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FBG sensors for low-speed flow analysis

An FBG based pressure and temperature measurement setup was developed for low speed aerodynamics studies. A bare FBG sensor for measuring dynamic pressure of flow and a specially designed strain-insensitive FBG temperature sensor were packaged in the form of a compact probe. The FBG temperature sensor probe was used for both temperature measurement of flow and temperature compensation of bare FBG sensor. The setup was calibrated for pressure and temperature using a calibrated flow generator that could produce low turbulence air jets at different velocities. The FBG sensor assembly was calibrated for flow velocities ranging from 5 m/s to 40 m/s. The flow of jet was arranged to be perpendicular to the axis of FBG sensors. A 2-D fluid structure interaction simulation was carried out in Comsol Multiphysics to validate the experiments. From simulation results, flow induced FBG strain was found to have a linear dependence with dynamic pressure of the flow with a slope of 0.038 με/Pa. Pressure values determined from FBG experiments were found to be in close agreement with the pressure values obtained from simulation within experimental errors. Because of their diminutive size and flexibility, FBG sensors can be used to measure pressure and temperature in ground based aerodynamic test facilities with minimum intrusion to the flow.