Numerical study of flapping filaments in a uniform fluid flow |
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| Institution: | 1. Aix Marseille Université, CNRS, Centrale Marseille, M2P2 UMR 7340, 13451 Marseille, France;2. School of Mechanical, Aerospace and Civil Engineering (MACE), University of Manchester, United Kingdom;3. School of Engineering and Mathematical Sciences (EMS), City University, London, United Kingdom;1. University of Genova 1 via Montallegro, Italy;2. Monash University, Australia;3. Monash University, Australia;4. Institut de Mécanique des Fluides de Toulouse, France;1. Department of Agricultural Sciences (DIPSA), University of Bologna, 40127 Bologna, Italy;2. Department of Technologies, University of Naples “Parthenope”, 80143 Naples, Italy;3. Industrial Engineering School, Department of Economy and Enterprise (DEIM), University of Tuscia, Largo dell'' Universita s.n.c., 01100 Viterbo, Italy;4. Department of Civil, Environmental and Materials Engineering (DICAM), University of Bologna, 40136 Bologna, Italy;1. Department of Aerodynamics, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China;2. Department of Mechanical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore;3. National Key Laboratory of Science and Technology on Hydrodynamics, China Ship Scientific Research Center, Wuxi, Jiangsu 214082, China;1. Aix-Marseille Université, CNRS, Centrale Marseille, M2P2 UMR 7340, 13451, Marseille, France;2. École Centrale de Nantes, LHEEA, ECN/CNRS, Nantes, France;3. Université de Sherbrooke, Faculté de génie, Département de génie mécanique, Sherbrooke, J1K 2R1, Canada |
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| Abstract: | The coupled dynamics of multiple flexible filaments (also called monodimensional flags) flapping in a uniform fluid flow is studied numerically for the cases of a side-by-side arrangement, and an in-line configuration. The modal behaviour and hydrodynamical properties of the sets of filaments are studied using a Lattice Boltzmann–Immersed Boundary method. The fluid momentum equations are solved on a Cartesian uniform lattice while the beating filaments are tracked through a series of markers, whose dynamics are functions of the forces exerted by the fluid, the filaments flexural rigidity and the tension. The instantaneous wall conditions on the filaments are imposed via a system of singular body forces, consistently discretised on the lattice of the Boltzmann equation. The results exhibit several flapping modes for two and three filaments placed side-by-side and are compared with experimental and theoretical studies. The hydrodynamical drafting, observed so far only experimentally on configurations of in-line flexible bodies, is also revisited numerically in this work, and the associated physical mechanism is identified. In certain geometrical and structural configuration, it is found that the upstream body experiences a reduced drag compared to the downstream body, which is the contrary of what is encountered on rigid bodies (cars, bicycles). |
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| Keywords: | Beating filaments Flapping flags Inverted hydrodynamic drafting Immersed Boundary Lattice Boltzmann |
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