Characterization of an Optical Moire Wall Shear Stress Sensor for Harsh Environments – AIAA Jan 2015

The ability to make time-resolved, direct wall shear stress measurements in harsh environments is an important measurement capability for improving understanding of complex fluid flow phenomena. This work presents the design, packaging, and characterization of a third-generation silicon-on-Pyrex moire optical wall shear stress sensor designed for use in environments up to 450C. Optical transduction of the floating element microelectromechanical systems (MEMS) sensor is accomplished by interrogation of the geometric moire fringe via a four-channel fiber optic array. Device performance is improved over previous generations by patterning discrete sections of the moire fringe and the use of a silicon nitride anti-reflective coating. Calibration of the sensor system yields a dynamic shear stress sensitivity of 12.6 mrad/Pa at 1.128 kHz, sensor resonance of 4.1 kHz, pressure rejection ratio of 87 dB, minimum detectable shear stress of 0.53 mPa at 1.128 kHz for a 1 Hz bin, and an experimentally verified dynamic range of 79 dB.

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