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Bidimensional laminar flow simulation around a circular cylinder 1. Description of the case Subject: A circular cylinder with a diameter of D = 0,04 m, submerged in a stream with an undisturbed speed of V = 5 m/s and ambient pressure. Hypotheses: - Incompressible flow - Laminar flow - Newtonian flow - Bidimensional flow () - Negligible gravitatory effects 2. Theoretical basis The continuity equation, The momentum equation, The Reynolds number, The Strouhal number (which describes oscillating flow mechanisms), The drag coeffcient (dimensionless force parallel to the flow), The behaviour of the flow around a circular cylinder is very complex and highly dependent on the Reynolds number. Due to the symmetry of the cylinder, a curious phenomenon appears named von Karman street, consisting of alternate vortices emitted by the cylinder. The vortices are detached periodically and their frequence is directly related to the Strouhal number. 3. Mesh generation The mesh for the case of the cylinder is not going to be uniform. Some areas of the domain need to contain a higher cell density (mainly the walls of the cylinder and its prolongation). Consequently, it is necessary to divide the domain in diferent blocks. Mesh stats: points: 355240 internal points: 0 faces: 708020 internal faces: 352780 cells: 176800 faces per cell: 6 boundary patches: 6 point zones: 0 face zones: 0 cell zones: 0 Overall number of cells of each type: hexahedra: 176800 prisms: 0 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 0 polyhedra: 0 4. File structure: In Bidimentional Cylinder case: 5. Results of the simulation The evolution over time of the velocity: file U.ogv The evolution over time of the pressure: file P.ogv
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