Numerical Analysis Research Articles

Numerical analysis and design of axially-loaded concrete-filled stainless-clad bimetallic steel tubular slender columns

Concrete-filled stainless-clad bimetallic steel tubular (CFBST) structures with stainless-clad bimetallic steel outer tubes combine the cost-effectiveness and high corrosion resistance of stainless-clad steel with the excellent load-bearing capacity inherent in traditional concrete-filled steel tubular (CFST) structures, making them well-suited for applications in demanding marine environments. This paper presents a comprehensive numerical study on CFBST slender columns with circular hollow section (CHS) outer tubes under axial compression. Finite element (FE) models were established and validated by comparing the load-axial displacement curves, ultimate loads, and failure modes obtained from the FE models with the existing experimental results. By employing the validated FE models, an extensive parametric analysis comprising 1120 models was undertaken to investigate the influence of length-diameter ratios, clad ratios and wall thicknesses of stainless-clad bimetallic steel outer tubes, as well as concrete strengths on the flexural buckling behavior of CFBST slender columns. The applicability of existing design codes for conventional CFST systems, including the European Standard EN 1994–1-1, Australian Standard AS/NZS 5100, American National Standard ANSI/AISC 360-22, as well as two Chinese Codes GB 50936-2014 and GB/T 51446-2021 was evaluated. It has been observed that the method outlined in EN 1994–1-1 is recognized for its accuracy in calculating flexural buckling resistance. However, it tends to yield overconservative predictions within the relative slenderness range of 0.2 to 0.35, where buckling effects are already considered. Consequently, a modification to EN 1994–1-1 has been proposed to adjust the limiting non-dimensional slenderness for CFBST slender columns to 0.35, thereby enhancing the accuracy and consistency in design capacity predictions.

Evaluation of a Multimodal Confocal Therapeutic Focused Ultrasound Apparatus: Bridging Cavitation, Thermal Ablation, and Histotripsy in Preclinical Treatments

ObjectivesThe development of versatile and user-friendly preclinical platforms is vital for therapeutic ultrasound research. We introduce a flexible ultrasound-guided focused ultrasound (FUS) platform with two confocal therapeutic transducers, allowing thermal and mechanical modalities, and present its design and, features, with validation of potential applications in preclinical studies. MethodsThe probe's acoustic properties, energy delivery efficiency, and thermal and mechanical modalities are characterized. A computational model predicts thermal effects while optimizing treatment parameters. Ex vivo tissue samples are used to validate system performance, safety, and usability. In vivo experiments on mice with MC38 tumors are presented with immunohistochemistry (IHC) to validate treatment outcomes. ResultsElectroacoustic conversion efficiency levels were 80% and 40% for 1.1 MHz and 3.3 MHz, respectively. Confocal therapy transducers at 1.1 MHz and 3.3 MHz successfully demonstrated cavitation histotripsy and thermal treatments. At 1.1 MHz, for histotripsy, −20 MPa negative peak pressure is achieved, while at 3.3 MHz used for thermal ablation a maximum of 35 MPa is reached for positive peak pressure. Numerical analysis provides thermal treatment planning, aligning with in vitro and in vivo experiments for lesion prediction. Real-time in vivo cavitation monitoring was consistent with in vitro chemical dosimetry, ensuring treatment uniformity. ConclusionThe ultrasound platform induces thermal or mechanical lesions with precise spatial resolution, validated by IHC tissue characterization. Integrated cavitation monitoring enables real-time treatment monitoring. Coupling with thermal simulations provides optimization of thermal treatment parameters. This versatile “all-in-one” therapeutic platform supports multiple treatment modalities including cavitation, thermal ablation, and histotripsy, facilitating direct comparisons to assess their efficacy in diverse therapeutic settings.

Seismic performance on PSPC beam - concrete encased CFST column frame with a built-in reduced beam section

The concrete-filled steel tubular (CFST) column is widely used to connect with a steel beam owing to the quick dry connection and acceptable seismic performance. Therefore, a partially steel-reinforced precast concrete (PSPC) beam with an embedded H-beam was developed to combine the merits of both the prefabrication in the precast concrete beam and the quick assembly in the steel beam. In this study, the developed beam was proposed to connect the concrete encased CFST column with a reduced beam section. A half-scaled frame substructure specimen with two floors and two bays was designed and tested under the cyclic loading to investigate the seismic performance. A series of seismic properties were analyzed, including the failure phenomena, hysteretic performance, stiffness degradation, and energy dissipation capacity. The dog-bone configuration was found to benefit the beam hinge failure mechanism and an acceptable deformation capacity (the ductility coefficient up to 2.77). The function of the H-beam contributed to stable energy absorption (the equivalent damping coefficient from 0.33 to 0.37). Finally, the proposed frame was compared with a reinforced concrete frame and a steel-reinforced concrete frame through numerical analysis. The partial steel-reinforced configuration had a positive influence on the bearing capacity, hysteretic performance, and safety storage. In addition, it could improve the cost-effectiveness with little decrease in the bearing capacity.

Complex heat transfer analysis in heat exchanger with constructal cylindrical fins

This paper documents a 3-D numerical analysis and theoretical prediction in novel micro-channel heat sinks comprise of three configurations. The first design has solid fins, the second model has half-hollow fins placed on micro-channel, while in the third design, hollow fins are mounted on the heat sink. The objective of the study is to maximise the dimensionless thermal conductance subject to fixed volume. A microelectronic device released high-density heat flux at the bottom of heat sink and liquid of Reynolds number range between 400 and 500, is applied at entrance of the boundary under laminar forced convection scheme to dispel heat deposited in the cooling channels and the internal parts of the hollows. A multi-objective broadscale step-by-step code is used to perform the optimisation and the results shows that the micro-channel with full-hollows has the highest thermal conductance at Rew<475, followed by solid fins before half-drilled fins. Theoretical analysis is conducted on the three configurations using the intersection of asymptotes method, and the results compared favorably with numerical solution. The findings indicate that the theoretical solution tends to over-predict the numerical results within a certain range of Bejan number. Code validation is performed, and the results align with existing literature.

Effect of Vertical Location of Post-Opening on Seismic Behaviour of RC Shear Wall: Experimental and Numerical Analysis

The seismic performance of reinforced concrete (RC) shear walls with post-openings is critical in civil engineering. This study investigates the influence of post-opening positions on the seismic behaviour of RC shear walls through both experimental and numerical approaches. Four shear wall specimens with varying positions of post-openings were subjected to pseudo-static tests. Additionally, Finite Element Method (FEM) simulations were employed to further analyse the structural responses of shear walls with post-openings. The results show that the vertical position of post-openings significantly affects the failure mode, peak bearing capacity, and overall seismic performance. Peak bearing capacity reductions were observed, with central and bottom openings diminishing capacity by up to 17.5% and 15.1%, respectively, while top openings had a minimal impact. Openings also influenced pre-crack initiation, yielding behaviour, and stiffness degradation, with central openings causing the most significant effects. The ductility and energy dissipation capacities of the shear walls were also affected by opening positions. Bottom post-openings led to a maximum ductility reduction of 18.4%, while top openings increased ductility by up to 24.6%. Energy dissipation capacity decreased with lower post-opening locations, with central and bottom openings reducing capacity by 78.9% and 63.0%, respectively. These findings emphasize the importance of considering opening location in the seismic design of RC shear walls to optimize structural performance.

Modeling effect of rock shape characteristics on run-out distribution of rockfalls

The aim of this study was to analyze and model the effect of rock shapes on the run-out distribution characteristics of rockfalls. To this end, we conducted a parametric study of rockfall simulations using the discrete element method, which is a numerical simulation method capable of directly representing rock shapes. The results indicated a strong correlation between the sphericity of rocks and the run-out distribution characteristics, expressed by two types of sphericity. Furthermore, we developed a regression model that can predict the run-out distribution using these two sphericities and the parameters of the calculation conditions as the explanatory variables. Although there is some room for improvement in terms of the developed regression model, it was confirmed that the relationship between the sphericity of rocks and the run-out distribution characteristics suggests the potential to enhance efficient rockfall risk assessments through numerical analysis.

Experimental and Numerical Investigation of Steel Panel Links with Different Trapezoidal Corrugations

A novel type of steel panel link with a trapezoidal corrugated section is developed, which is called the corrugated steel panel (CSP) link, aiming to improve both the strength and energy dissipation capacity of the steel links. Quasi-static tests were carried out on two specimens with different corrugation inclination angles to investigate their seismic performance. Test results indicated that Specimen CSP-V (corrugation inclination angle of 90°) and Specimen CSP-H (corrugation inclination angle of 0°) exhibited distinct failure modes due to the differing out-of-plane constraints provided by their corrugations. Numerical analysis was conducted using the general finite element program, ABAQUS, to supplement the test results. Analytical findings suggested that CSPs with a 90° corrugation inclination angle could provide superior ductility, both yield and peak strengths demonstrated a strong linear correlation with the aspect ratio (H/L ratio). For CSPs with a 0° inclination angle, superior strength and stiffness were observed, the relationship between lateral strength and the H/L ratio was better described by a power-law correlation. Furthermore, to achieve comparable seismic performance, the H/L ratio of CSPs with a 0° inclination angle should be at least twice that of CSPs with a 90° inclination angle.

An investigation of firm size distributions involving the growth functions

Following the ideas of prospect theory, a class of growth functions is used to characterize deterministic variations of firm size, which portrays the asymmetric efforts of the firm to achieve the desired size. Considering the differences in the ability of different firm size to cope with uncertainties, the Boltzmann equation for the evolution of firm size is constructed. Utilizing a suitable scaling limit, the Fokker–Planck equation is acquired and its explicit steady-state solution is derived. Our results illustrate that different choices of parameters in the growth function lead to various statistical laws for firm size, such as the Amoroso distribution, the lognormal distribution and Zipf’s law. Under certain conditions, inequality for the distribution of firm size decreases as firm size increases. The numerical analyses are presented to illustrate our results.

Experimental and Numerical Unsteady Aeroelastic Effect Analysis of Wing Model Triggered with Piezoelectric Material

Experimental and Numerical Unsteady Aeroelastic Effect Analysis of Wing Model Triggered with Piezoelectric Material

A high-resolution 3D sediment-dynamics model of a morphologically complex mesotidal estuarine river system (New Zealand): insights from model calibration and validation

Land use change and the associated change in sediment runoff to the receiving environment is a topic of concern for estuarine and coastal governing agencies around the world. Fine sediments can enter the receiving environment and have a plethora of potential negative impacts (e.g., ecological, and recreational) and present no real opportunities or positive impacts. In the present study, a Delft3D numerical model is presented. The model has been calibrated considering water levels, currents, temperature, salinity, and Suspended Sediment Concentrations (SSC). Delft3D-Wave was also coupled to the hydrodynamic model to investigate the role of wave related fine sediment resuspension due to wave bed shear stresses. The extent of this model covered the Wairoa River and estuary, just south of Auckland, New Zealand. The motivation for this study was to produce a method that could link the upstream SSC contribution to the subsequent distribution in the receiving environment. From there it can readily be used as input to a regional scale model to investigate and understand the fate of sediments in the Hauraki Strait. As part of an ongoing research programme, the present study formed part of an extensive measurement campaign. Measurement instruments and results are presented alongside numerical model sensitivity analyses. The model performance is discussed, and the physical dynamics are described via extensive tables and summarising plots.

Microstructure Evolution and Wear Behavior of Stellite12 Coating Prepared by Laser-Directed Energy Deposition on H13 Steel

Laser-directed energy deposition (LDED) was employed to apply a Stellite12 coating onto an H13 steel substrate. This study explored the effects of processing parameters on the dimensions of the deposited tracks. Comprehensive examinations were conducted on the coatings to assess their phase composition, microstructure, and wear resistance properties. The relationship between microstructural characteristics and thermal field was investigated through a synergy of numerical simulations and experimental analyses. The findings revealed that the Stellite12 coating displayed a heterogeneous microstructure with epitaxial growth and a slight texture across successive layers. The primary phase comprised a γ-Co solid solution and M23C6 carbides, contributing to a significant enhancement in hardness, which was observed to be 2.2 times higher than that of the substrate. The coating demonstrated superior performance in terms of lower friction coefficients and reduced wear rates at both room and elevated temperatures. The predominant wear mechanisms identified were oxidative wear. These results underscore the promising applications of Stellite12 coatings in industrial contexts facilitated by LDED technology.

Numerical simulation and energy consumption analysis of ventilation patterns in grain silo

Mechanical ventilation is an effective method to ensure the security of grain storage, which directly impacts the storage duration and storage quality. In this work, considering the coupling effect of grain physical parameters and gas-solid phase interaction on ventilation, the porous media, non-thermal equilibrium and turbulence models were employed to investigate the variation of velocity field and temperature field under four ventilation patterns: vertical ventilation duct (VD), transverse ventilation duct (HD), combined roof inhalation duct (CRD), and combined bottom inhalation duct (CBD). The relative standard deviation (RSD) and unit energy consumption were used to evaluate the performance of different ventilation patterns quantitatively. The results show a relative deviation of 5.12 % between simulation and experiments. Compared with VD and HD, CRD and CBD exhibit higher velocity values and gradient in the center of grain silo. The physical parameters of grain have obvious impacts on velocity field, and paddy has the highest velocity values due to its higher porosity. CRD has a significant advantage in cooling speed and effect, with the grain surface temperature at 12 m and 25 m lower than other patterns by 1.2 °C and 1.8 °C, respectively. The large porosity of paddy can advance cooling time by up to 5–10 h, while the lower specific heat capacity and higher thermal conductivity of peanut result in cooling temperatures 1.5 °C–2.4 °C lower than other grain. The temperature RSD of VD is lower than other ventilation patterns, and the unit energy consumption of CRD and CBD is better.

Comprehensive analysis of mode-I cracking in ice: Exploring full-range rate dependency

Ice, as a crystalline material, demonstrates a unique response in its mode-I fracture toughness to variations in loading rates, characterized by an initial decrease and subsequent increase in toughness. This phenomenon has been explored in limited studies. In this work, an extensive numerical analysis of mode-I ice cracking is conducted by using the distinct lattice spring model (DLSM). Norton-Bailey Drucker-Prager DLSM (NB-DP-DLSM) is initially employed to investigate the classical explanations of creep and stress relaxation for the anomaly observed in ice’s fracture toughness at lower loading rates, but this approach does not successfully replicate the experimentally observed strain rate dependency. Then, two rate-dependent constitutive models are introduced to further examine the mode-I fracture mechanics of ice. Our numerical simulations of three-point bending tests show that the relationship between fracture toughness and strain rate at lower levels is more accurately captured by rate-dependent models. For higher strain rates, our numerical modeling of notched semi-circular bending tests indicates that a rate-independent constitutive model can replicate the loading rate dependency of ice’s mode-I fracture toughness. In conclusion, these observations suggest that a reverse-stage-like dynamic constitutive model for DLSM can potentially capture the full range of loading rate dependencies observed in ice.

Featuring the aspects with temperature dependent viscosity of inclined MHD Williamson fluid along with heat source/sink, Soret and Dufour effects: A predictor-corrector approach

The boundary layer flow analysis of Williamson fluid moving on the stretched cylinder has applications in the polymer processing, drug delivery system, cooling systems, rheology of food products, dyeing, and finishing. The numerical solutions of governing Navier-Stokes equations at different scenarios of thermal and solutal aspects have lots of practical implications, including biomedical engineering, cooling and heating processes, chemical reactors, aerodynamics, environmental science, and thermal storage systems. From these practical applications, the authors were motivated to conduct a study in which the numerical behavior is examined by applying the Adams-Bashforth predictor and corrector approach of numerical analysis for the Williamson fluid model in the presence of varying viscosity, natural convection, and the inclined magnetic field. Furthermore, Joule heating, thermal radiation, and heat source/sink effects are included in the thermal aspects because these are the important concepts in thermal management and engineering and have applications in solar thermal energy systems, combustion engines, heat exchangers, nuclear reactors, thermal imaging, and safety. Apart from thermal aspects, the analysis of mass transfer focuses on the influence of chemical reactions and Soret-Dufour effects. The similarity transformations are adopted to convert partial differential equations into ordinary differential equations. Specifically, the well-known predictor and corrector numerical method named the Adams-Bashforth method in combination with the Runge-Kutta 4th order scheme is used to achieve the numerical solutions. The temperature, concentration, and velocity regions are displayed on the graphical and numerical conducts. A comparison is also made between the results obtained by the shooting method and the numerical findings of skin friction, Nusselt number, and Sherwood number determined by the Adams-Bashforth method. The determining results concluded that the restrictions in the flow of Williamson fluid are caused by variations in the inclination magnetic field, the surface curvature, and the Williamson parameter, whereas the motion of the fluid increases due to convection, which occurs due to thermal phenomena. The determined results indicate that the temperature distribution is enhanced due to the addition of thermal radiation, Eckert number, and magnetic field. The surface curvature, Soret number, and reaction coefficient marks the decrease impact on the concentration region. The temperature-dependent viscosity increases the drag force and friction coefficient. The Nusselt number is amplified by applying thermal radiation to the surface of the cylinder. The chemical reaction is the source of the increment in the Sherwood number.

HOPE: High-Order Polynomial Expansion of Black-Box Neural Networks.

Despite their remarkable performance, deep neural networks remain mostly "black boxes", suggesting inexplicability and hindering their wide applications in fields requiring making rational decisions. Here we introduce HOPE (High-order Polynomial Expansion), a method for expanding a network into a high-order Taylor polynomial on a reference input. Specifically, we derive the high-order derivative rule for composite functions and extend the rule to neural networks to obtain their high-order derivatives quickly and accurately. From these derivatives, we can then derive the Taylor polynomial of the neural network, which provides an explicit expression of the network's local interpretations. We combine the Taylor polynomials obtained under different reference inputs to obtain the global interpretation of the neural network. Numerical analysis confirms the high accuracy, low computational complexity, and good convergence of the proposed method. Moreover, we demonstrate HOPE's wide applications built on deep learning, including function discovery, fast inference, and feature selection. We compared HOPE with other XAI methods and demonstrated our advantages.

Multilayer deep-learning intelligent computing for the numerical analysis of unsteady heat and mass transfer in MHD Carreau Nanofluid model

The objective of this article is to investigate the mechanism of unsteady heat and mass transfer (HMT) in a magnetohydrodynamics Carreau nanofluid flow (MHD-CNFF). To accomplish this, we utilized a novel artificial intelligence-based (AI) method, deep learning predictive technique combined with Levenberg-Marquardt scheme (DLPT-LMS). The similarity transformation is applied to convert the partial differential equations (PDEs) into a set of non-linear ordinary differential equations (ODEs). We numerically solved these resulting ODEs using the Adam numerical approach in sophisticated “Mathematica” software. The influence of Brownian motion parameter, thermophoresis parameters, Prandtl number, Lewis number, and mass transfer parameters on the temperature, velocity, and concentration profile is analyzed using a synthetic dataset. This evaluation is conducted across different variation of MHD-CNFF by leveraging DLPT-LMS. The absolute error (AE) across various iteration of MHD-CNFF demonstrated a progressive drop, indicating the accuracy of DLPT-LMS. The outcomes of this investigation revealed that the AE ranged from 10-3 to 10-8 which shows a minimum error between actual and predicted value. Additionally, the MSE confirmed the accuracy of proposed DLPT-LMS in predicting the behavior of velocity, temperature, and concentration profiles, with lower values showing better predictions. The model accuracy was reinforced by performance results, including regression analysis and error histograms. Error values gradually decreased during training, validation, and testing phases, exhibiting a robust convergence and indicating the highly reliability of AI-based algorithm for investigating intricate fluid dynamics in MHD-CNFF systems.

Investigation of the Arrangement of Aluminum Fins on the Thermal Behavior of Lauric Acid as a Phase Change Material in a Two-pipe Heat Exchanger by CFD Simulation

BackgroundPhase change material (PCM) thermal storage systems store more thermal energy per unit volume than sensible heat storage systems. PCMs offer a potential solution to reduce energy consumption in various thermal engineering applications. This study aimed to examine how fin arrangement affected the thermal efficiency and melting time of PCMs. MethodsA two-dimensional numerical analysis of the melting process of lauric acid in a heat exchanger featuring two pipelines and fins was conducted using CFD simulation. In most previous investigations, the heat transfer fluid was a single-phase liquid. An enthalpy-porosity technique was used to model the solid and liquid phases of PCM. The governing equations were solved using the commercial software ANSYS Fluent 2021, and the pressure and velocity equations were coupled using the SIMPLE algorithm. Significant FindingsThe best model among the 13 tested was Model 5, which featured 6 fins and a consistent angle of 60 degrees. For Model 5, the melting time was 1818.3 seconds. Due to sensible heating, the fin's temperature (Temp) rose gradually from 300 K to 318 K. Temp then gradually increased as the PCM melted in the phase transition zone between 316.5 K and 321.2 K. Once the phase transition was complete, the PCM's Temp steadily rose from 324 K to 340 K. In Model 5, the inner wall Temp and the maximum Temp of the PCM were closest, at 327.34 K and 333.55 K, respectively. The thermal shock between the PCM and the ambient Temp caused a peak heat flux at the beginning of the PCM loading process.

Numerical analysis of industrial electrolytic pickling for cold-rolled flat stainless steel using secondary current distribution

Numerical analysis of industrial electrolytic pickling for cold-rolled flat stainless steel using secondary current distribution

Experimental and Numerical Analyses of Shear Failure Mechanisms of Rock Bolt Surrounded by Bedded Rock

Experimental and Numerical Analyses of Shear Failure Mechanisms of Rock Bolt Surrounded by Bedded Rock

Shaking Table Test and Numerical Analysis of a Precast Frame Structure with Replaceable Box Connectors

Shaking Table Test and Numerical Analysis of a Precast Frame Structure with Replaceable Box Connectors