High Frequency Surface Pressure, Shear Stress and Heat Flux Measurements for High Temperature Applications

The goal of the proposed project is to develop a robust, high-bandwidth, micromachined Moiré optical-based shear stress sensor with a remote photo-diode/fiber-optic array optical readout for high-temperature, unsteady high-speed flow measurement applications. The time-accurate, continuous, direct measurement of fluctuating wall shear stress is currently not possible. The realization of this capability not only benefits hypersonic vehicle development but impacts a broad application spectrum that ranges from fundamental scientific research to industrial process control, biomedical applications, etc. The proposed sensor consists of a miniature floating element sensor possessing process producing optical gratings on the backside of a floating element and on the top surface of the support wafer to permit backside optical transduction. This design represents a truly flush-mounted, miniature, direct wall shear-stress sensor that possesses immunity from EMI and transverse element movement due to pressure fluctuations and/or vibrations. The optical transduction of the floating element motion is achieved by imaging the Moiré fringe movement via a 16-channel high-temperature, fiber-optic array bundle. This bundle can be several meters long and is attached to a photo-diode array on the non-sensing end. This allows for the electronics to be remotely located away from the high temperatures of the measurement model and facility.