scholarly journals Space-time approximation of parabolic systems with variable growth

2019 ◽  
Vol 40 (4) ◽  
pp. 2505-2552 ◽  
Author(s):  
Dominic Breit ◽  
Prince Romeo Mensah

Abstract We study a parabolic system with $p(t,x)$-structure under Dirichlet boundary conditions. In particular, we deduce the optimal convergence rate for the error of the gradient of a finite element-based space-time approximation. The error is measured in the quasi norm and the result holds if the exponent $p(t,x)$ is $(\alpha _t,\alpha _x)$-Hölder continuous.

2008 ◽  
Vol 7 (2) ◽  
pp. 44
Author(s):  
E. C. Romão ◽  
J. B. Aparecido ◽  
J. B. Campos-Silva ◽  
L. F. M. Moura

In this work is presented a numerical solution for temperature profile in two-dimensional diffusion inside irregular multi-connected geometry. The special discretization has been done by two variants of the finite Element Method: Galerkin Finite Element Method (GFEM) and Least Squares Finite Element Method (LSFEM). Three applications are presented. The first for a regular double connected domain; the second for a regular multi-connected domain and the third application for an irregular multi-connected domain. In all applications are considered Dirichlet boundary conditions. The results obtained in the present work are compared with results from Ansys® simulations. The results of each method are presented and discussed and the characteristics and advantages of the methods are also discussed.


Author(s):  
Kevin N. Chiu ◽  
Mark D. Fuge

Abstract From engineering analysis and topology optimization to generative design and machine learning, many modern computational design approaches require either large amounts of data or a method to generate that data. This paper addresses key issues with automatically generating such data through automating the construction of Finite Element Method (FEM) simulations from Dirichlet boundary conditions. Most past work on automating FEM assumes prior knowledge of the physics to be run or is limited to a small number of governing equations. In contrast, we propose three improvements to current methods of automating the FEM: (1) completeness labels that guarantee viability of a simulation under specific conditions, (2) type-based labels for solution fields that robustly generate and identify solution fields, and (3) type-based labels for variational forms of governing equations that map the three components of a simulation set — specifically, boundary conditions, solution fields, and a variational form — to each other to form a viable FEM simulation. We implement these improvements using the FEniCS library as an example case. We show that our improvements increase the percent of viable simulations that are run automatically from a given list of boundary conditions. This paper’s procedures ultimately allow for the automatic — i.e., fully computer-controlled — construction of FEM multi-physics simulations and data collection required to run data-driven models of physics phenomena or automate the exploration of topology optimization under many physics.


2016 ◽  
Vol 18 (02) ◽  
pp. 1550018 ◽  
Author(s):  
Sun-Sig Byun ◽  
Jihoon Ok ◽  
Dian K. Palagachev ◽  
Lubomira G. Softova

We consider a parabolic system in divergence form with measurable coefficients in a cylindrical space–time domain with nonsmooth base. The associated nonhomogeneous term is assumed to belong to a suitable weighted Orlicz space. Under possibly optimal assumptions on the coefficients and minimal geometric requirements on the boundary of the underlying domain, we generalize the Calderón–Zygmund theorem for such systems by essentially proving that the spatial gradient of the weak solution gains the same weighted Orlicz integrability as the nonhomogeneous term.


2018 ◽  
Vol 18 (3) ◽  
pp. 373-381 ◽  
Author(s):  
Ramona Baumann ◽  
Thomas P. Wihler

AbstractWe present a numerical approximation method for linear elliptic diffusion-reaction problems with possibly discontinuous Dirichlet boundary conditions. The solution of such problems can be represented as a linear combination of explicitly known singular functions as well as of an {H^{2}}-regular part. The latter part is expressed in terms of an elliptic problem with regularized Dirichlet boundary conditions, and can be approximated by means of a Nitsche finite element approach. The discrete solution of the original problem is then defined by adding back the singular part of the exact solution to the Nitsche approximation. In this way, the discrete solution can be shown to converge of second order in the {L^{2}}-norm with respect to the mesh size.


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