Discontinuous Galerkin Finite Element Approximation of Nonlinear Second-Order Elliptic and Hyperbolic Systems

Ortner, Christoph and Suli, Endre (2006) Discontinuous Galerkin Finite Element Approximation of Nonlinear Second-Order Elliptic and Hyperbolic Systems. Technical Report. Unspecified. (Submitted)

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Abstract

We develop the convergence analysis of discontinuous Galerkin finite element approximations to second-order quasilinear elliptic and hyperbolic systems of partial differential equations of the form, respectively, $-\sum_{\alpha=1}^d \partial_{x_\alpha} S_{i\alpha}(\nabla u(x)) = f_i(x)$ , $i=1,\dots, d$ , and $\partial^2_t{u}_i-\sum_{\alpha=1}^d \partial_{x_\alpha} S_{i\alpha}(\nabla u(t,x)) = f_i(t,x)$ , $i=1,\dots, d$ , with $\partial_{x_\alpha} = \partial/\partial x_\alpha$ , in a bounded spatial domain in $\mathbb{R}^d$ , subject to mixed Dirichlet--Neumann boundary conditions, and assuming that $S=(S_{i\alpha})$ is uniformly monotone on $\mathbb{R}^{d\times d}$ . The associated energy functional is then uniformly convex. An optimal order bound is derived on the discretization error in each case without requiring the global Lipschitz continuity of the tensor $S$ . We then further relax our hypotheses: using a broken G ${\aa}$ rding inequality we extend our optimal error bounds to the case of quasilinear hyperbolic systems where, instead of assuming that $S$ is uniformly monotone, we only require that the fourth-order tensor $A=\nabla S$ is satisfies a Legendre--Hadamard condition. The associated energy functional is then only rank-1 convex. Evolution problems of this kind arise as mathematical models in nonlinear elastic wave propagation.

The authors acknowledge the financial support received from the European research project HPRN-CT-2002-00284: New Materials, Adaptive Systems and their Nonlinearities. Modelling, Control and Numerical Simulation, and the kind hospitality of Carlo Lovadina and Matteo Negri (University of Pavia).

Item Type:	Technical Report (Technical Report)
Subjects:	H - N > Numerical analysis
Research Groups:	Numerical Analysis Group
ID Code:	1118
Deposited By:	Lotti Ekert
Deposited On:	11 May 2011 10:56
Last Modified:	11 May 2011 10:56

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