Development of a multigrid accelerated euler solver on adaptively refined two- and three-dimensional cartesian grids

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2009

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Çakmak, Mehtap

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Cartesian grids offer a valuable option to simulate aerodynamic flows around complex geometries such as multi-element airfoils, aircrafts, and rockets. Therefore, an adaptively-refined Cartesian grid generator and Euler solver are developed. For the mesh generation part of the algorithm, dynamic data structures are used to determine connectivity information between cells and uniform mesh is created in the domain. Marching squares and cubes algorithms are used to form interfaces of cut and split cells. Geometry-based cell adaptation is applied in the mesh generation. After obtaining appropriate mesh around input geometry, the solution is obtained using either flux vector splitting method or Roe’s approximate Riemann solver with cell-centered approach. Least squares reconstruction of flow variables within the cell is used to determine high gradient regions of flow. Solution based adaptation method is then applied to current mesh in order to refine these regions and also coarsened regions where unnecessary small cells exist. Multistage time stepping is used with local time steps to increase the convergence rate. Also FAS multigrid technique is used in order to increase the convergence rate. It is obvious that implementation of geometry and solution based adaptations are easier for Cartesian meshes than other types of meshes. Besides, presented numerical results show the accuracy and efficiency of the algorithm by especially using geometry and solution based adaptation. Finally, Euler solutions of Cartesian grids around airfoils, projectiles and wings are compared with the experimental and numerical data available in the literature and accuracy and efficiency of the solver are verified.

Subject Keywords

Mechanical engineering.

URI

http://etd.lib.metu.edu.tr/upload/2/12610753/index.pdf
https://hdl.handle.net/11511/18575

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

M. Çakmak, “Development of a multigrid accelerated euler solver on adaptively refined two- and three-dimensional cartesian grids,” M.S. - Master of Science, Middle East Technical University, 2009.