Effect of acoustic resonance on the dynamic lift forces acting on two tandem cylinders in cross-flow |
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| Authors: | A Mohany S Ziada |
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| Institution: | 1. Atomic Energy of Canada Limited (AECL), Chalk River Laboratories, Ontario, Canada K0J 1P0;2. Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7;1. Department of Surgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, PR China;2. Department of Oncosurgery, Anyang Tumor Hospital, Anyang, Henan Province, PR China;3. Department of Pathology, Anyang Tumor Hospital, Anyang, Henan Province, PR China;1. Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA;2. Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA;1. Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany;2. SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom;3. The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany;1. Department of Materials Science & Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA;2. Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA;1. School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001, China;2. Information College of Electronic-Engineering, Xuchang University, Xuchang 461000, China;1. Institute of Physics, Unjong district, Phyongyang, Democratic People''s Republic of Korea;2. Institute of Laser, Unjong district, Phyongyang, Democratic People''s Republic of Korea;3. Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China |
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| Abstract: | Direct measurements of the dynamic lift force acting on two tandem cylinders in cross-flow are performed in the presence and absence of acoustic resonance. The dynamic lift force is measured because it represents the integrated effect of the unsteady wake and therefore it is directly related to the dipole sound source generated by vortex shedding from the cylinder. Three spacing ratios inside the proximity interference region, L/D=1.75, 2.5 and 3 are considered. During the tests, the first transverse acoustic mode of the duct housing the cylinders is self-excited. In the absence of acoustic resonance, the measured dynamic lift coefficients agree with those reported in the literature. When the acoustic resonance is initiated, a drastic increase in the dynamic lift coefficient is observed, especially for the downstream cylinder. This can be associated with abrupt changes in the phase between the lift forces and the acoustic pressure. The dynamic lift forces on both cylinders are also decomposed into in-phase and out-of-phase components, with respect to the resonant sound pressure. The lift force components for the downstream cylinder are found to be dominant. Moreover, the out-of-phase component of the lift force on the downstream cylinder is found to become negative over two different ranges of flow velocity and to virtually vanish between these two ranges. Acoustic resonance of the first mode is therefore excited over two ranges of flow velocity separated by a non-resonant range near the velocity of frequency coincidence. It is therefore concluded that the occurrence of acoustic resonance is controlled by the out-of-phase lift component of the downstream cylinder, whereas the effect of the in-phase lift component is confined to causing small changes in the acoustic resonance frequency. |
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