The merging of Kelvin–Helmholtz vortices into large coherent flow structures in a high Reynolds number flow past a wall-mounted square cylinder
| Autor: | Grégory Germain, Mikaël Grondeau, Emmanuel Poizot, Philippe Mercier, Philippe Druault, Jérôme Thiébot, Maria Ikhennicheu, Sylvain Guillou |
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| Přispěvatelé: | Laboratoire Universitaire des Sciences Appliquées de Cherbourg (LUSAC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut national des sciences et techniques de la mer (INTECHMER), Conservatoire National des Arts et Métiers [CNAM] (CNAM), Institut Jean Le Rond d'Alembert (DALEMBERT), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS) |
| Rok vydání: | 2020 |
| Předmět: |
Environmental Engineering
010504 meteorology & atmospheric sciences Lattice Boltzmann methods Ocean Engineering Numerical simulation Wake Large Eddy Simulation 01 natural sciences 010305 fluids & plasmas Physics::Fluid Dynamics symbols.namesake 0103 physical sciences ComputingMilieux_MISCELLANEOUS 0105 earth and related environmental sciences [PHYS]Physics [physics] Physics Turbulence Numerical analysis Coherent flow structure Mechanics Wall-mounted obstacles Vortex Helmholtz free energy Free surface symbols Lattice Boltzmann Method Large eddy simulation |
| Zdroj: | Ocean Engineering Ocean Engineering, Elsevier, 2020, 204, pp.107274. ⟨10.1016/j.oceaneng.2020.107274⟩ Ocean Engineering (0029-8018) (Elsevier BV), 2020-05, Vol. 204, P. 107274 (13p.) |
| ISSN: | 0029-8018 |
| Popis: | Flows at tidal-stream energy sites are characterised by high turbulence intensities and by the occurrence of highly energetic large and coherent flow structures. The interaction of the flow with seabed roughness is suspected to play a major role in the generation of such coherent flow structures. The problem is introduced with canonical wall-mounted square obstacles representing abrupt changes of bathymetry, with high Reynolds number flow (Re = 250000). Two methods are used: a numerical model, based on the LBM (Lattice Boltzmann Method) combined with LES (Large Eddy Simulation) and an experimental set-up in a circulating tank. The numerical model is validated by comparison with experimental data. In the case of a wall-mounted square cylinder, large-scale turbulent structures are identified in experiments where boils at the free surface can be observed. LBM simulation allows their three-dimensional characterisation. The dynamic of such large-scale events is investigated by temporal, spatial and spectral numerical analysis. Results show that periodical Kelvin–Helmholtz vortices are emitted in the cylinder wake. Then, they merge to form larger and more coherent structures that rise up to the surface. A wavelet study shows that the emission frequency of the Kelvin–Helmholtz vortices is not constant over time. |
| Databáze: | OpenAIRE |
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