Measurement of turbulent wall shear-stress using micro-pillars

TLDR

In experimental fluid mechanics, measuring spatially and temporally resolved wall shear‑stress (WSS) has proved a challenging problem. The paper presents the development of the micro‑pillar shear‑stress sensor (MPS3) by RWTH Aachen University and Purdue University to address this measurement challenge. The MPS3 consists of an array of flexible micro‑pillars flush‑mounted on the wall, whose deflection in a shear field directly measures WSS, and the study discusses its sensor concept, static and dynamic characterization, and data‑reduction issues. Demonstrative experiments in water and air show that the MPS3 can measure wall shear‑stress, and the study highlights its salient features, development challenges, current capabilities, and areas for improvement.

Abstract

In experimental fluid mechanics, measuring spatially and temporally resolved wall shear-stress (WSS) has proved a challenging problem. The micro-pillar shear-stress sensor (MPS3) has been developed with the goal of filling this gap in measurement techniques. The MPS3 comprises an array of flexible micro-pillars flush mounted on the wall of a wall-bounded flow field. The deflection of these micro-pillars in the presence of a shear field is a direct measure of the WSS. This paper presents the MPS3 development work carried out by RWTH Aachen University and Purdue University. The sensor concept, static and dynamic characterization and data reduction issues are discussed. Also presented are demonstrative experiments where the MPS3 was used to measure the WSS in both water and air. The salient features of the measurement technique, sensor development issues, current capabilities and areas for improvement are highlighted.