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Simulation of viscous Flow around a circular Cylinder with STAR-CCM+
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Marine Technology.
2013 (English)MasteroppgaveStudent thesis
Abstract [en]

In this thesis, three-dimensional modelling of the flow around a circular cylinder is accomplished. Two cases are considered. The first (Case 1) is a cylinder in steady, uniform current subjected to Reynolds number 3900. The second case (Case 2) is a cylinder in the vicinity of a rigid wall, also at Reynolds number 3900. For the second case, both a boundary layer velocity profile (Case 2a) and a uniform inlet velocity profile (Case 2b) is simulated. The gap-to-diameter ratio, e/D, is set to 0.2 for Case 2. Large eddy simulations (LES) with Smagorinsky subgrid scale (SGS) model are applied to simulate the flow. LES have ability to resolve fine structures in the turbulent wake of the cylinder. A mesh convergence study is accomplished for Case 2a. In the first part of the thesis, the background theory for the case is given in addition to information about the applied pre- and postprocessing tools. In the last part of the thesis, the case set-up is described and the results are presented and discussed. Velocity profiles in the cylinder wake, hydrodynamic values and pressure distribution on the cylinder wall are investigated to give a better understanding of the physics in the cases. The results are compared to published experimental measurements and numerical studies. For the first case, the results tend to agree well with published research. The softwaresystem with LES and the Smagorinsky subgrid scale model does successfully simulate the flow in the boundary layers, the shear layers and the near wake. The results are interesting in the context of flow bifurcation for at cylinder subjected to Reynolds number 3900. The vortex shedding is suppressed for both Case 2a and Case 2b, as expected. For the cylinder in Case 2a, a decreased drag coefficient is observed when compared to Case 1. This is not observed for the cylinder in Case 2b. The two cases are observed to have an increased mean lift coefficient caused by the vicinity of the wall. However, for Case 2b, the increase is of larger magnitude. This is addressed to the pressure distribution on the cylinder surface. There are also observed differences in the wake statistics for Case 2a and Case 2b. It is concluded that both gap-todiameter ratio and boundary layer thickness have a significant influence on the flow around a circular cylinder.

Place, publisher, year, edition, pages
Institutt for marin teknikk , 2013. , 97 p.
URN: urn:nbn:no:ntnu:diva-22378Local ID: ntnudaim:9371OAI: diva2:649621
Available from: 2013-09-19 Created: 2013-09-19 Last updated: 2013-09-19Bibliographically approved

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