Simulation Research Research Articles

Fire Behavior Characteristics and Computational Simulation Research on Historic Wooden Structures

Wooden structures are prone to fire hazards, and studying their combustion properties is vital for their protection. Samples of fresh pine wood (FP) and pine subjected to artificially accelerated aging (treated at 240 circulation) were collected and prepared for analysis. The heat-release rate, smoke production, and yields of carbon monoxide (CO) and carbon dioxide (CO2) from both types of pine were assessed using conical calorimetry to determine their combustion characteristics. A historic building in Xi’an was modeled using PyroSim to serve as a representative case. The experimentally obtained combustion characteristics of the two pine wood types were inputted into the model, and the Fire Dynamics Simulator (FDS) software was utilized to simulate the development of fire in both newly constructed and aging historic buildings. The results suggest that aging impairs the wood’s combustion properties and increases the susceptibility of pine to ignition. Consequently, this accelerates the spread of fire in wooden structures, leading to a rapid increase in temperature and swift smoke production during fires, thus amplifying the fire risk to historic wooden buildings.

Simulation and Experimental Research on the Energy Loss of Confluence Pipelines

Compared with T- and Y-shaped confluence pipelines, arc confluence pipelines have a smaller energy loss coefficient. In the study presented herein, numerical simulation analyses of the flow fields of T-shaped, Y-shaped, bifurcated, and arc confluence pipelines were carried out. An experimental system was designed to study the energy loss coefficient of the arc confluence pipeline by using five different pipe diameters and nine different radii with water as the working fluid and analyze the influence of pipe diameter, radius, and Reynolds number on the energy loss of the arc confluence pipeline. As the radius of the arc confluence pipeline increases, the energy loss coefficient of confluence first decreases and then increases, and the minimum energy loss corresponds to a radius of 65 mm; with an increase in Reynolds number, the energy loss coefficient of confluence first decreases gradually and tends to a certain value. With an increase in diameter, the energy loss coefficient of confluence decreases gradually.

Compact broadband high‐gain dielectric rod antenna with air–dielectric hybrid design for millimetre‐wave applications

AbstractThis paper presents a compact, broadband, high‐gain dielectric rod antenna. By utilising an air–dielectric hybrid method for designing the radiating and matching sections, gradual variations in the average equivalent permittivity along the rod are achieved, and the mechanism of the method is analysed. This approach facilitates a smooth impedance transition from the feed to the air, resulting in good impedance matching characteristics. Additionally, the antenna is fed through a tapered double‐ridged waveguide (DRW) with a coaxial line to tapered DRW transition. The proposed antenna achieves an impressive impedance bandwidth of 90.2%, covering the entire K and Ka bands. The unique structure of the proposed dielectric rod significantly enhances the antenna's gain, reaching a maximum value of 17.86 dBi. With its small aperture and compact longitudinal dimensions, this antenna is suitable for applications in settings like the Space Environment Simulation Research Infrastructure (SESRI).

Corrosion test and corrosion fatigue numerical simulation research on marine structures

The corrosion tests on Q235B steel in artificial seawater with conventional room temperature and high-temperature & high-humidity are first conducted. The test results show that increasing the acidity and temperature of the corrosion solution, as well as adopting the alternating dry-wet, can significantly enhance the corrosion rate of materials. In addition, the corrosion tests exhibit good simulation and acceleration characteristics compared to at sea tests. Then, the corrosion and corrosion-fatigue numerical simulation methods based on COMSOL and MATLAB are proposed. Meanwhile, the corrosion of Q235B steel in neutral artificial seawater and corrosion fatigue damage of a T-shaped structure under the coupling of artificial seawater with fatigue load are simulated and analyzed. The corrosion simulation results indicate that when the temperature is 40 °C and 20 °C, the average corrosion rates of specimens increase by 96.61% and 15.25%, respectively. Furthermore, when the temperature is 20 °C, the average corrosion rates obtained from numerical simulation and corrosion test are 0.068 mm/a and 0.062 mm/a, respectively, with a relative error of 9.7%, verifying the validity of the corrosion numerical simulation method. Based on the corrosion fatigue simulation, it is found that the maximum corrosion thickness increases by about 23% compared to pure corrosion condition in the weld region, and the structural fatigue damage increases by about 21.36% compared to pure fatigue condition after 10 years of corrosion.

A Review on the Water Invasion Mechanism and Enhanced Gas Recovery Methods in Carbonate Bottom-Water Gas Reservoirs

Carbonate gas reservoirs are crucial in gas field development, with carbonate bottom-water gas reservoirs being a significant subset. However, the development of these reservoirs often faces challenges such as water invasion, leading to a low gas recovery rate. Enhancing gas recovery is a primary goal for researchers in this field. This study provides a systematic review of the mechanisms, identification, and dynamic prediction of water invasion in these gas reservoirs. The technical adaptability and application range of different enhanced recovery methods are summarized, and their application effects are evaluated. The results indicate that carbonate gas reservoirs have diverse types of storage and permeability spaces, with a wide distribution of pore size scales, leading to various types of enclosed gas caused by water invasion. The prediction accuracy of water invasion models for bottom-water gas reservoirs with fractures and vugs is relatively low. Therefore, numerical simulation research on the basis of fine reservoir characterization is the key technology. The control of bottom-water invasion and the rescue measures after the bottom-water invasion are the keys to improving gas recovery, which can be divided into four types: drainage gas recovery, water control production, active drainage, and injection medium. Gas production by drainage is the main technology for improving gas recovery, among which foam drainage is the most widespread. The optimization of development parameters in production by water control has a good effect in the early stages of development. The active drainage technology on the water invasion channel is the bottom-up technology for the effective development of strong water-flooded gas reservoirs. CO2 injection may have great potential to improve the recovery of bottom-water gas reservoirs, which is one of the important research directions under the background of “carbon peaking and carbon neutrality”. The research provides theoretical and technical reference significance for enhanced recovery of carbonate bottom-water gas reservoirs.

Research and design of transient test platform for DC current transformer

This article studies the design and simulation of a transient test platform for DC current transformers to verify the effectiveness of the design scheme. DC current transformers convert large currents on the primary side into small currents on the secondary side through electromagnetic induction principles and are widely used in power systems. In order to verify the feasibility of the design scheme, simulation research was adopted, and the simulation parameters were the same as the actual scheme, including controllable current source parameters, cable parameters, and MOS switch branches. The simulation results show that the designed DC transient square wave current source can effectively compensate for the impulse current, and the output current waveform is stable, meeting the design requirements.

A numerical simulation research on fish adaption behavior based on deep reinforcement learning and fluid–structure coupling: The refuge–predation behaviors of intelligent fish under varying environmental pressure

The study of fish swimming behavior and locomotion mechanisms holds substantial scientific and engineering significance. With the rapid progression of artificial intelligence, the integration of artificial intelligence with high-precision numerical simulation methods presents a novel and highly efficient tool for investigating fish behavior. In this paper, we proposed a fish perception model that more closely reflects natural logic. By introducing the individual vision and partially visibility model, a physics-based visual system that mirrored the sensory capabilities of live fish was developed. Furthermore, through the construction of a flow vision using conventional neural networks, we enhanced the intelligent fish's ability to detect unsteady hydrodynamic parameters via numerical lateral line. The validity of the new model was demonstrated through experiments, which the intelligent fish hunts complex moving targets in unsteady flow. Finally, we applied the model to study the refuge/predation behaviors of coral reef fish under varying unsteady flow pressures. The results indicated that swimming capabilities significantly impact fish survival strategies in high flow velocity, highly unsteady hydrodynamic environments, shaping distinct evolutionary decision-making traits. These insights may help to understand the niche competition mechanisms of fish in different flow conditions.

Numerical Simulation for the Wave of the Variable Coefficient Nonlinear Schrödinger Equation Based on the Lattice Boltzmann Method

The variable coefficient nonlinear Schrödinger equation has a wide range of applications in various research fields. This work focuses on the wave propagation based on the variable coefficient nonlinear Schrödinger equation and the variable coefficient fractional order nonlinear Schrödinger equation. Due to the great challenge of accurately solving such problems, this work considers numerical simulation research on this type of problem. We innovatively consider using a mesoscopic numerical method, the lattice Boltzmann method, to study this type of problem, constructing lattice Boltzmann models for these two types of equations, and conducting numerical simulations of wave propagation. Error analysis was conducted on the model, and the convergence of the model was numerical validated. By comparing it with other classic schemes, the effectiveness of the model has been verified. The results indicate that lattice Boltzmann method has demonstrated advantages in both computational accuracy and time consumption. This study has positive significance for the fields of applied mathematics, nonlinear optics, and computational fluid dynamics.

Numerical simulation on metallurgical transport phenomena during DC casting of large-size Mg-Gd-Y alloy billet under various magnetic fields

The manufacture of large-size rare-earth Magnesium alloy billets by direct-chill (DC) casting process is now facing great technical challenges, mainly due to the high cost of casting experiments, and such casting defects like severe cracking, macrosegregation, and non-homogenized solidified structure. Based on the low-cost and high-efficiency numerical simulation method, the present study systematically explores the effects of single pulsed and alternating magnetic fields (PMF and AMF), differential-phase pulsed and alternating magnetic fields (DPMF and DAMF) on DC casting metallurgical transport phenomena of Φ750mm large-size Mg-Gd-Y magnesium alloy billet. The electromagnetic characteristics, flow behavior, and temperature distribution during casting process are clearly visualized. The results demonstrate that traditional DC casting process is optimized by applying magnetic fields. For one thing, pulsed magnetic fields (PMF and DPMF) generate larger and faster changing instantaneous Lorentz forces, which induce huge transient impact and oscillation effects on the melt. For another, alternating magnetic fields (AMF and DAMF) have greater time-average Lorentz forces, which can force the melt to flow continuously and steadily. Additionally, differential-phase magnetic fields (DPMF and DAMF) enhance the melt’s axial flow strength while reducing the small vortex generated at the edges, resulting in improved heat transfer efficiency and uniform temperature field. Among those magnetic fields, DPMF shows dual advantages of transient oscillation and homogenized temperature distribution. Based on the present simulated research, the Φ750mm large-sized rare earth Mg-Gd-Y alloy billet with high-quality and non-cracking has been manufactured during DC casting process under DPMF.

Design of a Hybrid Excitation Controller for Multimachine Infinite Bus Power System

Abstract: A significant portion of contemporary power networks is still conventional power system that uses synchronous generators to produce electricity. Conventional power systems are operated under various operating situations by means of excitation systems and turbine-governor systems of synchronous generators. This paper proposes an excitation controller for synchronous generators (SGs) in a multi machine infinite bus (MMIB) power system through combining the idea of the nonlinear backstepping (BS) and partial feedback linearization methods. The model of third-order has been linearized into a second-order linearized system that is independent of the rotor angle which is unmeasurable, using the partial feedback linearization approach. In this case, the BS is applied to the partially linearized system. The idea is to find a control input that drives the system towards a desired behaviour while ensuring the transformed states converge to their target values. Lastly, simulation research is carried out on an MMIB system to analyse how the proposed control mechanism (BS-PFLC) performs in stabilizing the system under a three phase-to-ground fault conditions of power networks. To demonstrate the effectiveness of the BS-PFLC, an existing excitation controller has been used to compare the performance.

Research Progress on Fatigue of Carbon Fiber Composite Materials and Their Bolted Connection Structures

This paper primarily investigates the fatigue performance of carbon fiber composites and their bolted joint structures. Carbon fiber composites have gained increasing attention due to their high strength, lightweight properties, and corrosion resistance. However, technical challenges remain regarding the fatigue characteristics of carbon fiber composites and the durability of their joint structures in practical applications. This paper reviews the research progress on fatigue performance testing of carbon fiber composites at home and abroad, focusing on failure mechanisms under cyclic loading, fatigue life prediction methods, and key influencing factors. Additionally, the paper discusses the current research status of bolted joint structures in carbon fiber composites, analyzing the impact of different joint methods on structural fatigue performance, as well as existing experimental and simulation research methods.

Carbon steel pipeline CO2 erosion-corrosion damage prediction model and numerical simulation research

CO2 erosion-corrosion (E-C) represents a significant and pervasive threat to the integrity of carbon steel pipeline in the oil and gas industry, which has attracted more and more attention. On this basis, a CO2 E-C damage prediction model considering the synergistic effect is established combining with multiphase flow model, corrosion model and CO2 corrosion model, in which the Eulerian-Lagrangian discrete particle method is employed in the multiphase flow model and the CO2 corrosion model is modified and verified by the erosion-corrosion test method. By using the CFD-DPM technology, the three-dimensional numerical simulation of the elbow is carried out to demonstrate the characteristics of the prediction model, and the dominant factors and extent of CO2 E-C damage can be determined based on the numerical simulation results. Both erosion and corrosion are non-negligible parts that lead to CO2 E-C damage, with corrosion factors being the more important factor to be considered. The prediction results can not only provide suggestions for improving the design of carbon steel pipelines in the oil and gas industry, but also provide protective measures for the operation of existing pipelines to extend their service life, which is helpful for the development and implementation of plans in the oil and gas industry.

Residential building forms and energy efficiency in the Saharan climate: the case of Adrar, Algeria

Algeria is a country that has witnessed rapid development as a result of its abundant oil supplies. The country’s GDP to energy consumption ratio clearly shows the need to adopt energy efficiency policies. Taking into account the regulation of excess solar radiation in the desert environment, this study examines the relationship between the shape of different buildings and their energy use. This research was divided into two stages. In the first stage, the ideal building shape for the city of Adrar, in terms of energy consumption, was determined by studying three basic geometric shapes, including square, rectangular, and triangle shapes. According to simulation research conducted using Design Builder (version 6.1.0), a square building was the best shape to maximize energy performance. To analyze the thermal behavior of different building shapes, all structures with expanded shapes were simulated based on the ideal shape discovered in the first stage. Of the three extended alternative cases, the case of the Mini Arrival offers the best energy efficiency and sufficient natural lighting thanks to its 90 cm depth and no vertical offset from the top of the window. By adding design principles to the design process, this study helps improve the energy efficiency of new buildings and also gives another angle on research methods for solving energy performance issues regarding desert buildings.

An Investigation of the Ventilation Systems of Whole-Indoor Urban Substations

The electricity load increases significantly with the development of the economy, which raises the issue of scarce land resources; therefore, the application of whole-indoor urban substations has become more and more extensive. However, both the closed environment of indoor substations and their unreasonable ventilation systems mean that the heat dissipation of the equipment cannot be discharged in time. In this study, a combination of natural and mechanical ventilation systems is developed to solve the problem of high indoor temperatures, and corresponding studies are conducted via both numerical simulation and experimental research. Firstly, the ventilation and heat dissipation problem of the whole-indoor urban substation was investigated using numerical simulation technology, and then the feasibility of the ventilation system was determined. Secondly, the experimental platform (including the heat dissipation equipment and ventilation system) was set up, the heat dissipation of the reactor room was analyzed, and the system was tested experimentally. Afterward, the noise generated by the experimental platform was measured and predicted. Finally, via the numerical simulation analysis, it was found that the ventilation effect would be improved regardless of the heat dissipation and that reducing the outdoor temperature or increasing the ventilation volume would reduce the indoor temperature, which could be controlled within 40 °C. The results of this study provide a reference basis and technical guidance for the engineering projects of ventilation systems for indoor substations, which can effectively solve the problem of excessive indoor temperature caused by heat dissipation from substation equipment while providing a favorable guarantee for sustainable operation of the substation.

The pressure control of independent load port electro-hydraulic load simulation system using fixed time integral sliding mode active disturbance rejection

To address the issues of motion disturbance and low loading accuracy in electro-hydraulic load simulation systems, and to effectively mitigate the impact of uncertainty on system performance, this paper proposes a novel independent load port electro-hydraulic load simulation system. A nonlinear variable structure state equation is derived to describe the pressure working states of the left and right chambers of the servo valve and hydraulic cylinder under loading conditions. In light of the presence of substantial motion disturbances, an integrated sliding mode automatic disturbance rejection composite controller is proposed with a focus on fixed-time convergence. To mitigate system chattering and enhance system loading performance and disturbance immunity, a fixed-time integral sliding mode controller was developed within the framework of active disturbance rejection control. Stability analysis was also carried out. Simulation research demonstrates that the pressure control accuracy of the composite controller is 99.88%, 99.86%, and 99.83% respectively when the system step command is given with disturbance frequencies of 1 Hz, 3 Hz, and 5 Hz. Similarly, under the same disturbance frequencies, the pressure control accuracy is 99.88%, 99.86%, and 99.84% respectively when the system sine command is given. The simulation results demonstrate that the independent load port electro-hydraulic load simulation system exhibits a notable energy-saving effect. Specifically, energy savings of around 45% and 48% were achieved compared to the original system. The research and exploration conducted have laid a strong groundwork for future in-depth studies on the independent load port electro-hydraulic load simulation system.

Validation of quantum espresso software in estimating the optical parameters of CaAlSiN3 crystal

This communication presents a theoretical analysis of certain optical properties of the CaAlSiN3 (CASN) crystal through first principles calculation. For the first time, this work validates the optical properties of the crystal performed using Quantum ESPRESSO (Acronym for opEn-Source Package for Research in Electronic Structure, Simulation, and Optimization) Plane Wave Self Consistent Field (PWscf). The calculated optical joint density of states show that the absorption begins at 4.8 eV and exhibits two sharp peaks and one broad peak at 48 nm, 64 nm, and 170 nm. The absorption range is in good agreement with our experimental observations. The dielectric function shows electric polarization between the 2p state of nitrogen and 3d state of calcium. The crystal’s static refractive index is 1.87 with a maximum value of 6.4 in the visible region, which is optimal for optical devices. The absorption coefficient confirms experimentally comparable optical states with no notable anisotropy.

Simulation and Experimental Research on Rolling Bearing with Rolling Body Defect under Starved Lubrication Condition

Simulation and Experimental Research on Rolling Bearing with Rolling Body Defect under Starved Lubrication Condition

Pressure Control of Multi-Mode Variable Structure Electro-Hydraulic Load Simulation System.

During the loading process, significant external position disturbances occur in the electro-hydraulic load simulation system. To address these position disturbances and effectively mitigate the impact of uncertainty on system performance, this paper first treats model parameter uncertainty and external disturbances as lumped disturbances. The various states of the servo valve and the pressures within the hydraulic cylinder chambers are then examined. Building on this foundation, the paper proposes a nonlinear multi-mode variable structure independent load port electro-hydraulic load simulation system that is tailored for specific loading conditions. Secondly, in light of the significant motion disturbances present, this paper proposes an integral sliding mode active disturbance rejection composite control strategy that is based on fixed-time convergence. Based on the structure of the active disturbance rejection control framework, the fixed-time integral sliding mode and active disturbance rejection control algorithms are integrated. An extended state observer is designed to accurately estimate the lumped disturbance, effectively compensating for it to achieve precise loading of the independent load port electro-hydraulic load simulation system. The stability of the designed controller is also demonstrated. The results of the simulation research indicate that when the command input is a step signal, the pressure control accuracy under the composite control strategy is 99.94%, 99.86%, and 99.76% for disturbance frequencies of 1 Hz, 3 Hz, and 5 Hz, respectively. Conversely, when the command input is a sinusoidal signal, the pressure control accuracy remains high, measuring 99.94%, 99.8%, and 99.6% under the same disturbance frequencies. Furthermore, the simulation demonstrates that the influence of sensor random noise on the system remains within acceptable limits, highlighting the effective filtering capabilities of the extended state observer. This research establishes a solid foundation for the collaborative control of load ports and the engineering application of the independent load port electro-hydraulic load simulation system.

Effect Verification in Ecological Landscape Design of Riverbank Leisure Space Based on Sketch Line Simulation Analysis

In order to improve the effectiveness of landscape design for riverbank leisure spaces, this article applies sketch line simulation technology to the design of leisure space landscapes, constructs a design model suitable for the needs of modern urban leisure space landscapes near rivers, and automatically generates high fidelity wireframes through hand drawn user interface sketches, thereby improving the efficiency of prototype design. The key to automatically generating high fidelity wireframes is to accurately detect the type and position of UI components from hand drawn UI sketches. In addition, a prototype software tool plugin was implemented to detect hand drawn UI sketches using an improved Faster R CNN and automatically convert the detection results into high fidelity wireframes. Through computer simulation research, we can see that sketch line simulation has a good effect in the landscape design of leisure spaces near riverbanks in cities.

Advances in machine learning methods in copper alloys: a review.

Advanced copper and copper alloys, as significant engineering structural materials, have recently been extensively used in energy, electron, transportation, and aviation domains. Higher requirements urge the emergence of high-performance copper alloys. However, the traditional trial-and-error experimental observations and computational simulation research used to design and develop novel materials are time-consuming and costly. With the accumulation of material research and rapid development of computational ability, the thorough application of material genome engineering has sped up the development of novel materials and facilitates the process of systematic engineering application. This review summarizes the benefits of data-driven machine learning techniques and the state of the art of machine learning research in the area of copper alloys. It also displays the widely used computational simulation approaches (e.g., the first-principles calculation, molecular dynamics simulation, phase-field simulations, and finite element analysis) and their combined applications in material design and property prediction. Finally, the limitations of machine learning research methods are outlined, and future development directions are proposed.