A fibre-optic grating sensor for the study of flow-induced vibrations

A fibre-optic Bragg grating sensor for flow-induced vibration measurement i s described. The sensor is based on monitoring shift in the Bragg wavelengt h of a fibre Bragg grating. The fibre Bragg grating, when bonded onto a str ucture, can measure local;axial strain variation of the structure. The sens or was used to measure the flow-induced vibrations on a circular cylinder i n a cross-flow. The measured strain epsilon is consistent with the transver se structural bending displacement Y obtained from a laser vibrometer in te rms of the natural frequency of the fluid-structure system and the vortex s hedding frequency. The experimental data further indicated that epsilon and Y are linearly correlated when the bending displacement is small. It is ex pected that the fibre Bragg grating sensor, because of its physical uniquen ess, has an important role to play in the study of fluid-structure interact ions. (C) 2000 Elsevier Science S.A. Ail rights reserved.