Worf, D. (2018). Numerical continuation for periodic pipe flow with finite element method [Diploma Thesis, Technische Universität Wien]. reposiTUm. https://doi.org/10.34726/hss.2018.48886
E101 - Institut für Analysis und Scientific Computing
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Date (published):
2018
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Number of Pages:
84
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Keywords:
numerical continuation; Navier Stokes; bifurcation; FEM
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Abstract:
This thesis is concerned with the continuation theory of incompressible periodic pipe flow. For describing the dynamics of incompressible fluids we use the incompressible Navier-Stokes equation. For a better understanding of it we'll look at its derivation. For a long time now the consensus has been that the laminar solution is linearly stable for all Reynolds numbers. The original idea of this thesis was to adapt a numerical continuation procedure to see if it is possible to jump from the laminar solution branch onto a turbulent one, as it happens in practical experiments. Therefore we inspect the different numerical methods that are used in this procedure. Especially we look at a preconditioner for the linearized problem as the matrix given by the finite element method, using Hood-Taylor elements, becomes less well conditioned as the Reynolds number increases. Prompted by this we look at the convection-diffusion equation and the streamline diffusion discretisation to be able to use it in a multigrid method. To motivate the use of the continuation procedure we look at bifurcation theory, with Fredholm operators and Crandall-Rabinowitz' theorem. We also take a short look at the Allen-Cahn equation to test if the algorithm is correctly defined.
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