Flow-induced vibration of two circular cylinders in tandem arrangement. Part 2: Suppression of vibrations

초록

This paper presents an experimental investigation on suppression of cross-flow vibrations of two circular cylinders in tandem arrangement, conducted at the fluid mechanics laboratory of Kitami Institute of Technology, Japan. To suppress the vibrations of the cylinders, tripping wires were deployed, attached symmetrically about the leading stagnation lines of the cylinders. Five spacing ratios were examined, i.e., L/D = 0.1, 0.3, 0.8, 2.0 and 3.2 (L is the gap spacing between the two cylinders; D is the diameter of cylinder), which are representative for five Regimes I (0.1 <= L/D < 0.2), II (0.2 <= L/D < 0.6), III (0.6 <= L/D < 2), IV (2 <= L/D < 2.7) and V (L/D >= 2.7), respectively, as classified in Part 1 [ Kim et al., 2009. Flow-induced vibrations of two circular cylinders in tandem arrangement (part 1: characteristics of vibration). journal of Wind Engineering and industrial Aerodynamics, submitted together for publication]. Tripping wire position theta measured from the leading stagnation lines of the cylinders was changed from 20 degrees to 60 degrees to determine the optimum range of theta for suppressing structural vibrations. The shear layers separated from the two cylinders were investigated based on flow visualization. The main findings are: (i) the flow-induced vibration on the two cylinders depends strongly on theta, (ii) at theta = 20-30 degrees the vibrations on both cylinders are almost completely suppressed for all regimes except V, and (iii) for theta >= 40 degrees the vibration amplitudes of both cylinders are considerably larger than those of the plain cylinders, particularly at theta = 40 degrees, where the vibration of the upstream cylinder becomes divergent. (C) 2009 Elsevier Ltd. All rights reserved.

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