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We propose and analyze a semi Lagrangian method for the convection-diffusion equation. Error estimates for both semi and fully discrete finite element approximations are obtained for convection dominated flows. The estimates are posed in terms of the projections constructed in [7, 8] and the dependence of various constants upon the diffusion parameter is… (More)

- Konstantinos Chrysafinos, Noel Walkington
- SIAM J. Numerical Analysis
- 2006

We analyze the classical discontinuous Galerkin method for a general parabolic equation. Symmetric error estimates for schemes of arbitrary order are presented. The ideas we develop allow us to relax many assumptions freqently required in previous work. For example, we allow different discrete spaces to be used at each time step and do not require the… (More)

- Konstantinos Chrysafinos, Noel Walkington
- Math. Comput.
- 2010

Numerical schemes to compute approximate solutions of the evolutionary Stokes and Navier-Stokes equations are studied. The schemes are discontinuous in time and conforming in space and of arbitrarily high order. Fully-discrete error estimates are derived and dependence of the viscosity constant is carefully tracked. It is shown that the errors are bounded… (More)

- Konstantinos Chrysafinos, Noel Walkington
- SIAM J. Numerical Analysis
- 2006

- Konstantinos Chrysafinos
- J. Computational Applied Mathematics
- 2009

- Eduardo Casas, Konstantinos Chrysafinos
- Numerische Mathematik
- 2015

- Eduardo Casas, Konstantinos Chrysafinos
- SIAM J. Numerical Analysis
- 2012

The velocity tracking problem for the evolutionary Navier–Stokes equations in two dimensions is studied. The controls are of distributed type and are submitted to bound constraints. First and second order necessary and sufficient conditions are proved. A fully discrete scheme based on the discontinuous (in time) Galerkin approach, combined with conforming… (More)

A discontinuous Galerkin finite element method for an optimal control problem related to semilinear parabolic PDE's is examined. The schemes under consideration are discontinuous in time but conforming in space. Convergence of discrete schemes of arbitrary order is proven. In addition, the convergence of discontinuous Galerkin approximations of the… (More)

- Konstantinos Chrysafinos, Efthimios N. Karatzas
- SIAM J. Numerical Analysis
- 2014

We consider fully discrete finite element approximations of a Robin optimal boundary control problem, constrained by linear parabolic PDEs with rough initial data. Conforming finite element methods for spatial discretization combined with discontinuous time-stepping Galerkin schemes are being used for the space-time discretization. Error estimates are… (More)

The minimization of the energy functional having states constrained to semi-linear parabolic PDEs is considered. The controls act on the boundary and are of Robin type. The discrete schemes under consideration are discontinuous in time but conforming in space. Stability estimates are presented at the energy norm and at arbitrary times for the state, and… (More)