Numerical evaluation of the clearance geometries effect on the flow field and performance of a hydrofoil |
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| Affiliation: | 1. College of Water Resources and Civil Engineering, China Agricultural University, Beijing, China;2. Department of Thermal Engineering, Tsinghua University, Beijing, China;3. Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, Beijing, China;1. Institut national de la recherche scientifique, Centre Eau Terre Environnement, 490 rue de la Couronne, Québec, QC, G1K 9A9, Canada;2. Département de génie mécanique, École de Technologie Supérieure, 1100 rue Notre-Dame Ouest, Montréal, QC, H3C 1K3, Canada;1. School of Engineering, University of Portsmouth, UK;2. Fluid Structure Interaction Research Group, Faculty of Engineering and the Environment, University of Southampton, UK;1. Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Ensenada, Baja California, C.P. 22860, Mexico;2. Centro de Investigación y Desarrollo Tecnológico en Electroquímica, Tijuana, Baja California, C.P. 22444, Mexico;3. Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, Morelia, Michoacán, 58060, Mexico;4. Institut de Recherches sur la Catalyse et l’Environnement de Lyon (IRCELYON), CNRS – Université Lyon I, Villeurbanne, France;1. Departamet d’Enginyeria Mecanica, Universitat Rovira i Virgili, Tarragona, Spain;2. Center of Computational Engineering and Integrated Design (CEID), Department of Mathematics and Physics, Lappeenranta University of Technology, Lappeenranta, Finland;1. IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal;2. Departamento de Física, Escola de Ciências e Tecnologia, Universidade de Évora, R. Romão Ramalho 59, 7002-554 Évora, Portugal;3. Department of Electrical Engineering and Automation, Instituto Superior de Engenharia de Lisboa, R. Conselheiro Emídio Navarro, 1950-062 Lisbon, Portugal |
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| Abstract: | The blade tip leakage flow with efficiency losses and cavitation phenomena is a concern for the low-head tidal power units. A simplified case of NACA0009 hydrofoil in a water tunnel is used to investigate the effects of tip clearance geometries including the foil tip shape and gap width on the flow features and foil performance. Steady non-cavitating simulations are implemented for a round tip foil and a sharp tip foil with two incidence angles (α = 10° and 5°) and different normalized gap width (τ). The minimum pressure is used to reflect the normalized vortex intensity (Γ*) and cavitation characteristics. The Γ*-τ curves at different streamwise positions show that the sharp tip foil generates relatively weaker tip leakage vortex with more flat curves, but its higher Γ* of tip separation vortex in wider gaps increases the risk of clearance cavitation. The flow features on a cross section inside the gap suggest that the sharp tip reduces the leakage flow losses and increases the velocity gradient due to the boundary layer separation. The lift coefficient is a little higher for the sharp tip foil than the round tip foil, with small differences for α = 5° but noticeable deviations for α = 10° especially within 0.3<τ < 1. |
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| Keywords: | Hydrofoil Clearance Tip leakage vortex Tip separation vortex Cavitation |
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