scholarly journals Robust nonconforming virtual element methods for general fourth-order problems with varying coefficients

2021 ◽  
Author(s):  
Andreas Dedner ◽  
Alice Hodson
Keyword(s):  
Fourth Order ◽  
Perturbation Parameter ◽  
Two Dimensions ◽  
Optimal Error Estimates ◽  
Projection Operators ◽  
Varying Coefficients ◽  
Virtual Element Methods ◽  
Virtual Element ◽  
Perturbation Problems ◽  
Fourth Order Problems

Abstract We present a class of nonconforming virtual element methods for general fourth-order partial differential equations in two dimensions. We develop a generic approach for constructing the necessary projection operators and virtual element spaces. Optimal error estimates in the energy norm are provided for general linear fourth-order problems with varying coefficients. We also discuss fourth-order perturbation problems and present a novel nonconforming scheme which is uniformly convergent with respect to the perturbation parameter without requiring an enlargement of the space. Numerical tests are carried out to verify the theoretical results. We conclude with a brief discussion on how our approach can easily be applied to nonlinear fourth-order problems.

scholarly journals On the locking-free three-field virtual element methods for Biot's consolidation model in poroelasticity

2020 ◽  
Author(s):  
Xialan Tang ◽  
Zhibin Liu ◽  
Baiju Zhang ◽  
Minfu Feng
Keyword(s):  
Time Discretization ◽  
Optimal Error Estimates ◽  
Specific Storage ◽  
High Order Scheme ◽  
Backward Euler ◽  
Consolidation Model ◽  
Order Scheme ◽  
Virtual Element Methods ◽  
Virtual Element ◽  
Biot’S Consolidation

We propose and analyze two locking-free three-field virtual element methods for Biot's consolidation model in poroelasticity. One is a high-order scheme, and the other is a low-order scheme. For time discretization, we use the backward Euler scheme. The proposed methods are well-posed, and optimal error estimates of all the unknowns are obtained for fully discrete solutions. The generic constants in the estimates are uniformly bounded as the Lamé coefficient λ tends to infinity, and as the constrained specific storage coefficient is arbitrarily small. Therefore the methods are free of both Poisson locking and pressure oscillations. Numerical results illustrate the good performance of the methods and confirm our theoretical predictions.

Virtual Element Method for general second-order elliptic problems on polygonal meshes

2016 ◽  
Vol 26 (04) ◽  
pp. 729-750 ◽  
Author(s):  
L. Beirão da Veiga ◽  
F. Brezzi ◽  
L. D. Marini ◽  
A. Russo
Keyword(s):  
Variable Coefficients ◽  
Second Order ◽  
Projection Operators ◽  
Virtual Element Method ◽  
Basic Principles ◽  
Order Elliptic Operator ◽  
Smooth Coefficients ◽  
Virtual Element Methods ◽  
Virtual Element ◽  
Element Method

We consider the discretization of a boundary value problem for a general linear second-order elliptic operator with smooth coefficients using the Virtual Element approach. As in [A. H. Schatz, An observation concerning Ritz–Galerkin methods with indefinite bilinear forms, Math. Comput. 28 (1974) 959–962] the problem is supposed to have a unique solution, but the associated bilinear form is not supposed to be coercive. Contrary to what was previously done for Virtual Element Methods (as for instance in [L. Beirão da Veiga, F. Brezzi, A. Cangiani, G. Manzini, L. D. Marini and A. Russo, Basic principles of virtual element methods, Math. Models Methods Appl. Sci. 23 (2013) 199–214]), we use here, in a systematic way, the [Formula: see text]-projection operators as designed in [B. Ahmad, A. Alsaedi, F. Brezzi, L. D. Marini and A. Russo, Equivalent projectors for virtual element methods, Comput. Math. Appl. 66 (2013) 376–391]. In particular, the present method does not reduce to the original Virtual Element Method of [L. Beirão da Veiga, F. Brezzi, A. Cangiani, G. Manzini, L. D. Marini and A. Russo, Basic principles of virtual element methods, Math. Models Methods Appl. Sci. 23 (2013) 199–214] for simpler problems as the classical Laplace operator (apart from the lowest-order cases). Numerical experiments show the accuracy and the robustness of the method, and they show as well that a simple-minded extension of the method in [L. Beirão da Veiga, F. Brezzi, A. Cangiani, G. Manzini, L. D. Marini and A. Russo, Basic principles of virtual element methods, Math. Models Methods Appl. Sci. 23 (2013) 199–214] to the case of variable coefficients produces, in general, sub-optimal results.

scholarly journals Divergence-preserving reconstructions on polygons and a really pressure-robust virtual element method for the Stokes problem

2020 ◽  
Author(s):  
Derk Frerichs ◽  
Christian Merdon
Keyword(s):  
Stokes Problem ◽  
Two Dimensions ◽  
Momentum Balance ◽  
Test Functions ◽  
Virtual Test ◽  
Right Hand ◽  
Virtual Element Methods ◽  
Divergence Free ◽  
Virtual Element ◽  
The Right

Abstract Nondivergence-free discretizations for the incompressible Stokes problem may suffer from a lack of pressure-robustness characterized by large discretizations errors due to irrotational forces in the momentum balance. This paper argues that also divergence-free virtual element methods on polygonal meshes are not really pressure-robust as long as the right-hand side is not discretized in a careful manner. To be able to evaluate the right-hand side for the test functions, some explicit interpolation of the virtual test functions is needed that can be evaluated pointwise everywhere. The standard discretization via an $L^2$-best approximation does not preserve the divergence, and so destroys the orthogonality between divergence-free test functions and possibly eminent gradient forces in the right-hand side. To repair this orthogonality and restore pressure-robustness, another divergence-preserving reconstruction is suggested based on Raviart–Thomas approximations on local subtriangulations of the polygons. All findings are proven theoretically and are demonstrated numerically in two dimensions. The construction is also interesting for hybrid high-order methods on polygonal or polyhedral meshes.

scholarly journals Hybrid high-order method for singularly perturbed fourth-order problems on curved domains

2021 ◽  
Author(s):  
Zhaonan Dong ◽  
Alexandre Ern
Keyword(s):  
Singular Perturbation ◽  
Fourth Order ◽  
Mesh Size ◽  
Perturbation Parameter ◽  
High Order ◽  
Singularly Perturbed ◽  
Optimal Error Estimates ◽  
Order Method ◽  
High Order Method ◽  
Type Boundary

We propose a novel hybrid high-order method (HHO) to approximate singularly perturbed fourth-order PDEs on domains with a possibly curved boundary. The two key ideas in devising the method are the use of a Nitsche-type boundary penalty technique to weakly enforce the boundary conditions and a scaling of the weighting parameter in the stabilisation operator that compares the singular perturbation parameter to the square of the local mesh size. With these ideas in hand, we derive stability and optimal error estimates over the whole range of values for the singular perturbation parameter, including the zero value for which a second-order elliptic problem is recovered. Numerical experiments illustrate the theoretical analysis.

scholarly journals Some estimates of virtual element methods for fourth order problems

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Qingguang Guan
Keyword(s):  
Error Estimates ◽  
Fourth Order ◽  
Numerical Solutions ◽  
Optimal Error Estimates ◽  
Virtual Element Method ◽  
Regularity Estimates ◽  
Interpolation Operators ◽  
Virtual Element ◽  
The Right ◽  
Element Method

<p style='text-indent:20px;'>In this paper, we employ the techniques developed for second order operators to obtain the new estimates of Virtual Element Method for fourth order operators. The analysis bases on elements with proper shape regularity. Estimates for projection and interpolation operators are derived. Also, the biharmonic problem is solved by Virtual Element Method, optimal error estimates were obtained. Our choice of the discrete form for the right hand side function relaxes the regularity requirement in previous work and the error estimates between exact solutions and the computable numerical solutions were proved.</p>

scholarly journals A polygonal discontinuous Galerkin method with minus one stabilization

2020 ◽  
Author(s):  
Silvia Bertoluzza ◽  
Daniele Prada
Keyword(s):  
Galerkin Method ◽  
Discontinuous Galerkin ◽  
Discontinuous Galerkin Method ◽  
Two Dimensions ◽  
Optimal Error Estimates ◽  
Virtual Element Method ◽  
Optimal Error ◽  
Numerical Tests ◽  
Virtual Element ◽  
Weak Shape

We propose a Discontinuous Galerkin method for the Poisson equation on polygonal tessellations in two dimensions, stabilized by penalizing, locally in each element K, a residual term involving the fluxes, measured in the norm of the dual of H 1 (K). The scalar product corresponding to such a norm is numerically realized via the introduction of a (minimal) auxiliary space  inspired by the Virtual Element Method. Stability and optimal error estimates in the broken H 1  norm are proven under a weak shape regularity assumption allowing the presence of very small edges. The results of numerical tests confirm the theoretical estimates.

Some Estimates for Virtual Element Methods

2017 ◽  
Vol 17 (4) ◽  
pp. 553-574 ◽  
Author(s):  
Susanne C. Brenner ◽  
Qingguang Guan ◽  
Li-Yeng Sung
Keyword(s):  
Error Estimates ◽  
Three Dimensions ◽  
Poisson Problem ◽  
Polyhedral Meshes ◽  
Virtual Element Methods ◽  
Virtual Element

AbstractWe present novel techniques for obtaining the basic estimates of virtual element methods in terms of the shape regularity of polygonal/polyhedral meshes. We also derive new error estimates for the Poisson problem in two and three dimensions.

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