Simulation Calculation Method Research Articles

Simulation of Total Harmonic Distortion of Solid Oxide Fuel Cells for Carbon Deposition Detection

Abstract Identifying the degradation mechanisms at the early stage of operation is important for the long-term operation of solid oxide fuel cells (SOFCs). Compared to conventional methods, total harmonic distortion analysis (THDA) can significantly reduce the test time for identifying performance degradation during SOFC operation. In this study, a one-dimensional transient elementary reaction kinetic model of an SOFC fueled with syngas is developed. The model incorporates the coupling effect of elementary chemical and electrochemical reactions, the electrode microstructure, the charge and mass transport processes, and the detailed evolution reaction of surface adsorbed carbon. A THDA simulation calculation method was developed and applied to determine the failure mode of anode carbon deposition. The amplitude, duration, and harmonic number of the perturbation signal are determined to improve fault detection for THDs. The results show that the use of THD can not only detect carbon accumulation behavior at the early stage of SOFC operation but also distinguish the specific degradation mechanism caused by carbon deposition: the hindered SOFC charge transfer reaction can be detected in the frequency range of 100-4000 Hz, and the hindered gas diffusion process inside the anode can be detected in the frequency range of 0.01-10 Hz.

Study on flow characteristics and structural properties of vertical axial pump with low guide vane height

Abstract With the full construction of the South to North Water Diversion Project and the renovation of pumping stations, vertical axial flow pump devices have been widely used in various pumping station projects. This article uses the streamlined method to design the impeller and guide vanes of a vertical axial flow pump device. To analyze the hydraulic and structural characteristics, this paper uses CFD numerical simulation and fluid-structure interaction calculation methods. And the trend of output power change under different flow conditions was divided into three stages, elucidating the reasons for the sudden change in output power under flow conditions of 0.8Q-1.0Q. This article focuses on analyzing the internal flow state of the designed lower height guide vane segment to explore the problem of low guide vane height that is prone to occur during the design process. According to the research results, it is found that the lower height guide vane can also play a good role in stabilizing flow and recovering circulation under certain operating conditions. This article also studied the structural characteristics of the impeller and guide vanes, explaining the stress and strain distribution under design flow conditions.

Determination on Effective Drainage Radius of In-Seam Borehole Based on Gas Content Test and Numerical Simulation Calculation Method.

In order to accurately and efficiently determine the effective drainage radius of the in-seam borehole, the advantages and disadvantages of the current effective drainage radius test methods are analyzed, and the method of combining the gas content field and numerical simulation calculation is proposed to accurately determine the effective drainage radius of the borehole, which is applied in the mine. The results show that the method combining gas content test and numerical simulation calculation has the advantages of a short measurement period and advanced means. The effective drainage radius of the borehole increases rapidly at the initial stage of gas drainage and then gradually slows, eventually reaching a limit value. The relationship between the effective drainage radius and drainage time follows a Langmuir function relationship. When the drainage time exceeds 300 days, the effect of the drainage time on the effective drainage radius becomes relatively small. The average error between the numerical simulation results of effective drainage radius and the field verification results of gas content is 2.2%, which validates the rationality of the constructed coal seam gas-solid coupling model. The research can provide theoretical references for accurately determining and reasonably laying out the effective drainage radius of the bedding borehole in the mining seam of the coal mine, which is of great practical significance for the safety production of the mine.

A review of high-entropy ceramics preparation methods, properties in different application fields and their regulation methods

High-entropy alloys (HEAs) provides a new way to develop new materials with adjustable performance due to their unique cocktail effect. Inspired by HEAs, a ceramic material with high-entropy effect has been developed, which was named high-entropy ceramics (HECs). With the introduction of the concept of entropy stability, research on HECs has developed rapidly. At present, research on the performance of HECs has extended to traditional performance such as thermomechanical performance, oxidation resistance, and magnetic properties, as well as emerging performance such as catalytic performance, optical properties, and radiation resistance. Based on the definition of HECs, this paper reviews the crystal structure and preparation methods of HECs and supplements the simulation calculation methods and descriptors which is suitable for HECs. In this paper, the performance of HECs at this stage is divided into traditional fields and emerging fields according to the application fields. A variety of performance regulation methods are reviewed, and the development and research directions of HECs are prospected.

Simulation of Modal Control of Metal Mode-Filtered Vertical-Cavity Surface-Emitting Laser.

In this study, a novel metal-dielectric film mode filter structure that can flexibly regulate the transverse mode inside vertical-cavity surface-emitting lasers (VCSELs) is proposed. The number, volume, and stability of transverse modes inside the VCSEL can be adjusted according to three key parameters-the oxide aperture, the metal aperture, and the distance between the oxide aperture and the metal aperture-to form a flexible window, and a new parameter is defined to describe the mode identification. This study provides a complete simulation theory basis and calculation method, which is of great significance for the optical mode control in VCSELs.

The Influence of Lobe Top Clearance on the Performance of High-Speed Centrifugal Pumps

High-speed centrifugal pumps are widely used in several industries due to their high efficiency and small footprint. In actual applications, there are issues such as low operational efficiency and a small high-efficiency flow interval; particularly, the leakage occurring in the impeller channel gap presents a significant barrier to the pump’s performance and stability. This study takes the fully open impeller miniature high-speed centrifugal pump as the object and uses a numerical simulation calculation method. The objective of this research endeavor is to analyze the effects of different flow conditions on a high-speed centrifugal pump’s external characteristics, flow field characteristics, and energy loss. The findings indicate that lobe top clearance exerts a substantial impact on the efficiency of high-speed centrifugal pumps. Increasing the lobe top clearance will result in a reduction in pump head and efficiency, particularly under high flow conditions. The lobe top clearance has a significant impact on the complexity of the flow in the impeller, particularly the flow close to the suction surface of the impeller, according to an analysis of the flow field characteristics. The energy loss analysis further confirms the importance of reducing lobe top clearance for improving pump performance and reducing energy loss. These results provide valuable guidance for optimizing centrifugal pump designs with lobe top clearance.

Research on simulation calculation method of local strength of swath ship stabilizing fins based on sub-model method

Abstract At present, there is little research on the strength simulation calculation method of local steel structure at the joint between the fin stabilizer and hull of SWATH at home and abroad. Aiming at the problems of high-stress levels and difficult local strength of the local structure at the joint of SWATH submersible and stable fin, this paper, based on APDL language, takes a SWATH ship as an example, establishes a whole ship simulation model, analyses and studies the modeling scope, modeling requirements, boundary conditions, and loading methods of the local calculation model of stable fin, and puts forward an efficient simulation calculation and analysis method, namely sub-model method, which is suitable for the local strength calculation of stable fin, and provides guidance for the structural design method of the stable fin of SWATH catamaran.

Analysis of the damage effects of carbon fiber composites under the mechanical impact loads of lightning based on a modified simulation calculation method

Mechanical effects contribute significantly to the multiphysical damage of carbon fiber-reinforced polymer (CFRP) composites induced by high-amplitude impulse lightning currents. In this paper, the mechanical impact loads (MILs) of lightning are decomposed into acoustic shock waves from arc channel expansion (AESW), electromagnetic force (EMF), and shockwave overpressure from surface explosion (SESW). A 3D finite element mechanical damage model of laminates was established based on the Hashin–Yeh initial creation and modified stiffness degradation matrix. The model was verified by comparison with pure mechanical impacts. The dynamic response and damage modes of laminates subjected to AESW, EMF, SESW, and MILs were studied and compared. The MILs are exponentially related to the current intensity. The damage effect of laminates under MILs is inversely related to the impact radius. The comparison shows that the effect of the EMF gradually exceeds that of the AESW as the current peak increases and its value is approximately twice that of the latter when the current peak Ip exceeds 165 kA. In contrast, SESW is the primary cause of the damage effect. Over 70 % of the deformation contribution to laminates under MILs comes from SESW (Ip = 165 kA). Furthermore, the strongest SESW is induced by the insufficient thermal conductivity of the CFRP laminates.

Humid heat aging of biphenyl epoxy resin: a combined study of experiments and simulations

Epoxy resins are commonly used as external insulating materials for high-voltage outdoor applications. To improve the moisture and heat resistance of epoxy resin materials, this research carried out experimental tests and theoretical simulations on a variety of epoxy resin materials, including the biphenyl type. The theoretical simulation used the Materials Studio software to model the biphenyl epoxy resin and bisphenol A-type epoxy resin at different humidities. The simulation results show that the biphenyl epoxy resin has a higher glass transition temperature, at which the water molecules have a smaller root-mean-square displacement and a lower probability of forming hydrogen bonds. Experimental tests illustrated that biphenyl-type epoxy resins exhibit enhanced stability, lower hygroscopicity, and minimal changes in the permittivity in hot and humid environments. The agreement between the theoretical simulations and experimental tests indicates that the simulation calculation method is applicable to studying the hygrothermal resistance of epoxy resin materials. This study also lays the foundation for improving various aspects of the performance of epoxy resin materials through simulations, thereby providing a theoretical basis for the development of hygrothermal-resistant epoxy resins.

The study on mechanical properties of the vibration isolator

First of all, the working principle of vibration reduction of the vibration isolator is briefly introduced. The vibration isolator adopts the design ideal of no formant and adopts a damping locking mechanism in the resonance region to solve the problem of vibration amplification of the system. The purpose of vibration attenuation is to use small damping in the attenuation region. Then, through the numerical simulation calculation method, it can be obtained that the isolator has a good vibration isolation effect under different effects of shock and impact, and the effective rate is about 90%, which fully guarantees the structural safety of the test equipment. Finally, according to an example, a model is established to study the influence of equipment weight and center of gravity design deviation on the natural frequency and natural frequency point vibration transmission efficiency of the equipment. Through analysis, it can be found that in the case of no abnormality of the equipment, the frequency is changed in the range of 1∼160 Hz, and the ratio of the system response to excitation is not more than 2, which meets the design requirements.

Main factors that control roadway damage when a steeply dipping coal seam crosses a fault

When the working face of a steeply dipping coal seam crosses a fault, the dynamic disturbance caused by the mining load induces fault activation, causing large deformation and failure of the roadway. In this study, a physical similarity simulation and numerical calculation method were used to determine the main factors that the deformation and failure of fault zone roadway and reveal the underlying mechanisms. The results show that when crosses a fault, the high static load formed by the coupling of mining stress and fault pillar stress induces mining stress-type fault activation, which leads to large deformation and damage to the roadway in the fault zone. The main controlling factors are the fault location and mining load intensity. In terms of fault location, the vertical stress concentration away from the roadway side of the fault surface was high, the principal stress deflection angle was large, and the surface deformation of the fault on the roadway left side was the greatest. In terms of mining load intensity, the deflection angle of the principal stress of the surrounding rock initially increased and then decreased, and tensile failure easily occurred near the fault surface. These results provide a reference for roadway support.

Research on mining-induced surface soil cracking mechanism and development depth of downward fracture

In order to reveal the cracking mechanism of surface soil layer caused by coal seam mining, and explore theoretical methods for predicting the development depth of downward fractures during mining. Based on the background of the No. 1–2 upper coal seam mining in Daliuta Coal Mine, combining with fracture mechanics, soil mechanics, physical similarity simulation and numerical calculation methods. The mining-induced cracking mechanism and criterion of surface soil layer were analyzed, the crack development pattern and expansion mechanism were revealed, and the prediction formula of downward crack development depth of surface soil layer was put forward. The research results show that surface cracks mainly occur in the tensile zone, the concentrated tensile stress produced by the subsidence of overburden in the tensile zone can lead to soil cracking. When the surface maximum horizontal tensile deformation exceeds the limit horizontal deformation of soil, the soil layer cracks, and the cracking criterion of the surface soil layer was given accordingly. The soil crack of coal seam mining belongs to the mixed mode crack, and the soil cracks tip starts cracking and expanding along the direction of the maximum principal stress, therefore, the initiation crack angle of soil crack tip was obtained, and the fracture criterion of soil crack was proposed. With the crack propagation and development, the microcosmic crack becomes the macroscopic downward fracture. When the horizontal stress of the soil decreases to the cohesive force of the soil, the downward fracture stops develop, and the calculation formula for the development depth of mining-induced downward fracture was proposed. The development and evolution law of downward fracture was revealed, after the surface cracks, with the advance of the longwall face, the downward crack continues to extend and develop to the deep. Downward fracture develops on the ground surface at the open cut side, the mined-out area and in front of the longwall face, the maximum development depth of downward fracture tends to be stable when the longwall face advances to a certain distance. According to the physical simulation, numerical calculation and theoretical calculation, the development depth of downward fracture in No 1–2 upper coal seam mining is 8.11 m, 8.21 m and 8.14 m respectively. The theoretical prediction formula is reliable, and the results can provide a new method for the research of the development depth of mining-induced surface downward fracture.

Stability analysis of pumped storage hydropower plant in abandoned open-pit mine affected by dynamic surface subsidence of combined mining.

The construction of a pumped storage hydropower plant (PSHP) in an abandoned open-pit mine is a potential alternative to green mining and energy storage, which can increase the utilization rate of renewable energy and develop residual resources of abandoned mines. Dynamic surface subsidence affected by combined underground and open-pit mining (CUOPM) seriously affects the construction and operation of the PSHP and is one of the critical scientific issues that needs to be solved immediately. The stability of the PSHP was analyzed and treatment scheme of the goafs was proposed based on on-site measurement, theoretical analysis, and numerical simulation. First, the distribution of goafs in the Haizhou open-pit mining area was investigated and surface subsidence value was obtained using InSAR technology and ground monitoring. Secondly, the surface subsidence mechanism affected by CUOPM is analyzed and indicates the subsidence maximum values and scope of influence are greater than those of single underground mining. A dynamic surface subsidence prediction model for combined mining is established based on the Knothe time function model. Thirdly, based on the CVISC model, the numerical calculation models were established by using FLAC3D, and the characteristics and laws of surface subsidence in different periods of CUOPM were studied. The comparative analysis of the observation results shows that the proposed model and numerical simulation calculation method have excellent applicability and accuracy. Finally, a stability evaluation method of PSHP was established, and the results of the evaluation show that the affected areas are the semi-ground powerhouse (SGPH) and the west side of the lower reservoir. The method of grouting filling was used to treat the goafs, and the results showed that it effectively alleviates the dynamic surface subsidence affected by CUOPM, and provides a safety guarantee for PSHP.

Study on Numerical Simulation of Surrounding Rock Structure Safety of Urban Underwater Shield Tunnel: A Case in Chongqing

Based on the engineering background of shield construction of a subway section in Chongqing, which needs to pass through a park and there is a lake inside this park, this paper adopts theoretical analysis methods and numerical simulation calculation methods to explore the distribution law of the seepage field and the characteristics of water pressure in lining segments during shield tunneling. The results show that, during the whole excavation of a double-track tunnel with EPB shield, the maximum vertical effective stress is about 4.24 MPa, which is located at the arch foot of the tunnel. The maximum effective stress in the horizontal direction is about 3.61 MPa, which is located on both side walls of the tunnel in the horizontal direction; after the left and right tunnels are excavated in sequence, a “double precipitation funnel-shaped” pore pressure distribution is formed around the tunnel; during the construction of the shield tunnel, the vertical displacement and horizontal displacement of the surrounding rock show an increasing trend and gradually tend to be stable values of 24.09 mm and 25.28 mm; the segment vault has settlement, the maximum settlement is 21.8 mm, the arch bottom has uplift, and the maximum uplift is 24.4 mm. The maximum horizontal displacement of the segment appears on both sides of the arch waist, and the maximum horizontal displacement decreases with the increase of excavation steps; the positive bending moment of the lining segment is mainly distributed on both sides of the arch crown, and the negative bending moment is mainly distributed on both sides of the arch bottom. The axial force of the lining segment is compressive stress, and the maximum axial force is mainly distributed on both sides of the arch waist. The maximum normal shear stress occurs on both sides of the segment arch bottom. The study conclusions provide theoretical foundation and a new guidance for long-term safety evaluation of underwater tunnel structures.

Fast assessment method of annual energy consumption for DSF and SSFs

Double skin façade (DSF) is widely used to improve energy efficiency in buildings. Many studies have analyzed the thermal performance of DSF and single skin façade (SSF) on just standard days or typical moments. However, in order to more accurately analyze its energy-saving effect, its annual thermal performance should be evaluated. For achieving this, a large number of simulations are needed and it is extremely time consuming and complicated. This study provides a new fast calculation method for annual thermal performance and energy consumption of DSF and SSFs. Firstly, based on CFD technique, a simulation method for obtaining indoor temperature of DSF during whole year was established, and the results were verified through experiments. Then, a new simulation calculation method for heating and cooling periods was established, thereby completing annual thermal performance simulation of different facades. Finally, based on total heat gain/loss of each facade, the energy consumption of mentioned facades was calculated, and facades’ various performance can be seen for entire year. As an overall result for Beijing located in cold region, by considering whole year energy consumption, DSF plays as the best one with 18 % energy saving in the whole year compared to the second one which is 3 glazing exterior shading SSF; however, this SSF can save 37 % building area compared to DSF. The result of this study can be useable for other cities with same climate as the Beijing. The analyze method proposed in this study is useable for optimizing building facades in different climates.

FACILE FABRICATION OF ANILINE SENSOR BY USING COMMERCIAL CALCIUM SILICATE HYDRATE NANOSHEETS AS SENSING MATERIAL

Various aniline sensing materials have excellent properties based on quartz crystal microbalance (QCM) transducer, but their synthesis processes are complex. Herein, commercial calcium silicate hydrate nanosheets (CSH-S) was utilized for facile fabrication of aniline sensor based on QCM platform. This sensor was capable of detecting 0.1 ppm aniline, and the response time (14 s) and recovery time (16 s) were short. Besides, the devices could restore sensitivity after 30 days, demonstrating excellent stability. In addition, variable temperature experiment combined with simulation calculation methods were carried out to study the adsorption of aniline on CSH-S surfaces, then the sensing mechanism was revealed. This work opens up a rapid and convenient method for detecting gaseous aniline.

Retracted: Molecular Dynamics Simulation Calculation Method for Elasticity and Plasticity of Metal Nanostructures

Retracted: Molecular Dynamics Simulation Calculation Method for Elasticity and Plasticity of Metal Nanostructures

Design and Characterization of New 3D Reentrant Rhombic Auxetic Structures with Enhanced Mechanical Properties

In this study, a new reentrant rhombic auxetic structure is first designed by replacing the reentrant strut of the regular reentrant structure with a rhombic structure. A simulation calculation method verified by experimental results is comprehensively developed to reveal the compressive behavior of the proposed structures in terms of deformation pattern, compression strength, Poisson's ratio, and energy absorption (EA). Based on the validated simulation method, the results indicate that compression load can give rise to an “X” deformation pattern of the rhombic auxetic structures. In the structure parametric study, it is further proved that the unit configuration exhibits a significant influence on the compression stress and EA of the structures. Furthermore, the rhombic auxetic structures present diverse Poisson's ratios with the structure parameters and compression global strain, that is, the structures with larger H, smaller D, and θ are found to present more pronounced auxetic effect. The compression direction also exhibits a remarkable effect on the performance of the structure, which accordingly indicates the anisotropic characteristic of the proposed structures. Moreover, compared with the other regular auxetic structures, the rhombic auxetic structures exhibit superior mechanical behavior and EA feature due to the introduction of the rhombic structure.

Structural and molecular investigation of the impact of S30L and D88N substitutions in G9R protein on coupling with E4R from Monkeypox virus (MPXV)

Understanding the pathogenesis mechanism of the Monkeypox virus (MPXV) is essential to guide therapeutic development against the Monkeypox virus. In the current study, we investigated the impact of the only two reported substitutions, S30L, D88N, and S30L-D88N on the G9R of the replication complex in 2022 with E4R using structural modeling, simulation, and free energy calculation methods. From the molecular docking and dissociation constant (KD) results, it was observed that the binding affinity did not increase in the mutants, but the interaction paradigm was altered by these substitutions. Molecular simulation data revealed that these mutations are responsible for destabilization, changes in protein packing, and internal residue fluctuations, which can cause functional variance. Additionally, hydrogen bonding analysis revealed that the estimated number of hydrogen bonds are almost equal among the wild-type G9R and each mutant. The total binding free energy for the wild-type G9R with E4R was −85.00 kcal/mol while for the mutants the TBE was −42.75 kcal/mol, −43.68 kcal/mol, and −48.65 kcal/mol respectively. This shows that there is no direct impact of these two reported mutations on the binding with E4R, or it may affect the whole replication complex or any other mechanism involved in pathogenesis. To explore these variations further, we conducted PCA and FEL analyses. Based on our findings, we speculate that within the context of interaction with E4R, the mutations in the G9R protein might be benign, potentially leading to functional diversity associated with other proteins. Communicated by Ramaswamy H. Sarma

Calculation and prediction of suspended span caused by erosion of deep water submarine pipelines

Submarine pipelines can be divided into three types based on their laying status: pipelines laid flat on the seabed, pipelines without buried, and pipelines buried in shallow trenches. In addition, there is also a suspended span state caused by waves and currents erosion. The four laying states of submarine pipelines indicate that the seabed, as the foundation supporting the pipeline, must provide sufficient support to ensure the stability of the pipeline. This article studies the erosion span data of existing pipelines, evaluates and predicts the pipeline span state through theoretical calculation and analysis, and then uses numerical simulation calculation methods to predict the pipeline span depth, and compares and verifies it with measured data.