Abstract
To establish a technique to measure the wall shear stress with high accuracy, along with the spatial and temporal resolutions, micro-scale sensors are fabricated and their responses to the wall shear stress are investigated. In this study, two types of micro-scale sensors are fabricated: a hot-film (HF)-type sensor and a floating-element (FE)-type sensor. First, the HF sensor is calibrated using a rotating cylinder. The calibration results show that the heating power of a constant temperature circuit (CTC) increases with the wall shear stress. The relationship between the square of the heating power of CTC (E12) and the wall shear stress to the 1/3 power (τw1/3) becomes linear in the range τw1/3 > 0.35 Pa1/3 as theoretically predicted. Second, the calibration of the FE sensor is performed using the Stokes layer excitation method. The calibration results show that the output voltage of the C-V conversion circuit connected to the FE sensor E2 is almost proportional to the wall shear stress τw as expected in the range τw > 2.5 × 10-4 Pa for 100 Hz stokes layer excitation and τw > 5.0 × 10-4 Pa for that of 200 Hz.
