3D Numerical Model Research Articles

Experimental and numerical investigation on vertical temperature gradient of concrete-filled steel tubular arch under sunlight

To investigate the effects of diameter and inclination on the vertical temperature gradient (VTG) of concrete-filled steel tubular (CFST) arches, this study conducted temperature field tests on three CFST segment specimens with diameters of 426mm, 750mm, and 1000mm, as well as an arch specimen with inclination angles varying from 48.76° to -48.76°. 2D and 3D numerical simulation models were developed to analyze the impact of diameter, wall thickness, inclination and orientation. The results indicate that as the diameter increases, the internal temperature becomes more uniform, forming a constant temperature zone in the middle of the VTG, with linear increases in temperature differences at the top (T1) and bottom (T2). Beyond approximately 600mm in diameter, the VTG stabilizes. The maximum T1 of the three segment specimens were 15.37 ℃, 22.40 ℃, and 23.81 ℃, respectively. Inclination affects the solar incidence angle and intensity, causing T1 to vary along the arch span, proportional to solar intensity. The maximum difference of T1 in the arch specimen reached 10.87 ℃. Wall thickness showed minimal effect on the VTG. The proposed VTG pattern was applicable to arches with various orientations and can assist in evaluating thermal effects in CFST arches.

Machine Learning‐Guided Design of 10 nm Junctionless Gate‐All‐Around Metal Oxide Semiconductor Field Effect Transistors for Nanoscaled Digital Circuits

In this paper, we introduce an innovative design approach based on combined numerical simulations and machine learning (ML) analysis to investigate the design key parameters of ultra‐low scale junctionless gate‐all‐around (JLGAA) field‐effect transistor (FET) devices. To this end, precise 3D numerical models that incorporate quantum effects and ballistic transport are employed to simulate the current–voltage (I–V) characteristics of 10 nm‐scale JLGAA FET devices. The influence of design parameter variations and high‐k dielectric material on the subthreshold characteristics is thoroughly examined. Various ML algorithms were employed to analyze and classify the key design parameters influencing the subthreshold figures‐of‐merit (FoMs), the subthreshold swing (SS) factor and ION/IOFF ratio. The obtained results highlight that channel radius and channel doping design parameters are particularly important for affecting swing factor behavior. Similarly, these features also play a significant role in predicting and affecting ION/IOFF current ratio values. Additionally, machine learning is used to determine the optimal design parameters for each figure of merit (FoM) output value. In this context, the models effectively predicted both ION/IOFF current ratios and SS classification, with Naive Bayes achieving an accuracy of 90.8% for ION/IOFF and 92.6% for SS, showcasing the model's robustness in these classification tasks.

Study on the Effect of Heat Transfer Characteristics of Energy Piles

The thermal performance of energy piles equipped with new metal fins to improve heat transmission is examined in this research. The solid heat transfer module of COMSOL Multiphysics was used to create a 2D numerical model of the energy pile, utilizing the energy pile at a field test site in Nanjing as an example. By contrasting the experimental data, the COMSOL Multiphysics model’s correctness was confirmed. After that, a new kind of energy pile fin was created to improve the heat transfer of the pile. The impact of the new fin type on the energy pile’s heat transfer efficiency was assessed, and the temperature change within the soil surrounding the pile before and after the fin was set was examined by contrasting the parameters of pipe configuration, buried pipe depth, and concrete thermal conductivity. The results indicate that after setting the fins to run for 336 h, the temperature of the concrete area increases by 10.8% to 12.3%, and the temperature of the region surrounding the pile increases by 5.3% to 8.7% when the tube diameter is chosen to be between 20 and 40 mm; The fins maximize the heat transfer temperature between the surrounding soil and the concrete, and as the tube diameter increases, the temperature drops. For 336 h of pile operation, the temperature of the concrete may be raised by 10.8% to 12.3% after the fins are set, and the temperature around the pile can be raised by 5.3% to 8.7%. The heat transmission efficiency of the energy pile can be improved by raising the temperature of the soil surrounding the pile through an increase in the concrete’s thermal conductivity; however, the degree of improvement diminishes as the conductivity rises. It is intended that this study will offer insightful information on the best way to design energy pile heat transfer efficiency.

Electromagnetic Modeling of Superconducting Bulks in Applied Time-Varying Magnetic Field

An integrodifferential model formulated in terms of the electric vector potential is developed for the 3D numerical modeling of the electromagnetic field in superconducting bulks, for AC losses evaluation. The Newton Raphson method is applied to accelerate the convergence. The model is validated on a benchmark. The comparison results show the accuracy of the model and its performances in terms of computation time compared to classical approaches.

Unraveling the Geodynamic Evolution of the Pre– and Early–Andean Margin: Insights From Numerical Modeling

AbstractAn outstanding question in the geological evolution of the Chilean Andes is the cause of the westward shift and relocation of magmatism from the High Andes (HA) to the Coastal Cordillera (CC) during the Late Triassic, Pre–Andean stage. The spatiotemporal distribution of Permian–Triassic–Jurassic igneous rocks in northern‐central Chile (20°S–32°S) reveals a significant westward magmatic shift of ∼120 km during the Norian time. Despite diverse proposed models, the precise geodynamic mechanism behind this shift remains unclear. To address this, we used 2D numerical modeling to investigate two contrasting scenarios: (a) subduction rollback and (b) subduction transference/jump and reinitiation by terrane accretion. Our modeling results strongly support Scenario B, where mantle density and the size of the oceanic plateau are crucial for triggering subduction jump and reinitiation. This model aligns with geological and geophysical evidence and offers new insights into unraveling the Pre– and Early–Andean evolution.

Quantitative characterisation of debris cloud-induced pitting damage in AL-Whipple shields of spacecraft using infrared thermography

ABSTRACT Quantitatively evaluating the debris cloud-induced pitting damage in the AL-Whipple structure of spacecraft, is still a challenge, let alone microstructural plastic deformation usually accompanied by geometric cratering defects, which may decrease material stress-carrying capacity and structural life. With this motivation, a dedicated modelling technique is proposed to gain an insight into various modalities (i.e., geometric and plastic defects) of pitting damage-induced thermal modulation for infrared inspection. Then, a sequence of infrared images is obtained and analysed using the gap smoothing algorithm and naive Bayes classification methods. On this basis, a quantitative characterization framework is proposed to characterize the damage modalities and their morphologies. This method is validated using a 3D numerical model which contains pitting damage acquired from the real-world structure. Modality classification and morphology evaluation results are well consistent with the artificial defects, in terms of the modality, diameter, and depth. Then they‘re experimentally corroborated, in which the severity and distribution of pitting damage are precisely characterized, in terms of the crater number and morphologies, as well as the size of plastic regions around these craters, which are consistent with the actual observations. This work proposes a non-destructive strategy for pitting damage evaluation, which is engineering-friendly.

Backtesting the iconic Polyfytos balanced-cantilever bridge to enhance condition assessment

This paper introduces a comprehensive framework for reliable damage assessment and decision-making for bridge intervention planning. By utilizing historical data and 3D-UAV photogrammetry, a detailed 3D numerical model is created, incorporating advanced modeling and scenario-based approaches. The methodology is applied to the Polyfytos bridge in Greece, which faces significant vertical deck deflections that disrupt traffic and impact local communities. This approach offers a reliable, cost-effective, and efficient process, allowing stakeholders to make informed decisions with minimal physical interaction with the bridge. The integration of advanced modeling with in-situ measurements and expert judgment is emphasized. For the Polyfytos bridge, the framework helps prioritize retrofits and assess the deck’s remaining strength under various loads, providing estimates of its overstrength. This aids in evaluating the bridge’s ability to handle additional vertical loads through pushdown analysis. Overall, the framework is valuable for rapid infrastructure assessment, identifying damage patterns, severity, and the urgency of interventions related to structural strength.

Predicting ignitability classification of thermally thick solids using hybrid GA-BPNN and PSO-BPNN algorithms

Two hybrid binary classification models combining the merits of GA (genetic algorithm) and PSO (particle swarm optimization) with BPNN (backpropagation neural network) are proposed to estimate the ignitability of thermally thick solids. A 1D numerical model verified by analytical correlation and experimental measurements is employed to yield training, validation and testing datasets. Surface absorptivity (ε), density (ρ), specific heat (Cp), thermal conductivity (k), critical temperature (Tcri), and incident heat flux (HF) which are highly related to solid ignition are selected as inputs, and ignitability serves as output. A one-hidden-layer BPNN is first constructed, and then GA and PSO are encoded to form GA-BPNN and PSO-BPNN where connection weights and biases are optimized by GA/PSO and the predicted error serves as objective function of GA/PSO. Results show that the optimal neuron number in hidden layer is 34. Compared to BPNN, GA-BPNN and PSO-BPNN feature higher accuracy but more training time. Accuracy and convergence efficiency of PSO-BPNN are higher than GA-BPNN, nevertheless GA-BPNN exhibits better robustness. Predictive accuracies of BPNN, GA-BPNN, and PSO-BPNN on testing dataset are 99.05%, 99.55%, and 99.55%, respectively. ROC (receiver operating characteristic) curves are plotted to rank the performance of the three models, revealing 0.5 is an appropriate threshold to classify ignitability. Feature importance of the models is analyzed using PI (permutation importance) and MIV (mean impact value) methods. It is found HF and Tcri are the most important two inputs followed by ε, while ρ, Cp, and k show least and approximately identical impact. Reliability of the three models is verified by predicting critical heat flux of ignition of three polymers, and good agreement with literature is observed.

Stability Assessment of the Maltravieso Cave (Caceres, Spain) Through Engineering Rock Mass Classification, Empirical, Numerical and Remote Techniques

Caves have long fascinated humanity, serving as shelters, canvases for artistic expression and now significant attractions in the realm of tourism. Among these remarkable geological formations, the Maltravieso cave in Extremadura, Spain, stands out for its rich archaeological and paleontological heritage, particularly its collection of Paleolithic rock art. Despite its cultural significance, there is a notable dearth of studies addressing the stability of the cave from an engineering perspective. This article presents a pioneering study aimed at assessing the stability of the Maltravieso cave through a multidisciplinary approach: using empirical geomechanical classifications such as the Q Index, Rock Mass Rating (RMR) and the recently formulated Cave Geomechanical Index (CGI), alongside other techniques like Structure from Motion (SfM), 2D numerical modeling and 3D wedge analysis. This research aims to fill the gap in our opinion of cave stability assessment. By combining field data collection with sophisticated analysis methods, this study seeks to provide valuable insights into the geomechanical properties of the Maltravieso cave and validate a simple yet effective methodology for evaluating the stability of natural caves. This work not only contributes to the body of knowledge regarding cave geomechanics but also underscores the importance of preserving these invaluable cultural and geological treasures for future generations.

Development and experimental validation of a 3D numerical model to investigate performance of phase change based cooling vest in hot environments

To ensure health and safety of outdoor workers exposed to harsh environment, particularly during summer, they must be protected against heat-related injuries. Personal cooling device like cooling vest are viable solution in such situations considering their cooling capabilities and ergonomic aspects. In the present study, a 3D numerical model is developed for analyzing performance of PCM vest and it is validated with experimental results obtained from a torso thermal manikin facility fabricated in-house. Thermal performance of the PCM vest is analyzed in terms of temperature, liquid fraction and energy storage of PCM and skin temperature for different thermophysical properties of PCM, ambient conditions and mode of operations. Based on the study, PCM with higher latent heat and melting temperature is recommended for the longer working duration of the vest. Increasing ambient temperature from 40 °C to 45 °C reduces the effectiveness time by 20 % while decreasing ambient temperature from 40 °C to 35 °C increases effectiveness time of the PCM vest by 32 %. Fraction of energy stored by the PCM from the body and environment remains unaffected by the change in the latent heat of PCM. Further, it is noticed that increasing the air flow rate or using the PCM vest in hybrid mode of operation is not recommended from the point of view of its effective useable duration. Overall, the study presents a comprehensive approach to estimate performance of the PCM vest realistically and provides guidelines for the design of effective cooling vest for various practical applications.

Experimental and numerical investigation of heat transfer modes on pot surfaces in a power range of a cooking porous burner

The investigation of convective and radiative heat transfers to a cooking pot in a porous burner, coupled with an analysis of the pot's bottom and side contributions to total heat transfer, remains an underexplored area of research. In this study, we adopt a comprehensive approach, combining experimental measurements and 3D numerical models, to explore the practical application of a Silicon carbide porous burner fueled with natural gas in cooking pots with power ranging from 12.15 kW to 31.04 kW. Three primary aspects are examined: differentiating between radiative and convective heat transfer contributions, investigating porous mixing characteristics, and analyzing the burner's thermal and combustion efficiencies. To facilitate this investigation, a dedicated test bench is meticulously designed and constructed, equipped with state-of-the-art measuring instruments to effectively monitor the thermal behavior of the heating process. The results reveal that the higher Damköhler number at higher power, driven by the dominance of chemical time over mixing time, accentuates the importance of chemical reactions in heat transfer to the pot. Moreover, increasing the power leads to a reduction in the burner's overall thermal efficiency, from 29.2% to 18.8%, due to a higher energy waste percentage, escalating from 45.12% at P = 12.15 kW to 65.31% at P = 31.04 kW. This increase in power also strengthens the downward movement of the flame and its detachment from the pot surface. The pot's bottom contribution to total heat transfer ranged from 76.7% to 95.5%, with convection alone accounting for over 98% in all cases. Consequently, optimizing the pot bottom geometry for the purpose of enhancing convection presents promising avenues for significantly boosting thermal efficiency. These findings highlight the potential of the investigated porous burner for efficient and clean combustion in cooking appliances.

Effect of Process Parameters on Yttria‐Stabilized Zirconia Particles In‐Flight Behavior and Melting State in Atmospheric Plasma Spraying

The preparation of coatings by atmospheric plasma spraying gives rise to complex physical processes, which present challenges to the study of plasma jet characteristics and particle in‐flight behavior. Herein, a 3D numerical model that integrates multiple physical phenomena, including electromagnetism and thermal and gas dynamics, to simulate the heating, acceleration, and melting of particles under the thermal–mechanical effect, is developed. Meanwhile, yttria‐stabilized zirconia (YSZ) coatings are prepared under varying process parameters. The DPV‐2000 system is employed for the diagnosis of particle velocity, surface temperature, and diameter. Following comparison, the simulation exhibits errors of 4.5% and 14.8% for the maximum temperature and velocity, respectively. An increase in current intensity from 500 to 600 A results in a rise in the proportion of particles exhibiting temperatures above the melting point (2963 K), from 75.1 to 93.4%, accompanied by an increase in average velocity of ≈16.6%. As the spraying distance increases from 60 to 100 mm, the proportion of particles melting decreases from 93.5 to 66.3%, and the average velocity decreases by ≈9.2%. This work will provide a theoretical foundation for the optimization of process parameters to adjust particle behavior and melting state, thus achieving an optimal spraying effect.

Investigation of a Novel Thermochemical Reactor for Medium- and Low-Temperature Heating Applications in Buildings

This research paper investigates a novel triangular honeycomb thermochemical energy storage reactor for low- and medium-temperature applications in buildings, emphasizing its potential to enhance sustainable heating. Using a validated 3D numerical model, the reactor’s performance is analyzed in depth across various configurations, focusing on key parameters such as energy storage density, pressure drop, internal air flow distribution, and round-trip efficiency. Results show that the reactor achieved an energy storage density of 872 kJ/kg and a round-trip thermal efficiency of 41.51% under optimal conditions. Additionally, the triangular honeycomb reactor (30°, 60, and 90°) configuration achieved the highest temperature lift of 48.7 °C. In a feasibility analysis for residential heating in northern China, the reactor with 30°, 60°, and 90° angles required 24.91% less volume to meet daily heating demands compared to other configurations. This study contributes valuable insights for the development of efficient, low-carbon heating solutions for low- and medium-temperature applications in buildings, offering interesting advancements in the field of thermochemical energy storage technology.

The effects of formation inclination on the operational performance of compressed carbon dioxide energy storage in aquifers

Compressed CO2 energy storage in aquifers (CAESA) is a net-zero energy storage technology. Due to the widespread existence of inclined aquifers in nature, it is of practical significance to study the influence of inclined reservoirs on CO2 migration, safety and energy efficiency of the storage system. We build 3D numerical models with different dips (0°–16°), analyze the hydrodynamic and thermodynamic behavior of the system, and discuss the effects of injection schemes (temperature and pressure) on wellbore pressure, temperature, and energy efficiency. The results show that formation dip affects the energy storage characteristics of the system mainly by affecting the migration and distribution of CO2 in the aquifer. The greater the formation dip, the greater the difference in CO2 distribution, and the farther the CO2 diffuses upward along the dip direction. The farthest migration distances in the low- and high-pressure aquifers, occurring in the case of 16° formation dip, increase by 100 and 53 m, respectively, compared with those of the flat formation. The average daily energy storage efficiency decreases with the increase in formation dip angle. The dip angle of aquifer which is selected for compressed CO2 energy storage should not exceed 8°.

Mechanical Characteristics of Deep Excavation Support Structure with Asymmetric Load on Ground Surface

The purpose of this paper is to capture the mechanical response of the support structure of deep excavation subject asymmetric load. A two-dimensional (2D) numerical analysis model was established by taking a pipe gallery deep excavation subject to asymmetric load as an example. The numerical analysis results were in good agreement with the measured data, thus verified the validity of the numerical model. On this basis, the stress and displacement of support structure caused by the change in foundation asymmetric load were studied. According to the numerical results, horizontal displacement of the diaphragm wall (DW) was dominant, and the maximum horizontal displacement of the DW was 7.54 mm when the deep excavation was completed. With the increase in asymmetric load, the left wall displacement continued to increase, while the displacement of the right DW continued to decrease, and the maximum horizontal wall displacement occurred near the excavation face. The DW was the main bending component, and the maximum wall bending moment when the deep excavation was completed was 173.5 kN·m. The maximum wall bending moment increased with the increase in asymmetric load, and the maximum wall bending moment on the left of the deep excavation was greater than that on the right. The inner support sustained the main component of axial force, with the axial force peaking at 1051.8 kN when the deep excavation was completed. The axial force of the inner support increased with increasing the asymmetric load, and the axial force of the second inner support was obviously greater than that of the first inner support. This research has a positive effect on the design and optimization of deep excavation support structure subject to asymmetric load on ground surface.

Influence of the vertical seismic component on the response of continuous RC bridges

This paper investigates the influence of vertical seismic accelerations on the seismic response of RC bridges through numerical simulations using an enhanced non-linear numerical model. Results confirm that the incorporation of vertical accelerations, either through actual records or scaled horizontal records, can considerably modify the seismic response and the collapse mechanism. In the case of actual vertical records, the vertical component significantly contributes to premature structural deterioration, intensifying demand and accelerating failure mechanisms. On the other hand, the study underscores the inadequacy of using scaled horizontal records to represent vertical accelerations, as suggested by some seismic codes, as it not only distorts seismic response evaluation but also alters failure modes. The analysis of vertical vibration reveals higher displacements, increasing flexural demand on the deck, and leading to a progressive loss of vertical support at the central column. The research establishes the need to accurately account for vertical seismic accelerations in bridge design evaluations, as their impact on structural response and failure mechanisms cannot be underestimated. The work highlights the importance of a highly detailed 3D numerical model in assessing traditional parameters and capturing complex collapse mechanisms arising from material and geometric nonlinearities.

Parametric modeling and optimization of the intake port in a naturally aspirated opposed rotary piston engine across the full speed range

The opposed rotary piston (ORP) engine offers advantages such as compact size, simple structure, and high power density, making it highly promising for long-endurance unmanned aerial vehicles (UAVs). Parametric modeling of intake ports and the investigation of structural parameters on intake characteristics for ORP engines are crucial for improving the intake performance. In this paper, based on the kinematic model of the ORP engine, parametric modeling of the intake and exhaust ports are performed, a 3D numerical model is established to explore the intake characteristics at different engine speeds. The impact of intake delayed closing angle (IDCA), intake inclination angle (IIA), and dual intake ports on the intake characteristics of the ORP engine are investigated. Finally, the combustion characteristics and performance metrics of the engine using optimized intake ports are compared against the baseline intake phase. The results indicate that the CGE and pumping loss of the ORP engine initially increase and then decrease with rising engine speed. The CGE exceeds 92 % at 1000 r·min−1 and 94 % at 5000 r·min−1 when the IDCA are set at 8° and the IIA at −20°. The pumping losses at 4000 r·min−1 and 5000 r·min−1 are reduced by 33.3 % and 30.9 %, respectively, after intake port optimization. The performance metrics at 1000 r·min−1 and 2000 r·min−1 show a slight decline compared to pre-optimization due to lower turbulence kinetic energy (TKE) and intake backflow. However, at 3000–5000 r·min−1, the optimized intake port structure significantly improves performance metrics of the ORP engine.

Kinematics and hydrodynamic performance of zebrafish C-type maneuvers: A comparison of two- and three-dimensional simulations

Two-dimensional (2D) and three-dimensional (3D) numerical models are commonly employed to investigate the kinematic and hydrodynamic characteristics of fish maneuvers. In this study, we captured the posture characteristics of zebrafish during C-type maneuvers using high-speed photography and constructed a midline curvature model via the tandem principal characteristics method, which exhibited a “double peak and single valley” structure. Based on this curvature model, self-propelled simulations were conducted using the immersed boundary method with adaptive mesh refinement. The results showed that, under identical deformation conditions, the 2D simulation exhibited a 16.8% higher centroid velocity, 6.1% greater overall angular velocity, and an 11.9% larger turning angle compared to the 3D simulation. This discrepancy is primarily due to the 2D model’s inability to accurately represent the fish body’s mass distribution and force characteristics, resulting in artificially elevated performance. Nevertheless, 2D simulations remain applicable for studying the propulsion performance of fish with elongated cross-sections and large fin areas. Comparison between the simulated and real motion performance reveals that, under the self-propelled computational model, both 2D and 3D numerical simulations consistently capture the qualitative motion patterns. The quantitative results also reflect the actual swimming performance of the fish within an acceptable margin of error.

Analysis of the influence of expansion gap on thermal stress and strain distribution of a hot blast stove

The hot blast stove is an important facility in the steel industry, which of the expansion gaps design has a significant buffering effect on the thermal stress with a high-temperature operating process. In this paper, a 3D numerical model of a hot blast stove was established to calculate the thermal stress distribution and analyze the remaining thickness of expansion gaps with different parts during the operating process. Young’s Modulus of the refractory linings was obtained by comparing with the experiment data and numerical data under the different temperatures and considering the influence of mortar. The result shows that Young’s Modulus of the refractory brick increased as the temperature, and the comparison of the experiment and simulation data of Young’s Modulus under three different temperatures displayed good agreement between the two sets of data. The first/third principle stress for the refractory linings can be reduced effectively by designing the expansion gap rationally, and the equivalent stresses of the shell are mainly concentrated at the joint and the neck. In addition, the expansion gaps are decreased under the thermal expansion and moved along a radial direction for the combustion/checker dome and the combustion/checker chamber.

Numerical investigation for the influence of suspended sediment on salinity distribution in the Qiantang Estuary, China

Numerous studies have demonstrated that high suspended sediment concentration (SSC) can change density distribution and affect water mixing, but few scholars have investigated this impact on numerical simulations of estuarian salinity distribution. The Qiantang Estuary is a macro-tidal estuary with high SSC, which has a more significant influence on water density than that of salinity. Therefore, this paper established a three-dimensional (3D) numerical model coupling flow, salinity and SSC based on Delft3D and first analyzes the impact of SSC on salinity distribution under different runoff and tidal conditions in the Qiantang Estuary. The results indicated that simulated salinity generally decreases when considering the impact of SSC, suggesting a weakening effect on saltwater intrusion. The distribution of salinity difference (ΔS) and SSC show a strong spatial and temporal correlation, and ΔS peak increases and shifts upstream as the tidal range increases or runoff discharge decreases. The mechanism of SSC influencing saltwater intrusion can be summarized as follows: On the one hand, SSC increases the water density, which weakens the driving force for saltwater to move upstream, causing a decrease in flood current velocity and water level, and thereby diminishing the advective transport of salinity. On the other hand, SSC enhances density stratification, which weakens vertical turbulence and reduces the dispersive transport of salinity. These combined effects reduce both the advective and diffusive salinity fluxes during the flood tide, ultimately leading to a decrease in upstream salinity. Therefore, neglecting this effect in estuaries with high SSC can cause significant deviations in salinity simulation results, especially under low-flow and high-tide conditions.