Numerical Simulation Procedure Research Articles

Multiscale formulation for materials composed by a saturated porous matrix and solid inclusions

Despite all the progress achieved in the characterization of heterogeneous materials by using multiscale paradigms based on the Representative Volume Element concept (RVE), there are still many aspects that demand ongoing development. We mention, for instance, in-homogeneous media with internal micro-structure comprising a mixture of components that require a dissimilar number/character of primary fields to describe their physical behavior. Micro-structures constituted by a saturated porous matrix (described through the pair displacement/pore pressure fields) endowed with impermeable non-porous solid inclusions (described only by the displacement field) are a typical example among many other practical applications. This new level of heterogeneity, between the set of primal descriptors for each micro-scale constituent, claims detailed revisions and novel adjustments in multiscale RVE-based theories.In this work, we present a first-order RVE-based formulation to address with the aforementioned phenomenology at a smaller length scale. At the macro-scale, the well-known poromechanics theory is preserved, where the constitutive response is provided by homogenization of the corresponding micro-scale problem. Two important attributes feature the model: (i) it is encompassed within the general framework posited by the “Method of Multiscale Virtual Power (MMVP)”, this leads to a variationally consistent methodology; (ii) our formulation preserves the objectivity with respect to the RVE-size (an indispensable but uncommon characteristic in RVE-based multiscale approaches for saturated porous media), due to it is based in a recent contribution of the authors (the so-called Selective Order Expansion technique “SOE”).The formulation is implemented following the squared Finite Element (FE2) numerical scheme. The potentialities of the model are demonstrated through a detailed series of numerical examples, including rigorous comparisons against the Direct Numerical Simulation (DNS) procedure.

Development of a Novel Lightweight Utility Pole Using a New Hybrid Reinforced Composite—Part 2: Numerical Simulation and Design Procedure

Development of a Novel Lightweight Utility Pole Using a New Hybrid Reinforced Composite—Part 2: Numerical Simulation and Design Procedure

Experimental and numerical exploration on improved heat transfer by continuous spiral flow in shell of spiral wound corrugated tube heat exchanger

A novel approach to heat exchangers is suggested, featuring a continuous spiral baffle structure in spiral wound corrugated tubes. In this study, an exploration of the flow field and thermal transfer characteristics within the shell pass was conducted via both experimental and numerical simulation procedures. Discoveries indicate that increasing the entry speed on the shell pass results in a drop in fluid temperature, shrinkage of the low-temperature segment, and escalated resistance within the heat exchanger. At the same time, we investigated the corrugated height and pitch and their impact on comprehensive thermal transfer performance Under the same operating conditions, with an increase in the corrugated height H or a decrease in the corrugated pitch P, compared to the continuous spiral wound circular tubes tube heat exchangers, the friction coefficient (f) increases by 15%–55%, the Nusselt number (Nu) of the continuous spiral wound corrugated tubes heat exchangers increases by 10%–40%. The overall heat transfer performance improves by 7%–21%.

Investigation of fracture parameters for a surface-cracked multi-pass T-joint considering welding residual stress

A numerical simulation procedure was carried out to evaluate the fracture parameters for a surface-cracked thick-plate T-joint considering welding residual stress (WRS) effect. Welding calculation was performed to simulate the welded joint then the results were verified against the experiment taken from the literature. The effect of the location of the final weld pass on WRS distribution was also analyzed numerically. Stress analyses were conducted using an intact T-joint model under different mechanical loading patterns, to determine the location of the hot spot stress and thereafter the location of the surface crack. Subsequently, the fracture parameters were thoroughly addressed under different conditions including external loading only and a combination of external loading and WRS. The effect of weld angle on the behavior of fracture parameters was also discussed. The numerical calculations succeeded in explaining the fundamental fracture characteristics of a multi-pass T-joint with a surface crack.

Numerical procedure for accurate simulation of photovoltaic modules performance based on the identification of the single-diode model parameters

The current work proposes a novel method for photovoltaic (PV) modules’ performance estimation at various weather conditions based on the extraction of the single-diode model’s five parameters. The new modeling technique is not built on any approximations or iterative processes, and this makes the approach combining two substantial benefits in the PV simulation field which are the accuracy of prediction and the rapidity of convergence. Moreover, the method is founded on the resolution of matrix equations based on reduced forms, and that assures its simplicity by avoiding tedious calculations. Indeed, only the mean points of the current–voltage characteristic are employed to get the values of the five parameters by calculating two of them using a numerical resolution of a two non-linear equations’ system. Then, the expressions giving the three last parameters are determined as functions of the two first parameters and regrouped in a matrix equation, which is solved analytically to get the values of these remaining parameters. The productiveness of the proposed method is tested using PV modules of various technologies and proved using eight well-known simulating methods for the one-diode model. Furthermore, the root mean squared errors matching the new method have not exceeded 0.093 A and the obtained convergence time is less than 0.27 s. The results attest to the relevance of the new method for dynamic applications and for PV designers requiring simple modeling techniques.

A Numerical Study of Scenarios for the Substitution of Pulverized Coal Injection by Blast Furnace Gas Enriched by Hydrogen and Oxygen Aiming at a Reduction in CO2 Emissions in the Blast Furnace Process

A numerical simulation procedure is proposed for analyzing the partial replacement of pulverized coal injection by hydrogen, oxygen, and blast furnace gas (BFG) injections mixed with pulverized coal (PCI) within the tuyeres of large blast furnaces. The massive use of hydrogen-rich gas is extremely interesting for ironmaking blast furnaces in the context of net-zero carbon hot metal production. Likewise, this new approach allows for increasing productivity and for reducing the specific emissions of carbon dioxide toward a net-zero carbon ironmaking technology. Nevertheless, the mixture of pulverized coal injection and gas injection is a complex technology. In addition to the impact on chemical reactions and energy exchange, the internal temperature and gas flow patterns can also change drastically. With a view to assessing the state of the furnace in this complex operation, a comprehensive mathematical model utilizing multiphase theory was developed. The model simultaneously handles bulk solids (sinter, pellets, small coke, granular coke, and also iron ore), gas, liquid metal and slag, and coal powder phases. The associated conservation equations take into account momentum, mass, chemical species, and energy while being discretized and solved using finite volume techniques. The numerical model was validated against the reference operating conditions using 220 kg per ton of pig iron (kg/tHM) of pulverized coal. Therefore, the combined injection of different concentrations of fuel hydrogen, blast furnace gas, and oxygen was simulated for replacing 40, 60, and 80 kg/tHM of coal injection. Theoretical analysis showed that the best scenario with stable operation conditions could be achieved with a productivity increase of 20% corresponding to a CO2 reduction of 15% and 60 kg/tHM of PCI replacement.

A Review on Solar Chimneys: From Natural Convection Fundamentals to Thermohydraulic Best-Performance Proposals

This work presents an overview of (passive) solar chimney research, from the natural convection fundamentals to the recent progress for achieving thermohydraulic best-performance. Solar chimneys are attractive because they contribute to increasing the efficiency in air conditioning processes for dwellings and buildings, and therefore also aid to reduction in greenhouse gas emissions. A wide number of works dealing with solar chimneys (and Trombe walls or similar) shape designs, as well as with the inclusion of obstacles for disturbing the airflow, is commented in detail. Several numerical simulation procedures used in the literature are specially discussed, and different recommendations are pointed out to be considered for the appropriate numerical simulation of the operating modes of a solar chimney. Investigations aiming for the best performance conditions (for both thermal, and dynamic or ventilation modes) deserve special attention.

A numerical simulation procedure for evaluating the accuracy of 3-dimensional photogrammetric models and its application to geometric parameters of discontinuities in rock masses

This study proposes a numerical simulation procedure to evaluate the accuracy of geometric parameters of 3-dimensional models reconstructed by photogrammetry based on the Open Graphics Library. As a technical mean to obtain photogrammetric photos and data, this method has achieved the goal of controlling the parameters in the photogrammetric process at will. The proposed method is validated by several physical model experiments using the unmanned aerial vehicle Phantom 4 Real-time kinematic (RTK). Through a series of numerical experiments, this study quantitatively analyzes the error of geometric parameters of discontinuities in rock masses caused by coordinate accuracy of camera positions and shooting distance, and some quantitative findings were obtained. These results conforming to common sense also validate the proposed simulation procedure. This numerical simulation procedure has a broad application prospect in guiding and optimization of photo acquisition of field outcrop balancing the accuracy and efficiency.

Identification of temperature-dependent elastic and damping parameters of carbon–epoxy composite plates based on experimental modal data

High-strength composite materials are receiving increased attention within the aerospace and transportation industries. These materials, although light in weight, still impart high stiffness when compared to conventional structural materials, e.g., aluminum and steel. Fibers and matrix are the basic constituents of composite materials. During high-speed maneuvering of aircraft and high-speed trains, the composite materials are subjected to dynamic loads in changing temperatures. The dynamic behavior of composites strongly depends on the ambient thermal environment. Furthermore, during the in-situ operation, the quantification of real-time dynamic loads is a challenging task. Therefore, the experimental investigation of the dynamic behavior of several carbon-fiber epoxy laminated composite plates at different temperatures, namely 0°C, 25°C, 50°C, 75°C, 100°C, and 125°C, is carried out using operational modal analysis, to identify the modal characteristics of the structure, and the temperature-dependent modal data of the tested composite plates is given in the supplementary data. The temperature-dependent elastic and damping parameters of the carbon–epoxy laminate are estimated using a genetic algorithm-based parameter identification scheme for different sets of modal contribution. A combined experimental and numerical simulation procedure is implemented to estimate deterministic material parameters at different temperatures. To obtain the in-situ material parameters for a given operating frequency range, the modal contribution is selected such that the operating frequency of interest lies within the considered resonance modes. As an example of matrix-dominated elastic parameter, the shear modulus, has been found to degrade significantly with increasing temperature, and shown a strong correlation with temperature.

Validation of models used to predict the effects of lateral spreading by comparison of experimental and numerical response surfaces

Following the LEAP-UCD-2017 and LEAP-ASIA-2019 exercises, an immense database of dynamic centrifuge data has been established for the purpose of validating numerical models that predict lateral spreading due to liquefaction. Using the experimental database and regression analyses, researchers have mapped a response surface to elucidate the relationship between soil density and shaking intensity to expected residual slope displacement. While it may not be practical to develop a database of experiments for every liquefaction scenario, the LEAP response surface may be conveniently used by others to assess that their numerical simulation procedures produce reasonable predictions for lateral spreading problems. To illustrate the value of response surfaces during the validation of numerical models, we developed a numerical response surface using the PDMY02 model implemented in the OpenSees finite element framework as an example test case. The methodology used to establish five PDMY02 constitutive model calibrations and the procedures to develop the numerical model are presented. One of the most important components of the calibration procedure, the attempted matching of the liquefaction triggering curves, is discussed in detail. Two input motions were considered for this work; one was a clean 1 Hz tapered sine wave, and the other included a 3 Hz component superimposed on the 1 Hz tapered sine wave. A numerical response surface was mapped for each input motion using the calibrations representing three relative density states. The greater transparency allows for comparisons between the numerical and experimental surfaces that illustrate the capabilities and limitations of numerical procedures, and therefore, this exercise should be integrated into future efforts to validate numerical models.

Direct FE numerical simulation for dynamic instability of frame structures

Dynamic instability analysis of structures has been a critical issue in the application of engineering and mechanical designs. Can we directly simulate the dynamic stability of structures like buckling analysis in finite element software? To address this question, in this study, we explore the dynamic instability of frame structures, discretized into finite element structures, through developing a direct FE numerical simulation procedure. Benefiting from the advances of eigenvalue analysis of partial differential equations and finite element technology, a direct numerical simulation procedure is developed by using Floquet theorem, harmonic balance methods and finite element method. Dynamic instability characteristics of frame structures, concerning fundamental vibration, multi-mode coupling vibration and flexural-torsional vibration deformation due to their spatial characteristics, are thoroughly investigated. The results reveal that, the developed procedure can achieve dynamic stability analysis of damped and non-damped structures. Frame's flexural-torsional vibration deformation can significantly enlarge the size and instability intensity of unstable regions, threatening dynamic stability of frame structures. Moreover, damping ratio has a slight impact on instability mitigation of the frame induced by flexural-torsional vibration. Unstable regions of mode-coupling vibration of frame have a hidden attribute. No existing approximate formula can be available to estimate instability regions of frame's flexural-torsional vibration and mode-coupling vibration. The dynamic instability index presented here can characterize unstable regions intuitively. The proposed insights can provide design guidelines for frame structures, the developed direct FE simulation procedure may be insightful for extending to explore instability mechanisms of generalized structures with complex forms owing to parametric resonance.

Accuracy comparison of rock discontinuity geometric parameters in photogrammetry based on two georeferencing methods: Control points and geotagged photos

During the reconstruction of the digital outcrop models (DOM) by photogrammetry, the geodetic coordinate systems of the models can be calibrated through the camera positions or the control points. This paper developed a procedure for constructing virtual digital outcrop model (VDOM) and proposed a numerical simulation procedure of photogrammetry to compare the measurement accuracy of the mentioned-above two methods. A physical model test indicated the validation of the proposed procedure. In addition, many numerical experiments about the accuracy of the camera positions and the control points are designed. The experiment results show that when the control points are used to georeference the DOMs, it is recommended to measure the coordinates of the control points by the device with high positioning accuracy, such as the total station or RTK equipment. If the device with high positioning accuracy is unavailable, better measurement accuracy can be obtained using the camera positions.

Entropy Flow Analysis of Thermal Transmission Process in Integrated Energy System Part I: Theoretical Approach Study

It is very important to accurately describe the dynamic processes of thermal energy transmission for coupling with Integrated Energy System (IES). In order to study the thermodynamic characteristics of heat supply, this paper theoretically suggested a generalized model of entropy flow by deducing the expression of entropy conduction and convection based on thermodynamic law and heat transfer analysis. Taking temperature and entropy as the intensity and extension properties, the equivalent distributed and lumped parameter models are established to describe the features of heat loss and transmission delay. The effectiveness of current models is verified by comparing with solutions of conventional Partial Differential Equations (PDE) of heat transfer. The numerical simulation and verification procedure were conducted by Matlab/simulink. The proposed models were applied to simulate the response of temperature and entropy flow of a pipe with length of 100 m under different discrete conditions. The results show that for a distributed parameter model the maximum relative error is 1.275% when the pipe is divided into 100 sections, and for a lumped parameter model, the overall relative error is in the order of 10−3, which can be ignored in practical applications. All these prove the correctness of proposed models in this paper.

Study on the coupled dynamics of rigid-liquid-flexible spacecraft by using isogeometric analysis for liquid sloshing

This paper focuses on the dynamics of a spacecraft coupled with propellant sloshing and flexible appendage vibration, which may lead to the inaccuracy and instability of the attitude control of spacecraft. The propellant sloshing is modeled and simulated by isogeometric analysis, combined with the level set method used for free surface tracking. A semi-slip boundary condition is proposed specifically for the numerical simulation procedure of liquid sloshing in a cylindrical tank. Based on the unique spatial mapping of isogeometric analysis, a method for evolving the level set function in the parameter domain of isogeometric analysis is presented. The vibration of a flexible solar panel is modeled based on the Kirchhoff–Love plate theory and the modal analysis method. The rigid-liquid-flexible coupled system of the spacecraft is divided into three modules coupled through interaction forces and torques. The effectiveness of the proposed modeling method for the rigid-liquid-flexible coupled spacecraft is verified by comparing with published experimental and analytical results. The simulation results show that due to the coupling effect, the small-amplitude liquid sloshing will cause a larger vibration of the flexible appendage, thus affecting the stability of spacecraft motion.

Bendability assessment of high strength aluminum alloy sheets via V-die air bending method

The bendability of high-strength aluminum alloy (AA) sheets for two different thicknesses was experimentally evaluated by the V-die air bending method and the numerical simulation procedure was attempted to comprehend the characteristics of the V-die air bending method. Despite similar bendability along the material direction for a given punch radius in the experiment, the distinguished fracture strains were predicted for each direction based on the punch force and displacement information. For the numerical simulation, V-die air bending was modeled with the full 3D non-quadratic anisotropic yield criterion and compared with the results of the isotropic yield function estimating that bendability along the rolling direction is higher than those along the transverse direction. The thinner material showed higher anisotropy in bendability and the characteristics of V-die air bending were also discussed suggesting a maximum value as an upper bound of the bendability. As a comparison, an anisotropic analytical formulation was also newly developed combined with the kinematic assumption and the limitation was also covered in the study. The analytical fracture strain was discussed as the equivalence to the maximum value suggested in the research.

Error Analysis in Numerical Simulation of the Static Pressure Capability of Magnetic Fluid Seals

Magnetic fluid is a typical type of functional fluid which can be magnetized and controlled by an external magnetic field. In magnetic fluid seals, magnetic fluid is attracted in sealing gaps by a magnetic field gradient to form non-contact sealing. Compared to traditional sealing methods, they possess unique advantages such as zero leakage, long lifetime, low friction torque, and high reliability. Although the design and performance estimation of magnetic fluid seals rely mostly on numerical simulation, a number of simplifications or even mistakes during the simulation process exist in previous studies. The error caused by simplifications and mistakes has not been studied, leading to a possible problem of simulation results in reliability and consistency with experimental data. Here, we examined the influence of common simplifications and mistakes in numerical simulation of the static pressure capability of magnetic fluid seals, including material properties, geometric modeling, and theoretical formulas. A novel method of structure optimization based on a derivative-free multiparameter algorithm is also presented. A test bench for magnetic fluid seals is established, and the difference between simulation and experimental results is discussed. This research provides a precise, efficient, and standard procedure for numerical simulation of magnetic fluid seals.

Numerical Simulation and Experimental Measurement of Residual Stresses in a Thick-Walled Buried-Arc Welded Pipe Structure

In this study, a numerical simulation of a single pass welding of two thick-walled pipes with the buried-arc method was performed in order to determine the residual stresses caused by welding. The numerical simulation procedure in the thermal analysis was performed by the element birth and death method while the structural analysis was performed simultaneously, without the application of the element birth and death technique in order to reduce the duration of the numerical simulation. The simulation results were validated by experimental residual stress measurements on the outside surfaces of the welded model using the X-ray diffraction technique. A good agreement between the results of the numerical simulation and experimental measurements was confirmed.

Crack Growth Propagation Prediction in Non-Proportional Mixed-Mode Missions

The present paper focuses on the prediction of cyclic crack propagation due to missions with varying mixed-mode loading conditions. Overall, 18 different loading conditions are simulated and the numerical results are compared with the corresponding experimental results. The deflection angle prediction in correspondence of the complete mission is based on the Maximum Tensile Stress (MTS) criterion, coupled with the dominant step approach. The entire numerical simulation procedure relies on the algorithms implemented in the commercial FRacture ANalysis Code 3D, FRANC3D, and ABAQUS software. Numerical and experimental fracture surfaces, in correspondence of tension-torsion tests with and without phase shift, are compared by using an MTU in house tool, CT3D_Validator, with the aim to assess the accuracy of the numerical simulation procedure in determining the crack propagation direction.

Decoupling mechanisms of “avalanche” phenomenon for laser ablation of C/SiC composites in hypersonic airflow environment

When C/SiC composites subjected to high-power laser irradiation under hypersonic airflow environment, “avalanche” phenomenon was found, i.e., the ablation rate was significantly higher than that under static air environment. To reveal this phenomenon, parallel experiments of laser ablation under static air, short-time and long-time hypersonic airflow environments were carried out. Ablation models including oxidation, sublimation and erosion considering coupling effects of airflow and C/SiC composites were introduced, and a coupled fluid-thermal-ablation numerical simulation procedure was proposed and carried out. The relationship between ablation rates and aerodynamic pressure was discussed, and the contributions of different ablation mechanisms were quantitively evaluated. In hypersonic airflow environments, sublimation rate was increased due to the decreased local pressure, and erosion rate was accelerated as a result of increased pressure head at downstream area. The combined effect of augmented sublimation and accelerated erosion accounted for the main reason of “avalanche” phenomenon under hypersonic airflow.

An overview on flooding induced uplift for abandoned coal mines

Flooding induced uplift for abandoned coal mines is monitored mainly by satellite data and geodetic levelling. Predictions are based on empirical formulas, but nowadays numerical simulation procedures provide an interesting alternative, because it is physically based and allows to consider complex mining, geological and hydrological conditions. According to the key driving mechanisms, the uplift process can be classified as either confined/unconfined (in respect to the mine water), isolated/connected (in respect to ponds) and with/without faults (in respect to the tectonic situation). The paper summarizes the state-of-the-art of monitoring and prediction of flooding induced uplift of abandoned coal mines. A workflow for using numerical simulations as tools for prediction of flooding induced uplift is proposed.