Abstract
A flexible hot-film sensor array for wall shear stress, flow separation, and transition measurement has been fabricated and implemented in experiments. Parylene C waterproof layer is vapor phase deposited to encapsulate the sensor. Experimental studies of shear stress and flow transition on a flat plate have been undertaken in a water tunnel with the sensor array. Compared with the shear stress derived from velocity profile and empirical formulas, the measuring errors of the hot-film sensors are less than 5%. In addition, boundary layer transition of the flat plate has also been detected successfully. Ensemble-averaged mean, normalized root mean square, and power spectra of the sensor output voltage indicate that the Reynolds number when transition begins at where the sensor array located is 1.82 × 105, 50% intermittency transition is 2.52 × 105, and transition finishes is 3.96 × 105. These results have a good agreement with the transition Reynolds numbers, as measured by the Laser Doppler Velocimetry (LDV) system.
Highlights
Wall shear stress is one of the most important fluid mechanical parameters in the boundary layer, which is a tangential force in the direction of motion due to the viscosity of the fluid [1,2]
Among all is of most these approaches, hot-film element sensor fabricate on polymer with a waterproof cover suitable for the flexible hot-film sensor fabricate on polymer substrate with a waterproof cover is most suitable underwater shear stress and transition measurements, since it has good water resistance, high for underwater resolution, shear stressless and transitiontomeasurements, it on hascurved good surfaces
The temperature coefficient of resistance (TCR) α is an important parameter for the operation of the thermal shear stress sensor, which is given by, α=
Summary
Baoyun Sun 1 , Pengbin Wang 1 , Jian Luo 1 , Jinjun Deng 1 , Shiqi Guo 2 and Binghe Ma 1, *. Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Northwestern Polytechnical. Received: 5 September 2018; Accepted: 11 October 2018; Published: 15 October 2018
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