{"title":"Asymptotic spectral properties and preconditioning of an approximated nonlocal Helmholtz equation with Caputo fractional Laplacian and variable coefficient wave number $μ$","authors":"Andrea Adriani, Rosita Luisa Sormani, Cristina Tablino-Possio, Rolf Krause, Stefano Serra-Capizzano","doi":"arxiv-2402.10569","DOIUrl":"https://doi.org/arxiv-2402.10569","url":null,"abstract":"The current study investigates the asymptotic spectral properties of a finite\u0000difference approximation of nonlocal Helmholtz equations with a Caputo\u0000fractional Laplacian and a variable coefficient wave number $mu$, as it occurs\u0000when considering a wave propagation in complex media, characterized by nonlocal\u0000interactions and spatially varying wave speeds. More specifically, by using\u0000tools from Toeplitz and generalized locally Toeplitz theory, the present\u0000research delves into the spectral analysis of nonpreconditioned and\u0000preconditioned matrix-sequences. We report numerical evidences supporting the\u0000theoretical findings. Finally, open problems and potential extensions in\u0000various directions are presented and briefly discussed.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"300 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902413","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}
Wietse M. Boon, Dennis Gläser, Rainer Helmig, Kilian Weishaupt, Ivan Yotov
{"title":"A mortar method for the coupled Stokes-Darcy problem using the MAC scheme for Stokes and mixed finite elements for Darcy","authors":"Wietse M. Boon, Dennis Gläser, Rainer Helmig, Kilian Weishaupt, Ivan Yotov","doi":"arxiv-2402.10615","DOIUrl":"https://doi.org/arxiv-2402.10615","url":null,"abstract":"A discretization method with non-matching grids is proposed for the coupled\u0000Stokes-Darcy problem that uses a mortar variable at the interface to couple the\u0000marker and cell (MAC) method in the Stokes domain with the Raviart-Thomas mixed\u0000finite element pair in the Darcy domain. Due to this choice, the method\u0000conserves linear momentum and mass locally in the Stokes domain and exhibits\u0000local mass conservation in the Darcy domain. The MAC scheme is reformulated as\u0000a mixed finite element method on a staggered grid, which allows for the\u0000proposed scheme to be analyzed as a mortar mixed finite element method. We show\u0000that the discrete system is well-posed and derive a priori error estimates that\u0000indicate first order convergence in all variables. The system can be reduced to\u0000an interface problem concerning only the mortar variables, leading to a\u0000non-overlapping domain decomposition method. Numerical examples are presented\u0000to illustrate the theoretical results and the applicability of the method.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139904279","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}
Ryan M. Aronson, Nicola Castelletto, François P. Hamon, J. A. White, Hamdi A. Tchelepi
{"title":"Pressure-stabilized fixed-stress iterative solutions of compositional poromechanics","authors":"Ryan M. Aronson, Nicola Castelletto, François P. Hamon, J. A. White, Hamdi A. Tchelepi","doi":"arxiv-2402.10469","DOIUrl":"https://doi.org/arxiv-2402.10469","url":null,"abstract":"We consider the numerical behavior of the fixed-stress splitting method for\u0000coupled poromechanics as undrained regimes are approached. We explain that\u0000pressure stability is related to the splitting error of the scheme, not the\u0000fact that the discrete saddle point matrix never appears in the fixed-stress\u0000approach. This observation reconciles previous results regarding the pressure\u0000stability of the splitting method. Using examples of compositional\u0000poromechanics with application to geological CO$_2$ sequestration, we see that\u0000solutions obtained using the fixed-stress scheme with a low order finite\u0000element-finite volume discretization which is not inherently inf-sup stable can\u0000exhibit the same pressure oscillations obtained with the corresponding fully\u0000implicit scheme. Moreover, pressure jump stabilization can effectively remove\u0000these spurious oscillations in the fixed-stress setting, while also improving\u0000the efficiency of the scheme in terms of the number of iterations required at\u0000every time step to reach convergence.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"186 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902509","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}
Wensi Wu, Mitchell Daneker, Kevin T. Turner, Matthew A. Jolley, Lu Lu
{"title":"Identifying heterogeneous micromechanical properties of biological tissues via physics-informed neural networks","authors":"Wensi Wu, Mitchell Daneker, Kevin T. Turner, Matthew A. Jolley, Lu Lu","doi":"arxiv-2402.10741","DOIUrl":"https://doi.org/arxiv-2402.10741","url":null,"abstract":"The heterogeneous micromechanical properties of biological tissues have\u0000profound implications across diverse medical and engineering domains. However,\u0000identifying the full-field heterogeneous elastic properties of soft materials\u0000using traditional computational and engineering approaches is fundamentally\u0000challenging due to difficulties in estimating local stress fields. Recently,\u0000there has been a growing interest in using data-driven models to learn\u0000full-field mechanical responses such as displacement and strain from\u0000experimental or synthetic data. However, research studies on inferring the\u0000full-field elastic properties of materials, a more challenging problem, are\u0000scarce, particularly for large deformation, hyperelastic materials. Here, we\u0000propose a novel approach to identify the elastic modulus distribution in\u0000nonlinear, large deformation hyperelastic materials utilizing physics-informed\u0000neural networks (PINNs). We evaluate the prediction accuracies and\u0000computational efficiency of PINNs, informed by mechanic features and\u0000principles, across three synthetic materials with structural complexity that\u0000closely resemble real tissue patterns, such as brain tissue and tricuspid valve\u0000tissue. Our improved PINN architecture accurately estimates the full-field\u0000elastic properties, with relative errors of less than 5% across all examples.\u0000This research has significant potential for advancing our understanding of\u0000micromechanical behaviors in biological materials, impacting future innovations\u0000in engineering and medicine.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"220 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902603","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":"Reduced Order Model Enhanced Source Iteration with Synthetic Acceleration for Parametric Radiative Transfer Equation","authors":"Zhichao Peng","doi":"arxiv-2402.10488","DOIUrl":"https://doi.org/arxiv-2402.10488","url":null,"abstract":"Applications such as uncertainty quantification and optical tomography,\u0000require solving the radiative transfer equation (RTE) many times for various\u0000parameters. Efficient solvers for RTE are highly desired. Source Iteration with Synthetic Acceleration (SISA) is one of the most\u0000popular and successful iterative solvers for RTE. Synthetic Acceleration (SA)\u0000acts as a preconditioning step to accelerate the convergence of Source\u0000Iteration (SI). After each source iteration, classical SA strategies introduce\u0000a correction to the macroscopic particle density by solving a low order\u0000approximation to a kinetic correction equation. For example, Diffusion\u0000Synthetic Acceleration (DSA) uses the diffusion limit. However, these\u0000strategies may become less effective when the underlying low order\u0000approximations are not accurate enough. Furthermore, they do not exploit low\u0000rank structures concerning the parameters of parametric problems. To address these issues, we propose enhancing SISA with data-driven ROMs for\u0000the parametric problem and the corresponding kinetic correction equation.\u0000First, the ROM for the parametric problem can be utilized to obtain an improved\u0000initial guess. Second, the ROM for the kinetic correction equation can be\u0000utilized to design a low rank approximation to it. Unlike the diffusion limit,\u0000this ROM-based approximation builds on the kinetic description of the\u0000correction equation and leverages low rank structures concerning the\u0000parameters. We further introduce a novel SA strategy called ROMSAD. ROMSAD\u0000initially adopts our ROM-based approximation to exploit its greater efficiency\u0000in the early stage, and then automatically switches to DSA to leverage its\u0000robustness in the later stage. Additionally, we propose an approach to\u0000construct the ROM for the kinetic correction equation without directly solving\u0000it.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"184 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902420","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}
Sajad Salavatidezfouli, Saeid Rakhsha, Armin Sheidani, Giovanni Stabile, Gianluigi Rozza
{"title":"A Predictive Surrogate Model for Heat Transfer of an Impinging Jet on a Concave Surface","authors":"Sajad Salavatidezfouli, Saeid Rakhsha, Armin Sheidani, Giovanni Stabile, Gianluigi Rozza","doi":"arxiv-2402.10641","DOIUrl":"https://doi.org/arxiv-2402.10641","url":null,"abstract":"This paper aims to comprehensively investigate the efficacy of various Model\u0000Order Reduction (MOR) and deep learning techniques in predicting heat transfer\u0000in a pulsed jet impinging on a concave surface. Expanding on the previous\u0000experimental and numerical research involving pulsed circular jets, this\u0000investigation extends to evaluate Predictive Surrogate Models (PSM) for heat\u0000transfer across various jet characteristics. To this end, this work introduces\u0000two predictive approaches, one employing a Fast Fourier Transformation\u0000augmented Artificial Neural Network (FFT-ANN) for predicting the average\u0000Nusselt number under constant-frequency scenarios. Moreover, the investigation\u0000introduces the Proper Orthogonal Decomposition and Long Short-Term Memory\u0000(POD-LSTM) approach for random-frequency impingement jets. The POD-LSTM method\u0000proves to be a robust solution for predicting the local heat transfer rate\u0000under random-frequency impingement scenarios, capturing both the trend and\u0000value of temporal modes. The comparison of these approaches highlights the\u0000versatility and efficacy of advanced machine learning techniques in modelling\u0000complex heat transfer phenomena.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"184 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902598","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}
Ivan Prusak, Davide Torlo, Monica Nonino, Gianluigi Rozza
{"title":"Optimisation--Based Coupling of Finite Element Model and Reduced Order Model for Computational Fluid Dynamics","authors":"Ivan Prusak, Davide Torlo, Monica Nonino, Gianluigi Rozza","doi":"arxiv-2402.10570","DOIUrl":"https://doi.org/arxiv-2402.10570","url":null,"abstract":"With the increased interest in complex problems, such as multiphysics and\u0000multiscale models, as well as real-time computations, there is a strong need\u0000for domain-decomposition (DD) segregated solvers and reduced-order models\u0000(ROMs). Segregated models decouple the subcomponents of the problems at hand\u0000and use already existing state-of-the-art numerical codes in each component. In\u0000this manuscript, starting with a DD algorithm on non-overlapping domains, we\u0000aim at the comparison of couplings of different discretisation models, such as\u0000Finite Element (FEM) and ROM for separate subcomponents. In particular, we\u0000consider an optimisation-based DD model on two non-overlapping subdomains where\u0000the coupling on the common interface is performed by introducing a control\u0000variable representing a normal flux. Gradient-based optimisation algorithms are\u0000used to construct an iterative procedure to fully decouple the subdomain state\u0000solutions as well as to locally generate ROMs on each subdomain. Then, we\u0000consider FEM or ROM discretisation models for each of the DD problem\u0000components, namely, the triplet state1-state2-control. We perform numerical\u0000tests on the backward-facing step Navier-Stokes problem to investigate the\u0000efficacy of the presented couplings in terms of optimisation iterations and\u0000relative errors.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"255 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139904119","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":"High-order reliable numerical methods for epidemic models with non-constant recruitment rate","authors":"B. M. Takács, G. Svantnerné Sebestyén, I. Faragó","doi":"arxiv-2402.10549","DOIUrl":"https://doi.org/arxiv-2402.10549","url":null,"abstract":"The mathematical modeling of the propagation of illnesses has an important\u0000role from both mathematical and biological points of view. In this article, we\u0000observe an SEIR-type model with a general incidence rate and a non-constant\u0000recruitment rate function. First, we observe the qualitative properties of\u0000different methods: first-order and higher-order strong stability preserving\u0000Runge-Kutta methods cite{shu}. We give different conditions under which the\u0000numerical schemes behave as expected. Then, the theoretical results are\u0000demonstrated by some numerical experiments. keywords{positivity preservation,\u0000general SEIR model, SSP Runge-Kutta methods}","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"81 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902414","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":"Wavelet compressed, modified Hilbert transform in the space-time discretization of the heat equation","authors":"Helmut Harbrecht, Christoph Schwab, Marco Zank","doi":"arxiv-2402.10346","DOIUrl":"https://doi.org/arxiv-2402.10346","url":null,"abstract":"On a finite time interval $(0,T)$, we consider the multiresolution Galerkin\u0000discretization of a modified Hilbert transform $mathcal H_T$ which arises in\u0000the space-time Galerkin discretization of the linear diffusion equation. To\u0000this end, we design spline-wavelet systems in $(0,T)$ consisting of piecewise\u0000polynomials of degree $geq 1$ with sufficiently many vanishing moments which\u0000constitute Riesz bases in the Sobolev spaces $ H^{s}_{0,}(0,T)$ and $\u0000H^{s}_{,0}(0,T)$. These bases provide multilevel splittings of the temporal\u0000discretization spaces into \"increment\" or \"detail\" spaces of direct sum type.\u0000Via algebraic tensor-products of these temporal multilevel discretizations with\u0000standard, hierarchic finite element spaces in the spatial domain (with standard\u0000Lagrangian FE bases), sparse space-time tensor-product spaces are obtained,\u0000which afford a substantial reduction in the number of the degrees of freedom as\u0000compared to time-marching discretizations. In addition, temporal spline-wavelet\u0000bases allow to compress certain nonlocal integrodifferential operators which\u0000appear in stable space-time variational formulations of initial-boundary value\u0000problems, such as the heat equation and the acoustic wave equation. An\u0000efficient preconditioner is proposed that affords linear complexity solves of\u0000the linear system of equations which results from the sparse space-time\u0000Galerkin discretization.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902412","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 variational discretizations for a convection-diffusion problem","authors":"Constantin Bacuta, Cristina Bacuta, Daniel Hayes","doi":"arxiv-2402.10281","DOIUrl":"https://doi.org/arxiv-2402.10281","url":null,"abstract":"For a model convection-diffusion problem, we obtain new error estimates for a\u0000general upwinding finite element discretization based on bubble modification of\u0000the test space. The key analysis tool is based on finding representations of\u0000the optimal norms on the trial spaces at the continuous and discrete levels. We\u0000analyze and compare the standard linear discretization, the saddle point least\u0000square and upwinding Petrov-Galerkin methods. We conclude that the bubble\u0000upwinding Petrov-Galerkin method is the most performant discretization for the\u0000one dimensional model. Our results for the model convection-diffusion problem\u0000can be extended for creating new and efficient discretizations for the\u0000multidimensional cases.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"147 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139902515","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}