Measurement of instantaneous wall stress distributions in turbulent flows with flexible micromirror sensors

The ability to resolve the shear and pressure forces concurrently carries a significant importance. In this study we have developed an array of microsensors that can resolve relevant scales of shear and pressure simultaneously. This technique attains information regarding complex dynamics near the wall, involving phenomena like the boundary layer, flow separation, and cavitation, providing insights into their dynamic interactions with the wall, and capturing deformations and stresses. The utilized method involves employing an array of wrinkle-free metallic thin film in polymer as sensors and each sensor is comprised of a micro-scale nanometer thin film sensor in a micro-well (µWell). Each µWell contains a metallic thin film encased in a soft polymer that acts as a flexible mirror within a 2D plane. The sensors are being validated and calibrated in a high-speed rotating disk shear flow facility, which proves attain diverse shear stress range. The sensors’ strain field is recorded via digital holographic microscopy interferometry, utilizing modeling and calibration, we will establish a direct correlation between deformations and wall and shear stresses.