On the wake-induced vibration of tandem circular cylinders: the vortex interaction excitation mechanism
Tóm tắt
The mechanism of wake-induced vibrations (WIV) of a pair of cylinders in a tandem arrangement is investigated by experiments. A typical WIV response is characterized by a build-up of amplitude persisting to high reduced velocities; this is different from a typical vortex-induced vibration (VIV) response, which occurs in a limited resonance range. We suggest that WIV of the downstream cylinder is excited by the unsteady vortex–structure interactions between the body and the upstream wake. Coherent vortices interfering with the downstream cylinder induce fluctuations in the fluid force that are not synchronized with the motion. A favourable phase lag between the displacement and the fluid force guarantees that a positive energy transfer from the flow to the structure sustains the oscillations. If the unsteady vortices are removed from the wake of the upstream body then WIV will not be excited. An experiment performed in a steady shear flow turned out to be central to the understanding of the origin of the fluid forces acting on the downstream cylinder.
Từ khóa
Tài liệu tham khảo
Maekawa, 1964, Study on wind pressure against ACSR double conductor, Electr. Engng Japan, 84, 21
Brankovic M. 2004 Vortex-induced vibration attenuation of circular cylinders with low mass and damping. PhD thesis, Imperial College, London, UK.
Blevins, 1990, Flow-Induced Vibration
Assi G. R. S. 2009 Mechanisms for flow-induced vibration of interfering bluff bodies. PhD thesis, Imperial College London, London, UK. Available at: www.ndf.poli.usp.br/~gassi.
Assi G. R. S. 2005 Experimental study of the flow interference effect around aligned cylinders. Master's thesis, University of São Paulo, São Paulo, Brazil (in Portuguese). Available at: www.ndf.poli.usp.br/~gassi.
Hahn S. L. 1996 Hilbert Transforms in Signal Processing. Artech House.
Price, 1976, The origin and nature of the lift force on the leeward of two bluff bodies, Aeronaut. Q., 26, 1154
Wardlaw, 1974, IEEE Power Engineering Society Summer Meeting
Zdravkovich M. M. 1977 Review of flow interference between two circular cylinders in various arrangements. J. Fluids Engng pp. 618–633.
Best, 1967, The forces on a circular cylinder in a shear flow, Tech. Rep., 103
Norberg, 1998, Advances in Understanding of Bluff Body Wakes and Flow-Induced Vibration, 1
den Hartog, 1956, Mechanical Vibrations