Numerical Simulation Techniques Research Articles

Study on the intrinsic mechanisms underlying enhanced geothermal system (EGS) heat transfer performance differences in multi-wells

The effectiveness of the multi-well arrangement mode in enhanced geothermal systems in large-scale fields has been well established. However, the mechanisms that lead to variations in heat transfer performance between different numbers of well arrangements have remained unclear. In this study, the multi-well pattern was segmented into several double-well units and a mathematical model was constructed to investigate seepage heat transfer in enhanced geothermal systems using numerical simulation techniques. The lifespan and heat transfer characteristics of both multi-well and corresponding double-well units were examined, with supplementary experimental validation. Additionally, a flow reduction coefficient for multi-well systems was proposed to explain the differences in heat transfer performance caused by the pressure superposition of multiple-well seepage fields. It was found that heat extraction from a multi-well enhanced geothermal system is equivalent to the linear superposition of corresponding double-well units. Furthermore, the lifespan of multi-well systems is significantly longer than that of corresponding double-well systems due to the influence of the multi-well flow reduction coefficient. In fact, this difference can exceed threefold in nine-well arrangements, resulting in reduced efficiency of multi-well heat exchange. This work provides a novel perspective on exploring the intrinsic mechanisms that underlie differences in heat transfer performance in enhanced geothermal systems from a flow field perspective. It contributes to a better understanding of optimal well arrangement modes for enhanced geothermal systems and supports the development of large-scale geothermal fields.

Fabrication parameters affecting the structural color of colloidal films: A combined numerical investigation

Colloidal assembly formed by drying of suspensions is expected to be applied to optical materials using their structural color resulting from the microstructure. We combine two numerical simulation techniques to investigate how the fabrication conditions of the self-assembled colloidal films affect their structural color. We first perform Langevin dynamics simulations to form colloidal films with various microstructures depending on the several fabrication parameters and then perform the finite-difference time-domain simulations of electromagnetic field analysis to calculate the structural color intensity of the obtained microstructures. To improve the structural color intensity, we show that the surface tension of the solvent should be sufficiently large so that capillary interactions exceed the interparticle adhesion by van der Waals force and furthermore that under this condition the smaller drying rate is favorable. This study suggests a guideline to design the fabrication process of colloidal films generating structural color.

Electrostatic lower hybrid turbulence due to magnetic islands and particle heating in magnetopause reconnection regions

This investigation presents a model to understand the magnetopause turbulence in the lower hybrid frequency range at reconnection regions as observed by the magnetospheric multiscale mission. We have modeled 3D electrostatic lower hybrid wave (LHW) in cold magnetized plasma in the presence of magnetic islands. In this model, we have developed the modified nonlinear Schrödinger equation, contemplating that nonlinear effects are due to ponderomotive force. The dynamical equation of the system thus obtained is solved using numerical simulation techniques. The simulation results illustrate the formation and evolution of localized structures and the current sheets. Due to the nonlinear effects and magnetic reconnection, the current sheets become turbulent with time. A semi-analytical model is also given to illustrate the scale size of current sheets. The turbulent power spectra have also been studied. The spectral index of the power spectrum is found to be −2.7 (approximately) in the perpendicular direction and −2.2 (approximately) in the parallel direction, indicating anisotropy. Using the Folker–Plank diffusion equation with the new velocity space diffusion coefficient, we find the distribution function of energetic electrons due to these turbulent structures. We propose that LHW may be responsible for plasma heating in magnetopause.

Разработка и апробация методики численного моделирования аэроупругого состояния крыла на основе методов конечных элементов и контрольных объемов

The paper considers a current trend in designing structural elements for the modern airliners. Calculation of the aerodynamic loads acting on the aircraft in flight is of primary interest at the initial design and development stages. Based on the experimental data, a CAD model was developed, and a computational grid for the CFD solver and the finite element model were constructed. The proposed technique for determining external loads on the airframe is based on the coupled solution of the aerodynamics and strength dynamic models. When using this technique, the serial data exchange between the solvers was actually implemented making it possible to simulate various periodic processes, including the structural vibrations. This work studies aerodynamic characteristics and eigenforms of the loaded wing using the example of the wing blowing calculated repetition in a cryogenic wind tunnel. The purpose of the work is to develop and test a technique for numerical simulation of the wing aeroelastic state, which allows performing calculations to determine the loads on both the lightly loaded elements and the critical units, including the wing box and the empennage. The results obtained testify to applicability of the developed technique at the transonic speeds, as well as a good convergence of the mathematical simulation results with the experimental data.

Seismic fragility assessment of aqueduct bent structures subjected to mainshock-aftershock sequences

This study aims to assess the seismic fragility of the aqueduct bent structure subjected to mainshock-aftershock (MS-AS) ground motion sequences by double incremental dynamic analysis method. The finite element model of the aqueduct bent structure is developed in OpenSees platform and numerical simulation technique is validated through physical test results. A series of nonlinear dynamic time-history analysis is carried out on the aqueduct bent structure to obtain its seismic response under different ground motion intensities. Furthermore, the incremental dynamic analysis (IDA) data cluster and median lines of the damage measure of the aqueduct bent structure are constructed. The advanced probabilistic seismic demand model (PSDM) of the aqueduct bent structure subjected to MS-AS ground motion sequences is proposed. Based on the proposed PSDM and the predefined damage states, the fragility surfaces of the aqueduct bent structure are also developed by adopting the vector-valued intensity measures considering the mainshock intensities (IMm) and aftershock intensities (IMa). Meanwhile, for the sake of comparation, the aftershock fragility curves of the aqueduct bent structure under different mainshock intensities are drawn, which emphasizes the importance of aftershocks in the seismic risk assessment. The analysis results indicate that the proposed piecewise probabilistic seismic demand model can better fit the logarithmic relationship between the aftershock intensities and the median of the reinforcement longitudinal tensile strain. The structural fragility probability increase with the increase of mainshock and aftershock intensities. It turns out that the mainshock intensities play a leading role in the damage probability of the aqueduct structure subjected to MS-AS ground motion sequences, the aftershock can cause additional damage to the aqueduct bent structure and reduce its seismic capacity. The meaningful results can provide supports for seismic optimization design, resilience improvement and post-earthquake repair-demand of the aqueduct structure in Southwest China.

Experimental and numerical investigation of mixed mode fracture of high‐performance grouting materials based on peridynamics

AbstractThis paper investigates the fracture behavior of high‐performance grouting materials in the grouted connection section of marine structures, where they are subjected to complex stress states. This study utilizes a combination of experimental and numerical simulation methods to establish a reliable numerical simulation technique for the fracture process of high‐performance grouting materials. The mixed mode fracture behavior is analyzed using six different types of specimens, and the strain contour is analyzed using the Digital Image Correlation technique. An extended peridynamics model is proposed for the numerical simulation, which adopts a fracture criterion based on strain energy density. The accuracy of the model is verified qualitatively and quantitatively, and the simulation results are consistent with the experiments. Overall, this study provides insights into the fracture behavior of high‐performance grouting materials in complex stress states and presents a reliable numerical simulation technique for the fracture process.

О звукоизлучении корпусов морской техники под действием силы на низких частотах

Object and purpose of research. This paper discusses induced noise radiation into water from spherical uniform bodies and spherical shells to estimate the acceptability of commonly used simplified approach to prediction of low-frequency acoustic signatures for marine objects. Materials and methods.The calculations were performed as per analytical expressions and numerical simulation techniques (FEM). Main results. The study has shown that increasing the density of radiating body and increasing mechanical resistance of shell at the location of exciting force reduces noise radiation. Resonant noise radiation typically occurs due to structural non-uniformities of marine objects, like local masses needed to ensure zero buoyancy, e.g. equipment or ballast. These nonuniformities create reactive forces that reach their peak values at resonant frequencies of the hull. Conclusion. The study concludes that reliable computational estimate of low-frequency acoustic signatures must take into account both mechanical resistance and non-uniform distribution of masses along hull, which can be done in numerical simulation packages.

Numerical simulation of solar parabolic trough collector with twisted tape insertion shielded within inner cylindrical tube

ABSTRACT In this study, the effects of variations in geometrical parameters of shielded twisted tape within the inner cylinder of the absorber tube on the performance enhancement of the parabolic trough collector (PTC) have been investigated. The objective is based on the prediction of the optimized value of geometrical parameters for the modified parabolic trough collector (MPTC) showing the best thermal performance among them. Numerical simulation techniques with Ansys-Aim2020R1 have been used for this investigation. It is desired to determine whether it is advantageous to use inner shielding around the inserts within the absorber tube; and if so, which geometrical parameter plays a crucial character in the prediction of the best possible thermal performance of the system. It was found that with a twisted tape thickness of 0.002 m, twisted tape gap of 0.001 m, inner cylinder center distance of 0.020 m, and the number of twists of the twisted tape of 50 turns the PTC has shown the best possible performance of the system. These findings reflect optimized geometrical parameters of the twisted tape insert shielded by an inner cylindrical tube. The thermal efficiency (η) of the MPTC was found to be 86.5% and approximately 2.063 times that of the conventional PTC. It is a novel endeavor regarding the approach of utilizing the shielding around the inserts within the absorber tube.

Aerosol exchange between pressure-equilibrium rooms induced by door motion and human movement

It is now widely recognised that aerosol transport is major vector for transmission of diseases such as COVID-19, and quantification of aerosol transport in the built environment is critical to risk analysis and management. Understanding the effects of door motion and human movement on the dispersion of virus-laden aerosols under pressure-equilibrium conditions is of great significance to the evaluation of infection risks and development of mitigation strategies. This study uses novel numerical simulation techniques to quantify the impact of these motions upon aerosol transport and provides valuable insights into the wake dynamics of swinging doors and human movement. The results show that the wake flow of an opening swinging door delays aerosol escape, while that of a person walking out entrains aerosol out of the room. Aerosol escape caused by door motion mainly happens during the closing sequence which pushes the aerosols out. Parametric studies show that while an increased door swinging speed or human movement speed can enhance air exchange across the doorway, the cumulative aerosol exchange across the doorway is not clearly affected by the speeds.

Research on Water Influx Issues in Carbonate Reservoir Development

The issue of water encroachment in the development of carbonate reservoirs has always been one of the significant factors limiting the effectiveness of reservoir development. The impact of water encroachment on well productivity cannot be ignored, making the study of water encroachment in carbonate reservoirs of great theoretical and practical significance. In this study, we focused on the problem of severe water encroachment in the fringe well group of the MX reservoir, and applied dynamic analysis and numerical simulation techniques to explore practical water management strategies. The research results indicate that in strong water encroachment reservoirs, active drainage from peripheral wells can consume water energy, reduce the pressure differential between gas and water zones, slow down the water encroachment rate, and significantly delay the occurrence of water breakthrough within the reservoir. This study provides technical references for the rational and effective development of strong water encroachment reservoirs.

Application of Particle Image Velocimetry and Computational Fluid Dynamics Methods for Analysis of Natural Convection over a Horizontal Heating Source

The objective of this article is to address the challenges associated with visualizing air flow over a heating source in an open laboratory environment. The study uses a combination of experimental visualization and numerical simulation techniques to generate a 3D model of the air flow and heat transfer between the heating source and the environment via natural convection. The Particle Image Velocimetry method is used to experimentally visualize the air flow, which is known for its benefits of high speed and accuracy, and for its ability to avoid disturbing the flow of the fluid being investigated. The data obtained from this experimental method are used as input for numerical simulations using the Ansys Fluent program. The numerical simulations identify air vortices and other elements that disrupt the airflow in the laboratory environment. The resulting 3D model accurately represents the actual situation in the laboratory and could be further optimized by adjusting parameters such as the output of the heater and the heating source temperature. These parameters play a crucial role in ensuring thermal comfort in the laboratory environment, which is of utmost importance for user comfort. In conclusion, the study provides valuable insights into the visualization of air flow over a heating source and demonstrates the effectiveness of combining experimental and numerical simulation techniques to generate accurate 3D models of air flow and heat transfer.

Ordinary state-based peri-ultrasound modeling to study the effects of multiple cracks on the nonlinear response of plate structures

Since it is almost impossible to carry out a comprehensive parametric investigation experimentally for internal cracks with different geometry and orientation, a good numerical modeling and simulation technique is necessary to have a clear understanding of the physics of wave propagation and its interaction with cracks. Such investigation is helpful for structural health monitoring (SHM) with ultrasonic techniques. This work presents a nonlocal peri-ultrasound theory based on ordinary state-based (OSB) peridynamics for modeling elastic wave propagation in three-dimensional (3-D) plate structures containing multiple cracks. A relatively new and promising nonlinear ultrasonic technique called Sideband Peak Count – Index (or SPC-I) is adopted to extract the nonlinearity generated from the interactions between elastic waves and multiple cracks. Effects of three main parameters – the distance between the acoustic source and the crack, the crack spacing and the number of cracks are investigated using the proposed OSB peri-ultrasound theory together with the SPC-I technique. For each of these three parameters investigation, different crack thicknesses were considered − 0 mm (crack-free), 1 mm (thin crack), 2 mm (intermediate thickness) and 4 mm (thick crack); thin and thick cracks are defined after comparing the crack thickness value with the horizon size mentioned in the peri-ultrasound theory. It is found that for obtaining consistent results the acoustic source should be placed at least one wavelength away from the crack and crack spacings also play an important role on the nonlinear response. It is concluded that the nonlinear response diminishes when the cracks become too thick, and thin cracks show higher nonlinearity than that of thick cracks and no cracks. Finally, the proposed method which is combining the peri-ultrasound theory and SPC-I technique is used for monitoring cracks’ evolution process. The numerical modeling results are compared with the experimental findings reported in the literature. Consistent qualitative trends in SPC-I variations predicted numerically and obtained experimentally are observed, thus it gives confidence in the proposed method.

A particle-resolved heat-particle-fluid coupling model by DEM-IMB-LBM

Multifield coupling is frequently encountered and also an active area of research in geotechnical engineering. In this work, a particle-resolved direct numerical simulation (PR-DNS) technique is extended to simulate particle-fluid interaction problems involving heat transfer at the grain level. In this extended technique, an immersed moving boundary (IMB) scheme is used to couple the discrete element method (DEM) and lattice Boltzmann method (LBM), while a recently proposed Dirichlet-type thermal boundary condition is also adapted to account for heat transfer between fluid phase and solid particles. The resulting DEM-IBM-LBM model is robust to simulate moving curved boundaries with constant temperature in thermal flows. To facilitate the understanding and implementation of this coupled model for non-isothermal problems, a complete list is given for the conversion of relevant physical variables to lattice units. Then, benchmark tests, including a single-particle sedimentation and a two-particle drafting-kissing-tumbling (DKT) simulation with heat transfer, are carried out to validate the accuracy of our coupled technique. To further investigate the role of heat transfer in particle-laden flows, two multiple-particle problems with heat transfer are performed. Numerical examples demonstrate that the proposed coupling model is a promising high-resolution approach for simulating the heat-particle-fluid coupling at the grain level.

Research Status of Numerical Simulation of Nonmetallic Inclusions Interfacial Removal

The removal of inclusions in liquid steel has always been the focus of research, and the removal of inclusions is mainly through the process of the inclusion through the slag–steel interface. The inclusion removal process can be subdivided into inclusions in molten steel grew up rise, in steel–slag interface through separation, adsorb dissolved in molten slag 3 steps. Based on the microscopic process of three steps, this article summarizes and discusses the mathematical model, fluid mechanics model, and experimental verification method of inclusion removal process, analyzes limiting and influencing factors of inclusion removal process, and comprehensively describes the numerical simulation research progress of inclusion removal process. With the development of numerical simulation techniques and experimental equipment, some progress has been made in the study of interfacial removal of inclusions. The inclusion interface removal behavior can be analyzed semiquantitatively based on dynamic force model. The computational fluid dynamics model has advantages in studying the phenomena of the inclusion interface, and the phase‐field method is often used to simulate the removal process of the inclusion interface. The combination of water model and numerical simulation, high‐temperature laser confocal method, and other methods is of great help to explore the interface behavior of inclusions.

Summary of the 10th Conference on Magnetically Confined Fusion Theory and Simulation (CMCFTS)

This paper gives a summary of the organization and the presentations delivered at the 10th Conference on Magnetically Confined Fusion Theory and Simulation (CMCFTS) held in Zhuhai, China, from 28th to 31st October 2022. The conference focused on the latest progress in the research of the magnetic confined fusion plasma theory and simulations, as well as the large-scale numerical simulation techniques developed in recent years. This conference is held both online and offline, with about 110 domestic participants from 18 institutes participating in the live conference, and the statistical data from the live broadcast platform indicated that the online conference attracted over 20 000 views per day. A summary of the conference is given, and the history of the CMCFTS is presented. A brief introduction to the poster section is also included in this paper.

Risk source identification and diffusion trends of metal(loid)s in stream sediments from an abandoned arsenic-containing mine

Stream sediments from mine area are a converging source of water and soil pollution. The risk and development trends of metal(loid)s pollution in sediments from an abandoned arsenic-containing mine were studied using modelling techniques. The results showed that the combined techniques of geographic information system (GIS), random forest (RF), and numerical simulation (NS) could identify risk sources and diffusion trends of metal(loid)s in mine sediments. The median values of As, Cd, Hg, and Sb in sediments were 5.01, 3.02, 5.67, and 3.20 times of the background values of stream sediments in China, respectively. As (14.09%) and Hg (18.64%) pollution in mine stream sediments were severe while As is the main potential risk source with a strong spatial correlation. High-risk blocks were concentrated in the landfill area, with the surrounding pollution shows a decreasing trend of “step-type” pollution. The risk correlation between Hg and As (55.37%) in the landfill area is high. As a case of arsenic, the diffusion capacity of As within 500m is strong and stabilizes at 1 km when driven by the flows of 0.05, 0.5, and 5 m3/s, respectively. With the worst-case scenario flow (86 m3/s), it would take only 147 days for the waters within 3 km to become highly polluted. The high pollution levels in a stream under forecast of different distance intervals (500, 1500, 2000 m) within 6.5 km is arrived at approximate 344, 357, and 384 days, respectively. The study suggested the combined technique of GIS, RF, and NS can serve the risk source identification of contaminated sites and risk forecast of toxic element diffusion in emergency situations.

Impact of Absorber Layer Thickness on Perovskite Solar Cell Efficiency: A Performance Analysis

Perovskite solar cells (PSCs) have a high-power conversion efficiency that exceeds 20%, distinguishing them from other new photovoltaic technologies. The Solar Cell Capacitance Simulator (SCAPS-1D) was used in this study to investigate the effects of absorber layer properties on photovoltaic solar cell performance. SCAPS simulation software employs a numerical simulation technique to fully comprehend the principles of solar cell operation and predict the best power conversion efficiency. A three-layer solar cell model comprised of an Electron Transport Layer (ETL), a Hole Transport Layer (HTL), and a Perovskite Absorber Layer was used in this study. The variations in Voc, Jsc, FF, and PCE were investigated by varying the thickness of the absorber layer. The purpose of this research is to find the absorber layer thickness that produces the highest efficiency for two different ETM layer ZnO and SnO2. This simulation model can significantly aid in the fabrication of high-efficiency ZnO and SnO2 based PSCs.

Structural Performance of Energy Efficient Geopolymer Concrete Confined Masonry: An Approach towards Decarbonization

Geopolymer concrete is preferred over OPC due to its use of energy waste such as fly ash, making it more sustainable and energy-efficient. However, limited research has been done on its seismic characterization in confined masonry, highlighting a gap in sustainable earthquake-resistant structures. Our study compares the performance of alkali-activated fly-ash-based geopolymer concrete bare frame and confined masonry wall panels with conventional concrete. Experimental results showed that geopolymer concrete bare frame has 3.5% higher initial stiffness and 1.0% higher lateral load-bearing capacity compared to conventional concrete. Geopolymer concrete confined masonry exhibited 45.2% higher initial stiffness and 4.1% higher ultimate seismic capacity than traditional concrete. The experimental results were verified using a numerical simulation technique with ANSYS-APDL, showing good correlation. Comparison with previously tested masonry walls revealed that GPC confined masonry has similar structural behavior to cement concrete masonry. This study demonstrates that geopolymer concrete made from waste energy such as fly ash is a sustainable and low-energy substitute for OPC concrete, particularly in highly seismic-prone areas, for a cleaner environment.

Numerical investigation of an innovative furnace concept for industrial coil coating lines

In this work, the engineering performance of an innovative furnace concept developed for continuous drying and curing of paint-coated metal sheets (coil coating process) is investigated through advanced modeling and numerical simulation techniques. Unlike the traditional and wide-spread coil coating furnaces – which operate according to the so-called convective air-drying technology –, the present furnace concept relies on infrared radiative heating to drive solvent evaporation and curing reactions. Radiative heat is provided by the operation of radiant porous burners which are fed with evaporated solvents. The current furnace concept consists of two main chambers (the radiant burner section and the curing oven section) with different gas compositions (atmospheres) that are separated by a semi-transparent window. The window allows energy transfer and prevents gas mixing between the two sections. To utilize the solvent-loaded atmosphere available in the curing oven section as fuel – and to prevent the development of explosive conditions therein –, a novel inertization concept shielding the curing oven section from the external environment is considered. The current furnace concept aims at improving process intensification and promoting energy efficiency. For the current furnace concept, numerical simulation results support a suitable and competitive performance for drying the applied coatings in comparison with the traditional approach. Simultaneously, a safe operation is predicted, without (i) solvent leakage from the furnace and (ii) oxygen entrainment from the surrounding ambient into the furnace. These conditions are satisfied demonstrating a safe operation and a complete evaporation of solvents from applied liquid film coatings.

On research of dispersion characteristics of multi-component surface waves from traffic-induced seismic ambient noise

As one of the commonly used sources in passive surface wave exploration, traffic-induced seismic ambient noise is widely used in urban underground velocity structure detection at present. However, characteristics of the dispersion curve extracted from such kind of ambient noise lack systematical research, especially for the multi-component surface wave. Due to the complex character of the real-world underneath structures, dispersion characteristics concluded from real-world traffic-induced seismic ambient noise that is hard to verify. The numerical simulation technique is a good choice for systematical research of characteristics of dispersion curves extracted from multi-component traffic-induced seismic ambient noise. Most of the numerical examples that appeared in the present literature, however, are based on the dispersion-curve-based numerical simulation technique. Hence, most of these can only simulate the vertical component. In this paper, the two-dimensional finite difference method is used to simulate multi-component traffic seismic ambient noise. The characteristics of original traffic noise are analyzed, and the effect of trace intervals on surface wave imaging of different types of traffic-induced noise is studied. Rayleigh wave dispersion energy image is extracted by the passive surface-wave frequency wavenumber transformed method. The differences in Rayleigh-wave dispersion images in traffic noise with different components are analyzed and compared. The results show that Rayleigh wave dispersion energy images appearing different characteristics in different components. The surface wave dispersion information presented by different types of traffic noise is frequency-dependent. The trace spacing also strongly affect the surface-wave dispersion energy images extracted from different types of traffic-induced noise. The numerical results are significant for guiding the traffic-induced seismic noise data acquisition and processing.