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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/1463

Title: 3D LES computations of a shallow lateral expansion using an immersed boundary method
Authors: Talstra, Harmen
Uijttewaal, Wim S.J.
Stelling, Guus S.
Keywords: Large eddy simulation;Turbulence modeling;Computational hydraulics
Issue Date: 11-Sep-2006
Publisher: Michael Piasecki and College of Engineering, Drexel University
Citation: Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732
Abstract: In environmental shallow flows, the phenomenon of flow separation often gives rise to large-scale turbulent structures (vortex shedding). In this study, 3D LES computations of three Shallow Lateral Expansion geometries are performed. The resolved large-scale turbulent structures are studied in detail in order to allow a comparison with laboratory experiments, carried out using the Particle Image Velocimetry (PIV) technique. When LES is applied for practical cases involving flow separation, immersed boundaries are often an essential part of the geometry. These boundaries can cause problems with respect to the Navier Stokes solver used, especially regarding the pressure correction module. A solution to this problem, known as Immersed Boundary Method (IBM), is found by using body forces to ensure the impermeability of internal boundaries. The classical IBM formulation, however, makes a systematic error regarding momentum transfer in the vicinity of solid walls. In this study an adjusted IBM is proposed, based on momentum fluxes instead of body forces. The adjusted model is applied to Shallow Lateral Expansion geometries of various aspect ratios. In order to analyze the real-time large-scale turbulent structures, the vector potential function of the velocity field is computed. This is a very suitable tool to detect large-scale flow structures. The turbulence features observed in the 3D LES computation are compared with the PIV data, especially regarding the vortex shedding behaviour. An analysis of Reynolds stresses and the downstream development of eddy length scales reveals the existence of two different regimes in the vortex shedding behaviour. The difference can be explained by the interaction of shed vortices with the primary and secondary recirculation cells that are present.
Description: Paper presented at The Seventh International Conference on HydroScience and Engineering (ICHE) hosted by the College of Engineering at Drexel Univeristy on September 10-13, 2006 in Philadelphia, Pennsylvania. The conference theme was IT in the Field of HydroSciences. It included several mini-symposia that emphasized IT topics in HydroSciences and the yearly meeting of the metadata group of the International Oceanographic Data and Information Exchange organization.
URI: http://hdl.handle.net/1860/1463
ISBN: 0977447405
Appears in Collections:Proceedings of the 7th International Conference on HydroScience and Engineering (ICHE 2006) [ISBN: 0977447405]

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