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

{"title":"Augmented fluid-structure interaction systems for viscoelastic pipelines and blood vessels","authors":"Giulia Bertaglia","doi":"10.4995/yic2021.2021.13450","DOIUrl":"https://doi.org/10.4995/yic2021.2021.13450","url":null,"abstract":"Mathematical models and numerical methods are a powerful resource for better understanding phenomena and processes throughout the fluid dynamics field, allowing significant reductions in the costs, which would otherwise be required to perform laboratory experiments, and even allowing to obtain useful data that could not be gathered through measurements.The correct characterization of the interactions that occur between the fluid and the wall that surrounds it is a fundamental aspect in all contexts involving deformable ducts, which requires the utmost attention at every stage of both the development of the computational method and the interpretation of the results and their application to cases of practical interest.In this work, innovative mathematical models able to predict the behavior of the fluid-structure interaction (FSI) mechanism that underlies the dynamics of flows in different compliant ducts is presented. Starting from the purely civil engineering sector, with the study of plastic water pipelines, the final application of the proposed tool is linked to the medical research field, to reproduce the mechanics of blood flow in both arteries and veins. With this aim, various linear viscoelastic models, from the simplest to the more sophisticated, have been applied and extended to obtain augmented FSI systems in which the constitutive equation of the material is directly embedded into the system as partial differential equation [1]. These systems are solved recurring to second-order Finite Volume Methods that take into account the recent evolution in the computational literature of hyperbolic balance laws systems [2]. To avoid the loss of accuracy in the stiff regimes of the proposed systems, asymptotic-preserving IMEX Runge-Kutta schemes are considered for the time discretization, which are able to maintain the consistency and the accuracy in the diffusive limit, without restrictions due to the scaling parameters [3]. The models have been extensively validated through different types of test cases, highlighting the advantages of using the augmented formulation of the system of equations. Furthermore, comparisons with experimental data have been considered both for the water pipelines scenario and the blood flow modeling, recurring to in-vivo measurements for the latter.REFERENCES[1] Bertaglia, G., Caleffi, V. and Valiani, A. Modeling blood flow in viscoelastic vessels: the 1D augmented fluid-structure interaction system. Comput. Methods Appl. Mech. Eng., 360(C):112772 (2020).[2] Bertaglia, G., Ioriatti, M., Valiani, A., Dumbser, M. and Caleffi, V. Numerical methods for hydraulic transients in visco-elastic pipes. J. Fluids Struct., 81:230-254 (2018).[3] Pareschi, L. and Russo, G. Implicit-explicit Runge-Kutta schemes and applications to hyperbolic systems with relaxation. J. Sci. Comput., 25:129-155 (2005).","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"17 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":"134343888","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":"Railway rolling noise mitigation through optimal track design","authors":"Víctor Tomás Andrés Ruiz, José Martínez Casas, Javier Carballeira Morado, Francisco David Denia Guzmán, D. Thompson","doi":"10.4995/yic2021.2021.12583","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12583","url":null,"abstract":"The main goal of the present work lies in the identification of the railway track properties that influence acoustic radiation, as well as in the analysis of these properties for the reduction of sound levels. This is achieved through a dynamic model of the railway wheel and track that allows the study of rolling noise, produced as a result of wheel/rail interaction. The vibroacoustic calculation methodology consists of characterising the railway wheel and track, using finite element techniques and periodic structure theory [1,2], respectively. Subsequently, the response of the railway components, which is caused by the roughness present in the surface of the wheel and rail, is determined. Finally, after having the vibrational response of the railway elements, the sound power radiated by them is calculated using the acoustic model developed by D. J. Thompson et al. and implemented in TWINS software [3]. The influence of the track properties on the sound radiation is analysed through statistical techniques applied to the acoustic power results of different track configurations. To do this, the geometry of the rail profile is parameterised and simulations are carried out by modifying these parameters and the viscoelastic properties of the track components. From the results obtained, a number of guidelines are presented for the noise mitigation of the involved railway subcomponents. Between the worst and the best track design, there are differences of approximately 7.5 dB(A) in the radiation (considering the wheel, rail and sleeper noise), which means that an optimised track design can be found with an acoustic radiation 5.5 times lower than another design.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"2015 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":"129216075","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":"Intrinsically Selective Mass Scaling with Hierarchic Structural Element Formulations","authors":"Bastian Oesterle, Jan Trippmacher, A. Tkachuk, M. Bischoff","doi":"10.4995/yic2021.2021.12418","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12418","url":null,"abstract":"Hierarchic shear deformable Reissner-Mindlin shell formulations possess the advantage of being intrinsically free from transverse shear locking [1], [2]. Transverse shear locking is avoided a priori through reparametrization of the kinematic variables. This reparametrization yields beam, plate and shell formulations with distinct transverse shear degrees of freedom.The efficiency of explicit dynamic analyses of thin-walled structures is limited by the critical time step size, which depends on the highest frequency of the discretized system. If Reissner-Mindlin type shell elements are used for discretization of a thin structure, the highest transverse shear frequencies limit the critical time step in explicit dynamic analyses, while being relatively unimportant for the structural response of the system. The basic idea of selective mass scaling is to scale down the highest frequencies in order to increase the critical time step size, while keeping the low frequency modes unaffected, see for instance [3]. In most concepts, this comes at the cost of non-diagonal mass matrices.In this contribution, we present recent investigations on selective mass scaling with hierarchic formulations. Since hierarchic formulations possess distinct transverse shear degrees of freedom, they offer the intrinsic ability for selective mass scaling of the shear frequency modes, while keeping the bending dominated modes mostly unaffected and retaining the diagonal structure of a lumped mass matrix. We discuss the effects of transverse shear parametrization, locking and mass lumping on the accuracy of results and a feasible time step.REFERENCES[1] R. Echter, B. Oesterle and M. Bischoff, A hierarchic family of isogeometric shell finite elements. Computer Methods in Applied Mechanics and Engineering, Vol. 254. pp. 170-180, 2013.[2] B. Oesterle, E. Ramm and M. Bischoff, A shear deformable, rotation-free isogeometric shell formulation. Computer Methods in Applied Mechanics and Engineering, Vol. 307, pp. 235-255, 2016.[3] G. Cocchetti, M. Pagani and U. Perego, Selective mass scaling and critical time-step estimate for explicit dynamics analyses with solid-shell elements. Computers and Structures, Vol. 27, pp. 39-52, 2013.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"82 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":"131810568","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":"An overview of p-refined Multilevel quasi-Monte Carlo Applied to the Geotechnical Slope Stability Problem","authors":"P. Blondeel, Pieterjan Robbe, S. François, G. Lombaert, S. Vandewalle","doi":"10.4995/yic2021.2021.12236","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12236","url":null,"abstract":"Engineering problems are often characterized by significant uncertainty in their material parameters. Multilevel sampling methods are a straightforward manner to account for this uncertainty. The most well known multilevel method is the Multilevel Monte Carlo method (MLMC). First developed by Giles, see [1], this method relies on a hierarchy of successive refined Finite Element meshes of the considered engineering problem, in order to achieve a computational speedup. Most of the samples are taken on coarse and computationally cheap meshes, while a decreasing number of samples are taken on finer and computationally expensive meshes. Classically, the mesh hierarchy is constructed by selecting a coarse mesh discretization of the problem, and recursively applying an h-refinement approach to it, see [2]. This will be referred to as h-MLMC. However, in the h-MLMC mesh hierarchy, the number of degrees of freedom increases almost geometrical with increasing level, leading to a large computational cost. An efficient manner to reduce this computational cost, is by means of the novel sampling method called p-refined Multilevel Quasi-Monte Carlo (p-MLQMC), see [3]. The p-MLQMC method uses a hierarchy of p-refined Finite Element meshes, combined with a deterministic Quasi-Monte Carlo sampling rule. This combination significantly reduced the computational cost with respect to h-MLMC. However, the p-MLQMC method presents the practitioner with a challenge. This challenge consists in adequately incorporating the uncertainty, represented as a random field, in the Finite Element model. In previous work, see [4], we have tackled this challenge by investigating how the evaluation points, used to calculate point evaluations of the random field by means of the Karhunen-Loève (KL) expansion, need to be selected in order to achieve the lowest computational cost. We found that using sets of nested evaluation points across the mesh hierarchy, i.e., the Local Nested Approach (LNA), yields a speedup up to a factor 5 with respect to sets consisting of non-nested evaluation points, i.e., the Non-Nested Approach (NNA). Furthermore, we have shown that p-MLQMC-LNA yields a speedup up to a factor 70 with respected to h-MLMC. Currently, our research focus lies on implementing the use of higher order Quasi-Monte Carlo rules, and hierarchical shape functions in p-MLQMC. Both paths show promising results for further computational savings in the p-MLQMC method. All the aforementioned implementations are benchmarked on a slope stability problem, with spatially varying uncertainty in the ground. The chosen quantity of interest (QoI) consists of the vertical displacement of the top of the slope.[1] Michael B. Giles. Multilevel Monte Carlo path simulation. Oper. Res., 56(3):607–617, 2008. [2] K. A. Cliffe, M. B. Giles, R. Scheichl, and A. L. Teckentrup. Multilevel Monte Carlo methods and applications to elliptic pdes with random coefficients. Comput. Vis. Sci., 14(1):3, Aug 2011. [3] Phili","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"18 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":"131371797","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":"The role of dynamic sea ice in a simplified general circulation model used for palaeoclimate studies","authors":"M. Adam, H. Andres, K. Rehfeld","doi":"10.4995/yic2021.2021.12383","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12383","url":null,"abstract":"AbstractObservational records provide a strong basis for constraining sea ice models within a narrow range of climate conditions. Given current trends away from these conditions, models need to be tested over a wider range of climate states. The past provides many such examples based on paleoclimate data, including abrupt tipping points. However, the millennial-duration of typical paleoclimatesimulations necessitates balancing the inclusion and sophistication of model processes against computational cost. We investigate the impact on climate mean states and variability of introducing sea ice dynamics into the simplified general circulation model PlaSim-LSG [1-3].Considering the technical constraints of PlaSim-LSG, we choose to integrate a modied version of the MITgcm's dynamical sea ice component [4, 5] into the model setup. We adapt the component to the structure and parallelization scheme of PlaSim-LSG, validate the physical consistency and stability of the component, and evaluate the impact of sea ice dynamics onto the simulated climate from decadal to millennial time scales. Specifically, we compare climatologies, variability and scaling of the extended model to control simulations of the preexisting setups, and quantify how additional sea ice dynamics affect well-known climatic biases of the PlaSim model family.With our extended PlaSim-LSG model we aim at capturing the key small-scale sea ice processes that are important to past climate tipping points while maintaining model efficiency for millennial simulations. Sea ice is a key component of coupled atmosphere-ocean processes that led to large-amplitude, abrupt climate variability in the past [6-8]. Therefore, the extended model can be usedto investigate the role of sea ice for such oscillations. This facilitates the understanding of processes that lead to current mismatches between palaeoclimate data and simulations, and that impact thesimulated surface climate variability [9].References[1] K. Fraedrich et al. Meteorol. Z. 14.3 (2005), 299-304. doi: 10.1127/0941-2948/2005/0043.[2] F. Lunkeit et al. Tech. rep. 2011. url: https://www.mi.uni-hamburg.de/en/arbeitsgruppen/theoretische-meteorologie/modelle/sources/psreferencemanual-1.pdf.[3] H. J. Andres et al. Clim. Past 15.4 (2019), 1621-1646. doi: 10.5194/cp-15-1621-2019.[4] J. Zhang et al. J. Geophys. Res. 102.4 (1997), 412-415.[5] M. Losch et al. Ocean Model. 33.1-2 (2010), 129-144. doi: 10.1016/j.ocemod.2009.12.008.[6] T. M. Dokken et al. Paleoceanography 28.3 (2013), 491-502. doi: 10.1002/palo.20042.[7] G. Vettoretti et al. Geophys. Res. Lett. 43.10 (2016), 5336-5344. doi: 10.1002/2016GL068891.[8] C. Li et al. Quat. Sci. Rev. 203 (2019), 1-20. doi: 10.1016/j.quascirev.2018.10.031.[9] N. Weitzel et al. presented at Fall Meeting AGU. 2020. url: https://agu.confex.com/agu/fm20/webprogram/Paper739241.html.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"24 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":"129469811","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":"Efficient and Higher-Order Accurate Split-Step Methods for Generalised Newtonian Fluid Flow","authors":"R. Schussnig, D. Pacheco, M. Kaltenbacher, T. Fries","doi":"10.4995/yic2021.2021.12217","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12217","url":null,"abstract":"In various practically relevant incompressible flow problems, such as polymer flow or biomedicalengineering applications, the dependence of fluid viscosity on the local shear rate plays an impor-tant role. Standard techniques using inf-sup stable finite elements lead to saddle-point systemsposing a challenge even for state-of-the-art solvers and preconditioners.For efficiency, projection schemes or time-splitting methods decouple the governing equations forvelocity and pressure, resulting in more, but easier to solve linear systems. Doing so, boundaryconditions and correction terms at intermediate steps have to be carefully considered in order toprohibit spoiling accuracy. In the case of Newtonian incompressible fluids, pressure and velocitycorrection schemes of high-order accuracy have been devised (see, e.g. [1, 2]). However, the exten-sion to generalised Newtonian fluids is a non-trivial task and considered an open question. Deteixet al. [3] successfully adapted the popular rotational correction scheme to consider for shear-ratedependent viscosity, but this resulted in substantial numerical overhead caused by necessarily pro-jecting viscous stress components.In this contribution we address this shortcoming and present a split-step scheme, extending pre-vious work by Liu [4]. The new method is based on an explicit-implicit treatment of pressure,convection and viscous terms combined with a Pressure-Poisson equation equipped with fully con-sistent Neumann and Dirichlet boundary conditions. Through proper reformulation, the use ofstandard continuous finite element spaces is enabled due to low regularity requirements. Addition-ally, equal-order velocity-pressure pairs are applicable as in the original scheme.The stability, accuracy and efficiency of the higher-order splitting scheme is showcased in challeng-ing numerical examples of practical interest.[1] Karniadakis, G. E., Israeli, M. and Orszag, S. A. High-order splitting methods for the incom-pressible Navier-Stokes equations. J. Comput. Phys., (1991).[2] Timmermans, L.J.P., Minev, P.D. and Van de Vosse, F. N. An approximate projection schemefor incompressible flow using spectral elements. Internat. J. Numer. Methods Fluids, Vol.22(7), pp. 673–688, (1996).[3] Deteix, J. and Yakoubi, D. Shear rate projection schemes for non-Newtonian fluids, Comput.Methods Appl. Mech. Engrg., Vol. 354, pp. 620–636, (2019).[4] Liu, J. Open and traction boundary conditions for the incompressible NavierStokesequations.J. Comput. Phys., Vol. 228(19), pp. 7250..7267, (2009).","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":"130153260","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 coupled lattice Boltzmann/finite volume method for turbulent gas-liquid bubbly flows","authors":"D. Lauwers, M. Meinke, W. Schröder","doi":"10.4995/yic2021.2021.12211","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12211","url":null,"abstract":"The study of gas-liquid multiphase flows has been an active research topic for many decades. They occur in processes belonging to industries including chemical, pharmaceutical, food, energy, and machinery industries. As processes in these fields become more refined, there is an increasing demand for the detailed analysis and accurate prediction of such flows. There are many categories of multiphase gas-liquid flows. We consider a dispersed phase in a carrier phase, such as small gas bubbles in liquids or liquid droplets in a gas. The technical application is a pulsed electrochemical machining (PECM) process, in which gas bubbles are generated in a liquid electrolyte during the electrochemical removal of material. The simulation method is based on an Eulerian-Eulerian model for the dispersed gas-liquid bubbly flow. The conservation equations are volumetrically averaged, resulting in one set of conservation equations per phase. The liquid phase is using a Lattice-Boltzmann method, while the gas phase is modelled by a Finite-Volume method. Interface terms between the phases result in a two-way coupled system. Both methods are formulated on a shared Cartesian grid similar to the concept in [1], which facilitates the exchange of information between the two solvers and an efficient implementation on HPC hardware. This coupled multiphase approach combines the advantages of the Lattice Boltzmann method as an efficient prediction tool for low Mach number flows with those of a finite-volume method for the Navier-Stokes equation used for the phase with larger density changes. To accurately model the turbulent motion of the liquid phase on all relevant scales, a cumulant-based collision step for the Lattice-Boltzmann scheme [2] is combined with a Smagorinsky sub-grid-scale turbulence model. In the finite-volume solver, the effects of the sub-grid-scale turbulence are incorporated according to the MILES approach. For the validation of the new method, large-eddy simulations (LES) of turbulent bubbly flows are performed. The accuracy of the predictions is evaluated comparing the results to reference data from experiments and other simulations for generic test cases, for which good agreement is found. The applicability of the method will be demonstrated for a bubbly turbulent channel flow, which mimics the phenomena in the PECM process.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"4 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":"127939283","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":"An Isogeometric Element Formulation for Linear Two-Dimensional Elasticity Based on the Airy Equation","authors":"Susanne Held, W. Dornisch, Nima Azizi","doi":"10.4995/yic2021.2021.12598","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12598","url":null,"abstract":"The aim of this work is to derive a formulation for linear two-dimensional elasticity using just one degree of freedom. With the Airy stress function, a measure without further physical meaning is chosen to this single degree of freedom. The corresponding Airy equation requires higher order basis functions for the discretization of the formulation [1]. Isogeometric structural analysis (IGA) is based on shape functions of the system in Computer-Aided design (CAD) software [2]. These shape functions can fulfill the requirement of high continuity and therefore the formulation is obtained through IGA methods. Non-Uniform Rational B-splines (NURBS) are used to discretize the domain and to solve the occurring differential equations within the Galerkin method [3]. The received one-degree of freedom formulation allows to compute stresses as direct solution of the underlying system of equations. Numerical examples demonstrate the accuracy for a quadratic plate under standard, but also under complex loading. For constant or linear loading functions only one element is sufficient to receive the exact solution – a general advantage of using higher order basis functions. The correct convergence behaviour of the proposed formulation is proved by the -error norm for a complex load situation. Here, only a few refinement steps yield a good approximation with a very small error of the stresses.","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":"131084782","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":"ITERATIVE QUASI-NEWTON SOLVERS FOR POROMECHANICS APPLIED TO HEART PERFUSION","authors":"J. Both, Nicolas A. Barnafi","doi":"10.4995/yic2021.2021.12324","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12324","url":null,"abstract":"Sequential block-partitioned solvers have in the recent past been quite popular for multi-physics and in particular poroelasticity models. Such enable tailored solver technology for the respective single-physics problems via iterative coupling, as well as suggest suitable block-preconditioners for monolithic solvers.In this talk, we focus on a thermodynamically consistent poroelasticity model recently proposed. It extends the classical quasi-static Biot equations by incoporating inertia contributions in both solid and fluid equations, aiming at biomedical applications; for instance, the perfusion of the heart.Following ideas and techniques from previous works, we present block-partitioned solvers for the fully dynamic poroelasticity model supported by theoretical convergence analysis.","PeriodicalId":406819,"journal":{"name":"Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference","volume":"89 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":"134488419","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":"An adaptive discrete Newton method for regularization-free Bingham model","authors":"Arooj Fatima, S. Turek, A. Ouazzi, M. Afaq","doi":"10.4995/yic2021.2021.12389","DOIUrl":"https://doi.org/10.4995/yic2021.2021.12389","url":null,"abstract":"Developing a numerical and algorithmic tool which correctly identifies unyielded region in the yield stress fluid flow is a challenging task. Two approaches are commonly used to handle the singular behaviour at the yield surface, i.e. Augmented Lagrangian approach and the regularization approach, respectively. Generally in the regularization approach, solvers do not perform efficiently when the regularization parameter gets very small. In this work, we use a formulation introducing a new auxiliary stress [1]. The three field formulation of yield stress fluid corresponds to a regularization-free Bingham formulation. The resulting set of equations arising from the three field formulation is solved efficiently and accurately by a monolithic finite element method. The velocity and pressure are discretized by higher order stable FEM pair $Q_2/P^{text{disc}}_1$ and the auxiliary stress is discretized by $Q_2$ element.Furthermore, this problem is highly nonlinear and presents a big challenge to any nonlinear solver. We developed a new adaptive discrete Newton's method, which evaluates the Jacobian with the directional divided difference approach [2]. The step length in this process is an important key: We relate this length to the rate of the actual nonlinear reduction for achieving a robust adaptive Newton's method. The resulting linear sub problems are solved using the geometrical multigrid solver. We analyse the solvability of the problem along with the adaptive Newton method for Bingham fluids by doing numerical studies for two different prototypical configurations, i.e. \"Viscoplastic fluid flow in a channel\" and \"Lid Driven Cavity\", respectively [2].REFERENCES[1] Aposporidis, A., Haber, E., Olshanskii, M. A. and Veneziani, A. A mixed formulation of the Bingham fluid flow problem: Analysis and numerical solution. Comput. Methods Appl. Mech. Engrg, Vol. 200, pp. 2434–2446, (2011).[2] Fatima, A., Turek, S., Ouazzi, A. and Afaq, M. A. An adaptive discrete Newton method for regularization-free Bingham model. Ergebnisberichte des Instituts fuer Angewandte Mathematik Nummer 635, Fakultaet fuer Mathematik, TU Dortmund University, 635, 2021.","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":"114084633","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}