Local Flow Velocity Measurements Using an In-Fibre Bragg Grating Sensor

A prototype flow velocity sensor has been developed based on flow-induced bending of an in-fibre Bragg grating (FBG). This sensor retains key features that make FBGs attractive for sensing applications: small size, mechanical compliance, immunity to electromagnetic interference and robustness. Unlike hot-wire anemometry, the sensor does not introduce heat or electrical current into the flow. The sensor was tested in an open-channel water tunnel. A splitter plate was mounted to the downstream side of the sensor to minimize the effects of vortex shedding. The spatial resolution of the sensor is comparable to the sensing length of the fibre, the smallest of which was 4 mm. Flow measurement resolution was 0.17 m/s and measurements showed good repeatability. With further development, there is potential to increase both the spatial and flow measurement resolution of this sensor.