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This paper conducts a comparative study into the hydrodynamic loads and bearing reaction forces between T-deck and box-deck bridges under freak waves. Initially, a high-fidelity numerical flume is established and validated to accurately simulate the freak wave-bridge interaction. Subsequently, a comprehensive analysis distinguishes the hydrodynamic characteristics associated with equivalent-sized freak waves, Stokes fifth-order waves, and solitary waves. Utilizing the developed numerical flume, the detailed comparisons of hydrodynamic loads on T-deck and box-deck bridges under freak waves are conducted, considering various focus locations, wave height to significant wave height ratios (α 2), and wave crest to wave height ratios (α 3). The study then delves into the seaward and landward bearing reactions for both bridge types. Additionally, the ultimate resistance envelope for a tension-compression bearing is explored through a finite element model, and the safety evaluation of the bearings under freak waves is carried out. Key findings reveal that (a) freak waves pose a more significant threat to structures than the other two wave types; (b) strengthening the seaward bearing for the box-deck and the landward bearing for the T-deck is recommended in the bridge design under the impact of freak waves; and (c) the ultimate resistance capacity envelope efficiently evaluates the bearing capacity when encountering freak waves with the working conditions used in this paper. • The force induced by freak wave, Stokes-5th order wave, and solitary wave is compared. • Hydrodynamic distinctions between T-deck and box-deck under freak waves is examined. • The bearing reaction force under varying parameters of freak waves is analyzed. • An ultimate resistance envelope is obtained for a tension-compression bearing. [ABSTRACT FROM AUTHOR]

Rotor unbalances failure due to various factors such as manufacturing defects, mounting errors, and material inhomogeneity is inevitable, and will be aggravated by bearing pulse displacement excitation caused by maneuvering flight. Therefore, the purpose of this paper is to study the vibration of the rotor system under disk unbalance forces and bearing pulse displacement excitation. Firstly, the differential equation of motion for four-disk flexible hollow shaft rotor system modeling with a simple finite element model(SFEM) is established by the Lagrangian method in non-inertial systems, and the shaft is modeled using Timoshenko beam theory. Then, the dynamic characteristics of the four-disk flexible hollow shaft rotor are analyzed and compared with the 3D finite element model(3D FEM) to verify the accuracy of the model. To analyze the effects of different disk unbalanced positions and pulse displacement excitation on the vibration characteristics of the rotor, the characteristic vector method and the Runge–Kutta method are used to obtain the steady-state solution and the transient solution, respectively. In addition, the simulation results show that suitable in-shaft damping has a stable effect on the rotor during the start-up. Disk 2 and Disk 3 are more sensitive to synchronous harmonic excitation and pulse displacement excitation than Disk 1 and Disk 4. The research of this paper provides an important basis for vibration monitoring and control, and vibration transmission analysis of aero-engine rotor system. [Display omitted] • The 3D FEM verifies SFEM of four-disk hollow shaft rotor with Timoshenko beam. • Natural frequency of rotor confirms proper inner diameter of hollow shaft id. • The vibration transmission law is studied with unbalanced or pulse excitation. • High-order whirling frequency is excited in transient response. • In-shaft damping has the stabilizing effect during rotor start-up. [ABSTRACT FROM AUTHOR]

Cylindrical shells with corrugation are widely used in deep sea, underground pressure structures, and other fields. It is mainly subjected to uniform and concentrated external pressure. The current research mainly includes circumferentially corrugated shells and longitudinally corrugated shells. These two kinds of corrugations improve the strength of the cylindrical shell but also have some problems such as stress concentration, buckling extension, and so on. To solve these problems, a shell with composite corrugation is proposed and it has the structural characteristics of both circumferential and longitudinal corrugations. In this paper, the numerical analysis method is used to explore the stability of the composite corrugated shell under uniform and concentrated pressures. It is analyzed by Donnell's large deflection equation. In addition, it can reduce the area of damage caused by buckling. The excellent mechanical properties of the composite corrugated shell are proven. The influence of the number of corrugations and "diameter to thickness ratio" on the buckling performance is studied by using the control variate method. It is compared with a cylindrical shell without corrugation with equal volume and weight. The concentrated pressure tests of composite corrugated shells and shells without corrugation are finished. The results show that the curve of "radial compression-reaction load" obtained by the experiment is consistent with the simulation. The ultimate load of the composite corrugated shell is 34.96% higher than the shell without corrugation. The composite corrugation can effectively enhance the compressive strength and stiffness of the cylindrical shell. Composite corrugation can make more material of the shell to be involved in resisting external deformation. This method of increasing material utilization is effective. • The advantages of the composite corrugated shell are verified from mechanical theory, finite element analysis and test. • The influence of local curvature on the buckling performance of cylindrical shell is verified. • Donnell's large deflection equation has been applied and innovated in this paper. [ABSTRACT FROM AUTHOR]

Locally resonant phononic crystals (LRPCs) materials have elastic wave bandgap characteristics and have good application prospects in many fields. However, the traditional LRPCs materials have the shortcomings of narrow bandgap width and small effective attenuation of elastic waves within the bandgap range, which is limited in practical engineering applications. To solve the problem of narrow bandgap width of traditional cement-based LRPCs materials, this paper proposes a new cement-based LRPCs composite material with multiple oscillators based on local resonance theory. Firstly, the band structure of the multiple oscillators cement-based LRPCs composite material is calculated by finite element method, the bandgap mechanism is analyzed, and the bandgap width widening method is discussed. Secondly, the frequency response function is calculated to evaluate its attenuation effect within the bandgap frequency range. Finally, a spring-mass system equivalent model and an effective mass model of the multiple oscillators cement-based LRPCs are established to solve the bandgap range and the effective mass expression. The bandgap range calculated by theory agrees well with the finite element calculation. The results show that the multiple oscillators cement-based LRPCs composite material open two low-frequency bandgaps in the frequency range of 0–200 Hz, and the attenuation values within the bandgap frequency range are mostly above 15 dB. Compared with the corresponding single oscillator cement-based LRPCs, the open bandgap range is wider, the bandgap width is significantly increased, and the overall attenuation effect is better. The relevant results of this paper provide a specific reference for designing the structure of multiple oscillators cement-based LRPCs composite materials, widening the bandgap width of LRPCs materials, and materials design in the field of low-frequency vibration control. • This paper proposes a new multiple oscillators cement-based LRPCs composite material. • It has a wider low-frequency bandgap and better attenuation effect. • This paper provides a new design idea and method for obtaining a wide low-frequency band gap in LRPCs materials. • This paper provides a reference for the design of vibration reduction and isolation structures. [ABSTRACT FROM AUTHOR]

To establish the correlation between monitoring indexes and damage indexes for the purpose of rapid assessment of dam damage, this paper takes the Baihetan arch dam as an example and establishes a three-dimensional finite element model for dynamic analysis. Focusing on the crown cantilever, the study analyzes the correlation between different monitoring indexes and damage indexes using DCCA correlation coefficient, and constructs a Random Forest prediction model based on time history information of indexes. Using this model, the paper predicts the volume ratio of damage for the crown cantilever over time and its maximum value, comparing the results with those obtained from a model based on maximum value information, through error analysis. The results of the correlation analysis indicate a close relationship between the increase in the maximum upstream displacement, maximum upstream acceleration, and the widening of the transverse joint opening width, and the development of damage in the monolith. The error analysis results demonstrate that the prediction network established based on time history information performs well in both point prediction and interval prediction. The research presented in this paper provides a feasible approach for the comprehensive assessment of real-time seismic damage in arch dams. • Quantitative correlation studies of indexes were conducted by DCCA coefficient. • The acceleration, displacement and opening width of transverse joints closely associated with the increase of monolith damage. • Establishing a prediction model for real-time and rapid evaluation of the monolith damage. • Damage prediction model based on time history data has good prediction accuracy and precision. [ABSTRACT FROM AUTHOR]

In zero-emission solutions for the hydrogen supply chain, high-pressure hydrogen storage in Type IV composite overwrapped pressure vessels (COPVs) is crucial for being safe and secure for a variety of stationary and transport applications. These COPVs consist of a polymeric liner material that works as a barrier for the stored hydrogen, while the carbon fiber-based composite provides the strength to hold the high-pressure hydrogen (of nominal working pressure more than 70 MPa to achieve the competitive driving range). Several experimental studies and simulation work have been performed on the viability of various polymers as low-permeability materials under low-pressure conditions. However, because of their proprietary nature and commercialized research, the characteristics of hydrogen permeation through polymers and their behavior at high pressure are still readily available in the literature. It is a major concern and the most crucial component of Type IV COPVs that these polymeric liners hold high pressure and maintain the necessary density of hydrogen (state of charge) toward operational requirements and safety concerns related to the cause of failures due to permeation (such as blistering, buckling, cracking, and so on). This paper investigates the role of polymeric liners on hydrogen permeation behavior using finite element modeling. For this, a UMATHT subroutine is developed within the Abaqus software to implement a new hydrogen permeation transport model with extended governing equations. Through the simulations and material modeling, the role of hydrogen transport properties (permeability, diffusivity, and solubility), structural characteristics (crystallinity, free volume, thickness) of plastic liners, and the role of operational parameters (concentration, pressure) are combined to validate the model from the experimental data in the literature to estimate the effective thickness required to maintain the permeation limit of the polymeric liner of 70 MPa Type IV COPVs. • A comprehensive review for polymeric materials is provided which are generally acts as liner material for high pressure hydrogen permeation barrier used in compressible high pressure hydrogen storage pressure vessels. • A mechanism of hydrogen permeation and exhaustive material model for polymeric liner material has been described to implement into Finite Element Analysis (FEA) using UMATHT a user subroutine. • Firstly, the investigation of material properties of HDPE polymer, geometry as representative volume element (RVE) of polymeric liner material of Type IV COPV for 2D sample with loading and boundary conditions described. • Then, the material model and all the FEA input implemented to validate the experimental published paper of Fujiwara et al. 2020, 2021 for HDPE material of thickness 1.5 mm and operating pressure up to 90 MPa. • The modeling framework of hydrogen permeation analysis considers the effect of pressure and concentration within the HDPE polymer sample with increasing thickness up to 5 mm that able to satisfy the permeation limit of hydrogen through the wall of 70 MPa Type IV composite pressure vessel (COPV). The hydrogen saturation inside the polymer has shown in terms of flux to evaluate the hydrogen transport properties through the polymeric liner material using time lag method. • The role of high-pressure cause compression of the HDPE polymer sample and corresponding crystallinity enhancement reported. • The results obtained from our study provide valuable insights into understanding the role of high-pressure hydrogen gas on the polymeric liner permeation behavior at various pressure. These insights can help determine their potential to model the complex behavior of hydrogen permeation modeling to evaluate the liner material permeation limit for 70 NWP of Type IV COPVs. [ABSTRACT FROM AUTHOR]

Large waves used to cause a lot of ship collapse accidents, resulting in the loss of many lives and property. The response of ships to collapse, including plasticity and buckling, has aroused focused concern among researchers. This paper carries out a hydroelasto-plastic experiment and numerical investigation of a three-cabin ship model to study its structural collapsed response. Firstly, a hydroelasto-plastic model experiment is conducted in a wave tank. A three-cabin experimental model which is made of stiffened plate, has been designed and manufactured. Then the model is forced to collapse in tank waves with measuring wave elevation, wave pressures, structural stress and rotational deformation of model. Secondly, a hydroelasto-plastic numerical approach coupling of CFD (Computational Fluid Dynamics) and nonlinear FEM (Finite Element Method) is used to co-calculate the wave loads and structural collapsed response of a ship model. A hydrodynamic model is constructed and utilized to solve wave loads in the CFD platform, while a nonlinear FEM model of the three-cabin structure is also constructed and solved using a nonlinear FEM solver to obtain the structural collapse response. Finally, hydroelasto-plastic experimental results and numerical results are compared and analysed, the structural collapsed characteristics of the three-cabin structure, which is very similar to a ship structure, are analysed. The numerical approach of two-way coupling of CFD and nonlinear FEM is verified for the hydroelasto-plastic problem. In this paper, the water elastic-plastic test of stiffened cabin structure under wave action is carried out, which provides a new perspective for ship structural design. [ABSTRACT FROM AUTHOR]

Slender webs in welded steel plate I-girders (often used for long spans or load transfer in bridges and buildings) develop initial out-of-flatness imperfections as a result of fabrication (e.g., rolling, forming, welding, and assembly). Previous research has suggested that these imperfections can reduce the shear strength of the web; therefore, various specifications since the 1960s have included out-of-flatness imperfection tolerance limits for webs in steel plate girders. The research presented in this paper (1) provides a comprehensive review of current web out-of-flatness tolerance limits and measurement approaches, (2) introduces an alternative measurement technique for the out-of-flatness of webs (which collects a wide array of equispaced measurements), and (3) presents field measurements of 23 web panels (bounded by transverse stiffeners) across 12 different girders (with depths ranging from 0.914 to 2.08 m) that were commercially fabricated for bridge applications. The peak value for the out-of-flatness of the web, averaged across all measurements for each panel, was d / 170 (where d represents the least panel dimension). However, the location of peak out-of-flatness is seldom at the middle of the panel and has a 'dimpled' shape, meaning that the peak out-of-plane bulge covers only a small portion of the panel. The measurements demonstrated in this paper provide significantly more data resolution, thus enabling a better evaluation of the true impact of realistically irregular imperfection shapes and magnitudes on the shear strength of the plate. Such an evaluation based on the measurements presented in this paper is documented in a companion paper and is performed via numerical finite element analysis. [Display omitted] • Extensive field measurements to capture the initial web out-of-flatness imperfection magnitude and shape of plate girders were conducted. • A comprehensive review of current and past web out-of-flatness tolerance limits and measurement approaches were investigated. • A new measurement technique is introduced as an alternative to improve the accuracy, repeatability, and efficiency of field measurements. • Overall, the post-fabrication magnitudes of the out-of-flatness imperfections in the web do not exceed tolerance limits prescribed by code-based specifications, the location of the peak value of the out-of-flatness in the web has dimpled shapes and is seldom at the center of the web panel. [ABSTRACT FROM AUTHOR]

Bedding layer refers to a layer of material that is placed under and around a pipe to provide support and prevent damage to the pipe. The impact of the bedding layer can be evaluated based on various bedding factors. However, current pipe design methods only evaluate the impact of bedding layers under static and traffic load. Isolating the effects of traffic loads for separate analysis is not possible, which may cause errors in determining the bedding factors. In this work, a 3D finite element model was developed to analyze the interaction between pipeline and surrounding soil, incorporating a Concrete Damaged Plasticity (CDP) model and an interfacial cohesive model. The results calculated from the FEM was used to develop prediction models for bedding factors of different backfills under static and traffic loads by Evolutionary polynomial regression (EPR). And then, bedding factor calculation paradigms were developed by considering pipe diameter, wall thickness, buried depth, initial pipe deterioration, and backfill type. The results indicate that the proposed stiffness model in this paper provides a Cured-In-Place Pipe (CIPP) lining repair wall thickness that is 39.68 %, 20.64 %, and −20.64 % higher than the values specified by the ASTM standard for deteriorated Class I, II, and III reinforced concrete pipeline structures, respectively. Moreover, the lining design method based on the overall structural stiffness proposed in this paper is more flexible than the ASTM standard. These paradigms enable the design of more cost-effective and durable CIPP rehabilitation designs for drainage pipes. [ABSTRACT FROM AUTHOR]

The most common and practical connection between CLT walls can be realized with inclined screws. This choice avoids the realization of more elaborated half-lap or spline joints. The failure mechanism of CLT-to-CLT screwed connections is highly ductile. However, the epistemic and aleatoric uncertainties associated with the capacity estimation of the connection might lead to an undesired overstrength, compromising the expected hierarchy between failure mechanisms. This paper presents the results of an extended experimental campaign to estimate the overstrength of CLT-to-CLT screwed connections. However, the overstrength directly obtained from the experimental tests could be underestimated. In the experimental campaign, the same wood and screw stock is used, which might not represent the actual scatter of the material properties and construction uncertainties of the as-built connection (e.g., the screw inclination). Therefore, this paper attempts to provide a model-driven assessment of the overstrength factor, assuming more realistic values for the parameter uncertainties. The authors propose a method for removing the contribution of epistemic uncertainty to the model-driven estimation of the overstrength based on experimental tests with two Montecarlo simulations. Following the proposed method, the paper compares the overstrength estimations from the experimental tests to the predictions of analytical and nonlinear finite element models. This study has proven that an overstrength factor between 1.8 and 2 can represent the actual uncertainties in as-built CLT-to-CLT screwed connections. • Overstrength assessment of CLT-to-CLT screwed connections. • Proposal of a novel formulation for overstrength. • Experimental tests on CLT-to-CLT screw connections. • Epistemic and aleatoric uncertainties in the overstrength estimate. • Uncertainty propagation in analytical and FE models. [ABSTRACT FROM AUTHOR]

This paper formulates quadrilateral elements for the NURBS-enhanced finite element method (NEFEM). The objective is to extend the application of NEFEM to problems where the use of quadrilateral elements is preferred. By leveraging a mapping, between reference and physical spaces, that encapsulates the exact boundary representation of the domain, a tight integration with computer aided design (CAD) systems is achieved. The contribution of this work is an enhanced quadrilateral finite element that incorporates the exact CAD geometry purely from the boundary representation (B-rep) from CAD and without the need for a whole volume representation (V-rep) as a NURBS entity. Numerical examples involving heat transfer and linear elastic problems are used to numerically demonstrate the optimal convergence properties of the method under mesh refinement. [Display omitted] • This paper aims to reduce the gap between CAD and analysis. • A new NEFEM bilinear superparametric element is presented. • The shape functions are redesigned and solely reside in the parametric space. • Heat transfer and elasticity problems show that NEFEM achieves higher accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes a temporal second-order fully discrete two-grid finite element method (FEM) for solving nonlinear time-fractional variable coefficient diffusion-wave equations. The method involves introducing an auxiliary variable and utilizing a reducing order technique for the fractional derivative. This reduces the original fractional wave equations to a coupled system consisting of two equations with lower order derivative in time. The time-fractional derivative is discretized using the L2- 1 σ formula, while a second-order scheme is used for discretizing the first-order time derivative. The spatial direction is discretized using an efficient two-grid Galerkin FEM. The paper demonstrates that the optimal error estimates in L 2 -norm and H 1 -norm of the two-grid methods can achieve optimal convergence order when the mesh size satisfies H = h 1 2 and H = h r 2 r + 2 , respectively. To handle the initial singularity of the solution and the historical memory of the fractional derivative term, the paper presents the nonuniform and fast two-grid algorithms. The numerical results validate the theoretical analysis and demonstrate the effectiveness of the proposed two-grid methods. • We establish an efficient two-grid method for the nonlinear time-fractional variable coefficient diffusion-wave equations. • We provide stability and convergence results for both fully discrete scheme and two-grid scheme, respectively. • The L2- 1 σ formula is employed to discretize Caputo fractional derivative to achieve second-order numerical accuracy. • Two-grid methods achieve optimal convergence order when coarse and fine grids satisfy H = h 1 2 and H = h r 2 r + 2 , respectively. • Considering the initial singularity and historical memory, the nonuniform and fast two-grid algorithms are presented. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative hybrid processing method that combines in-situ laser assisted with mechanical ruling. The innovative diamond ruling tool can facilitate laser incidence from both the A and B faces. Additionally, this paper establishes a thermal-mechanical coupled finite element simulation model for in-situ laser-assisted mechanical ruling of single-crystal silicon with varying cutting depths. It aims to analyze the material removal process and the effect of temperature on the ductile-to-brittle transition. In the process, an in-situ laser assisted mechanical ruling setup is designed to investigate the impact of different laser powers on the ductile-to-brittle transition. The experimental results align with the simulation outcomes. When the laser power was set to 30W, the critical ductile-to-brittle transition depth reached 320.69 nm, successfully suppressing brittle fracture, validating that the proposed in-situ laser assisted mechanical ruling hybrid processing method can enhance the critical depth of ductile-to-brittle transition and improve the surface quality of microgrooves. [ABSTRACT FROM AUTHOR]

Structural safety of functionally graded material considering multi-source uncertainties significantly impacts its application in thermal protection systems. To accurately quantify the uncertain factors and evaluate the structural safety, this paper presents a novel reliability analysis method for functionally graded plates based on the ellipsoid-interval formed evidence theory. Firstly, the thermal behavior of a corrugated sandwich panel with webs made of functionally graded material is analyzed by the finite element method. Subsequently, considering the inconsistent correlation of uncertain variables, this paper develops an ellipsoid-interval formed evidence theory model which consists of ellipsoid-formed frame of discernment for correlated variables and interval-formed discernment for independent variables. On this basis, a novel evidence theory-based reliability analysis framework is constructed for structural safety assessment considering multi-source uncertainties. Meanwhile, to improve the computational efficiency of the limit state function, a new active learning Kriging model, which utilizes a variance reduction function as the sampling strategy, is developed as the surrogate model. Finally, a mathematical example and an engineering case of a thermal protection system are provided to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the buckling and post-buckling behavior of inclined stiffened composite panels under axial compression load. Two types of stiffened composite panels with two inclined stringers and one longitudinal stringer were manufactured and tested, and the buckling load, ultimate load and other required Structural properties of the inclined stiffened composite panels were obtained. The test results show that the failure load of two type panels are 3.19 times and 7.79 times of buckling load, respectively, indicating that such inclined stiffened panels have a large post-buckling capacity. The combination of Hashin failure criterion and Cohesive model was used to conduct finite element modeling, which accurately predicts the buckling, post-buckling and damage modes of the panel. Based on the classical lamination theory, stiffness calculation method of inclined stringer was proposed. The linear relationship between the stiffness of inclined stringer and buckling load was verified. The engineering calculation methods for buckling load and failure load have been established to improve calculation efficiency. The research in this paper can provide reference for aircraft Structural design. [ABSTRACT FROM AUTHOR]

The present paper suggests a new method to obtain pure mode and mixed mode traction-separation laws of adhesives using semi-circular bend (SCB) specimen by employing the digital image correlation (DIC) technique. This specimen was recently proposed by the same authors for fracture energy assessment of adhesives. This test method doesn't require any special apparatus or loading jig for mixed mode fracture tests ranging from pure mode I to pure mode II. Lower cost and higher precision than conventional methods are the most advantages of using SCB fracture tests. The primary drawback of this test method lies in its data reduction process. To address this limitation, this paper introduces a direct approach for measuring fracture energy and cohesive law parameters of the adhesive. In this method, substrate strains at the interface are used to calculate the cohesive stress applied to the adhesive layer at each desired section. Shear and normal separation values are obtained directly from DIC displacement results. The proposed method was applied to the SCB specimen subjected to pure modes I and II and for mixed-mode I/II cohesive laws. Four different SCB specimens were manufactured and tested to cover different mode mixities between pure mode I and pure mode II. The experimentally obtained cohesive laws were evaluated using finite element analysis (FEA). Good agreement between the experimental and numerical results were observed. [ABSTRACT FROM AUTHOR]

As basic units of oil tankers and bulk carriers, corrugated bulkheads are usually subjected to lateral loads such as liquid cargo pressure. In this paper, the experiments have been designed and carried out to investigate the collapse modes and ultimate strength of corrugated bulkheads and plane bulkheads under lateral pressure. In the experiment, pure air pressure was used to apply uniformly distributed lateral pressure. The results show that ultimate capacity of corrugated bulkhead is significantly larger than that of traditional T-shaped stiffened plane bulkhead under the same weight of materials. The corrugated bulkhead reaches the ultimate limit state after three plastic hinges formed on the corrugation, and experimental results agree well with the nonlinear finite element analysis. In addition, through numerical analysis, it is found that the boundary conditions considered in this paper have little effect on the ultimate strength of corrugated bulkheads when in-plane displacements are restrained, and the stress and displacement distributions of the mid-span corrugation are similar with five bays of corrugations and above, and can well reflect the corrugated bulkheads in real ships. The results of this paper are helpful to understand the mechanism of corrugated bulkheads collapse and provide references for ultimate strength experimental designs of corrugated bulkhead structures. • Experiments have been designed and carried out for both corrugated and plane bulkhead structures under lateral pressure, by using the test method of pure air pressure loading without any intermediate medium between the tank and the air. This experimental setup can be further extended to such experiments with combined axial and lateral loads. •Numerical analyses are carried out, and both the ultimate strengths and collapse modes match well with the experiments. Collapse behavior has been carefully discussed based on experimental and numerical results. • The design advantages of the corrugated bulkhead are verified by the comparative experimental and numerical analysis of the corrugated bulkhead and the plane T-shaped stiffened plate bulkhead. • The elastic behavior, inelastic behavior and ultimate limit state of corrugated bulkhead under lateral pressure are obtained by comprehensive experimental test and finite element analysis. Also, it has reference value for the evaluation of the ultimate capacity of the corrugated bulkhead model in the actual ship. • The collapse mode of corrugated bulkheads has similarity with that of fixed/simply supported beams at both ends. It is found that when three plastic hinges are generated in middle and ends of the center corrugation, the corrugated bulkhead has reached ultimate limit state. • The results by NFEM show that the discrepancy on the ultimate pressure of corrugated bulkhead under clamped and simply supported boundary conditions is small only when the in-plane displacement is fully restrained at the boundaries, and the clamped supported boundary conditions have better robustness and matches well with the experimental results. • It is found that when the number of corrugations is small (e.g., three in this study), the distribution of stress and displacements of the central corrugations changes obviously compared with original case, indicating that it is greatly affected by boundary constraints. [ABSTRACT FROM AUTHOR]

Feeding is a crucial issue during the aquaculture process. The feed delivery method determines the efficiency of aquaculture on the one hand and the degree of environmental pollution of the aquaculture process on the other hand. A good fish feed delivery method helps increase fish feeding rate, reduce the waste of fish feed and reduce the pollution of the aquaculture environment, which is beneficial to the sustainable development of aquaculture. This paper establishes a numerical model based on the CFD method. The model uses DPM to simulate the diffusion and distribution behavior of particles in still water condition, current condition and wave-current coupling condition, and design the particle diffusion experiment for validation. However, only through the feed diffusion area and feed leakage situation obtained by numerical calculation cannot accurately analyze and compare the feed diffusion effect. Therefore, this paper proposes a method to quantitatively evaluate the feed diffusion effect and verify its reliability. The quantitative evaluation method is based on the finite element method and the weighted average method, considering the factors affecting the diffusion and distribution of feed and the eating habits of aquaculture fish. The method can comprehensively and intuitively judge the diffusion effect of feed. The quantitative evaluation results can help to select a feed delivery method with better feed diffusion and adjust the feed delivery method correctly when the aquaculture sea condition changes. • The diffusion law of particles under the condition of still water, current and wave-current coupling is described. • The accuracy of the DPM simulation of particle diffusion was verified by comparison with particle diffusion experiments. • The results of quantitative evaluation methods can reliably reflect the diffusion effect of feed inside the cages. • The diffusion effect law of feeds under different sea conditions and different feed delivery methods is described. [ABSTRACT FROM AUTHOR]

Due to the increasing complexity and size of ships, fine mesh finite element analysis (FEA) is no longer practical for large ships' early design phases due to its high computational and time costs. This paper presents an equivalent single plate (ESP) approach for ship stiffened panels with full consideration of compression and bending coupling effect. Based on the force equilibrium and compatibility equations, the area ratio and the moment of inertia ratio of the stiffened panel and the plating in the orthogonal direction are introduced respectively, to achieve the equivalence of in-plane stiffness and out-of-plane stiffness of the stiffened panel. Furthermore, an equivalent single plate can be simplified by coupling the equivalent in-plane stiffness and out-of-plane stiffness. Finite element analysis is carried out for a typical stiffened panel to verify the availability of the ESP approach proposed in this paper, and the results demonstrate that the ESP approach has high prediction accuracy and is suitable for all types of loading cases, including in-plane loads, out-of-plane loads, and coupling loads. Finally, according to a comparative analysis on the application area of the ESP approach, a hybrid simplified model of fine mesh and ESP is proposed, with recommendations given to provide a reference for engineering practice application. [ABSTRACT FROM AUTHOR]

Accurate prediction of structural response under earthquake is of great significance for structural damage and performance evaluation. In order to improve the efficiency of structure time history response prediction, this paper proposes a novel SeisFormer model based on the self-attention mechanism and deep learning technology. Through autoregressive prediction, the SeisFormer can achieve real-time prediction of the response time histories of a large number of nodes in the structure under seismic action and can effectively solve the problem of data scarcity. Four case studies are performed to verify the accuracy and efficiency of the proposed methodology, including validation on datasets obtained from elastoplastic seismic analysis of a single-story structure, a three-story structure, and an eleven-story structure, and measured data of a shaking table test model. In addition, this paper further studies the prediction accuracy of the SeisFormer through ablation experiments and comparative experiments. The experimental results show that the SeisFormer can accurately predict the acceleration, velocity, and displacement time histories of numerous nodes in the structure. The prediction accuracy outperforms the LSTM model, and the prediction speed is 193–109,824 times faster than finite element method. Furthermore, with data augmentation through autoregressive prediction, the SeisFormer model can achieve efficient and accurate predictions when training data is exceptionally scarce, enabling engineering applications. • A self-attention mechanism-based method for real-time refined structural response prediction. • An autoregressive data utilizing strategy. • A new deep learning model called SeisFormer. • The SeisFormer outperforms LSTM in structural response prediction under seismic action. • The SeisFormer predicts structural response 193 to 109,824 times faster than the traditional finite element method. [ABSTRACT FROM AUTHOR]

Parallelogram mechanisms are widely used in microgrippers due to their translational output. However, the parasitic displacement generated by the rotation of the parallelogram mechanism affects the gripping accuracy of the microgripper. Aiming at this problem, a symmetrical parallelogram mechanism with displacement compensation characteristics is proposed in this paper, and it is successfully applied to microgrippers. The piezoelectric actuator is placed outside the amplification mechanism (AM), which solves the parasitic displacement caused by the bending of the bridge-type AM side wall caused by the built-in method. Based on the pseudo-rigid body model (PRBM) method and the flexure beam deformation theory, the performance of the mechanism is calculated. Finite element analysis (FEA) software is used to optimize the structure size and performance analysis of the mechanism. In addition, the experimental model is processed and the experimental platform is built. The experimental results show that compared with similar microgrippers, the microgripper designed in this paper has a higher resonance frequency and lower parasitic displacement, which proves the rationality of the design. [Display omitted] • This paper proposes a symmetrical parallelogram mechanism. • This paper reports a low parasitic displacement microgripper and mechanical modeling. • This article designs a mechanism with high resonance frequency. [ABSTRACT FROM AUTHOR]

In recent years, there has been a notable increase in the utilization of multi-celled corrugated-plate CFST (MC-CFST) walls. In this paper, a connection joint between a steel beam and an MC-CFST wall was proposed. The joint consisted of MC-CFST walls, end columns, horizontal diaphragms, vertical plates, and steel beams, with each steel component being interconnected through welding. To investigate its mechanical properties, a refined finite element model was developed, and the accuracy of the modeling method was validated through existing test results. The stiffness and moment capacity of the joints were analyzed, focusing on the effects of various factors, including the insertion depth of the horizontal diaphragm, beam-to-column linear stiffness ratio, width-to-thickness ratio of the end column plate, diameter of the horizontal diaphragm opening, axial compression ratio, and concrete and steel strengths. Based on numerical and theoretical analyses, a calculation method for determining the moment capacity of the joint and establishing the lower limit value for the steel tube thickness of the end columns was proposed by using the yield line analysis. The predicted value of the moment capacity of the joint was found to deviate from the finite element result by no more than 10%, suggesting that the formula exhibited excellent accuracy and applicability. The minimum steel tube thickness of the end columns was determined by considering the yield of the beam flange section. The design method presented in this paper has the potential to offer a valuable reference for practical designs of the proposed connection joint. • A novel connection joint between a steel beam and a multi-celled corrugated-plate CFST wall was proposed. • A validated FE model was established for further investigation. • A parametric analysis was conducted to investigate the influence on the stiffness of the joints. • The effect of various parameters on the moment capacity of the joints was discussed. • Based on numerical and theoretical analyses, a formula for determining the moment capacity of the joint was proposed. [ABSTRACT FROM AUTHOR]

Stainless steel exhibits strain hardening characteristics under cyclic loading, hence presenting significant potential for application in seismic design. However, the current stainless steel structural design code fails to account for this beneficial effect in the cross-section classification. Given the scarcity of research about the behavior of structural stainless steel members under cyclic stress, this paper establishes the preliminary finite element model for the austenitic stainless steel (EN 1.4301) H-section. Firstly, finite element model validation of the existing cyclic tests on stainless steel members from literature was performed, followed by numerical analyses of a total of 370 beam and beam-columns members with different axial compression ratios and plate width-thickness ratios, and subsequently evaluated the cross-section classifications specified in prEN 1993-1-4, AISC 370 and CECS 410 through extensive parametric studies. The results indicate that the current design codes are conservative in the provisions for cross-section classification because they neglect the influence of plate interactions and material strengthening effects during cyclic loading. In this paper, limit and generalized expressions for austenitic stainless steel H-section with different axial compression ratios and cross-section classes under cyclic loading about major-axis are proposed. Additionally, the effect of material strengthening on cross-section classification under cyclic loading is examined. • Classification criteria for austenitic stainless steel H-section under cyclic loading about major-axis are studies. • Cross-section classification criteria according to EC3, AISC 370 and CECS 410 design codes are evaluated. • A new cross-section classification criterion for H-section under cyclic loading is proposed. • Effect of material strain hardening on cross-section classification under cyclic loading is discussed. [ABSTRACT FROM AUTHOR]

Reported studies on T-head Square-neck One-side Bolts (TSOBs) bolted I-beam to Hollow Section Square Column (HSSC) connections demonstrated the potential of TSOB applications in terms of mechanical properties, installation construction, and cost savings [11–14]. However, existing research was limited to the connection tests and lack a systematic and complete design approach. In this paper, the method for predicting the bending moment capacities and failure modes of the connections was proposed based on the existing test researches. Besides, the Finite Element Model (FEM) of the connections was established and validated by the reported test results. A sensitive analysis on the geometric parameters of the plastic hinge line pattern for calculating the bending moment capacity of the HSSC connecting face was carried out by the validated FEM. The proposed method was compared with the numerical simulation method in terms of the predicted results of the connection structural behavior. The results show that the prediction method proposed in this paper for the connection bending moment capacities and failure modes is accurate and reliable. Moreover, the mixed patterns of Type-H bolt holes and Type-V bolt holes are recommended for the TSOBC design because of the higher bending moment capacity than the unitary bolt hole patterns. • Method for predicting the bending moment capacity of TSOBC was proposed. • Failure mode of TSOBC was predicted based on design information. • Mixed patterns of Type-H and Type-V bolt holes are recommended for TSOBC. [ABSTRACT FROM AUTHOR]

With the development of railway transit networks, the number of twin shield tunnelling undercrossing intercity high-speed railway (HSR) is increasing. However, the understanding of the settlement mechanism of HSR subgrades induced by shield tunnelling undercrossing is still limited. Based on the case of twin tunnels passing through the Xulan HSR in Xi'an, China, a three-dimensional (3D) elaborate finite element model is established in this paper considering HSR subgrades, CFG pile reinforcement area (CFGPRA) and twin shield tunnels. The rationality and validity of the numerical results were verified by comparison with field measurements. The settlement and development process of HSR tracks caused by shield tunnelling were analysed. Additionally, some studies were performed on the internal force of CFG piles before and after tunnelling. The results show that the soil settlement near the tunnel crown in the CFGPRA model was approximately twice that in the greenfield stratum at the same depth. The settlement transfer in the CFGPRA appears in a "linear interval". This suggests that the settlement near the top of the shield tunnel can be directly transferred to the surface in a linear manner. However, the transfer mode of deep strata subsidence to the surface is gradual line development. On this basis, two settlement rate indices (tangent slope and secant slope) were defined to obtain the specific range of the "linear interval", which is 75% of the original pile length. Moreover, based on the mechanical analysis of the CFG piles, the relationship between the effective length of the piles and the linear interval was determined. The results obtained in this paper can provide an important reference for similar projects of shield tunnel undercrossing HSR. [ABSTRACT FROM AUTHOR]

Nuclear graphite commonly serves as the moderator and constructs the coolant flowing channel in liquid fuel molten salt reactors. Under irradiation and high temperature, graphite components will experience obvious deformation due to irradiation creep, thermal expansion, dimensional change, elastic deformation, and thermo-mechanical properties change. The lifespan of graphite components is a limiting parameter of liquid fuel molten salt reactors, determining by the deformation of the graphite components. An improved approach based on the finite element method for graphite deformation analysis was proposed in this paper. Then this method was utilized to analyze a 10-year deformation history of a typical graphite component. The findings show that the stress-strain field of the graphite component significantly varies with the increasing irradiated neutron fluence. The dimensional change plays a primary role in influencing the deformation of the graphite components, determining the overall deformation trend. The irradiation creep plays a secondary role in influencing the deformation, alleviating the deformation of the graphite components to prolong the graphite lifespan. The improved method, which considers various factors like irradiation creep, thermal expansion, dimensional change, and elastic deformation, tends to provide more accurate results compared to the traditional method that focuses solely on the dimensional changes. Over 10 years, the contraction deformation of graphite components results in a reduction in graphite volume of up to 3.87%. The space for graphite contraction is filled with molten salt, resulting in a maximum increase of 22.49% in fuel volume. The alteration in volume of both graphite and fuel leads to a reduction in reactivity of up to 840 pcm. • A computational method for determining the lifespan of LFMSR graphite components using the finite element method and a graphite constitutive model is proposed in this paper. • Dimensional change determines the trend of graphite deformation, while irradiation creep alleviates the deformation. Taking into account related physical characteristics, it is calculated that the lifespan of graphite components is extended. • The deformation of the graphite components results in a change in the volume of the fuel, which can reduce reactivity by up to 984 pcm. [ABSTRACT FROM AUTHOR]

• A new method for locating liver tumors without radiation is proposed. • An improved ICP algorithm is proposed to complete accurate registration of livers. • The deformation model of liver is proposed on the basis of position dynamics. • A 3D non-rigid localization framework for liver tumors is proposed. • The localization accuracy of intraoperative liver tumor is verified by experiment. In this paper, a new localization method of liver tumors based on structured light is proposed to achieve the accurate resection of liver tumors. Firstly, the preoperative liver model and intraoperative liver surface are completed respectively based on CT sections and structured light. Secondly, the 3D reconstruction of liver surface based on structured light is used as the reference surface for registration. A common ICP algorithm and an improved ICP algorithm based on statistics are proposed to complete the rough and fine registration of liver surface. In this paper, the theory of PBD is introduced, and the registration results are used to guide the preoperative deformation of the liver model. Finally, the method of 3D non-rigid localization of liver tumors proposed in this paper is verified by experiments. In addition, the effectiveness of the proposed method is compared with that of the tumor localization obtained by the finite element analysis and Coherent point drift methods. The experimental results show that the average localization error of liver tumor is 1.24 mm. The time spent during the entire process of tumor localization is kept under fifteen seconds. The method presented in this paper meets the needs of surgeons in the intraoperative process. [ABSTRACT FROM AUTHOR]

In this paper, we develop a finite element method (FEM) to solve the Drude metamaterial perfectly matched layer (PML) model by edge elements. Both the stability analysis and error estimate for the scheme are established. To our best knowledge, this is the first paper on developing and analyzing a FEM for this Drude PML model. Numerical results are presented to justify the theoretical error estimate and demonstrate the effectiveness of this PML in absorbing outgoing waves in the Drude metamaterial. [ABSTRACT FROM AUTHOR]

Partial data is a common challenge in many applied problems, where we can measure only the part of the solution. This paper considers the poroelasticity problem in fractured media, where only partial measurements of fracture pressures are available. The poroelasticity models have applications in many engineering and scientific fields, such as geomechanics, hydrology, and reservoir simulation. This paper aims to develop a Bayesian decision making approach using partial data and consider its application to the poroelasticity problem in fractured media. The methodology of the proposed approach combines Proper Orthogonal Decomposition, Discrete Empirical Interpolation Method, Bayesian Inversion Approach, and Bayesian Decision Theory. It allows us to compute posterior probabilities and decide according to the optimal decision rule based on the partial data. Moreover, we apply partially explicit temporal discretization to solve forward problems efficiently. For testing the proposed approach, we consider a two-dimensional model problem. We simulate the cases when we need to make a single decision about the reservoir or decisions about the elements of the set of reservoirs. The results show that the proposed approach can efficiently compute the posterior probabilities and make a decision in the presence of only partial data for both cases. [ABSTRACT FROM AUTHOR]

Abstract: Recently, in the pulp and paper industry, black liquor gasification (BLG) has been of interest as a potential replacement for the Tomlinson recovery boiler. Some commercial-scale BLG units have been developed. However, the full potential of high temperature gasifiers has not been realized because of the refractory failure. Computer simulation of existing materials will accelerate materials research in developing new refractory materials. A model based on continuum damage mechanics is presented to analyze the failure behavior of gasifier refractory lining under high temperature and chemical reactive environments by using the finite element method. This work provides a new methodology for the failure analysis of refractory material and would provide a powerful tool in the development of the high temperature gasifier refractories. [Copyright &y& Elsevier]

This paper develops and investigates a new method for the application of Dirichlet boundary conditions for computational models defined by point clouds. Point cloud models often stem from laser or structured-light scanners which are used to scan existing mechanical structures for which CAD models either do not exist or from which the artifact under investigation deviates in shape or topology. Instead of reconstructing a CAD model from point clouds via surface reconstruction and a subsequent boundary conforming mesh generation, a direct analysis without pre-processing is possible using embedded domain finite element methods. These methods use non-boundary conforming meshes which calls for a weak enforcement of Dirichlet boundary conditions. For point cloud based models, Dirichlet boundary conditions are usually imposed using a diffuse interface approach. This leads to a significant computational overhead due to the necessary computation of domain integrals. Additionally, undesired side effects on the gradients of the solution arise which can only be controlled to some extent. This paper develops a new sharp interface approach for point cloud based models which avoids both issues. The computation of domain integrals is circumvented by an implicit approximation of corresponding Voronoi diagrams of higher order and the resulting sharp approximation avoids the side effects of diffuse approaches. Benchmark examples from the graphics as well as the computational mechanics community are used to verify the algorithm. All algorithms are implemented in the FCMLab framework and provided at https://gitlab.lrz.de/cie%5fsam%5fpublic/fcmlab/. Further, we discuss challenges and limitations of point cloud based analysis w.r.t. application of Dirichlet boundary conditions. [ABSTRACT FROM AUTHOR]

In [13] , we derived stress intensity factors (SIF) extraction formulas of a biharmonic equation Δ 2 u = f in a cracked domain whose crack faces have clamped boundary conditions. In this paper, we extend our investigation to the derivation of the SIF extraction formulas of the biharmonic equation in non-convex polygonal domains containing cracks or reentrant corners when various BC such as clamped (CC), simply supported (SS), free (FF), or mixed conditions (CS, FC, SF) are imposed on the boundary. We prove that the SIF is expressed as the integral of f Ψ s k ⁎ − u Δ 2 Ψ s k ⁎ for a cut-off function Ψ and a dual singular function s k ⁎ on a small neighborhood of the singularity. The dual singular function is determined in this paper. For a numerical approximation of u , we proposed an iteration method as well as a direct finite element method. For a finite element solution of Δ 2 u = f , we have to use C 1 -continuous basis functions. For continuous differentiable basis functions, we use either C 1 -continuous B-spline basis functions or the conventional Hermite basis function. Because of several advantages of B-spline functions in imposing complex boundary conditions, we choose B-spline basis functions for the finite element approximation of u. Moreover, in the direct numerical method, we propose to use implicitly enriched basis functions that resemble the singularities. [ABSTRACT FROM AUTHOR]

Recent work in on-line Statistical Process Control (SPC) of manufactured 3-dimensional (3-D) objects has been proposed based on the estimation of the spectrum of the Laplace-Beltrami (LB) operator, a differential operator that encodes the geometrical features of a manifold and is widely used in Machine Learning (i.e., Manifold Learning). The resulting spectra are an intrinsic geometrical feature of each part, and thus can be compared between parts to assess the state of the manufacturing process while avoiding part to part registration (or "part localization") pre-processing or the need for equal size meshes, characteristics which are required in previous approaches for SPC of 3D parts. The recent spectral SPC methods, however, are limited to monitoring surface data from objects such that the scanned meshes have no boundaries, holes or missing portions. In this paper we extend spectral methods by first considering a more accurate and general estimator of the LB spectrum that is obtained by application of Finite Element Methods (FEM) to the solution of Helmholtz's equation with boundaries. It is shown how the new spectral FEM approach, while it retains the advantages of not requiring part localization/registration or equal size datasets scanned from each part, it provides more accurate spectrum estimates, which results in faster detection of out of control conditions than earlier methods, can be applied to both mesh or volumetric (solid) scans, and furthermore, it is shown how it can be applied to partial scans that result in open meshes (surface or volumetric) with boundaries, increasing the practical applicability of the methods. The present work brings SPC methods closer to contemporary research in Computer Graphics and Manifold Learning. MATLAB code that reproduces the examples of this paper is provided in the supplementary materials. ∙ New Manifold Learning methods for Statistical Process Control of 3D parts given. ∙ Methods based on the Laplace-Beltrami operator in Helmholtz PDE, estimated via FEM. ∙ New methods are ''intrinsic", do not require part localization or registration. ∙ New FEM SPC methods outperform previous SPC methods that require registration. ∙ Can be applied to surface mesh and volumetric mesh (voxel) data, with boundaries. [ABSTRACT FROM AUTHOR]

The geoelectric fields induced during geomagnetic disturbances (GMD) may affect the normal operation of technological systems at the Earth's surface. The non-uniform Earth conductivity structure, especially large lateral conductivity contrasts, can lead to the enhancement of geoelectric fields near boundaries such as a coastline. In this paper, we give an overview of the applicability of a two-dimensional finite element method (2D-FEM) for studying lateral variations of the Earth's conductivity, which can be considered as one of magnetotelluric sounding forward modelling methods, including both the E and the H polarization cases. Then the spatial distribution of the geoelectric field near a continent-ocean boundary is calculated with different models. This is compared with analytic solutions for simple models to verify the accuracy of the FEM modelling, which is calculated by using the ANSOFT software. More realistic scenarios are then developed to emphasize the advantages of FEM. The factors influencing the coast effect are discussed. Results show that frequency, the shape of seafloor boundaries, and the depth of ocean have a significant impact on the geoelectric fields. Therefore, these factors should attract more attention when assessing risk for man-made conducting systems located within the coastal influence range. [ABSTRACT FROM AUTHOR]

Processing waste tires into rubber granules for secondary use can effectively alleviate the problem of environmental pollution. Therefore, this paper prepares foam concrete by replacing cementitious materials with recycled rubber granules to recycle resources. The dry density, water absorption, cubic compression, and prismatic flexure tests are carried out with the foam admixture and rubber substitution rate as the test parameters to study the effects of foam admixture and rubber substitution rate on the performance of foam concrete. Using Monte Carlo method simulation and non-linear fitting, a numerical analysis model was developed to predict recycled rubber foam concrete's mechanical properties. The ABAQUS finite element simulation method was used to explore the changes in the stress–strain relationship and damage development of the recycled rubber foam concrete, combined with microscopic observation, SEM, and XRD tests to reveal the specimens' damage mechanism, microscopic morphology, and physical structure. The experimental results show that the foam admixture has a more significant effect on the specimens' dry density, water absorption, and strength index than the effect of the rubber replacement rate. In addition, the strength prediction model, strength conversion model, and uniaxial compression finite element model of recycled rubber foam concrete were established. [ABSTRACT FROM AUTHOR]

The energy absorption structure of a train is an important part of passive safety protection during train collisions and is the last line of defense to protect both passengers and trains. In the design process of a train energy absorption structure, improved stability and greater energy absorption capacity is required. A cutting anti-climbing energy absorption structure offers good stability and energy absorption in a collision, but it can easily generate considerable heat in the energy absorption process. Therefore, it is important to conduct thermal–solid coupling simulations and crashworthiness optimization for cutting energy absorption structures. To improve the passive safety protection capability of high-speed trains, this paper experimentally and numerically explored the crashworthiness of a cutting-type energy-absorbing structure composed of an anti-creeper device, an energy-absorbing tube, cutting knives and knife-supporting tools. By adopting the Johnson–Cook material model, a finite element model was developed to study its energy absorption characteristics in a coupled heat–solid state. The effects of cutting depth (D), cutting knife front angle (A) and cutting width (W) on energy absorption (EA), cutting platform force (F mean) and peak cutting force (PCF) were analyzed based on the validated simulation model. The results showed that EA , F mean and PCF increase with increasing D and W , while EA , F mean and PCF decrease with increasing A. The GRSM was employed as the optimization algorithm, and a gain matrix–cloud model optimal worst method (G-CBW) multiobjective decision algorithm was proposed to obtain the most satisfactory configurations from the Pareto front solution. The relative errors from the optimal and finite element results of EA , F mean and PCF were 3.5%, 2.1% and 2.2%, respectively. All the crashworthiness indicators were improved considerably. [ABSTRACT FROM AUTHOR]

In this paper, second-order rotational velocity correction (RVC) finite element method is designed for solving the two-dimensional/three-dimensional (2D/3D) incompressible thermally coupled magnetohydrodynamics (MHD) system. This format not only reduces the complexity of solving the model, i.e. the strongly coupled nonlinear saddle-point problem is transformed into a series of small elliptic equations, but also the limitation of artificial Neumann numerical boundary layer of pressure is overcome and the precision of pressure is improved. Then, we use the Gauge-Uzawa formula to convert the rotation term into a telescopic symmetrical form to establish and prove the stability of the second-order RVC algorithm in a linear case. Finally, the numerical results demonstrate the effectiveness and stability of second order rotational velocity corrected projection finite elements in solving the problem. [ABSTRACT FROM AUTHOR]

In this paper, the fully discrete finite element approximation for parabolic optimal control problems with pointwise control constraints is studied. We use standard piecewise linear finite elements for the space discretization of the state, and Crank-Nicolson scheme for time discretization. For control discretization we consider piecewise linear finite elements approximation and variational discretization. We derive a priori error estimates for state, adjoint state and control. Finally, some numerical examples are provided to confirm our theoretical results. • We use the fully discretization based on the Crank-Nicolson time discretization. • We discuss piecewise linear and variational control discretization. • For both cases, it is proved that the error estimates are under the L 2 norm. • We provide three-dimensional examples to verify the theoretical results. [ABSTRACT FROM AUTHOR]

This article presents a detailed study of the non-Newtonian transient Casson fluid flow behavior in three different rectangular domains with their upper and bottom parallel walls moving horizontally either in same direction or in opposite direction to each other. The numerical computations are carried out applying the dynamic subscales approach of the Algebraic Sub-Grid multi-Scale (ASGS) stabilized finite element method upto a sufficiently high Reynolds number, Re =10000. The flow patterns, which include the generation of the primary and secondary vortices, are highly impacted by the Re values, the structures of the domains and the directions in which the parallel walls are moving. We have observed the appearances of both the symmetric and stable as well as unstable asymmetric types of primary vortices in the domains of aspect ratios ≤ 1, with walls moving in the same direction. On the other hand, we notice the existence of multiple phases of the solutions for the Casson fluid flowing in the rectangular domains of aspect ratio > 1, with walls moving in the opposite direction. Besides, the evolution of the solutions with time are also carried out here. In most of the cases, the solutions achieve the steady state after a certain point of time, except for a particular type of domain, where the fluid flow solutions show time dependent behavior after reaching a critical value of Re. This paper has reported the ranges, where the critical Reynolds number (R e c) lies, indicating the appearance of the first Hopf bifurcation for the fluid flow problem. [ABSTRACT FROM AUTHOR]