Numerical Analysis Methodology Research Articles

Optimisation of solar-hydrogen power system for household applications

A numerical method was developed for optimising solar–hydrogen energy system to supply renewable energy for typical household connected with the grid. The considered case study involved household located in Diyala Governorate, Iraq. The solar–hydrogen energy system was designed to meet the desired electrical load and increase the renewable energy fraction using optimum fuel cell capacity. The simulation process was conducted by MATLAB based on the experimental data for electrical load, solar radiation and ambient temperature at a 1-min time-step resolution. Results demonstrated that the optimum fuel cell capacity was approximately 2.25 kW at 1.8 kW photovoltaic power system based on the average of the daily energy consumption of 6.8 kWh. The yearly renewable energy fraction increased from 31.82% to 95.82% due to the integration of the photovoltaic system with a 2.25 kW fuel cell used as a robust energy storage unit. In addition, the energy supply, which is the economic aspect for the optimum system, levelised electricity cost by approximately $0.195/kWh. The obtained results showed that the proposed numerical analysis methodology offers a distinctive property that can be used effectively to optimise hybrid renewable energy systems.

Numerical modeling of confined brick masonry structures with parametric analysis and energy absorption calculation

The objective of this paper is to propose a new modeling methodology for numerical analysis of full-scale confined brick masonry structures. Two modeling strategies are used within a single structure, where the in-plane walls are modeled using “simplified micro-modeling” approach and out-of-plane walls are modeled using “macro-modeling” approach. The lateral load capacity is associated with the in-plane shear resistance of masonry elements, therefore more detailed analysis is required for in-plane walls to achieve a comprehensive understanding of the damage mechanism and load transfer. The investigation of the in-plane shear behavior of confined brick masonry structures is of significant importance. Additionally, the proposed hybrid model is validated by comparing the results of experimental studies of confined brick masonry structure. A parametric study is then conducted to investigate the effect of brick and mortar properties on the structural response metrics (e.g. base shear coefficient, effective stiffness, response modification factor, the three performance levels (i.e. Immediate Occupancy, Life Safety and Collapse Prevention limits) and the energy absorption properties). It is observed that these structural response metrics, changed considerably by varying the material properties. Apart from that, the damage behavior and damage pattern are also assessed for the better understanding of effect of these parameters on the response of the structure. The proposed hybrid-modeling approach gives sufficient accuracy in predicting the lateral load behavior as well as the damage mechanism of confined brick masonry structure, subjected to lateral loading.

A Numerical Pinch Analysis Methodology for Optimal Sizing of a Centralized Trigeneration System with Variable Energy Demands

The energy and power sectors are critical sectors, especially as energy demands rise every year. Increasing energy demand will lead to an increase in fuel consumption and CO2 emissions. Improving the thermal efficiency of conventional power systems is one way to reduce fuel consumption and carbon emissions. The previous study has developed a new methodology called Trigeneration System Cascade Analysis (TriGenSCA) to optimise the sizing of power, heating, and cooling in a trigeneration system for a Total Site system. However, the method only considered a single period on heating and cooling demands. In industrial applications, there are also batches, apart from continuous plants. The multi-period is added in the analysis to meet the time constraints in batch plants. This paper proposes the development of an optimal trigeneration system based on the Pinch Analysis (PA) methodology by minimizing cooling, heating, and power requirements, taking into account energy variations in the total site energy system. The procedure involves seven steps, which include data extraction, identification of time slices, Problem Table Algorithm, Multiple Utility Problem Table Algorithm, Total Site Problem Table Algorithm, TriGenSCA, and Trigeneration Storage Cascade Table (TriGenSCT). An illustrative case study is constructed by considering the trigeneration Pressurized Water Reactor Nuclear Power Plant (PWR NPP) and four industrial plants in a Total Site system. Based on the case study, the base fuel of the trigeneration PWR NPP requires 14 t of Uranium-235 to an average demand load of 93 GWh/d. The results of trigeneration PWR NPP with and without the integration of the Total Site system is compared and proven that trigeneration PWR NPP with integration is a suitable technology that can save up to 0.2% of the equivalent annual cost and 1.4% of energy compared to trigeneration PWR NPP without integration.

ERTMS/ETCS Virtual Coupling: Proof of Concept and Numerical Analysis

Railway infrastructure operators need to push their network capacity up to their limits in high-traffic corridors. Virtual coupling is considered among the most relevant innovations to be studied within the European Horizon 2020 Shift2Rail Joint Undertaking as it can drastically reduce headways and thus increase the line capacity by allowing to dynamically connect two or more trains in a single convoy. This paper provides a proof of concept of Virtual coupling by introducing a specific operating mode within the European rail traffic management system/European train control system (ERTMS/ETCS) standard specification, and by defining a coupling control algorithm accounting for time-varying delays affecting the communication links. To that aim, we define one ploy to enrich the ERTMS/ETCS with Virtual coupling without changing its working principles and we borrow a numerical analysis methodology used to study platooning in the automotive field. The numerical analysis is also provided to support the proof of concept with quantitative results in a case-study simulation scenario.

An Overview: Different Manufacturing Techniques used for Fabricating Functionally Graded Material

Abstract The industrial applications of functionally graded material (FGM) have increased with its specific capability. This makes curiosity among the researchers how to optimize the design and manufacturing technique as well as the numerical analysis methodology in the priority basis. Contrast to composite material, the properties of the FG material can be varied through the dimension. Usually, the properties are varied along the thickness direction by power distribution formula. However, it is possible to vary the properties of FG material along longitudinal and transverse direction with better improvised technique. Present study is an overview of FGM modelling, design and various manufacturing techniques used by past researchers as well as achieved current stage industrial applications. Further, this study can show a road map to current authors for improvising fabrication techniques in their research on FGM.

Fatigue damage on CFRP plates under bending by thermographic and UT analysis, aided with FEM-DIC prediction

In this article, a combination of numerical and experimental methodology for delamination evolution analysis on unidirectional CFRP elements under fatigue is suggested. Fiber-reinforced composite structures exhibit continuous damage accumulation with degradation of effective mechanical properties during cyclic HCF loads. Since advanced composites applications are allowed after extensive experimental certification tests, proposed work is based on experimental procedures to better detect and predict damage initiation and growth, monitoring static displacements and strains under 4-points bending by digital image correlation and measuring compliance variation under fatigue. In addition, non-destructive investigation of composite plates is conducted during cycling tests by using infrared thermography and ultrasonic measurements to detect damage location and validate FEM predictions. Experimental results are analyzed and compared, employing also digital image correlation technique; in addition, thermographic and ultrasonic monitoring inspection with Matlab elaborated measurements are implemented to check results for fatigue damage analysis of same specimens.

Numerical analysis and structural intervention methodology for a wood floor of a medieval building

PurposeThe case-study building of this work is the Medieval Inn of Gralheira (“Pousada Medieval da Gralheira”) located in Vila Pouca de Aguiar, Portugal. This building is an example of the structures of that time, located in Trás-os-Montes, Portugal. A large amount of the built heritage suffers from advanced degradation, making the recovery, increasing the complexity of the rehabilitation and restoration intervention and implying a highly specialized interdisciplinary component. Therefore, the purpose of this paper is to carry out a study of the building in order to perform an analysis of its wood floor and assess its structural behaviour and conservation status. This work also presents some examples of intervention methods and rehabilitation techniques used to solve problems in the masonry structure and wood structures.Design/methodology/approachIn this work, a numerical model of a wood pavement of a medieval building is presented, which was developed and calibrated with values obtained in an experimental campaign of wood specimens extracted from the floor structure and the deformation measured in situ. This model aims to analyse and predict the behaviour of the structure in terms of serviceability limit states. Rehabilitation and reinforcing techniques are described, for specific damages, complemented with a critical comparative analysis to define the most appropriate rehabilitation measures for each situation.FindingsIn this work, for the numerical model of the medieval building under consideration, the support of the beams in the walls between 50 per cent embedded and simply supported (hinge supports) was used. Since the beams have some restriction imposed by the wall, they have a delivery about 20 cm in the wall. The consideration of the delivery between beam and columns as simply supported (hinge supports) is a reasonable approximation. There is a difference between the values of deformation obtained in the numerical model and in situ due to the support conditions and also due to the consideration of the pavement loads as a distributed load, which does not correspond entirely to reality, since the pavement confers rigidity to the floor, behaving like a diaphragm. The presented intervention techniques are not applicable in all structures because each building has different characteristics, in terms of materials and construction. The pathologies occur due to many sources and each case is unique, and must be carefully studied before taking decisions about the rehabilitation methods to use.Originality/valueThis work presents a numerical model of wood pavement of a medieval building developed according to some experimental values obtained in an experimental campaign using wood specimens extracted from original beams and based on in situ measurements. This study is part of master thesis of Michael Andrade, an original research work.

Numerical methodology for fluid-structure interaction analysis of nuclear fuel plates under axial flow conditions

Shell-type fuel elements are widely used in nuclear research reactors. The nuclear fuel is contained in parallel shells, flat or curved, that are separated by narrow channels through which the fluid flows to remove the heat generated by fission reactions. A major problem of this fuel assembly design is the hydraulic instability of the shells caused by the high flow velocities. The objective of the study presented here is the development of a fluid-structure interaction methodology to investigate numerically the onset of hydroelastic instability of flat-shell-type fuel elements, also known as plate-type fuel assemblies, under axial flow conditions. The system analyzed consists of two nuclear fuel plates bounded by three-equal coolant channels. It is developed using the commercial codes ANSYS CFX for modeling the fluid flow and ANSYS Mechanical to model the plates. The fluid-structure interaction methodology predicts a behavior consistent with other theoretical and experimental works. Particularly, the maximum deflection of the plates is detected at the leading edge and it is a linear function of the square of the fluid velocity up to the Miller’s theoretical value. For velocities above this value, a nonlinear relationship is observed. This relationship indicates that structural changes are taking place in the plates. Furthermore, for fluid velocities greater than the Miller’s velocity, an extra deflection peak is observed near the trailing edge of the plates. Thus, structural alterations also happen along the length of the flat-shells.

МЕТОДИКА ЧИСЛЕННОГО ИССЛЕДОВАНИЯ ДИНАМИЧЕСКОЙ ПРОЧНОСТИ КИРПИЧНОЙ КЛАДКИ С УЧЕТОМ ФРАГМЕНТАЦИИ

A methodology for numerically analyzing a 3D problem of nonstationary deformation and damage accumulation in brickwork is presented. The defining equation set is formulated in Lagrange variables. The equation of motion is derived from the balance of virtual work power. Kinematic relations are determined in the metrics of the current state. Brickwork is modeled as a continual hetero-modular medium, the properties of which depend on the stressed-strained state type and the current level of damage of the material. To analyze fragmentation of the brickwork, a simplified model is used, accounting for deformability of the seams, tensile and shear strengths of the brick 108 and mortar, as well as the contact interaction of the brickwork fragments. The problem is analyzed using the moment scheme of the finite-element method and the “cross”-type explicit finite-difference time integration scheme. The discretization of the computational area is based on eight-node finite elements with poly-linear approximation of displacement velocity. The finite element methodology is verified by analyzing the problem of deformation and failure of a brickwork block under explosive loading. The results of the numerical analysis of the problem are compared with experimental data for the failure form of the brickwork and the displacement of its center. Good agreement with the experimental data corroborates the reliability of the computations and effectiveness of the developed numerical analysis methodology. Keywords: brickwork, dynamic effect, damage accumulation, fragmentation, finite-element method.

Numerical methodology for analyses of tubular KK multiplanar steel joints

Abstract Herein is presented a numerical methodology for a static resistance analysis of symmetrically loaded multiplanar KK joints in circular hollow steel sections. This methodology addresses factors related to the simulation of KK joints such as the material properties, the boundary conditions, mesh generation and refinement, incremental load steps and failure criteria. An objective criterion is proposed to identify the two failure modes most often occurring in KK joints. Failure mode 1 is observed when two neighboring diagonal braces loaded in the same sense act as one brace penetrating the chord together. In the failure mode 2, excessive deformation is observed in the chord region between two neighboring braces, folding the chord wall. However, in some cases the failure mode is not easily identified or both failure types are present. The proposed criterion objectively identifies the failure mode. In order to compute the joint resistance, an important failure criterion often adopted in literature for uniplanar K joints is the one known as Lu's deformation. In this paper, a strategy is proposed, which is an extension of Lu's criterion for multiplanar KK joints.

Numerical analysis of crimping and inflation process of balloon-expandable coronary stent using implicit solution.

The paper presents an applied methodology for numerical finite element analysis of coronary stent crimping and the free inflation process with the use of a folded noncompliant angioplasty balloon. The use of an implicit scheme is considered as the most original part of the work, as an explicit finite element procedure is very often preferred. Hitherto, when the implicit solution was used for the finite element solution, the simulated issue was largely simplified. Therefore, the authors focused on the modelling methodology with minimum possible simplification, ie, a full load path (compression and inflation in single analysis), solid element discretization, and sophisticated contact models (bodies with highly different stiffness). The obtained results are partially compared with experimental data (radial force during the crimping procedure) and present satisfactory compliance. The authors believe that presented methodology allow for significant improvement of the obtained results, as well as potential extension of the research scope, compared to previous efforts performed using the explicit integration scheme. Moreover, the presented methodology is believed to be suitable for sensitivity and optimization studies.

Numerical methodology for dynamic analysis of buildings with friction dampers

A number of studies on using friction based energy dissipation system for seismic protection of the building have been published in the recent past. The studies show that numerical approximation of the effectiveness of the friction based energy dissipation system depends on the accurate solution of the relevant nonlinear equations of motion. The available numerical models to idealize the behaviour of friction dampers can be categorized into equivalent linearization method, approximation by rigid-perfectly plastic hysteric model and stick-slide condition model. However, it has been observed that the minimum difference in relative velocity or non-identification of exact time of phase transition from stick to slide condition results in a noticeably high fluctuation of relative velocity in the stick-slide model. To identify the exact time for phase transition, this paper presents a numerical methodology for dynamic analysis of buildings with friction damper, leading to improved accuracy of solutions of equations of motion. The mathematical formulation and solution procedure of the proposed methodology has been presented in detail in this paper. The results obtained have been validated with examples from published literature. The response of single degree of freedom (SDOF) system with friction device when subjected to nine different ground motions are presented. The selected ground motion encompasses three ground motions each from soft soil, medium soil and hard soil to evaluate the likely response of the structure under the likely range of expected ground motion characteristics. The spectral variation with reference to pretension force has been investigated and presented. The results indicate that for a particular range of pretension force, beyond a particular stiffness ratio, the reduction in spectral response of the damper added system is independent of frequency of the SDOF system, which shows the robustness of friction devices.

Numerical study of effect of wall parameters on catalytic combustion characteristics of CH4/air in a heat recirculation micro-combustor

Premixed combustion of methane/air mixture in heat recuperation micro-combustors made of different materials (corundum, quartz glass, copper and ferrochrome) was investigated. The effects of wall parameters on the combustion characters of a CH4/air mixture under Rhodium catalyst as well as the influence of wall materials and convection heat transfer coefficients on the stable combustion limit, temperature field, and free radicals was explored using numerical analysis methodology. The results show that with a decrease of thermal conductivity of wall materials, the temperature of the reaction region increases and hot spots becomes more obvious. The combustor with copper baffles has uniform temperature distribution and best preheating effectiveness, but when inlet velocity is too small, the maximum temperature in the combustor with copper or ferrochrome baffles is well beyond the melting point of the materials. With an increase in thermal conductivity, the preheat zone for premixed gas increases, but the influence of thermal conductivity on OH(s) coverage is negligible. With an increase of the wall convection heat transfer coefficient, the methane conversion rate firstly increases, then decreases reaching a maximum value at h=8.5W/m2K, however, the average temperature of both the axis and exterior surface of the combustor decrease.

Spectroscopic and Chemometric Analysis of Binary and Ternary Edible Oil Mixtures: Qualitative and Quantitative Study.

The aim of this study was to investigate the feasibility of FTIR-ATR spectroscopy coupled with the multivariate numerical methodology for qualitative and quantitative analysis of binary and ternary edible oil mixtures. Four pure oils (extra virgin olive oil, high oleic sunflower oil, rapeseed oil, and sunflower oil), as well as their 54 binary and 108 ternary mixtures, were analyzed using FTIR-ATR spectroscopy in combination with principal component and discriminant analysis, partial least-squares, and principal component regression. It was found that the composition of all 166 samples can be excellently represented using only the first three principal components describing 98.29% of total variance in the selected spectral range (3035-2989, 1170-1140, 1120-1100, 1093-1047, and 930-890 cm(-1)). Factor scores in 3D space spanned by these three principal components form a tetrahedral-like arrangement: pure oils being at the vertices, binary mixtures at the edges, and ternary mixtures on the faces of a tetrahedron. To confirm the validity of results, we applied several cross-validation methods. Quantitative analysis was performed by minimization of root-mean-square error of cross-validation values regarding the spectral range, derivative order, and choice of method (partial least-squares or principal component regression), which resulted in excellent predictions for test sets (R(2) > 0.99 in all cases). Additionally, experimentally more demanding gas chromatography analysis of fatty acid content was carried out for all specimens, confirming the results obtained by FTIR-ATR coupled with principal component analysis. However, FTIR-ATR provided a considerably better model for prediction of mixture composition than gas chromatography, especially for high oleic sunflower oil.

Numerical analysis of stent expansion process in coronary artery stenosis with the use of non-compliant balloon

In the paper the authors present an applied methodology, data and numerical results for numerical analysis of the stent crimping process and stent implantation in the coronary artery stenosis with the use of a non-compliant angioplasty balloon. The authors focused on the modeling methodology of balloon angioplasty with minimum possible simplification, i.e.: a full load path (compression and inflation in single analysis), 3D unsymmetrical geometry and discretization, highly nonlinear material models (hyperelasticity, plastic kinematic formulation, crushable foam) and sophisticated contact models (bodies with highly different stiffness). The use of a highly compressible crushable foam material model for an arterial plaque is considered as the most original part of the work. The presented results allow for better understanding of the mechanisms governing stent crimping and implementation.

Integrated numerical and experimental methodology for thermal-energy analysis and optimization of heritage museum buildings

Research effort was dedicated to the analysis of museums microclimate for the preservation of artifacts and indoor environment. In this paper, continuous monitoring and dynamic simulation of an ancient exhibition site are carried out to evaluate indoor microclimate and energy performance. The aim is to develop a multidisciplinary methodology for preserving artworks and historic buildings in the view of sustainability and comfort. The paper also shows how the environmental conditions of two thermal zones different for geometry, occupancy, ventilation rate, and heating, ventilation, and air conditioning (HVAC) systems are far from the values suggested by the regulations for the preservation of artifacts and from human comfortable set points of temperature and relative humidity. This work highlights the need for further investigation of historical exposition sites to reduce artworks' damaging and occupants' environmental stress. Practical application: Many historical buildings in European countries host exhibition sites. Indoor microclimate of such areas is often inappropriate for visitors' comfort, for artworks', and building preservation. In fact, usually HVAC systems operate according to simple temperature-based control protocols. This study shows how old architectures could present indoor environmental conditions far from the target, for artworks' preservation, for occupants' comfort, and for the building maintenance. This paper presents a numerical–experimental methodology applied to an architectural heritage. The analysis gives insight on this issue, and could guide building operators and service management to investigate and optimize indoor environmental conditions where artworks are preserved.

항공기용 가스터빈 엔진의 고압터빈에서 열유동 특성해석을 위한 전산해석기법 연구

In this study, a numerical analysis methodology is studied to predict thermal and flow characteristics of C3X vane with internal cooling. Effects of turbulence models, transition models and viscous work term on temperature and pressure distributions on the vane surface are investigated. These optional terms have few effects on the pressure distributions over the vane surface. However, they have great influence on prediction of the temperature distributions on the vane surface. The combination of k-ω based SST turbulence model, γ transition model and viscous work term are better than RSM turbulence model on prediction of the surface temperature. The average temperature difference between CFD results and experimental results is calculated 2 % at the pressure side and 1 % at the suction side. Furthermore computing time of this combination is half of the RSM turbulence model. When k-ω based SST turbulence model and γ transition model with viscous work term are applied, more accurate predictions of thermal and internal flow characteristics of high pressure turbine are expected.

Design and calibration of a new compact radiative heat-flux gauge (RHFG) for combustion applications

It is important to develop an inexpensive and robust gauge for measuring the contribution of radiation heat-flux component while operating in high temperature conditions without the need of cooling water supply. This work presents a new compact radiative heat-flux gauge (RHFG) for measuring the radiative heat-flux from combustion systems operating at high operating temperatures (∼1200K). Various types of total heat-flux meters (convective and radiative) are available for measuring heat-flux. In this study, pure radiative heat-flux measuring gauge (RHFG) is developed. Quartz plate is used as a window of RHFG acting as media to transfer pure radiative heat from the heat source. Copper plate is used as the heat sensing element. A thermocouple is brazed to the copper plate to measure the rate of heat transfer to the sensing element. The mathematical modeling, numerical analysis and construction methodology of RHFG is discussed. Initially, a large sized gauge (G1) is fabricated and calibrated with cone calorimeter. The measured response time of 670s is observed for G1. Numerical analysis is carried out to optimize the size of RHFG and reduce the response time. Four different gauges with various dimensions (G2, G3, G4 and G5) are analyzed numerically and a response time of 208, 17, 14 and 12s respectively is observed. The gauge, G5 is manufactured and calibrated with cone calorimeter with known radiative heat-flux and the experimental response time of 13s is observed. This RHFG is of low cost, simple to manufacture, rugged and requires no water cooling even for high temperature combustion applications.

Fatigue analysis of box-girder webs subjected to in-plane shear and transverse bending induced by railway traffic

The analysis of slender reinforced concrete box-girder webs, in bridge decks, must be carried out considering the effects of in-plane shear and transverse (out-of-plane) bending. In the case of structures subjected to important cyclic loads, such as railway bridge decks, fatigue must also be taken into account. This paper presents a numerical methodology for fatigue analysis of reinforced concrete girder webs, considering the combined effects of in-plane shear and transverse bending. Fatigue lives are calculated by using the damage accumulation method, which makes it possible to analyse variable amplitude stress histories due to real traffic. The main specificity of the proposed methodology lies in the algorithm for calculation of stress histories in the stirrups and in the web concrete. This algorithm is validated through the comparison with experimental results reported in the bibliography, which demonstrates that the proposed approach provides results on the safe side. The interest and practical consequences of employing this methodology in fatigue analyses of new structures are illustrated through the application to a real case study.

Parameter sensitivity analysis of stochastic models: Application to catalytic reaction networks

A general numerical methodology for parametric sensitivity analysis is proposed, which allows to determine the parameters exerting the greatest influence on the output of a stochastic computational model, especially when the knowledge about the actual value of a parameter is insufficient. An application of the procedure is performed on a model of protocell, in order to detect the kinetic rates mainly affecting the capability of a catalytic reaction network enclosed in a semi-permeable membrane to retain material from its environment and to generate a variety of molecular species within its boundaries. It is shown that the former capability is scarcely sensitive to variations in the model parameters, whereas a kinetic rate responsible for profound modifications of the latter can be identified and it depends on the specific reaction network. A faster uptaking of limited resources from the environment may have represented a significant advantage from an evolutionary point of view and this result is a first indication in order to decipher which kind of structures are more suitable to achieve a viable evolution.