1,634 research outputs found
Dual weighted residual based error control for nonstationary convection-dominated equations: potential or ballast?
Even though substantial progress has been made in the numerical approximation
of convection-dominated problems, its major challenges remain in the scope of
current research. In particular, parameter robust a posteriori error estimates
for quantities of physical interest and adaptive mesh refinement strategies
with proved convergence are still missing. Here, we study numerically the
potential of the Dual Weighted Residual (DWR) approach applied to stabilized
finite element methods to further enhance the quality of approximations. The
impact of a strict application of the DWR methodology is particularly focused
rather than the reduction of computational costs for solving the dual problem
by interpolation or localization.Comment: arXiv admin note: text overlap with arXiv:1803.1064
Primal dual mixed finite element methods for indefinite advection--diffusion equations
We consider primal-dual mixed finite element methods for the
advection--diffusion equation. For the primal variable we use standard
continuous finite element space and for the flux we use the Raviart-Thomas
space. We prove optimal a priori error estimates in the energy- and the
-norms for the primal variable in the low Peclet regime. In the high
Peclet regime we also prove optimal error estimates for the primal variable in
the norm for smooth solutions. Numerically we observe that the method
eliminates the spurious oscillations close to interior layers that pollute the
solution of the standard Galerkin method when the local Peclet number is high.
This method, however, does produce spurious solutions when outflow boundary
layer presents. In the last section we propose two simple strategies to remove
such numerical artefacts caused by the outflow boundary layer and validate them
numerically.Comment: 25 pages, 6 figures, 5 table
Space Decompositions and Solvers for Discontinuous Galerkin Methods
We present a brief overview of the different domain and space decomposition
techniques that enter in developing and analyzing solvers for discontinuous
Galerkin methods. Emphasis is given to the novel and distinct features that
arise when considering DG discretizations over conforming methods. Connections
and differences with the conforming approaches are emphasized.Comment: 2 pages 2 figures no table
A subgrid viscosity Lagrance-Galerkin method for convection-diffusion problems
We present and analyze a subgrid viscosity Lagrange-Galerk
in method that combines the subgrid eddy viscosity method proposed in W. Layton, A connection between subgrid scale
eddy viscosity and mixed methods. Appl. Math. Comp., 133: 14
7-157, 2002, and a conventional Lagrange-Galerkin method in the framework of P1⊕ cubic bubble finite elements. This results in an efficient and easy to implement stabilized method for convection dominated convection diffusion reaction problems. Numerical experiments support the numerical analysis results and show that the new method is more accurate than the conventional Lagrange-Galerkin one
Numerical Analysis of a Second Order Pure Lagrange--Galerkin Method for Convection-Diffusion Problems. Part II: Fully Discretized Scheme and Numerical Results
This version of the article has been accepted for publication, after peer
review, but is not the Version of Record and does not reflect post-acceptance
improvements, or any corrections. The Version of Record is available online
at: https://doi.org/10.1137/100809994[Abstract]: We analyze a second order pure Lagrange-Galerkin method for variable coefficient
convection-(possibly degenerate) diffusion equations with mixed Dirichlet-Robin boundary conditions.
In a previous paper the proposed second order pure Lagrangian time discretization scheme
has been introduced and analyzed for the same problem. More precisely, the l1(H1) stability and
l1(H1) error estimates of order O(_t2) has been obtained. Moreover, for the particular case of
incompressible flows, stability inequalities with constants independent of the final time have been
stated. In the present paper l1(H1) error estimates of order O(_t2) + O(hk) are obtained for the
fully discretized pure Lagrange-Galerkin method. To prove these results we use some properties
obtained in the previous paper. Finally, numerical tests are presented that confirm the theoretical
results.This work was supported by Xunta de Galicia under research project INCITE09 207 047 PR, and by Ministerio de Ciencia e Innovación (Spain) under research projects Consolider MATHEMATICA CSD2006-00032 and MTM2008-02483.
Xunta de Galicia; INCITE09 207 047 P
A first order system least squares method for the Helmholtz equation
We present a first order system least squares (FOSLS) method for the
Helmholtz equation at high wave number k, which always deduces Hermitian
positive definite algebraic system. By utilizing a non-trivial solution
decomposition to the dual FOSLS problem which is quite different from that of
standard finite element method, we give error analysis to the hp-version of the
FOSLS method where the dependence on the mesh size h, the approximation order
p, and the wave number k is given explicitly. In particular, under some
assumption of the boundary of the domain, the L2 norm error estimate of the
scalar solution from the FOSLS method is shown to be quasi optimal under the
condition that kh/p is sufficiently small and the polynomial degree p is at
least O(\log k). Numerical experiments are given to verify the theoretical
results
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