Experimental verification of wall shear stress measurement with MEMS sensors array for underwater applications with flat plate benchmark tests

Abstract

Underwater wall shear stress measurement based on a newly developed MEMS sensors array is experimentally verified utilizing a set of flat plate benchmark tests conducted in a precision water flume. The array is firstly calibrated in a well-defined 2D flow and then flush embedded on the plate surface to measure WSS directly. The local freestream velocities ranging from 0.1 m/s to 0.7 m/s are adopted for the test cases of naturally developing flow and deliberately stimulated turbulence. The boundary layer profiles of interests are correspondingly detected with LDV, and mean WSS values are extrapolated from suitable fits to known profile shapes for flat plate with a zero pressure gradient. The results from the MEMS sensors match well with those from the LDV velocity profile fits and are in good agreement with empirical estimations with an overall bias of less than 5%. Also, the direct simultaneous measurements from multiple sensors on the MEMS array favorably exhibit the streamwise variation of the wall-bounded flow. Generally, the MEMS sensors array-based underwater wall shear stress measurement is characterized by desirable accuracy and spatial resolution for further practical applications.