Numerical Simulation Research Research Articles

The Active Roof Supporting Technique of a Double-Layer Flexible and Thick Anchorage for Deep Withdrawal Roadway under Strong Mining Disturbance

Due to the strong disturbance of a mining face, the surrounding rock of the withdrawal roadway is susceptible to deformation and failure, which restricts the safe and efficient evacuation of mining equipment. To resolve this longstanding technical problem in mine production, an engineering investigation, numerical simulation, theoretical analysis, and other research methodologies were conducted in this study. Furthermore, the influence mechanism of mining-induced stress on the withdrawal roadway was revealed, the anti-disturbance principles of thick-layer anchorage of roadway roofs were elucidated, and a novel double-layer flexible support technique was proposed. The front abutment pressure, stress superposition, damage accumulation of the surrounding rock, and the fluctuation of mining-induced stress are the primary factors contributing to the significant deformation of the surrounding rock in a withdrawal roadway. However, the fluctuation of mining-induced stress has usually been ignored in previous studies, and it may be the most crucial cause of the significant deformation and instability of the surrounding rock. The thickness of the anchored rock beam is the most vital factor affecting the maximum subsidence and maximum tensile stress of the roof, and increasing the thickness of the anchored rock beam can significantly improve the stability and anti-disturbance performance of the roof. In the proposed double-layer flexible supporting technique, flexible steel strands serve as the carrier, which overcomes the constraint of the roadway height on the length of roof support components. The first layer of flexible support is used to construct a thick fundamental anchorage layer, while the second layer is employed to construct a thicker reinforced anchorage layer, facilitating the effective resistance of the roof against strong mining disturbances. The effectiveness of this technique was further validated through the application of an engineering practice. The research results have reference value for solving the difficult problem of mining roadway support.

Numerical simulation research on multiphase flow of aviation centrifugal pump based on OpenFOAM

This paper aims to tackle the calculation efficiency problem raised in the cavitation-flow simulation of the aviation centrifugal pump due to the fading-away interface resulting from the dissipation of numerics used in the phase-change control equation for unstructured-grid multiphase flow, and due to the limitation of flow time-step in whole flow regimes, the control equation of vapor–liquid two-phase flow considering cavitation mass transport is established firstly, modifying the momentum equation by introducing the surface tension, and adding the artificial convective flow to the phase equation to solve the numerical dissipation problem. Secondly, in consideration of the local time step principle and based on the multi-dimensional general limiter algorithm with explicit solutions under the OpenFOAM platform, a solution method of steady-state VOF (Volume of Fluid) model considering cavitation two-phase change is constructed, and the feasibility of this method is verified by NACA hydrofoil and NASA flat plate inducer. Finally, based on the platform developed, the cavitation performance of an aviation centrifugal pump inducer is analyzed. The research results show that the error of the calculated cavitation pressure distribution for NACA hydrofoil between the simulation test and the experimental-test is less than 5%, and the maximum error of calculated cavitation number at pump head dropping for NASA high-speed flat plate inducer between the simulation test and the experimental-test is 2.1%. The cavitation area observed in the simulation test is the same as that obtained in the high-speed photography test. Based on the OpenFOAM simulation method, the position of pump head dropping of the fuel centrifugal pump can be accurately captured. The error of the calculated cavitation number at pump head dropping between the simulation test and the experimental test is about 3.7%, showing high calculation accuracy.

Multi-physical fields distribution in billet during helical electromagnetic stirring: A numerical simulation research

Multi-physical fields distribution in billet during helical electromagnetic stirring: A numerical simulation research

Routes from stationary dissipative solitons to chaos in a Mamyshev oscillator

Mamyshev oscillators (MOs), a new type of femtosecond fiber laser, can produce not only high-performance stationary dissipative solitons (SDSs), but also exhibit chaotic dynamics. Since chaotic behavior may lead to dramatic degradation of the performance, it is particularly important to investigate chaotic dynamics in MOs. Here, using numerical simulation and experimental research methods, we systematically investigate different routes from SDSs to chaos in an MO. Specifically, by simply increasing the gain saturation energy under different polarization states, we obtained different routes from SDSs to chaos, including via a cascade of period-doubling bifurcations (CPDB), via a quasi-cascade of period-doubling bifurcations, and via a double CPDB. In addition, the evolution from dissipative soliton molecules to chaos via CPDB was also observed by increasing the gain saturation energy with a small filter wavelength separation. This finding shows that the evolution from SDSs to chaos is a generic property of laser systems and can appear in various pulse patterns such as single pulse, dissipative soliton molecules, and harmonic mode-locking pulses, which may be beneficial for better understanding chaotic dynamics in MOs.

Numerical Simulation of Heat Transfer of Roller Slag in Centrifugal Preparation of Inorganic Fiber

The synergistic preparation of aluminum silicate ceramic fibers from dust removal ash and fly ash is a newly developed process that achieves green and high added value treatment of solid waste. In this process, the centrifugal fiber forming method is used to treat molten slag to obtain aluminum silicate ceramic fibers. During the production process, the centrifugal roller, as a key component in fiber forming, is in long-term contact with high-temperature slag. The heat transfer between the two causes a huge temperature gradient inside the roller material, causing significant thermal stress inside the material, which has a significant impact on the stability of the centrifugal roller structure and its working condition. This article mainly conducts numerical simulation research on the heat transfer between the roller and the slag during the centrifugal fiber forming process, providing theoretical support for ensuring the structural stability of the roller and improving its service life. The research was carried out using the FLUENT module of the ANSYS software (V2021R1), and the heat transfer model of the slag and roller was established. The effects of the internal circulating water, different slag temperatures, different slag film widths, and different boundary layer thicknesses on the heat transfer of the roller were analyzed. The results show that the water temperature at the outlet is about 6 °C higher than that at the inlet on average; when the temperature of the slag increases by 1 °C, the temperature of the roller surface in contact with the slag increases by 0.91 °C; when the width of the slag on the roll surface is 11–17 mm and the slag thickness (boundary layer thickness) is less than 1 mm, it is beneficial for fiber production.

Gas Evolution Principle during Gas Drainage from a Drill Hole along the Coal Seam and Reasonable Borehole Layout Spacing.

The efficiency of coal seam gas drainage can be further improved by the accurate mastery of the gas evolution principle during gas drainage from the drill hole along the coal seam and reasonable optimization of borehole layout spacing. Based on the actual geological conditions of the no. 2 coal seam in a coal mine in Guizhou, China, and relevant control equations, a fluid-structure interaction model of gas drainage from a drill hole along the coal seam was established in this paper. Besides, numerical simulation research on the gas evolution principle during gas drainage along the coal seam and optimization of the borehole layout spacing was carried out with the COMSOL simulation software; and these were verified in combination with the project site. The results showed that in the early stage of gas drainage the gas pressure in the area near the drill holes decreased significantly. As the gas drainage went on, the degree of influence decreased gradually. During the gas drainage from adjacent drill holes, the gas pressure in the coal body between the holes decreased rapidly, and the migration was obvious. With the increase of the spacing between the drill holes, the drainage superposition effect between these holes gradually decreased until the influence area around a single hole is independently distributed in a circle-like shape, indicating that the optimization and the reasonable spacing of the drill holes are directly related to the effect of the gas drainage. With the increase of drilling spacing, the superposition effect of extraction between the holes gradually decreased until the influence area around a single hole is independently distributed in the shape of a circle, indicating that the optimization of drilling spacing is directly related to the effect of gas drainage. The results of numerical simulation were verified by analyzing the three-dimensional map of the gas pressure during the period of gas drainage at the project site and by comparing and examining the rational borehole layout spacing of the drill hole along the coal seam. The results of this study can be used to determine the spacing of gas extraction boreholes and improve the efficiency of gas extraction in the no. 2 coal seam of a coal mine in Guizhou, China, as well as to provide a reference for the gas pressure evolution, velocity field distribution, the prediction of effective drainage area, and the selection of rational borehole layout spacing during gas drainage.

Numerical simulation and experimental research on submerged arc welding of stainless steel composite plate

Numerical simulation and experimental research on submerged arc welding of stainless steel composite plate

Experimental Study and Numerical Simulation of Gas Dryer Structure Improvement

The dryer is an important part of the paper drying process, and the uniformity of the dryer wall temperature distribution has an important influence on paper production quality and efficiency. In this paper, improving the temperature uniformity of the traditional gas dryer wall is taken as the research goal, and the distribution trend and uniformity of the traditional gas dryer wall temperature are studied and analyzed, and the structural improvement plan is put forward. On the basis of this, in order to further improve the uniformity of the wall temperature of the improved gas dryer, the optimization scheme of applying endothermic coating in the low-temperature area of the inner wall of the dryer is proposed. The numerical simulation and experimental research methods are used to compare and analyze the temperature uniformity of the wall of the improved gas dryer. The results show that the axial uniformity of the wall temperature of the modified gas dryer is significantly improved. Compared with the traditional gas dryer, the temperature difference of the cylinder wall is reduced from 40 °C to 13 °C, the maximum axial temperature difference of the cylinder wall is reduced by 57%, and the temperature uniformity is increased from 66.7% to 89.6%. Compared with the improved gas dryer, after the endothermic coating is applied to the low-temperature area of the inner wall of the dryer, the temperature difference of the cylinder wall is reduced from 13 °C to 7 °C, the maximum axial temperature difference of the cylinder wall is further reduced by 46%, and the temperature uniformity is increased from 89.6% to 94.4%.

Macroscopic Fundamental Diagram Estimation Considering Traffic Flow Condition of Road Network

A macroscopic fundamental diagram (MFD) is an important basis for road network research. It describes the functional relationship between the average flow and average density of the road network. We proposed an MFD estimation method based on the traffic flow condition. Firstly, according to statistical theories, the road network data are divided into three traffic flow conditions (free flow, chaotic and congested) bounded by a 95% confidence interval of the maximum traffic capacity of each intersection in the road network. Then, in each condition, we combined principal component analysis and the Jolliffe B4 method to reduce dimension for extracting critical intersections. Finally, the full-scale dataset of the road network was reconstructed to estimate the road network MFD. Through numerical simulation and empirical research, it is found that the root mean square error and absolute percentage error between estimated MFD and true MFD considering the traffic flow condition are smaller than those without considering the traffic flow condition. The MFD estimation and the division of the traffic states of the road network were completed at the same time. The proposed method effectively saves the time cost of road network research and is highly accurate.

Numerical simulation and structure optimization of spiral wound heat exchanger with novel spacing bars

AbstractSpiral wound heat exchangers are widely used in industrial production for their advantages, such as large heat transfer areas and compact structures. However, their compact design also poses significant difficulties for numerical simulation and experimental research. The spacing bar between tube bundles has an essential impact on the performance of wound tube heat exchangers. This paper presents a new type of spacing bar vertically installed on the core barrel of the spiral wound heat exchanger to enhance the comprehensive heat transfer performance. A numerical model of a new type of wrapped tube heat exchanger has been constructed, which agrees with experimental results. Under the same working conditions, the comprehensive heat transfer performance on the shell side of the spiral wound heat exchanger with new spacing bars is increased by 7.4%–10.5% compared with the traditional structure. On this basis, the influence of the new spacing bar's structural parameters on the heat exchanger's performance was studied, and the empirical correlation between the structural parameters and operating conditions of the new spacing bar and the performance of the heat exchanger was fitted. The research results have guiding significance for the design of spiral wound heat exchangers.

Study on Mechanism of Static Blasting-Induced Hard Rock Fracture Expansion

How to deal with hard rock cheaply and safely is a pressing issue in today’s coal mining. Weakening fractures of hard rock have always been a significant concern in China’s coal mine engineering. In this study, mechanical derivation, laboratory experiments, and numerical simulation research methodologies are used to evaluate the fracturing process of the static crushing agent (SCA). From a mechanical standpoint, the mechanism of fracturing hard rock by a crushing agent is investigated. It is assumed that single-hole fracturing is separated into three stages: the microfracture stage, the fissure development stage, and the breaking stage. The swelling and fracturing properties of SCA were quantitatively analyzed. It was found that the swelling pressure of SCA increased with the increase in pore diameter, and the range of the swelling pressure was 43.5 MPa to 75.1 MPa. SCA exhibited a delayed fracture initiation, but the rate of breakage was relatively high. The cracking effect of a single-hole specimen under no peripheral pressure was simulated using PFC2D, and the results were consistent with experimental observations. The internal dynamic effect, crack extension, distribution characteristics, and the development law of double-hole expansion pressure were analyzed for double-hole specimens with different hole diameters, hole spacings, and circumferential pressures. It was observed that the cracking effect was positively correlated with the pore diameter, while the pore spacing and surrounding pressure were negatively correlated. The size of the expansion pressure was negatively correlated with the pore diameter, while the pore spacing and surrounding pressure were positively correlated.

Mechanical properties and acoustic emission evolution of water-bearing sandstone under triaxial conditions

Accidents occur frequently in underground chambers owing to the high-stress environment, poor stability of rocks, and unreasonable mining and construction layout. Significant damage to the deep surrounding rock mass by confined water can result in water inrush and flooding accidents. This study numerically investigated the mechanical properties and acoustic emission (AE) signal evolution mechanism of water-bearing sandstone in deep high-stress mining environments. The results showed that, the lower the confining pressure, the lower is the compressive strength of the specimen, resulting in evident failure. The confining pressure inhibited the radial strain and enhanced the strength of the specimen. Furthermore, under the same confining pressure and different water pressure, the higher the water pressure value, the more evident was the failure phenomenon, and the lower was the peak stress. The water pressure decreased the strength of the specimen and its ability to resist damage. Moreover, for the same water pressure, the smaller the confining pressure, the larger was the maximum AE number and the total cumulative amount of acoustic emissions. When the specimen reached the peak stress and produced macroscopic failure, the AE number reached the maximum value. Finally, the AE activity decreased as the water pressure increased, and the higher the water pressure, the smaller was the cumulative AE number. Owing to the existence of water pressure, the internal structure of the model specimen was affected by the softening effect, which decreased the model strength, thereby suppressing the AE activity of the specimen. Our findings can provide a basis for numerical simulation research on mechanical properties and AE evolution mechanism of water-bearing sandstone under three-way stress state.

Numerical study on the influence of centroid‐to‐buoyancy center ratio on the motion stability of supercavitating vehicle

SummaryIn order to study and solve the influence of the change of the position of the centroid of the supercavitating vehicle on the motion stability, the influence law of the position of the centroid of the supercavitating vehicle on the motion stability is found, and the quantitative criterion that can guide the design of the supercavitating vehicle is summarized. On the basis of theoretical analysis, the dynamic mesh technology combined with the volume of fluid multiphase flow model and the rigid body six degrees of freedom motion calculation model is used to carry out the supercavitating vehicle motion and supercavitating flow field coupling numerical simulation research for supercavitating vehicles with different cavitator shapes. The results show that the position relationship between the centroid position and the buoyancy position has a great influence on the motion stability of the vehicle. When the center of buoyancy is before the center of mass, the vehicle is unstable; when the center of buoyancy is behind the center of mass, the vehicle sails stably, and when the position of buoyancy action coincides with the center of mass, the amplitude of the tail beat of the vehicle is the smallest, and the navigation is the most stable, which is the best position of the centroid. In this article, the concept of centroid‐to‐buoyancy center ratio is proposed. The so‐called centroid‐to‐buoyancy center ratio refers to the ratio of the length from the centroid to the top of the head of the supercavitating vehicle to the length from the center of buoyancy to the top of the head of the vehicle. When the centroid‐to‐buoyancy center ratio fluctuates in the range of [0.8–1], it is an ideal condition for the stable navigation of the vehicle. When the centroid‐to‐buoyancy center ratio is in the range of (0, 0.8), the tail beat frequency is high, which accelerates the kinetic energy consumption and the rapid instability of the vehicle. Therefore, under the same constraint conditions, it is not that the closer the center of mass is, the better the stability of the vehicle motion is. The optimal centroid position is not a certain “point,” but a “periodic fluctuation interval” that changes with the buoyancy center.

Simulation of Particle Breakage in Vibration Mill Based on Tavares Model

In this paper, discrete element simulation software EDEM and Tavares crushing model were used to carry out numerical simulation research on the motion characteristics and crushing characteristics of materials in the MZ100 vibration mill during the grinding process. The influence of material characteristics, shape characteristics and filling rate of grinding media, vibration frequency, and amplitude of vibration mill on the efficiency and effect of vibration mill was analyzed. The factors affecting the distribution characteristics of the rotary center of mass and the low-energy region of the grinding medium in the grinding cavity are discussed. The extreme inflection point of the crushing efficiency of the grinding material in the grinding cavity with respect to the increase of the excitation frequency is obtained. In order to improve the grinding efficiency and reduce the low energy zone, the optimum process parameters of eccentric vibration grinding were discussed, which provided theoretical guidance for the efficient crushing of grinding materials.

Numerical investigation on the rotor-turbulence interaction noise

Noise from a turbomachinery component, such as compressors and turbines, is an important issue to be resolved in aerospace and ocean engineering applications. The rotor of a turbomachinery assembly usually could operate downstream to other flow structures (fuselages, stators, control surfaces, etc.) that produce either large-scale or small-scale turbulence structures, which are highly complex and are being distorted while they are ingested into the rotor, which generate the rotor-turbulence interaction noise. The presented work conducted numerical simulation research on a ten-bladed rotor ingesting different turbulence structures. The large eddy simulation (LES) and Ffowcs-Williams and Hawkings (FW-H) methods were used to predict the flow-induced noise from the rotor. The results show that the time-space evolution of the upstream turbulent structure when it passes towards the rotor. In addition, the differences in the turbulence ingestion noise at different inflow speeds and rotational speeds were studied. Furthermore, the sound generation mechanism of turbulent ingestion noise was explored using a newly proposed near-field sound source analysis method. In summary, this study can help to improve the understanding of the physical mechanisms of unsteady forces and noise generated by a rotor when it interacts with ingesting turbulent flows.

TBM Rapid Tunneling Roadway Support Parameters Design and Process Research

Taking the specific production geological conditions of the auxiliary transportation lane in the west area of Gaojiabao coal mine of Shaanxi Zhengtong Coal Industry as the research background, based on the anchorage support theory and the characteristics of the TBM digging process, numerical simulation, theoretical analysis, and other research methods were used to investigate the depth of the destruction of the plastic zone of the surrounding rock of the roadway to form the reasonable support parameters of a large cross-section of hard rock roadway suitable for TBM digging and to propose an intelligent digging and support process of the TBM corresponding to the on-site practice. The proposed intelligent tunneling support technology corresponds to a field practice of TBM. The study shows that: combined with the field industrial test and adjusted by the peripheral rock deformation and damage law, the anchor diameter of 20 mm, the length of 2500 mm left-hand threaded steel anchors, row spacing of 1100 mm, spacing of 1200 mm, and the anchor diameter of Φ21.8 mm, the length of 6200 mm left-handed threaded steel anchors, row spacing of 1100 mm, spacing of 1200 mm are the most reasonable solutions, which can ensure the control of the tunnel peripheral rock. The program is the most economically efficient in ensuring the control of deformation of the roadway perimeter rock and maintaining normal use.

Three-Dimensional Numerical Simulation Research on Discharge Characteristics of Storm-Drain Inlet in Low-Lying Areas

Three-Dimensional Numerical Simulation Research on Discharge Characteristics of Storm-Drain Inlet in Low-Lying Areas

Safety Performance and Failure Criteria of Lithium-Ion Batteries under Mechanical Abuse

With the increasing global focus on environmental issues, controlling carbon dioxide emissions has become an important global agenda. In this context, the development of new energy vehicles, such as electric vehicles, is flourishing. However, as a crucial power source for electric vehicles, the safety performance of lithium-ion batteries under mechanical abuse has drawn widespread attention. Evaluating the safety performance of lithium-ion batteries requires in-depth research. This paper provides a review of recent experimental and numerical simulation studies on the mechanical abuse of lithium-ion batteries. It showcases the main methods and conclusions of experimental research, compares different response forms under quasi-static and dynamic loading, discusses the causes of strain-rate dependence in lithium-ion batteries, and briefly describes the impact of the state of charge (SOC) on safety performance under mechanical abuse, as well as the influence of mechanical abuse on battery capacity and impedance characteristics. Furthermore, this paper summarizes the methods of numerical simulation research, analyzes the advantages and disadvantages of detailed modeling and homogenized modeling methods, summarizes the strain-based internal short circuit failure criteria, and reviews numerical predictive models based on multiphysics coupling. Finally, it presents the latest progress in studying the safety performance of battery packs through numerical simulations.

Numerical Simulation and Experimental Research on the Quenching Process of 1045 Steel Based on Thermo–Fluid–Solid Coupling Model

In the numerical simulation research on quenching, the heat transfer coefficient is an important input parameter. However, owing to its complexity and various influencing factors, the measured results are not universal and will significantly increase the simulation complexity and error. This article proposes a new numerical simulation method for quenching processes by extending the simulation domain and introducing the coupled heat exchange between the liquid quenching medium and workpiece, replacing the role of the heat transfer coefficient in the numerical simulation. The method is validated through experimental studies on 1045 steel rod quenched in water, with the maximum relative errors of the simulation results compared to the experimental results being 3.6%, 9%, and 5.1% for hardness, cooling curve, and residual stress, respectively. Furthermore, the article investigates the effect of different flow parameters of quenching media on the quenching effect. Under the studied conditions, the 1045 steel rod has the lowest risk of cracking and the highest hardness value when quenched in water at 50 °C. The proposed method improves the universality and convenience of numerical simulation for the quenching process and can be used to guide the formulation of quenching process parameters when the heat transfer coefficient is unknown.

Identification and extraction of lateral target signals in tunnel geological prediction with the Karhunen-Loéve beamforming method

Before the construction of a tunnel, effective and accurate advanced prospecting techniques are required to detect unexpected geological heterogeneity around the tunnel. However, because the data collected during tunnel advance prediction include waves reflected from different directions and a large amount of environmental noise, the seismic records collected are extremely complex, and it is difficult to extract the target signals from the lateral area of the tunnel effectively. The beamforming method can create a focused wave front through the stack of the wavefield, improving the data quality of the target signal. This paper incorporates the Karhunen-Loéve method in the beamforming procedure to extract the lateral signal of the tunnel. First, the test principle of Karhunen-Loéve beamforming (KLBF) based on the tunnel seismic prediction (TSP) observation system is discussed, and the corresponding delay parameters are estimated according to different application conditions. In addition, ray tracing and three-dimensional wave equation methods are used to carry out numerical simulation research on the models of faults, karst caves and underground rivers. Finally, the corresponding KLBF method can be used to improve the quality of effective signals by different delay time calculation methods, which can better identify and extract the lateral reflected signals.