Fibre Bragg grating use in fluid dynamic studies

The application of fibre Bragg grating sensors for strain and force measurements in fluid dynamic experimental studies is presented. In the first example, a fibre Bragg grating is used as both a tether and a strain gauge for studies of neutrally buoyant spheres. The measured strains on the tether were found to agree well with the theory for the flow rates tested (0.14 to 0.33 m/s). In the second example a Bragg grating sensor has been used to monitor the forces acting on a cylinder as a function of flow rate and when the cylinder is translated in a stationary fluid. Excellent agreement was found between the vibration frequencies of the cylinder as measured by the Bragg grating and with a camera use to record the motion of the cylinder.