Wake-induced vibrations of an elastically mounted cylinder located downstream of a stationary larger cylinder at low Reynolds numbers |
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| Affiliation: | 1. State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, No. 800, Dongchuan Road, Shanghai 200240, China;2. Laboratory for Hydraulics Saint-Venant, Université Paris-Est, 6 quai Watier, 78400 Chatou, France;1. School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, No. 800, Dongchuan Road, Shanghai 200240, China;2. State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, No. 800, Dongchuan Road, Shanghai 200240, China;1. School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore 639798, Republic of Singapore;2. Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China;3. Singapore Institute of Technology, Singapore 179104, Republic of Singapore;1. School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran;2. Department of Civil Engineering, K.N.Toosi University of Technology, Tehran, Iran;1. School of Computing, Engineering and Mathematics, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia;2. School of Civil, Environmental and Mining Engineering, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;3. Center for Deepwater Engineering, Dalian University of Technology, Dalian 116024, China |
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| Abstract: | Two-dimensional numerical simulations of flow past two unequal-sized circular cylinders in tandem arrangement are performed at low Reynolds numbers (Re). The upstream larger cylinder is stationary, while the downstream cylinder has both one (transverse-only) and two (transverse and in-line) degrees of freedom (1-dof and 2-dof, respectively). The Re, based on the free stream velocity U∞ and the downstream cylinder diameter d, varies between 50 and 200 with a wide range of reduced velocities Ur. The diameter of the upstream cylinder is twice that of the downstream cylinder, and the center-to-center spacing is 5.5d. In general, for the 1-dof case, the calculations show that the wake-induced vibrations (WIV) of the downstream cylinder are greatly amplified when compared to the case of a single cylinder or two equal-sized cylinders. The transverse amplitudes build up to a significantly higher level within and beyond the lock-in region, and the Ur associated with the peak amplitude shifts toward a higher value. The dominant wake pattern is 2S mode for Re=50 and 100, while with the increase of Re to 150 and 200, the P+S mode can be clearly observed at some lower Ur. For the 2-dof vibrations, the transverse response characteristics are similar to those presented in the corresponding 1-dof case. The in-line responses are generally much smaller, except for several significant vibrations resulting from in-line resonance. The obvious in-line vibration may induce a C (chaotic) vortex shedding mode for higher Re (Re=200). With regard to the 2-dof motion trajectories, besides the typical figure-eight pattern, several odd patterns such as figure-double eight and single-looped trajectories are also obtained due to the wake interference effect. |
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| Keywords: | Two unequal-sized circular cylinders Tandem arrangement Wake-induced vibrations Low Reynolds number |
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