Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference最新文献

{"title":"Block strategies to compute the lambda modes associated with the neutron diffusion equation","authors":"A. Carreño, Antoni Vidal Ferrándiz, Damián Ginestar Peiró, G. Verdú","doi":"10.4995/yic2021.2021.13470","DOIUrl":"https://doi.org/10.4995/yic2021.2021.13470","url":null,"abstract":"Given a configuration of a nuclear reactor core, the neutronic distribution of the power can beapproximated by means of the multigroup neutron diffusion equation. This is an approximationof the neutron transport equation that assumes that the neutron current is proportional to thegradient of the scalar neutron ux with a diffusion coeffcient [1]. This approximation is known asthe Fick's first law. To define the steady-state problem, the criticality of the system must be forced.In this work, the -modes problem is used. That yields a generalized eigenvalue problem whoseeigenvector associated with the dominant eigenvalue represents the distribution of the neutron uxin steady-state.The spatial discretization of the equation is made by a continuous Galerkin high order finite elementmethod is applied [2] to obtain an algebraic eigenvalue problem. Usually, the matrices obtainedfrom the discretization are huge and sparse. Moreover, they have a block structure given by the different number of energy groups. In this work, block strategies are developed to optimize thecomputation of the associated eigenvalue problems.First, different block eigenvalue solvers are studied. On the other hand, the convergence of theseiterative methods mainly depends on the initial guess and the preconditioner used. In this sense,different multilevel techniques to accelerate the rate of convergence are proposed. Finally, the sizeof the problems can be suffciently large to be unfeasible to be solved in personal computers. Thus,a matrix-free methodology that avoids the allocation of the matrices in memory is applied [3].Three-dimensional benchmarks are used to show the effciency of the methodology proposed.REFERENCES[1] Stacey, W. M. Nuclear reactor physics (Vol. 2). Weinheim: wiley-vch, 2018[2] Vidal-Ferrandiz, A., Fayez, R., Ginestar, D., and Verdú, G. Solution of the Lambda modesproblem of a nuclear power reactor using an h-p finite element method. Annals of NuclearEnergy, 72, pp. 338{349, 2018[3] Carreño Sánchez, A. M. Integration methods for the time dependent neutron diffusion equationand other approximations of the neutron transport equation. Doctoral dissertation, 2020.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"151 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":"114441018","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}

{"title":"Equilibrium-Based Finite Element Formulation for Timoshenko Curved Tapered Beams","authors":"H. Santos","doi":"10.4995/yic2021.2021.12567","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12567","url":null,"abstract":"Due to their excellent mechanical performance and structural efficiency, curved tapered beams have been widely used in many engineering applications, such as, bridge structures, piping systems, biomedical devices, aerospace and aeronautical structures, etc. Their complex geometries pose challenges to the development of robust approaches for the modelling of their mechanical behaviour. Among the various approaches available in the literature for their analysis, those that are based on the finite element method have been the most successful, particularly due to their versatility. Nonetheless, when applied to Timoshenko based structural models, some of these finite element approaches are prone to shear locking when the beam elements become slender and to membrane locking when the curvature of the beam centroid curves increases [1]. The aim of the present contribution is to introduce a novel, simple and effective, finite element formulation for the analysis of two-dimensional Timoshenko curved tapered beams. This formulation relies on a complementary variational approach based on a set of approximations that satisfy in strong form all equilibrium conditions of the boundary-value problem [2], resulting thus in a formulation that is free from both shear and membrane locking phenomena. The effectiveness of the formulation is numerically demonstrated through its application to a circular clamped-clamped beam subjected to a mid-span concentrated load, and the obtained results are analysed and discussed. REFERENCES [1]      H. Stolarski and T. Belytschko, “Shear and membrane locking in curved C0 elements”, Comput. Meth. Appl. Mech. Eng., Vol. 41, pp. 279–296, (1983). [2]      H.A.F.A. Santos, “Complementary-energy methods for geometrically non-linear structural models: an overview and recent developments in the analysis of frames”, Archives of Computational Methods in Engineering, Vol. 18, (2011): 405.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"304 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":"131027635","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}

{"title":"A Space-Time FE Level-set method for convection coupled phase-change processes","authors":"L. Boledi, Benjamin Terschanski, S. Elgeti, J. Kowalski","doi":"10.4995/yic2021.2021.12329","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12329","url":null,"abstract":"Phase transition processes have great relevance for both engineering and scientific applications. In production engineering, for instance, metal welding and alloy solidification are topics of ongoing research.In this contribution we focus on the convection coupled solid-liquid phase change of a single species, e.g. water. The material is assumed to be incompressible within the two phases, but we account for density changes across the phase interface. To describe the process, we need to solve the incompressible Navier-Stokes equations and the heat equation for both phases over time. The position of the phase interface is tracked with a Level-set method. The Level-set function is advected according to the propagation speed of the phase interface. Such velocity field depends on local energy conservation across the interface and is modelled as the Stefan condition. This formulation requires us to approximate the heat flux discontinuity across the interface based on the evolving temperature and velocity fields.To model the temperature and velocity fields within each phase, we employ the Space-Time Finite Element method. However, commonly used interpolation functions, such as piecewise linear functions, fail to capture discontinuous derivatives over one element that are needed to assess the Level-set's transport term. Available solutions to this matter, such as local enrichment with Extended Finite Elements, are often not compatible with existing Space-Time Finite Element codes and require extensive implementation work. Instead, we consider a conceptually simpler method and we decide to extend the Ghost Cell technique to Finite Element meshes. The idea is that we can separate the two subdomains associated with each phase and solve two independent temperature problems. We prescribe the melting temperature at an additional node close to the interface and we retrieve the required heat flux.In this work we describe the Ghost Cell method applied to our Space-Time Finite Element solver. First, we verify numerical results against analytical solutions, then we demonstrate more complex test cases in 2D and 3D.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"47 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":"114551638","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}

{"title":"Energy-momentum time integration of gradient-based models for fiber-bending stiffness in anisotropic thermo-viscoelastic continua","authors":"J. Dietzsch, M. Groß, I. Kalaimani","doi":"10.4995/yic2021.2021.12358","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12358","url":null,"abstract":"For our research, we are motivated by dynamic simulations of 3D fiber-reinforced materials in lightweight structures. In such materials, the material reinforcement is performed by fiber rovings with a separate bending stiffness, which can be modelled by a second order gradient of the deformation mapping. Therefore, we extend a thermo-viscoelastic Cauchy continuum for fiber-matrix composites with single fibers by an independent field for the gradient of the right Cauchy-Green tensor. On the other hand, we focus on numerically stable dynamic long-time simulations with locking free meshes, and thus use higher-order accurate energy-momentum schemes emanating from mixed finite element methods. Hence, we adapt the variational-based space-time finite element method to the new material formulation, and additionally include independent fields to obtain well-known mixed finite elements. As representative numerical example, Cook’s cantilever beam is considered. We primarily analyze the influence of the fiber bending stiffness, as well as the spatial and time convergence up to cubic order. Furthermore, we look at the influence of the physical dissipation in the material.  ","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":"130038755","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}

{"title":"Finite Element Simulation and Comparison of Piezoelectric Vibration-Based Energy Harvesters with Advanced Electric Circuits","authors":"Andreas Hegendörfer, J. Mergheim","doi":"10.4995/yic2021.2021.12177","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12177","url":null,"abstract":"A system simulation method based on the Finite-Element Method (FEM) is applied to simulate a bimorph piezoelectric vibration-based energy harvester (PVEH) with different electric circuits: The standard circuit, the synchronized switch harvesting on inductor (SSHI) circuit and the synchronized electric charge extraction (SECE) circuit are considered. Moreover, nonlinear elasticity of the piezoelectric material is taken into account and different magnitudes of base excitations are applied. The holistic FEM-based system simulation approach allows the detailed evaluation of the influences of the considered electric circuits on the vibrational behavior of the PVEH. Furthermore, the harvested energy of the different applied electric circuits with respect to the magnitude of base excitation is compared and results from literature regarding the efficiency of electric circuits are confirmed.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"259 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114004040","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}

{"title":"Rolling noise reduction through GA-based wheel shape optimization techniques","authors":"X. Garcia-Andrés, Jorge Gutiérrez-Gil, V. Andrés, J. Martínez-Casas, F. Denia","doi":"10.4995/yic2021.2021.12577","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12577","url":null,"abstract":"Railway rolling noise is nowadays a major source of acoustic pollution in urban areas, with nearly up to 12 million people daily affected in Europe by this phenomenon [1]. Hence, the search for ways of decreasing such noise radiation has become a highly active and significant research field. Following this approach, a Genetic Algorithms-based shape optimization of the railway wheel [2] is developed with the aim of minimizing rolling noise. Different approaches are considered to address the problem, such as directly minimizing radiated Sound poWer Level (SWL) or using the maximization of the natural frequencies if computational efficiency is especially critical. A parametric Finite Element model is implemented for the wheel based on the most relevant geometric parameters in rolling noise radiation. For the acoustic calculation, the sound radiation models used in the TWINS software [3] are adopted, which also accounts for the whole dynamics of the wheel/rail system. Furthermore, for every candidate wheel proposed, a structural analysis is computed in order to check design feasibility in accordance with the corresponding standard [4]. In all cases, new geometries for the wheel cross section are achieved that reduce the radiated rolling noise. REFERENCES [1]      WHO European Centre for Environment and Health, “Burden of disease from environmental noise”, WHO, Tech. Rep., 2011 [2]      X. Garcia-Andrés, J. Gutiérrez-Gil, J. Martínez-Casas and F. D. Denia, “Wheel shape optimization approaches to reduce railway rolling noise”, Struct. Multidiscipl. Optim., Vol. 62, pp. 2555-2570, (2020). [3]      D. J. Thompson, B. Hemsworth and N. Vincent, “Experimental validation of the TWINS prediction program for rolling noise, part 1: Description of the model and method”, J. Sound Vib., Vol. 193 (1), pp. 123–135, (1996). [4]      UNE, “Railway applications. Wheelsets and bogies. Monobloc wheels. Technical approval procedure. Part 1: Forged and rolled wheels. UNE-EN-13979-1:2006”, Asociación Española de Normalización (UNE), Technical Standard, 2011.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"660 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":"133366947","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}

{"title":"Sea ice strength development from freezing to melting in the Antarctic marginal ice zone","authors":"F. Paul, T. Mielke, R. Audh, D. Lupascu","doi":"10.4995/yic2021.2021.12249","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12249","url":null,"abstract":"Sea ice growth in the Marginal Ice Zone of the Antarctic is one of the largest annual changes on earth with a huge impact on the global climate and ecology system. The principles of sea ice growth and melting in the MIZ of the Antarctic is yet not as well researched as its polar counterpart in the north.For this study, pancake ice, consolidated ice and floe ice were analyzed with a compression test in July, October and November 2019 in the marginal ice zone of the Antarctic. Newly formed pancake ice in July showed the highest compressive strength in the bottom layer (3 MPa), whereas consolidated ice was strongest at the top (5 MPa). Consolidated ice in October and November had the highest compressive strength in a middle layer with up to 13.5 MPa, the maximum strength at the top was 3 MPa. Floe ice, consisting of destroyed pack ice, did not show a clear strength development over sea ice depth.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"78 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":"115505056","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}

{"title":"A mixed isogeometric plane stress and plane strain formulation with different continuities for the alleviation of locking","authors":"Lisa Stammen, W. Dornisch","doi":"10.4995/yic2021.2021.12554","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12554","url":null,"abstract":"Isogeometric analysis was founded by Hughes et al. and tries to unify computer aided design (CAD) and finite element analysis (FEA) by using the same model for geometry representation and analysis. Therefore, non-uniform rational B-splines (NURBS) and other kinds of splines are used as shape functions of the finite elements. Due to the exact representation of the geometry, analysis results can be improved. Furthermore, many fast and numerically stable algorithms have been developed that exhibit favourable mathematical properties.In mixed formulations stresses and/or strains or pressures are approximated independently and in addition to the usual displacement approximation. Using such methods is more robust and offers more accurate results. Hence, mixed formulations are employed to solve incompressible elasticity problems for instance.Recent investigations have already combined isogeometric analysis and mixed formulations in order to benefit from the advantages of both methods.In this contribution, a mixed isogeometric method is proposed in order to improve the analysis results and to counteract locking. Therefore, spline basis functions are used and the displacement shape functions of a two-dimensional isogeometric plane stress and plane strain element are supplemented by independent stress shape functions. These additional stress shape functions are chosen to be of one order lower compared to the displacement shape functions, but with adapted continuity.Evaluating the error norms for several examples, it is shown that the proposed mixed method leads to an improved accuracy of results compared to a standard isogeometric formulation and is able to counteract locking. Furthermore, the influence of the continuity of the stress shape functions is shown.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"39 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":"131240149","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}

{"title":"Comparison of numerical and experimental strain distributions in composite panel for aerospace applications","authors":"W. Mucha, W. Kuś, J. Viana, J. Nunes","doi":"10.4995/yic2021.2021.12572","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12572","url":null,"abstract":"In structural applications of the aerospace industry, weight efficiency, understood as minimal weight and maximal stiffness, is of great importance. This criterion can be achieved by composite lightweight structures. Typical structures for the aforementioned applications are sandwich panels (e.g. with honeycomb core) and stiffened panels (e.g. with blade ribs, T-bar ribs, or hat ribs) [1-3]. In the paper, hat-stiffened panel, made of carbon/epoxy woven composite, is considered. Results of experiments, consisting of loading the panel and measuring exciting forces and strains (using strain gages), are presented. The results are compared to strains distribution obtained from finite element model of the panel. An idea of real-time system for load monitoring of the structure, using artificial intelligence techniques [4], is also presented. An high fidelity digital model with a big compliance of the computed and measured strain distributions is crucial for the performance of such a cyber-physical system.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"68 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120994601","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}

{"title":"On Total Reuse of Krylov Subspaces for an iterative FETI-solver in multirate integration","authors":"Andrea Seibold, D. Rixen, Javier Del Fresno Zarza","doi":"10.4995/yic2021.2021.12306","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12306","url":null,"abstract":"Recycling techniques for Krylov subspaces in parallel FETI-solvers are able to increase efficiency of solution processes with repeated right-hand-sides. One simple technique consists in a Total Reuse of the Krylov Subspace (TRKS) provided by conjugate directions generated during the solution of previous problems. This applies especially for linear structural dynamics and recycling also reduced global iterations for nonlinear structural dynamics. The structure of the interface-operator's eigenvalues governs the possible efficiency-gain. Only if high clustered eigenvalues are captured early enough, global FETI iterations will be reduced accordingly. Besides these advances, multirate integrators have been proposed, that enable adapted time-step-sizes on each substructure and are expected to accelerate the parallel simulation of nonlinear dynamic simulations with local highly nonlinear processes, e.g. damaging. Based on the linear BGC-macro and nonlinear PH-method, a nonlinear BGC-macro method has been proposed and on the other hand a more flexible and accurate multirate-integrator has been derived from the variational principle. These multirate-integration schemes require several local integration-steps in each global iteration, leading to a non-symmetric structure of the linearized local problems and the local boundary conditions are altered compared to FETI for standard singlerate integration. So, we have to solve the global interface-problem with a GMRes-solver. In this contribution, we show our recent results on the eigenvalues and application of a TRKS to these new problems.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"13 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":"127890088","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}