Pub Date : 2021-07-07DOI: 10.4995/yic2021.2021.12571
M. Bastidas, S. Sharmin, C. Bringedal, Sorin Pop
A porous medium is a highly complex domain, in which various processes can take place at different scales. Examples in this sense are the multi-phase flow and reactive transport. Here, due to processes like dissolution or precipitation, or chemical deposition, which are encountered at the scale of pores (the micro-scale), the local structure and geometry of the pores may change, impacting the fluid flow. Since these micro-scale processes depend on the model unknowns (e.g., the solute concentration), free boundaries are encountered, separating the space available for flow from the solid, impermeable part in the medium. Here we consider a phase-field approach to model the evolution of the evolving interfaces at the micro-scale. For mineral precipitation and dissolution, we have evolving fluid-solid interfaces. If considering multi-phase flow, evolving fluid-fluid interfaces are also present. After applying a formal homogenization procedure, a two-scale phase-field model is derived, describing the averaged behavior of the system at the Darcy scale (the macro-scale). In this two-scale model, the micro and the macro scale are coupled through the calculation of the effective parameters. Although the resulting two-scale model is less complex than the original, the numerical strategies based on the homogenization theory remain computationally expensive as they require the computation of several problems over different scales, and in each mesh element. Here, we propose an adaptive two-scale scheme involving different techniques to reduce the computational effort without affecting the accuracy of the simulations. These strategies include iterations between scales, an adaptive selection of the elements wherein effective parameters are computed, adaptive mesh refinement, and efficient non-linear solvers.
{"title":"A numerical scheme for two-scale phase-field models in porous media","authors":"M. Bastidas, S. Sharmin, C. Bringedal, Sorin Pop","doi":"10.4995/yic2021.2021.12571","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12571","url":null,"abstract":"A porous medium is a highly complex domain, in which various processes can take place at different scales. Examples in this sense are the multi-phase flow and reactive transport. Here, due to processes like dissolution or precipitation, or chemical deposition, which are encountered at the scale of pores (the micro-scale), the local structure and geometry of the pores may change, impacting the fluid flow. Since these micro-scale processes depend on the model unknowns (e.g., the solute concentration), free boundaries are encountered, separating the space available for flow from the solid, impermeable part in the medium. Here we consider a phase-field approach to model the evolution of the evolving interfaces at the micro-scale. For mineral precipitation and dissolution, we have evolving fluid-solid interfaces. If considering multi-phase flow, evolving fluid-fluid interfaces are also present. After applying a formal homogenization procedure, a two-scale phase-field model is derived, describing the averaged behavior of the system at the Darcy scale (the macro-scale). In this two-scale model, the micro and the macro scale are coupled through the calculation of the effective parameters. Although the resulting two-scale model is less complex than the original, the numerical strategies based on the homogenization theory remain computationally expensive as they require the computation of several problems over different scales, and in each mesh element. Here, we propose an adaptive two-scale scheme involving different techniques to reduce the computational effort without affecting the accuracy of the simulations. These strategies include iterations between scales, an adaptive selection of the elements wherein effective parameters are computed, adaptive mesh refinement, and efficient non-linear solvers.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124390569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-07DOI: 10.4995/yic2021.2021.13262
Shubiao Wang, L. Khalij, R. Troian
At present, the Finite Element Analysis (FEA) method is indispensable in the field of simulation technology, as this kind of numerical analysis method can help engineers to predict results, whic hare often difficult to obtain from experimental tests. However, the problem is that during the mesh generation process in FEA, it is required to spend a long time. It is estimated that about 80 percent of analysis time are devoted to mesh generation in some fields, such as automotive or shipbuilding industries. On the other hand, the imperfections of mesh models can lead to inaccurate problems. Inthis studying, we adopted a new numerical analysis method, Isogeometric Analysis (IGA) to develop a random vibration fatigue analysis. Two different numerical models were developed inLs Dyna software with IGA and FEM analysis: a plate with a hole and a wind turbine tower model.Convergence analyses were developed to investigate the differences in the aspect of computation time, maximum stress, etc. From the convergence analysis, it was shown that IGA and FEA convergence analyses provide similar maximum stress values, in which IGA is more time-efficientcompared with FEA. Secondly, isogeometric random vibration fatigue analysis was developed on the models. The objective was to compare the fatigue analysis results by IGA with the ones of FEA. In terms of fatigue analysis, IGA can predict the fatigue life using fewer NURBS elements and integration points in the thickness direction, which corresponds very well to the fatigue life computed by FEA.
目前，有限元分析(Finite Element Analysis, FEA)方法在仿真技术领域是不可或缺的，因为这种数值分析方法可以帮助工程师预测通常难以从实验测试中获得的结果。然而，问题是有限元分析中网格生成过程需要花费较长的时间。据估计，在某些领域，例如汽车或造船工业，大约80%的分析时间用于网格生成。另一方面，网格模型的不完善会导致不准确的问题。在本研究中，我们采用了一种新的数值分析方法——等几何分析(IGA)来进行随机振动疲劳分析。在ls Dyna软件中进行IGA和FEM分析，建立了两种不同的数值模型:带孔板模型和风力机塔架模型。采用收敛性分析研究了两种方法在计算时间、最大应力等方面的差异。从收敛性分析来看，IGA和FEA的收敛性分析得到了相似的最大应力值，其中IGA比FEA更省时。其次，对模型进行了等几何随机振动疲劳分析。目的是将IGA的疲劳分析结果与有限元分析结果进行比较。在疲劳分析方面，IGA可以利用较少的NURBS元素和厚度方向积分点预测疲劳寿命，与有限元计算的疲劳寿命吻合较好。
{"title":"Random vibration fatigue analysis with the method of Isogeometric Analysis (IGA)","authors":"Shubiao Wang, L. Khalij, R. Troian","doi":"10.4995/yic2021.2021.13262","DOIUrl":"https://doi.org/10.4995/yic2021.2021.13262","url":null,"abstract":"At present, the Finite Element Analysis (FEA) method is indispensable in the field of simulation technology, as this kind of numerical analysis method can help engineers to predict results, whic hare often difficult to obtain from experimental tests. However, the problem is that during the mesh generation process in FEA, it is required to spend a long time. It is estimated that about 80 percent of analysis time are devoted to mesh generation in some fields, such as automotive or shipbuilding industries. On the other hand, the imperfections of mesh models can lead to inaccurate problems. Inthis studying, we adopted a new numerical analysis method, Isogeometric Analysis (IGA) to develop a random vibration fatigue analysis. Two different numerical models were developed inLs Dyna software with IGA and FEM analysis: a plate with a hole and a wind turbine tower model.Convergence analyses were developed to investigate the differences in the aspect of computation time, maximum stress, etc. From the convergence analysis, it was shown that IGA and FEA convergence analyses provide similar maximum stress values, in which IGA is more time-efficientcompared with FEA. Secondly, isogeometric random vibration fatigue analysis was developed on the models. The objective was to compare the fatigue analysis results by IGA with the ones of FEA. In terms of fatigue analysis, IGA can predict the fatigue life using fewer NURBS elements and integration points in the thickness direction, which corresponds very well to the fatigue life computed by FEA.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128122043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-07DOI: 10.4995/yic2021.2021.12580
A. Korczak, W. Mucha
The presented article deals with inverse problems in nanoscale heat transfer identification problems [1]. Heat flow in solids can be modelled using various models. When dealing with objects of small dimensions, of the order of nanometres, and with fast heating processes, comparable to relaxation times, then it is reasonable to use molecular dynamics or the Boltzmann transport equation (BTE) [2]. The presented coupled system of Boltzmann transport equations has the advantage over molecular dynamics that it has a less complicated mathematical apparatus and calculations proceed faster. A thin film irradiated by ultrashort laser pulse is modeled using BTE. Heat transfer parameters of the model are identified using evolutionary algorithm – an optimization algorithm inspired on biological evolution of species. Multicriterial identification is characterized as an optimization problem where the difference between obtained and expected results is minimized.
{"title":"Solution of heat transfer inverse problem in thin film irradiated by laser","authors":"A. Korczak, W. Mucha","doi":"10.4995/yic2021.2021.12580","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12580","url":null,"abstract":"The presented article deals with inverse problems in nanoscale heat transfer identification problems [1]. Heat flow in solids can be modelled using various models. When dealing with objects of small dimensions, of the order of nanometres, and with fast heating processes, comparable to relaxation times, then it is reasonable to use molecular dynamics or the Boltzmann transport equation (BTE) [2]. The presented coupled system of Boltzmann transport equations has the advantage over molecular dynamics that it has a less complicated mathematical apparatus and calculations proceed faster. A thin film irradiated by ultrashort laser pulse is modeled using BTE. Heat transfer parameters of the model are identified using evolutionary algorithm – an optimization algorithm inspired on biological evolution of species. Multicriterial identification is characterized as an optimization problem where the difference between obtained and expected results is minimized.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125780855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-07DOI: 10.4995/yic2021.2021.12283
Juan Carlos Sánchez Quesada, E. Moliner, A. Romero, P. Galvín, M. D. Martínez-Rodrigo
A significant number of railway bridges composed by simply-supported (SS) spans are present in existing railway lines. Special attention must be paid to short to medium span length structures, as they are prone to experience high vertical acceleration levels at the deck, due to their low weight and damping, compromising the travelling comfort and the structural integrity. The accurate prediction of the dynamic response of these bridges is a complex issue since it is affected by uncertain factors such as structural damping and complex interaction mechanisms such as vehicle-bridge, soil-structure or track-bridge interaction. Concerning track-bridge interaction, experimental evidences of a dynamic coupling exerted by the ballasted track between subsequent SS spans and also between structurally independent single-track twin adjacent decks have been reported in the literature [1, 2]. Nevertheless, this phenomenon is frequently disregarded due to the computational cost of models including the track and due to the uncertainties in the mechanical parameters that define the track system. The present work contributes to the study of the coupling effect exerted by the ballasted track between independent structures in railway bridges. With this purpose two 3D finite element (FE) track-bridge interaction models are implemented. The former includes a continuous representation of the track components meshing the sleepers, ballast and sub-ballast with solid FE. In the latter, the track is represented as a 2D discrete three-layer model where the mass, stiffness and damping of the components are concentrated at the sleepers locations. The numerical models are updated with experimental measurements performed on an existing railway bridge in a view to evaluate (i) the influence of the track continuity on the bridge modal parameters and on the train-induced vibrations; (ii) the adequacy of the implemented numerical models and (iii) the importance of the track-bridge interaction for an accurate prediction of the vertical acceleration levels under operating conditions.
{"title":"Influence of track modelling in modal parameters of railway bridges composed by single-track adjacent decks","authors":"Juan Carlos Sánchez Quesada, E. Moliner, A. Romero, P. Galvín, M. D. Martínez-Rodrigo","doi":"10.4995/yic2021.2021.12283","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12283","url":null,"abstract":"A significant number of railway bridges composed by simply-supported (SS) spans are present in existing railway lines. Special attention must be paid to short to medium span length structures, as they are prone to experience high vertical acceleration levels at the deck, due to their low weight and damping, compromising the travelling comfort and the structural integrity. The accurate prediction of the dynamic response of these bridges is a complex issue since it is affected by uncertain factors such as structural damping and complex interaction mechanisms such as vehicle-bridge, soil-structure or track-bridge interaction. Concerning track-bridge interaction, experimental evidences of a dynamic coupling exerted by the ballasted track between subsequent SS spans and also between structurally independent single-track twin adjacent decks have been reported in the literature [1, 2]. Nevertheless, this phenomenon is frequently disregarded due to the computational cost of models including the track and due to the uncertainties in the mechanical parameters that define the track system. The present work contributes to the study of the coupling effect exerted by the ballasted track between independent structures in railway bridges. With this purpose two 3D finite element (FE) track-bridge interaction models are implemented. The former includes a continuous representation of the track components meshing the sleepers, ballast and sub-ballast with solid FE. In the latter, the track is represented as a 2D discrete three-layer model where the mass, stiffness and damping of the components are concentrated at the sleepers locations. The numerical models are updated with experimental measurements performed on an existing railway bridge in a view to evaluate (i) the influence of the track continuity on the bridge modal parameters and on the train-induced vibrations; (ii) the adequacy of the implemented numerical models and (iii) the importance of the track-bridge interaction for an accurate prediction of the vertical acceleration levels under operating conditions.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116881213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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