Influence of free-stream turbulence on the movement-induced vibrations of an elongated rectangular cylinder in cross-flow

We present an experimental study of the galloping oscillations of an elongated cylinder. The shape ratio of the rectangular section is 1:2 and we study the influence of free-stream turbulence on the vibrations. The main studied parameter is the turbulence intensity. In smooth flow, the structure is also submitted to vortex shedding lock-in, which disappears in turbulent flow. At low intensity (4-5%). the critical velocity decreases by comparison with smooth flow. A jump of the Strouhal number is reported and can explain this decrease. At 6% intensity, the critical velocity increases, then the system becomes stable at 7.5%. (C) 2001 Elsevier Science Ltd. All rights reserved.