3D Numerical Model Research Articles

The Implication of the Helium-to-proton Flux Ratio in Galactic Cosmic Rays

The measurement of daily proton and helium fluxes by AMS-02 shows that the helium-to-proton flux ratio (He/H) is negatively correlated with the solar activity at rigidity 1.7–7 GV. What is the behavior of He/H at rigidity lower than 1.7 GV? How can this phenomenon be described quantitatively and linked to the underlying mechanisms? In this work, based on a theoretical derivation, we find that the slope (S) of versus ln(H) is a good indicator of the variation of He/H. S > 0 means the variation of He/H is anticorrelated with the solar activity, and vice versa. Furthermore, the value of S is quantitatively related to the difference in protons and helium nuclei in the local interstellar spectrum (LIS) and in solar modulation. A 3D time-dependent numerical model is used to reproduce the observed proton and helium data. The results of the simulation show that, with increasing rigidity, the parameter S increases from negative values to positive values at around 1 GV, reaches a maximum value at around 2 GV, and then decreases until it approaches 0. Interestingly, S is equal to 0 at around 1 GV. This means that He/H at this rigidity is almost unchanged with the variation in solar activity. Finally, the expression for S is validated by changing the LIS used in the numerical procedure. This shows that the overall profile of S as a function of rigidity is mainly determined by the mass-to-charge ratio, and the specific value of S is strongly affected by the difference in the LIS between protons and helium nuclei.

Vertical tearing of subducting plates controlled by geometry and rheology of oceanic plates

Lateral non-uniform subduction is impacted by continuous plate segmentation owing to vertical tearing of the subducting plate. However, the dynamics and physical controls of vertical tearing remain controversial. Here, we employed 3D numerical models to investigate the effects of trench geometry (offset by a transform boundary) and plate rheology (plate age and the magnitude of brittle/plastic strain weakening) on the evolution of shear stress-controlled vertical tearing within a homogenous subducting oceanic plate. Numerical results suggest that the trench offset geometry could result in self-sustained vertical tearing as a narrow shear zone within the intact subducting oceanic plate, and that this process of tearing could operate throughout the entire subduction process. Further, the critical trench offset length for the maturation of vertical tearing is impacted by plate rheology. Comparison between numerical modelling results and natural observations suggests that vertical tearing attributed to trench offset geometry is broadly developed in modern subduction and collision systems worldwide.

Influence of buoyancy on phase separation during laser melting of Silicon and Iron ore

Phase separation is a well-known effect in liquid-liquid interactions, which can also occur during laser-related processes such as laser melting and laser alloying. However, the mechanism of phase separation between immiscible liquids on a millimeter scale during rapid laser processes has not been fully investigated, in which the extent of buoyancy’s contribution to it has remained unclear. Therefore, this investigation focused on the effect of buoyancy on liquid phase separation during the laser melting of silicon (Si) and iron ore. A simplified 2D numerical model was established to simulate the motion of a single Si liquid droplet in iron ore melt with and without the impact of gravity, respectively. The rise velocity of the droplet was calculated and analyzed under the effect of gravity. In addition, the phenomena of simultaneous laser remelting of Si and iron ore in layers were recorded with a high-speed camera, and the element and phase distributions of the target nugget were analyzed by Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). By combining the simulation, high-speed imaging, and SEM/EDS analysis, the effect of buoyancy on phase separation has been qualitatively analyzed. This investigation revealed that buoyancy is not the main driving force of liquid-liquid phase separation during rapid laser processing.

Deciphering Solar Coronal Heating: Energizing Small-scale Loops through Surface Convection

The solar atmosphere is filled with clusters of hot small-scale loops commonly known as coronal bright points (CBPs). These ubiquitous structures stand out in the Sun by their strong X-ray and/or extreme-ultraviolet (EUV) emission for hours to days, which makes them a crucial piece when solving the solar coronal heating puzzle. In addition, they can be the source of coronal jets and small-scale filament eruptions. Here we present a novel 3D numerical model using the Bifrost code that explains the sustained CBP heating for several hours. We find that stochastic photospheric convective motions alone significantly stress the CBP magnetic field topology, leading to important Joule and viscous heating concentrated around the CBP’s inner spine at a few megameters above the solar surface. We also detect continuous upflows with faint EUV signals resembling observational dark coronal jets and small-scale eruptions when Hα fibrils interact with the reconnection site. We validate our model by comparing simultaneous CBP observations from the Solar Dynamics Observatory (SDO) and the Swedish 1‐m Solar Telescope (SST) with observable diagnostics calculated from the numerical results for EUV wavelengths as well as for the Hα line using the Multi3D synthesis code. Additionally, we provide synthetic observables to be compared with Hinode, Solar Orbiter, and the Interface Region Imaging Spectrograph (IRIS). Our results constitute a step forward in the understanding of the many different facets of the solar coronal heating problem.

Design of a cobweb bionic flow field for organic redox flow battery

The organic redox flow battery (ORFB) has garnered attention due to its environmentally friendly nature, safety features, and design flexibility, making it an ideal choice for large-scale energy storage. A novel cobweb bionic flow field is designed to significantly improve the battery performance of the ORFB. The battery performance including the charge-discharge voltage, overpotential, concentration distribution and uniformity factors of the cobweb bionic flow field were compared with those of the serpentine flow field and the parallel flow field by a three-dimensional (3D) numerical model. The results indicate that the discharging voltage of the cobweb flow field is 3.35 % higher than that of the serpentine flow field. The uniformity factor of the cobweb flow field is 15.55 % higher than that of the serpentine flow field. The average concentration value of the cobweb flow field is 13.86 % higher than that of the serpentine flow field. Therefore, the design of the cobweb bionic flow field enhances the mass transfer behaviors in the flow field and improves the battery performance. The impacts of the number of branches on the battery performance are studied, and the results show that the cobweb flow field achieves optimal performance with 6 branches.

Numerical analysis of the effect of trench on indoor vibration adjacent to railway ground line

By establishing a 3D finite element numerical simulation analysis model of railway-soil-trench-building, the accuracy of the simulation analysis model is verified using on-site measured data of surface vibration attenuation law. Install vibration isolation trenches with different depths at different locations between the building and the railway, and analyze and compare the impact of indoor vibration in different situations. The results indicate that; The surface vibration caused by railways attenuates rapidly around 30m~76m from the line, and then shows a slight amplification trend around 120m. The surface vibration near the railway is mainly concentrated in the range of 15-90Hz; The vibration reduction effect of trench on different indoor rooms in buildings varies greatly. By optimizing the parameters of trench, the average indoor vibration reduction effect can be close to 5dB, and the vibration reduction effect of trench at different positions varies greatly. The increase in trench from 6m to 12m increases the indoor vibration isolation effect.

1D higher-order theories for quasi-static progressive failure analysis of composites based on a full 3D Hashin orthotropic damage model

This work investigates the crack propagation in composites by adopting a novel full three-dimensional (3D) Hashin-based orthotropic damage model combined with higher-order one-dimensional (1D) finite elements based on the Carrera Unified Formulation (CUF). Previous literature has proven that CUF provides structural formulations with great accuracy and improved computational efficiency. Moreover, a Layer-Wise (LW) formulation can be implemented within the CUF framework, allowing an accurate description of the 3D stress state in composite laminate, representing crucial information for progressive failure analysis. A Newton–Raphson predictor–corrector algorithm is used for the numerical solution of classical case tests, i.e., compact tension and three-point bending tests. The obtained results are compared with experimental outcomes and with solutions from well-established 2D damage models and a 3D Abaqus numerical model, demonstrating the capability of the proposed method to efficiently capture both the failure load and shape of the crack pattern.

Observations and modeling of tidally generated high-frequency velocity fluctuations downstream of a channel constriction

Abstract. We investigate data from an acoustic Doppler current profiler deployed in a constricted ocean channel showing a tidally dominated flow with intermittent velocity extrema during outflow from the constriction but not during inflow. A 2D numerical ocean model forced by tides is used to examine the spatial flow structure and underlying dynamical processes. We find that flow-separation eddies generated near the tightest constriction point form a dipole pair which propagates downstream and drives the observed intermittent flow variability. The eddies, which are generated by an along-channel adverse pressure gradient, spin up for some time near the constriction until they develop local low pressures in their centers that are strong enough to modify the background along-channel pressure gradient significantly. When the dipole has propagated some distance away from the constriction, the conditions for flow separation are recovered, and new eddies are formed.

Influence mechanism of the three-zone synergistic efficiency-enhancing pattern on the 3D flow field and thermal resistance characteristics for wet cooling towers

For a super-large natural draft wet cooling tower (S-NDWCT) equipped in a 1000 MW unit, a 3D numerical model of the three-zone synergistic efficiency-enhancing pattern (TSEP) was established and validated. This study focused on the influence mechanism of the three-zone parameters on the 3D flow field and thermal resistance characteristics, including the installation height h, installation angle θ, total coverage area S, length L and number n of the split-flow plate, water distribution partition radius R1, the proportion of inner zone water amount P, and fillings partition radius R2. The results showed that the TSEP reconfigures and comprehensively optimizes the airflow field, and presents the more uniform air-water ratio and water temperature fields. The volumetric heat transfer coefficient hv increases and then reduces as h, θ, S, n, R1, P and R2 increase, and increases continuously with increasing L in the range studied. Additionally, the ventilation G increases and then reduces with the increase of h, θ, R1 and P, increases with rising S, n and R2, and reduces with L increases. Finally, the relatively optimized values of the three-zone parameters are obtained. In this case, compared with a conventional tower, the hv and G increase by 11.3% and 10.6%, respectively.

Performance evaluation on full-scale proton exchange membrane fuel cell: Mutual validation of one-dimensional, three-dimensional and experimental investigations

The coupling of multiple physical processes such as gas multi-component transport, gas–liquid multiphase flow, and electrochemical reactions within the proton exchange membrane fuel cell (PEMFC) makes its hydrothermal management exceptionally complicated. Therefore, the complex heat and mass transfer processes in the full-scale PEMFC are investigated in single cell with single channel serpentine flow field (FF). Firstly, the reliability of the proposed three-dimensional (3D) computational fluid dynamics (CFD) numerical model is verified by using the experimental test results of a single cell. Among them, the trend of simulation and experiment performance curves is consistent, and the minimum error of current density is 0.665%. Secondly, the ionomer model of cathode catalyst layer (CCL) is considered in CFD simulation, which is closer to the actual working condition of fuel cell (FC). The resistance of ionomer film and liquid water film mainly affects the diffusion rate of oxygen in CCL, resulting in a decrease in both current density values and power density values. Subsequently, the electrochemical reaction platform of one-dimensional (1D) FC is constructed, and the performance curves of multi-scale FCs are analyzed. The results demonstrate that the error of stack level is the largest, followed by single cell and single channel is the smallest. Finally, the 1D numerical model and the 3D PEMFC multiphase flow CFD model are utilized to investigate the cell voltage losses in the bionic spider flow field, the variable path flow field, and the serpentine flow field, respectively, under different operating conditions.

Assessing the impact of an arch-dam breach magnitude and reservoir inflow on flood maps

Abstract Different scenarios of an arch-dam breach and their impact on the time-space evolution of flood waves are analysed using numerical modelling. As the accidents involving this type of dam are among the most catastrophic ones, the 108 m in height Paltinu arch-dam, Romania, was chosen as a case study due to its problems in the past. Three dam breach magnitudes and two inflow hydrographs for the worst-case scenario of Normal Operating Pool elevation in the reservoir were chosen as variable parameters, to assess their influence on the dam break wave characteristics and downstream flooded areas. The flood was routed along the 18 km reach of the Doftana River down to the confluence with the Prahova River. A 2D numerical model was set up with the help of HEC-RAS software, which was also used to analyse the resulting hazard maps under a GIS environment. Comparison of inundation boundary, maximum depths and velocities, as well as the arrival time at control sections allow for conclusions to be drawn. These predictive results of shape, magnitude, and time to peak of the flood waves are essential for flood risk management to obtain the risk maps, estimated damage costs, and possible affected areas.

A 3D Numerical Study on the Tidal Asymmetry, Residual Circulation and Saline Intrusion in the Gironde Estuary (France)

A full 3D numerical model is used for studying tidal asymmetry, estuarine circulation, and saline intrusion in the Gironde estuary. The model is calibrated and verified using the data measured during two field surveys in the Gironde estuary. Harmonic analysis of numerical results is proposed to understand how the superposition of M2, M4 and M6 components generate a complex estuarine circulation and salinity intrusion in the Gironde estuary. The numerical results show that the M6 component plays a significant role as important as the M4 one in modifying the nature of tidal asymmetry, especially in the Gironde upper estuary. In this case, the use of the phase lag between M2 and M4, neglecting M6, to predict the tidal asymmetry nature could produce errors. The effect of asymmetrical tides on saline intrusion and residual circulation is specifically discussed here.

Electrokinetic Effect of a Two-Liquid Interface within a Slit Microchannel.

This paper presents an investigation of the electrokinetic effect at a two-liquid (immiscible liquid-aqueous solution) interface within a slit microchannel using a three-dimensional (3D) numerical model, with a particular focus on the impact of the surface ζ-potential and liquid phase height on the interface electrokinetic velocity. The findings indicate that the direction of the interface movement depends on the ζ-potentials at the two-liquid interface and the microchannel wall. When the absolute value of the negative ζ-potential at the interface is smaller than that at the wall, the interface moves toward the negative pole of the applied direct current (DC) electric field; conversely, it moves in the opposite direction. The velocity of interface motion decreases as the height of the aqueous phase and the dynamic viscosity ratio between the immiscible liquid and the aqueous solution increase. Conversely, the velocity increases with an elevation in the height of the immiscible liquid phase and the DC electric field intensity. This study holds significant importance in elucidating the patterns of change in fluid interface electrokinetic effects and their potential applications in manipulating and separating particulate pollutants within water systems.

Fault detection methods for 2D and 3D geomechanical numerical models

AbstractWe develop automated methods for fault detection utilizing static stress and deformation fields at the onset of failure derived from numerical analysis. We calculate combinations and normalization of the distance from the Mohr circle to the Coulomb envelope, and of the second deviatoric strain invariant. A variation of the Cauchy distribution of these fields allows us to focus on the low values indicating rupture, with the help of the scale parameter δ. A threshold is then applied to decide at each spatial node of the mesh whether the material has reached failure or not. We then determine fault lines and planes from these isolated failure zones using image processing techniques, such as the Hough and the Radon transforms, or through a combined approach involving automated sorting of the nodes reaching failure through the k‐means clustering technique followed by polynomial fitting to retrieve analytic expressions of the fault curves (in 2D) or fault surfaces (in 3D). The methods are efficient except when the stress field results in diffuse rupture zones that do not localize onto fault surfaces despite tuning δ. We also highlight the advantages of using the combined clustering/poly‐fitting approach for 3D models compared to the image processing techniques. These automated fault detection methods should be useful in the interpretation of diverse failure mechanisms obtained through parametric sensitivity analyses requiring hundreds of simulations. The stress and strain fields used were derived from a numerical implementation of limit analysis, but classical finite‐difference or finite‐element techniques could have been used.

Adaptation of rectangular and trapezoidal time functions to simulate the rotational motion of the brake disc

Numerical modeling of the rotational motion of the brake disc during frictional heating requires the use of specialized software. In this paper, an alternative approach was proposed consisting in the simulation of the displacement of the heating region contained within the boundaries of the friction surface of the brake pad relative to the stationary disc. The moving heat source effect was obtained using rectangular time functions generated based on the operating parameters and dimensions of the brake components. The first part of the article discusses the mathematical basis for the construction of time curves in relation to the solid brake disc combined with a pad in the shape of the angular section of a ring. Braking simulations were carried out using the finite element method (FEM) based software for 3D, 2D axisymmetric and 1D models of the disc. The calculated temperature filed changes were confronted with the results obtained using the 3D model developed based on standard methods. The temperature on the contact surface of the disc in the position of the mean radius at the end of braking, determined using the 2D axisymmetric and the 3D model with adaptation of rectangular time functions as well as the 3D reference model agreed well and were equal to 157.83 °C, 157.87 °C, and 157.90 °C, respectively. In the second part of the study, the 3D model of periodic heating was extended to the disc brake of a railway vehicle. The results of the calculations for the ventilated disc and segmented brake pad were compared with the experimental data obtained during testing on a full-scale dynamometer test stand. The maximum temperature values obtained on the basis of the 3D-pulse, 3D numerical models and measured on the test stand were equal to 73.3 °C, 74.4 °C and 75.6 °C, respectively. The insignificant temperature difference, i.e. below 3 %, obtained using the 3D-pulse heating model and measured using a thermocouple, confirms the correctness of the developed algorithm for simulating the rotational motion of the disc as well as the calculation methodology incorporating the heat partition coefficient (HPC).

Simulation Method for Rubber Compounding under Isothermal Partial Filling Conditions

Rubber mixing is an important link in the production of rubber products. Computational fluid dynamics (CFD) simulation is often used to explore the effect of rubber mixing parameters on rubber mixing effect. Previous CFD-based rubber mixing simulation studies did not consider the impact of using 2D or 3D numerical calculation models on the numerical simulation results. In order to investigate the differences between 2D and 3D numerical computational models in rubber compounding CFD simulation problems, in this paper, we compare and analyze the results obtained from 2D and 3D computational models under different rotational speed conditions to investigate the differences between the models in the numerical simulation of rubber compounding. Three different experimental speeds of the rubber mixer—39, 44, and 49 r/min—were set during the study using 2D and 3D asynchronous rotor models with a speed ratio of 1.15, respectively. The rubber was processed using the Bird–Carreau model. The phase interface between rubber and air was calculated using the volume of fluid (VOF) method. The numerical simulation results of different models show that the rotational speed set to 49 r/min shows the best dispersion distribution effect; the mixing effect and speed change rule obtained by the 2D model are consistent with the results obtained by the 3D model. The performance of the results of the two models is consistent when exploring the numerical simulation of rubber compounding.

A three-dimensional numerical simulation method for seismic nonlinear response of underground structure in liquefiable site and analysis of structural damage

Considering the effect of dynamic interaction between liquefiable soil and underground structure, simulating the nonlinear seismic response of underground structures through simple, convenient, and reliable 3D numerical model is still a great challenge at present. A three-dimensional numerical simulation method for dynamic response of underground structure in liquefiable site is proposed based on the centrifuge shaking table test designed for a subway station buried in liquefiable interlayer site carried out in the previous period. The numerical model takes into account the characteristics of sand prone to large deformation after liquefaction and the nonlinear characteristics of the contact between saturated soil and structure. The typical numerical calculation results are compared with the experimental results to verify the correctness of the numerical model, and the extended analysis of the structural damage is carried out, which visually shows the damage distribution of structure under different functional states after earthquake. The analysis of structural damage shows that the junction position of middle column and longitudinal beam is more prone to tensile damage under the horizontal earthquake action; while after considering the horizontal-vertical seismic effect, the middle column will produce additional compressive damage due to the vertical inertia force, and the end of middle column should be paid attention to in seismic design.

The artificial roughness effect on the thermal performance of a submerged combustion vaporizer

The submerged combustion vaporizer (SCV) is a popular vaporizer used for the peak regulation of liquefied natural gas (LNG) in large cities or as a primary vaporizer in cold regions. Due to the consumption of produced natural gas as a heat source for gasification during SCV operation, the thermal efficiency and gasification rate of SCV must be improved urgently. One of the effective methods to improve the heat transfer of a heating tube is adding artificial roughness inside the tube. Hence, this paper establishes a 3D numerical model of the serpentine heating tube with artificial roughness cubes in SCV and explores the impact of artificial roughness on the heat transfer and thermal performance of SCV. To strengthen the heat transfer between the LNG heating tube and the water bath in the straight tube section and avoid the water freezing outside the tube due to the supercooling at the bend section simultaneously, critical factors, such as the arrangement of artificial roughness, especially on the bend region, and the heat flux obtained from the water bath, are discussed. The results indicate that the artificial roughness positively affects the heat transfer of the LNG heating tube. However, it is better to add the artificial roughness only in the straight section of the serpentine tube to suppress the ice formation on the bend regions. The LNG flow becomes chaotic, and the region of forced convection increases due to artificial roughness and centrifugal force. The serpentine tube with artificial roughness exhibits similar thermal behaviour under different heat fluxes, and its influence on the friction factor and irreversible energy loss is more significant than that of smooth tube. Moreover, the comprehensive evaluation coefficient of the heating tube is enhanced obviously by the artificial roughness, and the outlet temperature of LNG is larger by 17.63% and 16.34% respectively with different configurations of artificial roughness than that of the smooth one under the same heated condition, and the gasification rate is improved significantly.

Concrete spalling damage detection and seismic performance evaluation for RC shear walls via 3D reconstruction technique and numerical model updating

Current three-dimensional (3D) reconstruction technique-assisted damage detection research focuses on identifying, classifying, and locating surface damage on concrete components, challenging to quantify the effect of the identified damage on structural capacity. This paper attempts to present a novel method based on the 3D reconstruction technique and numerical model updating to detect concrete spalling damage and evaluate the adverse effects of the detected damage on the seismic performance of reinforced concrete (RC) shear wall components. Through a new concept of information transition point matrix, the mapping relationship between the defective information concealed in the reconstructed 3D point cloud model of the inspected wall and the performance variation of its corresponding finite element model is established. Experimental results demonstrate that the newly proposed method can successfully locate the concrete spalling damage and quantify the bearing capacity variation of the inspected specimen, which has excellent potential for future applications in civil engineering.

Numerical Analysis of Concrete Deep Beams Reinforced with Glass Fiber-Reinforced Polymer Bars

This research aimed to generate data through a verified numerical model. The data were subsequently used to introduce a simplified analytical expression for the prediction of the shear strength of concrete deep beams reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars. A three-dimensional (3D) numerical simulation model for a large-scale GFRP-reinforced concrete deep beam (300 × 1200 × 5000 mm) was developed and validated against published experimental data. A parametric study was then conducted to examine the effects of key variables on the behavior and shear strength of GFRP-reinforced concrete deep beams. Eighteen 3D numerical models were developed to study the interaction between the concrete compressive strength (f’c), the shear span-to-depth ratio (a/h), the spacing between web reinforcement (s), and the shear strength. The a/h value was either 1.0 or 1.5. The values of f’c were 28, 37, and 50 MPa. The spacings between the web reinforcement, if present, were 100 and 200 mm. The results of the parametric study indicated that the shear strength of deep beam models increased almost linearly with an increase in f’c and a decrease in the stirrup spacing irrespective of the value of a/h. The strength reduction caused by increasing a/h was more pronounced for the beam models with the lower f’c and greater stirrup spacing. The simplified analytical expression introduced in the present study provided a reasonable prediction for the shear strength of GFRP-reinforced concrete deep beams.