Abstract
A micro-floating element wall shear stress sensor with backside connections has been developed for accurate measurements of wall shear stress under the turbulent boundary layer. The micro-sensor was designed and fabricated on a 10.16 cm SOI (Silicon on Insulator) wafer by MEMS (Micro-Electro-Mechanical System) processing technology. Then, it was calibrated by a wind tunnel setup over a range of 0 Pa to 65 Pa. The measurements of wall shear stress on a smooth plate were carried out in a 0.6 m × 0.6 m transonic wind tunnel. Flow speed ranges from 0.4 Ma to 0.8 Ma, with a corresponding Reynold number of 1.05 × 106~1.55 × 106 at the micro-sensor location. Wall shear stress measured by the micro-sensor has a range of about 34 Pa to 93 Pa, which is consistent with theoretical values. For comparisons, a Preston tube was also used to measure wall shear stress at the same time. The results show that wall shear stress obtained by three methods (the micro-sensor, a Preston tube, and theoretical results) are well agreed with each other.
Highlights
Accurate measurements of wall shear stress are crucial for judging flow phenomena in the laminar/turbulent boundary layer [1,2]
Wall shear stress was obtained by three ways in this study: theoretical calculation, a Preston tube, In Figure 9b, the red fitting line gives the static property of the calibrated micro-sensor, which is and the floating element wall shear stress sensor
A micro-floating element wall shear stress sensor with capacitive sensing has been developed for accurate measurements of wall shear stress under the high-speed turbulent boundary layer
Summary
Accurate measurements of wall shear stress are crucial for judging flow phenomena in the laminar/turbulent boundary layer [1,2]. Wall shear stress can be measured by Preston tubes [3], hot wires/films [4,5], micro-pillars [6,7], sub-layer fences [8], and micro-floating element wall shear stress sensors [9,10,11,12,13,14,15] These techniques have been developed for many years and have been proved a good prospect in aerodynamic measurements. Some researchers think direct measurements of wall shear stress are preferred because no assumptions of flow conditions are required [18] Given such the point, MEMS-based floating element wall shear stress sensors have shown a good potential for various aerodynamic applications. By the floating element wall shear stress sensor and the Preston tube agree well
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