Two-dimensional Model Research Articles

SPECIFIC FEATURES OF TIDAL EXCHANGE IN THE KURIL STRAITS ACCORDING TO MODELING DATA

Specific features of tidal fluctuations of sea level and tidal currents in the straits of the Kuril Islands are studied using numerical modeling. Two-time intervals, i. e. 02.06.1977-03.06.1977 and 11.10.1977-12.10.1977, were taken to compare the parameters of tropical and equatorial tides. The simulation results were verified with the field data. It was found that the straits of the northeastern part of the Kuril Ridge have a mixed type of tides with a predominance of the diurnal course, and in the southwestern part a semi-diurnal course prevails. The highest tides (up to 2,5-3 m) in the study period were observed on 02.06.1977 near the Kamchatka Peninsula and the Hokkaido Island, as well as large islands of the Kuril Ridge. Four main oscillation periods of 12, 12,4, 24 and 25,8 hours were identified, which corresponds to the S2, M2, K1 and O1 harmonics. Analysis of the data obtained showed that the maximum velocities of the depthaveraged currents reach 4,5 m/s. The highest speeds were recorded in the Kruzenshtern, Frieze and Sredny Straits. Estimates of the tidal flow have shown that semi-daily fluctuations are more pronounced in the straits with lower average depths during a tropical tide. In deeper straits, semi-daily fluctuations at tropical tides are very weak or absent at all, an example is the Boussol Strait. It is calculated that when using a two-dimensional model, the maximum values of the tidal flow are observed in the Boussol Strait, reaching ~40 Sverdrups (Sv).

An analytical solution to ground stresses induced by tunneling considering ground surface boundary conditions and gravity

Accurately predicting the stress distribution around the tunnel is crucial for designing safe and economical support systems. The stress distribution is closely related to the ground stress release induced by tunneling, as well as the initial gravity stress and boundary conditions. In this study, a two-dimensional analytical model considering the ground surface boundary conditions and gravity is presented to investigate the stress field around the tunnel. Then, a numerical model was developed to validate the proposed analytical model. Finally, parametric analyses were conducted, and the limitations of the load calculation method of the code for design of shield tunnel in China were discussed. The results indicate that: (a) Tunnel excavation induces stress redistribution in the soil, resulting in a soil arching effect around the tunnel. This arching effect causes nonlinear load changes around the tunnel. (b) The soil mass around the tunnel can be divided into undisturbed and disturbed zones. Above the tunnel, the disturbance range is C-2D(C and D represent the burial depth and the tunnel diameter), while below and on both sides of the tunnel, the disturbance ranges are 4D and 1.5D, respectively. (c) Once the stress release rate reaches 0.6, a combined arching effect zone, consisting of both major and minor principal stresses, is formed in the disturbance zone above and below the tunnel. (d) The load distribution pattern calculated by the code for design of shield tunnel in China is gourd-shaped, and this calculation method is insufficient for accurately evaluating the load around the tunnel. The research results can provide a reference for the design of the shield tunnel.

Crystal surface heat transfer during the growth of 300mm monocrystalline silicon by the Czochralski process

This paper investigated the lower heat transfer efficiency of ingot after increasing the size of Czochralski monocrystalline silicon. To improve the heat transfer efficiency, industrial Czochralski monocrystalline furnaces use water-cooling jackets to enhance crystal heat transfer. Through two-dimensional modeling, radiative heat transfer between monocrystalline silicon and the water-cooling jacket was investigated. The results showed that the effective radiation on the crystal surface decreased, then increased, and then decreased again. Numerical simulations showed that the maximum effective radiation on the surface was greater than 60 000 W/m2, which represents a significant increase in the heat flow density compared with the radiation of the crystal without using water cooling. According to the angle factor definition, a model of the radiative heat transfer angle factor between the water-cooling jacket and silicon rod was established. The dynamic correlation equation between the radiation angle factor and geometrical parameter of the hot zone, solidification rate, and solidification time was derived. Finally, a water-cooling jacket suitable for growing large monocrystalline silicon rod was designed according to the model, which improved the growth efficiency of the crystals. The results of the study are of great significance for optimizing water-cooling jackets.

Bionic Walking Control of a Biped Robot Based on CPG Using an Improved Particle Swarm Algorithm

In the domain of bionic walking control for biped robots, optimizing the parameters of the central pattern generator (CPG) presents a formidable challenge due to its high-dimensional and nonlinear characteristics. The traditional particle swarm optimization (PSO) algorithm often converges to local optima, particularly when addressing CPG parameter optimization issues. To address these challenges, one improved particle swarm optimization algorithm aimed at enhancing the stability of the walking control of biped robots was proposed in this paper. The improved PSO algorithm incorporates a spiral function to generate better particles, alongside optimized inertia weight factors and learning factors. Evaluation results between the proposed algorithm and comparative PSO algorithms were provided, focusing on fitness, computational dimensions, convergence rates, and other metrics. The biped robot walking validation simulations, based on CPG control, were implemented through the integration of the V-REP (V4.1.0) and MATLAB (R2022b) platforms. Results demonstrate that compared with the traditional PSO algorithm and chaotic PSO algorithms, the performance of the proposed algorithm is improved by about 45% (two-dimensional model) and 54% (four-dimensional model), particularly excelling in high-dimensional computations. The novel algorithm exhibits a reduced complexity and improved optimization efficiency, thereby offering an effective strategy to enhance the walking stability of biped robots.

Application of bursting pressure and conventional drained behavioural theory to the Brumadinho failure

The Brumadinho tailings dam failure in 2019 has had a profound impact on the way tailings engineers analyse and interpret stability, with the focus of assessments moving away from conventional drained behaviour to consideration of undrained and post-liquefaction resistance. One of the contributing reasons is that the Expert Panel investigation of the failure concluded that, despite the drained factor of safety being adequate, the failure took place in an undrained manner. This paper examines the Brumadinho failure from a conventional drained perspective using two-dimensional limit equilibrium and finite difference modelling. Collectively, these analyses show that the failure can also be explained by a drained triggering mechanism and therefore suggest that several additional lessons may be learnt from the failure.

Three-dimensional modeling of 500 kV transmission lines by airborne LiDAR

This study aims to enhance the accuracy of three-dimensional (3D) modeling in the planning, design, operation management, and risk assessment of 500 kV transmission lines. Addressing the limitations of traditional two-dimensional (2D) or low-precision 3D models, a new method based on airborne Light Detection and Ranging (LiDAR) technology is proposed. Initially, high-density, high-precision 3D point cloud data are collected using airborne LiDAR technology. This data is then processed using specialized software for noise removal, terrain classification extraction, and Geographic Information System (GIS) data integration. Subsequently, a Convolutional Neural Network (CNN) is employed to classify the 3D point cloud data to enhance the accuracy of complex structure recognition. Lastly, the point cloud data are converted into linear and planar entities using Computer-Aided Design (CAD) technology, achieving high-precision 3D reconstruction of the 500 kV transmission lines and their complex terrain environment. Experimental results show that the spatial resolution of the constructed model reaches 0.1 m per pixel, with overall geometric accuracy within ±5 cm. Compared to traditional aerial imagery and ground survey methods, the model based on airborne LiDAR technology achieves improvements of 30 % in detail richness and 35 % in terrain adaptability, with a 45 % increase in decision-making efficiency. These improvements significantly enhance the accuracy of line operations, safety assessments, and environmental impact analyses, providing solid data support for the modernization and intelligent development of the power industry.

Numerical study of proton exchange membrane water electrolyzer performance based on catalyst layer agglomerate model

In this work, a two-dimensional two-phase model of proton exchange membrane water electrolyzer (PEMWE) is developed, in which the catalyst layer (CL) is represented using agglomerate model. The effects of CL composition, porous transport layer (PTL) material properties and operating conditions on PEMWE performance are investigated. The results indicate that small size of catalyst agglomerate around 0.25 μm would benefit PEMWE performance. Appropriate increase of catalyst loading, porosity and ionomer volume fraction in the CL improves PEMWE performance, but their further increment leads to high mass transfer resistance, limiting the improvement of electrolyzer performance. The porosity and ionomer volume fraction of the catalyst layer are suggested to be lower than 0.5 and 0.6, respectively. The catalyst loading should be lower than 1.5 mg cm−2 when the CL porosity is higher than 0.3. The PTLs with high permeability, porosity and low contact angle is beneficial for the gas–liquid two-phase flow and avoiding the overheat and water shortage in the electrolyzer. Increasing the inlet velocity accelerates the bubble removal process, but might results in significant temperature drop, degrading the PEMWE performance. The most suitable temperature of inlet liquid is around 353.15 K. The results provide important guidance for the optimization design of high-performance PEMWE.

Two-Dimensional Physical Model Experimental Study on Sweep Efficiency of Offshore Heavy Oil Hot Water Flooding

Abstract The conventional water flooding approach for the development of ordinary heavy oil faces challenges such as high injection-production mobility, rapid increase in water cut, and low final recovery. By using the temperature-sensitive properties of heavy oil, the viscosity can be effectively reduced, and the flow capacity within porous media can be enhanced by increasing the temperature of injected water. Onshore hot water flooding is primarily used to exploit the remaining oil potential during the later stages of steam stimulation, while offshore is used to enhance efficiency during the mid to late stages of water flooding. The key to the success of hot water flooding technology lies in the improvement of the sweep coefficient. Firstly, a two-dimensional physical experiment model is designed in accordance with the geological and reservoir characteristics of the target oilfield, based on the principle of similarity. Secondly, parameters that quantitatively characterize the development law of the plane temperature field, such as the effective sweep coefficient, regular factor, and plane expansion speed of the high-temperature region, are studied. Then, through two-dimensional experiments, the effects of injection medium, formation rhythm, and timing of hot water injection on sweep efficiency and temperature field development were discussed. Finally, on the basis of two-dimensional experiments, the effects of heat injection temperature, timing of heat injection, hot water injection speed, and high permeability strip on the improvement of sweep efficiency were quantitatively analyzed by numerical simulation. The results show that compared with hot water flooding, hot water composite flooding can increase the effective sweep coefficient from 15.05 % to 28.71 %. The anti-rhythm is helpful to the upward expansion of the high temperature zone, which can increase the oil displacement efficiency by 1.5 %. Water channeling can be effectively controlled by injecting hot water with low water cut. The increase of heat injection temperature is helpful to increase the proportion of high temperature heating area. The higher the injection speed, the greater the expansion speed of the heating chamber. The research results provide a direction for the development of heavy oil conventional water flooding to improve oil recovery in offshore heavy oil.

Heat transfer characteristics of methane-air premixed jet flames with flat/hemispherical walls

Abstract The in-depth study of the mutual coupling between the flame and the wall can significantly enhance the efficiency of actual combustion devices. A two-dimensional numerical model of the heat transfer characteristics of methane-air premixed jet flames with flat/hemispherical walls has been developed. An examination of the effects of wall shape on the heat transfer characteristics of methane/air flames was conducted as a function of the equivalence ratio (ϕ=0.9-1.5), the mixture Reynolds number (Re=300-800), and the burner-to-plate distance (H/d=1-6). As the equivalence ratio and Reynolds number increase, the flame temperature increases on the surface near the wall, and the temperature near the flame centerline is higher under the influence of a hemispherical wall than it is under the influence of a plate. In addition, the wall's heat flux increases as both the equivalence ratio and the Reynolds number increase. It is observed that the heat flux of the hemispherical wall is greater than that of the flat plate near the stagnation point, whereas it is smaller at a distance from the stagnation point. Due to the burner-to-plate distance, thermal efficiency is maximized when the flame premixed cone contacts the impact surface, which is the desired condition for optimal performance. Due to different operating conditions, the efficiency of heat transfer is always higher under the action of a flat plate than under the action of a hemispherical wall.

Study of self-assembly between two magnetic particle chains in magnetorheological fluids

The self-assembly behavior of individual magnetic particles in magnetorheological liquids has been extensively analyzed in previous studies, but the self-assembly behavior between chains of magnetic particles has rarely been investigated. In this paper, the self-assembly mechanism between chains of magnetic particles is investigated using simulation and experimental methods. Firstly, a two-dimensional coupling simulation numerical model of particle-magnetic field-flow field is constructed by analyzing the magnetic force, fluid force and contact interaction force between magnetic particles. The accuracy of the simulation model was verified through experiments. Then the attraction and repulsion dividing line of two magnetic particle chains are analytically calculated by simulation combined with parametric scanning. And analyze the law of the influence of the number of magnetic particles between magnetic particle chains on the attraction and repulsion dividing line. Finally, the different self-assembly behaviors that occur when magnetic particle chains are in different regions of attraction and repulsion between them are experimentally verified. Thus, this study provides new insights into the self-assembly mechanism between chains of magnetic particles in magnetorheological fluids in terms of the effect of the number of magnetic particles on the attraction–repulsion dividing line.

Numerical study on positive streamer in parallel-rod dielectric barrier discharge in atmospheric air

In this work, a parallel-rod dielectric barrier discharge (DBD) operating in atmospheric air is investigated through the two-dimensional plasma fluid model. The effects of applied voltage (Vp), secondary electron emission coefficient (γ), and photoionization are examined. Photoionization can significantly influence streamer dynamics by accelerating and broadening both volumetric and surface streamers and enhance the impact of the applied voltage. Without photoionization, the propagation distance of the surface streamer along the curved dielectric surface is limited to 0.1–0.2 mm under applied voltages of 8–8.5 kV. In contrast, with photoionization, this distance can extend to 0.3–0.6 mm. Achieving the same distance requires much higher voltages (10–11 kV) if without photoionization. The “double-layer” structure of the surface streamer is investigated, revealing that γ predominantly affects the surface branch with little impact on the volumetric branch. The critical charge density for streamer onset is found to be about 1018 m−3, and the volume-to-surface streamer transition is attributed to the lateral electric field provided by the space charges. This work provides insights into the regulation strategies and underlying mechanisms of streamer dynamics in parallel-rod DBDs in atmospheric air.

Pressure oscillation and suppression method of large-aspect-ratio solid rocket motors

A two-dimensional large eddy simulation numerical model is proposed to study the transient vortex flow and pressure oscillation of a large-aspect-ratio solid rocket motor. The numerical model is validated through experimental data, finite element analysis and cumulative error analysis. The numerical simulations are executed to obtain the characteristics of the vortex-acoustic and pressure oscillation. The results show that the burning surface regression decreases the motor aspect ratio, increasing the corresponding natural frequency from 260 Hz to 293 Hz. The pressure oscillation phenomenon is formed due to the vortex-acoustic coupling. Decreasing the corner vortex shedding intensity shows negative effects on the dimensionless amplitude of the pressure oscillation. The head cavity without the injection can decrease the vortex-acoustic coupling level at the acoustic pressure antinode. The modified motor with head cavity can obtain a lower dimensionless oscillating pressure amplitude 0.00149 in comparison with 0.00895 of the original motor. The aspect ratio and volume of the head cavity without the injection have great effects on the pressure oscillation suppression, particularly at the low aspect ratio or large volume. The reason is that the mass in the region around the acoustic pressure antinode is extracted centrally, reducing the energy contribution to the acoustic system. With the volume increasing, the acoustic energy capacity increases.

Exploring the mechanisms of benzanilide crystal growth and morphology: Crystal surface structure, solvent diffusion and solvent-interface interactions

Flaky crystals are fragile, rendering them unsuitable for various applications including use, processing, storage and transportation. This work investigates the growth and morphology regulation mechanisms of flaky crystals using benzanilide as a model material. Initially, block-like crystals are prepared by solvent screening and cooling crystallization with its morphology greatly improved. Subsequently, growth kinetics of (111), (1–10) and (020) faces are established with crystal growth experiments. The crystal growth of (001) face is also determined to follow a two-dimensional nucleation model with the microscopic surface analysis using atomic force microscopy. The changes of the surface integration resistance and the growth step height are regarded as kinetic mechanisms of the growth behavior and crystal morphology modulation by solvent and supersaturation. Finally, the molecular mechanism of the modulation of the solvent in crystal morphology is revealed base on crystal surface structure analysis and molecular dynamics simulations. The weak solvent-interface polar interactions facilitate the incorporation of benzanilide molecules into the weak polarity (001) face, leading to the surface roughening and increased crystal thickness when employing strongly polar solvents such as acetonitrile. Unlike the former, the relatively weak hydrogen bonding interactions between solvents and strong polarity (020) face, and the higher diffusion ability of molecules promote the rapid growth and disappearance of (020) face in ethanol and acetonitrile with strong hydrogen bond formation ability. This study can contribute to a deeper understanding of the solvent effect on crystal morphology and provide guidance for optimizing crystallization conditions to obtain shape-tailored crystal products.

A novel urban flood risk assessment framework based on refined numerical simulation technology

Due to urbanization and climate change, urban areas are becoming more susceptible to flooding, posing significant risks to human life and property. Numerical simulation techniques can provide valuable support in mitigating urban flood risks. The objective of this study is to establish a novel framework for flood risk assessment based on refined urban flood simulations. To achieve refined urban flood simulations, the Torricelli’s law is incorporated into a two-dimensional fluid dynamics model, and a numerical analysis model is developed to estimate the inundation within buildings and accurately simulate the entire inundation process. The model was used to reproduce a real flood event in Omihachiman City, Japan, with the Nash-Sutcliffe Efficiency (NSE) values of 0.6488 and 0.7182, demonstrating the credibility of the model. Based on the simulation results, the hydrological causes of the flood event were analyzed, and flood prevention measures were proposed. After implementing these measures, the maximum water depths at the study area were reduced to 0.14 m, 0.62 m, and 0.12 m, respectively, proving the effectiveness of the flood prevention measures. To address the issue of inundation depth not fully reflecting flood risk, the instability of human bodies in floodwaters is conducted to evaluate flood risk for adults and children in the target area. In response to increasingly frequent extreme rainfall events, the extreme precipitation events of three different return periods (10-year, 50-year, and 100-year) are used to assess the flood risk and the effectiveness of flood prevention measures. Based on the assessment results, the flood prevention measures not only reduced the flood risk levels but also decreased the flood risk area, further confirming their effectiveness.

Effect of nonpolar solute on the local structure of aqueous solution: Orientation-dependent integral equation study of nonpolar solute in rose water model

The presence of solute in water, even in small quantities, changes the properties of water. The ability of water molecules to form hydrogen-bonds is decisive for the structural and thermodynamic properties. When the solute is added to water, the network of hydrogen bonds is disrupted, changing the structure and properties of the water. In this work, we have used a simple two-dimensional rose water model together with orientation-dependent integral equation theory (ODIET) to gain insight into the effects of nonpolar solutes on the local structure of aqueous solutions. The theory shows good agreement with the radial distribution functions and enthalpies of solvation obtained with simulations, while improving the results of the orientation-averaged version of the theory. The advantage of the two-dimensional water model together with ODIET is that angle-dependent properties can be calculated relatively quickly and easily visualised. Using the potential of the mean force derivatives, the effect of added nonpolar solute on the local structure of the solution was investigated. Depending on the size of the solute, two different regimes of the effect of the solute on the structure of the solution were identified. Small solutes increase the tendency of water to form hydrogen-bonds and at the same time decrease solvation and association of the solute. On the other hand, large solutes have the opposite effect - they decrease the HB tendency of water and increase solvation and association of the solute.

Torque ripple reduction and increasing of torque per volume for hybrid electrical vehicle

Hybrid electrical vehicles (HEV) should be designed somehow torque is smooth. Because torque ripple not only reduces control precision but also increases elements vibration that causes acoustic noise, mechanical instability and early aging parts. Furthermore, torque per volume should be maximized and heat removal should be accomplished without torque weakening. It is proposed the volume and internal dimensions are determined due to the thermal considerations and maximize torque per volume. The mentioned application is neglected heat removal so volume is constant. Therefore, HEV is manufactured by two objective functions: either minimum fluctuations or maximum average torque. In this paper series hybrid excitation synchronous machine (SHESM) is utilized as HEV. Two-objective optimization problems are solved by MOEA/D, NSGA II, PESA II and SPEA II algorithms based on a two-dimensional (2-D) model. The performance indices of optimal structure are evaluated by 2-D and confirmed by numerical method.

SLIDING FRICTION IN CONTACTS WITH ONE- AND TWO-DIMENSIONAL VISCOELASTIC FOUNDATIONS AND VISCOELASTIC HALF-SPACE

Solid viscoelasticity is one of the essential origins of sliding friction, as every solid exhibits energy dissipation due to it during deformation processes. In this paper, we first show theoretical solutions for one-dimensional (1D) problems of viscoelastic friction with a 1D viscoelastic foundation. Then, we extend the 1D model to a two-dimensional (2D) model to find theoretical solutions for 2D problems of viscoelastic friction. Finally, we apply the Method of Dimensionality Reduction (MDR) to the theoretical solutions for the 1D problems to discuss three-dimensional (3D) problems of viscoelastic friction.

Beam halo studies of double-periodic focusing structures at the low-energy end of superconducting linac

This paper presents a comprehensive study on the beam halo evolution in the low-energy end of high-current superconducting linear accelerators (SLAs) with double-period focusing structures. The structure consists of cryogenic cooling modules (macro-period structures) and focusing units composed of RF cavities and solenoids within each module (micro-period structures). We utilized a three-dimensional particle-core model based on an ellipsoidal bunch to study the mechanism of halo formation with greater realism and reference value.Numerical simulations indicate that, in line with envelope instability theory, maintaining the zero current phase advance (σ0s) below 90° is critical for the formation of halo structures. Using 90° as the demarcation line, the resonance behavior between particles and the core shows significant differences. Fourier analysis of the envelope oscillation spectrum reveals that when the σ0s of each micro-period structure is less than 90°, the resonance types differ between emittance-dominated beams and space-charge-dominated beams. 2:1 resonance occurs between particles and the 3rd harmonic of the envelope oscillation in space-charge-dominated beams; while 4:1 resonance occurs in emittance-dominated beams. As σ0s increases, the influence of lower harmonics in the resonance becomes more significant. When σ0s is slightly greater than 90°, 4:1 resonance form with higher harmonics of the envelope oscillation (specifically related to the number of micro-period structures in each module). When σ0s reaches 110° or higher, 1:1 resonance form with the 2nd harmonic of the envelope oscillation. Unlike most previous studies based on two-dimensional particle-core models, we found that the longitudinal envelope significantly alters the charge density distribution of the core, leading to halo formation. This finding highlights the importance of three-dimensional effects in beam dynamics, especially under high current conditions.Additionally, we analyzed the impact of the number of micro-period structures within a module and their envelope modulation. Specifically, fewer micro-period structures within a module result in the envelope oscillation spectrum power to be concentrated at lower frequencies, making resonance with low harmonics more likely. Finally, we provide guidelines for the beam matching design at the low-energy end. By adjusting the focusing parameters of the matching structures, the likelihood of beam halo formation can be effectively suppressed.In summary, this study not only reveals the key mechanisms of halo formation in double-period focusing structures but also provides an effective approach to optimizing beam quality by adjusting structural parameters and matching methods. These findings offer clear guidance for beam design in the low-energy end of SLAs.

Experimental Study on Effects of Various Factors on Bottom-Water Reservoir Sweep Based on A Two-Dimensional Plate Physical Model

Abstract Horizontal Wells have obvious technical advantages in developing bottom-water reservoirs. Scholars at home and abroad have conducted many physical simulation studies on the development mechanism of horizontal wells in bottom-water reservoirs. In this paper, physical simulation experiments of sweep coefficients with or without intercalation and different displacement velocities, different permeability, different fluid viscosity and different reservoir thickness are carried out. The water sweep of the horizontal well bottom under different conditions is analyzed. The experimental results show that the existence of intercalation can delay the water appearance time, increase the anhydrous oil recovery period, and increase the final recovery factor. Controlling the liquid production rate can alleviate the bottom water coning phenomenon, expand the sweep area and increase the ultimate recovery factor. When the reservoir permeability is too high, the flow resistance is small, the water appearance is early, the anhydrous oil production period is short, and the final recovery factor is low. When the reservoir oil viscosity is high, the water sweep area is small and the final recovery factor is low. As the thickness decreases, it becomes easier for water to break through and reach a smaller area, resulting in lower final oil production.

Dynamics of Destruction of Two-dimensional Analog Models Discrete Environments with Different Organization of their Structural Compositions

Based on the main phenomenological features of the Coulomb-Navier rheological body, several most characteristic simulated models of discrete environments with different structural compositions have been proposed. Mechanical testing of the specified simulator models allows for investigating the dynamics of deformation (restructuring of composition) of discrete (including loose) environments with varying organization (within a wide range) of their structural compositions. The main thermodynamic peculiarities of the deformation and destruction processes of discrete environment structures under different variations of external loading application schemes have been identified.