 170, 200, 270, and 325.The density of magnetic materials was determined by the principle of mass and volume ratio. The magnetic susceptibility was tested by using a Bartington MS2B susceptibility meter. Meanwhile, the characterization of the elements and their oxides used non-magnetic methods, namely the X-Ray Fluorescence test.The research results show that the magnetic material fraction of Yeh Gangga black sand reach 84.84% with 58.39% of the grains having sizes in the range 150r ≥90 μm. The magnetic susceptibility value is 28.26 10-6 m3/kg with an Fe element content of 85.15% w. The hematite (Fe2O3) content reaches 81.69%. This magnetic material has a density of 1914.43 kg/m3.

Development and experimental investigation of magnetic abrasive finishing of 17-4PH steel

Magnetic abrasive finishing (MAF) is a promising process for achieving better surface finish, not only on softer materials, but also on harder materials. In several industries, 17-4PH steel has predominantly being used due to its exceptional properties of better corrosion resistance, high strength-to-weight ratio, and ease of weldability. In this article, the details of a developed MAF attachment for a CNC vertical milling machine are presented. The developed attachment was used to finish the surface of 17-4PH steel and is suitable for plane workpiece surface. Effect of various MAF process parameters such as rotational speed of electromagnet, supply voltage/current, abrasive mesh number, and working gap were studied on 17-4PH steel for material removal rate (MRR) and percentage change in surface roughness (PCSR) using one-factor) using one-factor-at-a-time approach (OFAT). Based on experimental results, on increasing voltage/current, increase in MRR and PCSR was observed; however, decrease in PCSR and MRR was noticed with increase in the working gap. PCSR was increased up to 600 rpm of electromagnet and 600 mesh number. However, on further increase in speed and mesh number, resulted in decrease in PCSR. Supply voltage/current was the most significant input process parameter on PCSR for the constant values of others parameters. Maximum PCSR of 90.37% was observed at 1.5 mm working gap, 600 rpm rotational speed, 600 mesh number and 24 V/0.9A voltage/current. The results reported in the article are useful in identifying the relative significance of parameters for the selected workpiece material.

SolidWorks Flow Simulation: Selecting the optimal mesh for conducting CFD analysis on a centrifugal fan

The accuracy of mesh use determines the suitability of simulation results with experimental test results, therefore it is necessary to study the type and number of mesh used for flow simulation. This study aims to investigate the type of mesh and the number of cells that are appropriately used in the simulation of centrifugal fans using the Solidworks Flow Simulation module. The research was conducted by comparing the simulation results with the experimental results on centrifugal fans that have been carried out by previous studies. In this research, the type of mesh used is global mesh. The parameter of determining the number of cells is done by varying the mesh level because the mesh level affects the number of cells. In this simulation study, the boundary condition is set to one flow volume of 5 m3/h and a rotation speed of 92.362 rad/s. In this study, the total pressure and efficiency of the centrifugal fan are the things that are seen from the comparison of flow simulation with the experiment. Based on the simulation results that have been carried out, mesh levels 1 to 4 show results that differ significantly from the experimental results. At machine levels 5 to 7, the results are close to the experimental results, but the closest total pressure and efficiency values are at mesh level 5. The results of this study can be a reference for research that simulates centrifugal fans.

Unveiling the role of differential growth in 3D morphogenesis: An inference method to analyze area expansion rate distribution in biological systems

The three-dimensional (3D) morphologies of many organs in organisms, such as the curved shapes of leaves and flowers, the branching structure of lungs, and the exoskeletal shape of insects, are formed through surface growth. Although differential growth, a mode of surface growth, has been qualitatively identified as 3D morphogenesis, a quantitative understanding of the mechanical contribution of differential growth is lacking. To address this, we developed a quantitative inference method to analyze the distribution of the area expansion rate, which governs the growth of surfaces into 3D morphology. To validate the accuracy of our method, we tested it on a basic 3D morphology that allowed for the theoretical derivation of the area expansion rate distribution, and then assessed the difference between the predicted outcome and the theoretical solution. We also applied this method to complex 3D shapes and evaluated its accuracy through numerical experiments. The findings of the study revealed a linear decrease in error on a log–log scale with an increase in the number of meshes in both evaluations. This affirmed the reliability of the predictions for meshes that are sufficiently refined. Moreover, we employed our methodology to analyze the developmental process of the Japanese rhinoceros beetle Trypoxylus dichotomus, which is characterized by differential growth regulating 3D morphogenesis. The results indicated a notably high rate of area expansion on the left and right edges of the horn primordium, which is consistent with the experimental evidence of a higher rate of cell division in these regions. Hence, these findings confirm the efficacy of the proposed method in analyzing biological systems.

Empowering nuclear reactor analysis: OpenNode for accurate 3D core simulation through nodal expansion neutron diffusion equations solving

OpenNode is a sophisticated reactor core simulation tool, meticulously designed for educational purposes. Its main function is to solve the complex partial differential equation governing multi-group neutron diffusion in a Cartesian geometry. OpenNode relies on the second- and fourth-order Nodal Expansion Method (NEM) to provide accurate solutions to three-dimensional steady-state problems, encompassing both the direct and adjoint modes. At the heart of this method, the neutron balance equation serves as the fundamental framework for calculating the nodal neutron flux and the effective multiplication factor, enabling the complex evaluation of neutron flux distributions within individual nodes.The NEM methodology, carefully programmed in Fortran-90 in OpenNode, meticulously decomposes the reactor core into nodes of reasonable size. This approach balances computational efficiency and accuracy, achieving outstanding precision even when using a reduced number of computational meshes. To further increase the number of equations while maintaining the balance between unknowns, OpenNode judiciously incorporates two essential approximations: the Weighted Residual Method (WRM) and the Quadratic Transverse Leakage (QTL) approximation.OpenNode transcends simple computational prowess by adopting an intuitive Graphical User Interface (GUI), meticulously developed by combining Python 3, Qt Designer, and Blender software. This Python-powered graphical interface offers users a seamless, user-friendly experience, facilitating tasks such as data entry, execution of complex simulations, calculation of results, data visualization, 3D design of nuclear core geometry, and in-depth analysis of results. One of OpenNode’s key features is its innate flexibility, enabling it to solve problems in both 2D and 3D Cartesian geometries. This adaptability makes it a versatile tool suitable for a wide range of research and power reactor applications, offering users the ability to model and design reactors with unrivaled ease.To substantiate OpenNode’s reliability, comprehensive criticality calculations are carried out in various scenarios, including single-cell verification, BIBLIS, KOEBERG cores in two dimensions (2D), and IAEA cores in three dimensions (3D). The results clearly demonstrate OpenNode’s robustness and reliability in multidimensional criticality analysis. In particular, OpenNode adheres to an open-source philosophy, making it readily available for download. This commitment to open access fosters collaboration and paves the way for wider adoption within the education and research communities, nurturing a thriving ecosystem of shared knowledge and exploration.

Three-dimensional evaluation of social smile asymmetry in patients with unilateral impacted maxillary canine: a 3D stereophotogrammetry study.

This study aimed to evaluate social smile asymmetry in patients with unilateral impacted maxillary canine on 3D stereophotogrammetric images. The 3D social smile images of participants with unilateral impacted maxillary canine (n:20) and without impaction as a control group (n:20) were included. The images were recorded with a hand-held 3D stereophotogrammetry device (Fuel3D® Scanify®) and Geomagic Essentials 2 reverse engineering software were used for analyses. After the orientation process of the 3D records, the tissues around the smile area were divided into five morphological regions: cheek, upper lip lateral and medial, and lower lip lateral and medial. The deviation margins in the negative and positive directions for the 95% mesh rate and the total percentages of meshes between - 0.5- and + 0.5-mm deviations were calculated. ICC, paired samples t test, independent samples t test, and the Mann-Whitney U test were used for statistical analyses. In individuals with impacted canine, the amount of maximum positive deviation in the upper lip medial was 5.64mm ± 1.46 and maximum negative deviation was - 4.6mm ± 1.17. In the control group, mean of deviation limits for all parameters was less than 1.19mm ± 2.62, while in individuals with unilateral impacted maxillary canine, the maximum value was 8.34mm ± 2.23. The mesh percentage between - 0.5 and 0.5-mm deviations was over 95% in all morphological areas in the control group, while in the impacted canine group, the number of meshes within the specified deviation limits was less than 95%. Individuals with unilateral impacted maxillary canine exhibit greater asymmetry in social smile compared to the control group, with the asymmetry being most prominent near the corners of the mouth and cheeks. Amount of asymmetry was higher in impaction group compared to the control group in social smile. The quantification of a possible smile asymmetry due to the impacted canine is crucial for the diagnosis and treatment planning of orthodontic and/or orthognathic cases for ideal aesthetic results. Hence, smile asymmetry should not be overlooked and should be considered in diagnosis and treatment planning.

PHARE: Parallel hybrid particle-in-cell code with patch-based adaptive mesh refinement

Modeling multi-scale collisionless magnetized processes constitutes an important numerical challenge. By treating electrons as a fluid and ions kinetically, the so-called hybrid Particle-In-Cell (PIC) codes represent a promising intermediary between fully kinetic codes, limited to model small scales and short durations, and magnetohydrodynamic codes used large scale. However, simulating processes at scales significantly larger than typical ion particle dynamics while resolving sub-ion dissipative current sheets remain extremely difficult. This paper presents a new hybrid PIC code with patch-based adaptive mesh refinement. Here, hybrid PIC equations are solved on a hierarchy of an arbitrary number of Cartesian meshes of incrementally finer resolution dynamically mapping regions of interest, and with a refined time stepping. This paper presents how the hybrid PIC algorithm is adapted to evolve such mesh hierarchy and the validation of the code on a uniform mesh, fixed refined mesh and dynamically refined mesh.

Thermal performance of integration between semi-circular channels and connecting pipes in PCHE employed for SCO2 Brayton cycle

A semi-circular channel with connecting pipes is proposed to improve the overall heat transfer performance of the Printed Circuit Heat Exchanger (P CHE) used in the regenerator of the SCO2 Brayton cycle. Two semi-circular channels at the top and bottom, which are horizontally placed, were filled with hot and cold CO2, respectively. Thermophysical properties of SCO2 were solved by integrating NIST into the FLUENT 2020. A mesh number of 5.0M and the SST k-ω turbulence model were selected via comparison with experimental data. As results show, the overall heat transfer performance of the semi-circular channel with connecting pipes is improved by 1.1-2.5 times. The vortex structure induced by the connecting pipes increases turbulent kinetic energy and further enhances the heat transfer. This indicates that the connecting pipe proposed in this study is beneficial to activate heat transfer and reduce flow resistance.

Key features and highly effective prediction of complete startup from frozen state for high-temperature heat pipe in heat pipe reactor

High-temperature heat pipe is an efficient phase change heat transfer device, widely applied in the space nuclear reactors, the China Fusion Engineering Test Reactor, solar collectors, and the thermal protection of hypersonic vehicles. In order to understand the startup characteristics of the heat pipe and to predict its transient behavior with high accuracy, this paper first experimentally investigated the startup performance of a sodium heat pipe from the frozen state under different heating powers from 534 W to 1897 W. Then, a new compressible flow model for startup from the frozen state was developed and verified, solved the independence problems of mesh number and time-step used in the numerical treatments of most traditional heat pipe codes. Finally, based on the assessed model and experimental data, the startup procedure and the influences of heating power on the working temperature, kick-in time, and temperature difference were analyzed respectively. The comparisons indicated that the new model is extremely informative and effective, and the results provided knowledge for understanding the safe and optimum working regime of a high-temperature heat pipe using in heat pipe reactor.

Overview of Method of ChAracteristics based Neutron TRAnsport Code (MANTRA) and its validation

An in-house computer code MANTRA is developed to solve the neutron transport equation at lattice or assembly level (in 2D) applying Method of Characteristics (MOC) for reactor design calculation. The code has the capability to divide the lattice into triangular meshes. By default, the code assumes constant neutron source inside the meshes. If required, it is possible to use linear source assumption to reduce the number of meshes for speeding up the solution. Using MOC, the solution of transport equation is obtained along a number of parallel lines or rays traced through the meshes in different directions and connect them through reflective or periodic boundary condition. In the code, there is option to choose either Power or Krylov subspace iteration technique to converge the solution with desired accuracy. The code is coupled with multigroup cross section library WIMSD. Performance of MANTRA is tested against a number of benchmark problems and overall good agreement is observed with the results obtained from internationally recognized codes like WIMSD, DRAGON, MCNP etc.

NUMERICAL INVESTIGATION OF NATURAL CONVECTION IN A RECTANGULAR CAVITY BY CFD CODES

In this study, natural convection in an air-filled rectangular cavity is studied numerically by two commercial CFD codes. Numerical simulations are carried out for air and water for different aspect ratios and wall temperatures. Calculations are compared with experimental correlations in the literature and with each other. Calculation time and mesh number are the main parameters considered in this study. According to the numerical results, SIMCENTER FLOEFD is an effective CFD code as ANSYS FLUENT and gives accurate results for this type of problem.

Numerical Investigation of Mold Heating Power and Time in Metal Layered Composite Production

Curing time of epoxy resin is an important phenomenon in the production of metal layered composites. In order to reduce the curing time, the heating of the mold and epoxy was carried out in this study and numerically investigated on time dependent. The most consistent mesh structure was chosen among five different mesh number in terms of difference between temperature results. 10 different cases were created to examine different heater powers and different operating patterns. The results were examined by creating a temperature-time graph and contours showing the temperature distribution. As the number of cartridges and heater power increase, higher temperatures are reached in a shorter time. Even with the same heater power, different operating patterns can lead to differences in results in terms of temperature. Different operating pattern was seen as an independent parameter in heater power for obtaining a homogeneous temperature distribution.

Experimental investigation on the effects of a mesh in the downstream region of a combustion-driven Rijke tube on self-excited thermoacoustic oscillations

Self-excited thermoacoustic oscillations are undesirable in most combustion systems due to their negative influence on combustion efficiency and structural vibration. Nonlinear thermoacoustic oscillations driven by combustion can be sensitive to changes in the heat and flow conditions. Therefore, a comprehensive study on self-excited thermoacoustic oscillations was conducted to investigate the effect of incorporating a woven mesh with varying mesh numbers and positions into the downstream region of a Rijke tube. This study determined system frequency and amplitude response and revealed dynamic properties of the system by applying recurrence analysis. To obtain temperature distributions, a thermal imaging system was employed, comprising a short wavelength infrared (SWIR) camera for the mesh and a long wavelength infrared (LWIR) camera for the tube wall. A high-speed schlieren imaging system was utilised for visualising heat and flow conditions at the tube end. The study demonstrated the effect of including a mesh in changing the oscillation eigenfrequency, suppressing the oscillation amplitude by up to 50 % and influencing the system dynamics. Higher mesh number demonstrated greater effectiveness. The captured thermal and schlieren images clearly evidenced the mesh’s significant influence on the downstream heat and flow conditions. The insights gained from this work provide a potential control method of self-excited, nonlinear thermoacoustic oscillations.

Mesh-Based Two-Step Convex Optimization for Spacecraft Landing Trajectory Planning on Irregular Asteroid

The problem investigated in this paper is how to rapidly optimize a landing trajectory on an arbitrarily shaped asteroid, subject to practical constraints and a gravitational model suitable for irregular asteroids. The fundamental idea is to convert the nonlinearity involved in the gravitational field into an equivalent convex version and further generate the optimal trajectory using the two-step convex optimization technique to achieve efficient and robust computation. For a given mission area, the positional space is discretized as an exactly sufficient number of small tetrahedron meshes, within which the real gravitations are interpolated as the linear gravitational representation with nonconvex mesh tracking constraints. A solution space relaxation–penalization technique is proposed to convexify the mesh tracking constraints and keep the feasibility of the resulting convex optimization problem. A series of optimal active meshes are generated by solving this problem and transcribed as corresponding convex active meshing constraints, and further imposing them on the landing trajectory to construct the final convex optimization problem equaling to the original problem. The strength and correctness of this method are demonstrated from both perspectives of theoretical analyses and numerical simulations for landing on 4769 Castalia asteroid, with the comparisons of the state-of-the-art convex-optimization-based methods.

Experimental study on proppant-carrying migration and settlement of slickwater in narrow plate fractures based on PIV / PTV

Hydraulic fracturing is the primary method used for oilfield stimulation, and the migration and settlement pattern of proppant plays a crucial role in the formation of high conductivity propping fractures in the reservoir. This study summarizes two growth modes of sand dune: the ‘overall longitudinal growth’ mode and the ‘push growth along fracture length direction’ mode. To investigate these modes, a two-phase velocity test is conducted using PIV, and the exposure difference is utilized to separate the tracer and track the single-phase velocity. By analyzing the slickwater flow field and proppant velocity field, the micro-motion mechanism behind the two dune growth modes is quantitatively examined. The results indicate that mode 1 growth of the sand dune occurs when a pump with a large mesh number, high polymer viscosity, and large displacement is used. On the other hand, mode 2 growth is observed when a pump with a small mesh number, low polymer viscosity, and small displacement is employed. It is important to note that there is no clear boundary for the migration and sedimentation mode of proppant, as they can transition into each other under certain conditions. These modes only exist during specific stages of sand dune growth. In the case of the ‘backflow’ pattern, the settlement of proppant is primarily influenced by the vortex structure of slickwater. Conversely, in the ‘direct’ pattern, the proppant is propelled forward by the drag of the fluid and settles due to its own gravity. Once the proppant placement reaches equilibrium, the direction of proppant velocity follows a normal distribution within 0°. This approach establishes a connection between the overall placement of the sand dune and the microscopic movement of the proppant and slickwater. Optimizing construction parameters during fracturing construction can enhance the effectiveness of distal proppant placement in fractures.

Fitted exact difference method for solutions of a singularly perturbed time delay parabolic PDE

A novel numerical method has been proposed for solving singularly perturbed parabolic time delay PDE by using a fitted mesh exact finite difference method. The traditional numerical methods on uniform mesh fail to accurately approximate the solution of the considered PDE, due to the presence of a boundary layer. Therefore, developing a numerical scheme that can effectively handle the boundary layer behaviour is of great interest. The proposed scheme utilizes Crank–Nicolson method for temporal discretization and fitted mesh exact finite difference method for spatial discretization. The scheme satisfies the discrete maximum principle, stability bound, and uniform convergence with the boundary layer resolving property. Numerical test examples have been conducted to validate the scheme for different values of the perturbation parameter and mesh numbers. The results show that the proposed scheme outperforms existing methods in the literature in terms of accuracy. The proposed approach holds significant potential for solving similar PDEs that exhibit boundary layer behaviour.