Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Finite Element Based Stabilized Methods for Time Dependent Convection-Diffusion Equation and Their Analysis(Izmir Institute of Technology, 2016) Yılmaz, Kemal Cem; Tanoğlu, GamzeThis study is focused on a Fourier stability and accuracy analysis of the time integration algorithms using generalized trapezioidal family of methods of scalar unsteady convection–diffusion equation with periodic boundary conditions. The discretization in space dimension is performed by standard Galerkin finite element formulation for low Peclet numbers and stabilized finite element formulation for large Peclet numbers. The stability analysis is performed namely by von-Neumann stability analysis. Accuracy is measured in terms of damping errors and phase speed errors. The behaviour of these temporal errors of the particular time stepping algorithms, i.e. forward Euler, Crank-Nicolson and backward Euler methods are compared with each other. Particular attention is given to the stabilized finite element formulation, that is the case where we consider high Peclet numbers. For this case, it is concluded that the Crank-Nicolson time stepping represents a better approximate solution compared to the other time integrators on transport process of an initial wave profile. Finally, at the end of the study, we derive a stabilization parameter under a particular condition on Courant number, which provides the relative phase speed error being almost equivalent to its optimal level, that is, the waves with different Fourier modes propagate almost in the same speed. Theoretical results are confirmed by a number of numerical experiments.Master Thesis Convergence Analysis and Numerical Solutions of the Fisher's and Benjamin-Bono Equations by Operator Splitting Method(Izmir Institute of Technology, 2014) Zürnacı, Fatma; Tanoğlu, GamzeThis thesis is concerned with the operator splitting method for the Fisher’s and Benjamin-Bono-Mahony type equations. We showthat the correct convergence rates inHs(R) space for Lie- Trotter and Strang splitting method which are obtained for these equations. In the proofs, the new framework originally introduced in (Holden, Lubich, and Risebro, 2013) is used. Numerical quadratures and Peano Kernel theorem, which is followed by the differentiation in Banach space are discussed In addition, we discuss the Sobolev space Hs(R) and give several properties of this space. With the help of these subjects, we derive error bounds for the first and second order splitting methods. Finally, we numerically check the convergence rates for the time step ∆t.Master Thesis Operator Splitting Methods for Non-Autonomous Differential Equations(Izmir Institute of Technology, 2011) Korkut, Sıla Övgü; Tanoğlu, GamzeIn this thesis, convergency and stability analysis are studied for the non-autonomous differential equations. Not only classical operator splitting methods; Lie Trother splitting, symmetrically weighted splitting and Strang splitting but also iterative splitting method which is recent popular technique of operator splitting methods are considered. We concentrate on how to improve the operator splitting methods with the help of the Magnus expansion. In addition, we construct a new symmetric iterative splitting scheme. Then, we also study its convergence properties by using the concepts of stability, consistency and order. For this purpose, we use C0 semigroup techniques. Finally, several numerical examples are illustrated in order to confirm our theoretical results by comparing the new symmetric iterative splitting method with frequently used operator splitting methods.