Direct Wall Shear Stress Measurement for Rotor Blades

The Interdisciplinary Consulting Corporation (IC2), in partnership with the Applied Research Laboratories, the University of Texas at Austin (ARL-UT), proposes the development of a wall shear stress measurement system for use in the development of future vertical lift (VL) vehicle platforms.  The goal of this effort is to develop a low-profile, acceleration-compensated wall shear stress sensor package capable of providing mean and fluctuating shear stress data on a rotating frame.  The resulting system will enable direct, quantifiable wall shear stress measurements which are crucial to understanding and characterizing unsteady separating flows. The proposed system will leverage IC2’s existing commercial DirectShear™ wall shear stress sensor system and extend its capabilities to include measurement on thin, rotating bodies.  The sensor system will enable localized, acceleration-compensated, non-intrusive, direct measurement of mean and fluctuating wall shear stress in three-dimensional unsteady flows such as those encountered in rotorcraft.  The differential capacitive measurement scheme offers high sensitivity to in-plane shear stress as well as common-mode rejection of pressure fluctuations. An integrated accelerometer will compensate for acceleration effects to optimize sensor accuracy.  Backside electrical contacts using IC2's patented fabrication and packaging process (U.S. Patent No. 10,461,239) enable a low-profile form factor and smooth sensor surface while significantly reducing fabrication complexity and cost.  Analog and digital electronics will be collocated with the sensor, and the use of slip rings and/or wireless transmission methods will be used to provide power and transmit the sensor signal to a data acquisition system.