Modelling and calibration of microthermal sensor for underwater wall shear stress measurement

To measure underwater wall shear stress, a calibration method for a microthermal sensor is studied. In CC (constant current) mode, a mathematical model which quantitatively describes the relationship between the output of the thermal sensor and the wall shear stress is presented. A well-characterised water tunnel was set up to provide a series of known wall shear stresses in the range of 0-5 Pa. Calibration results prove the proposed model and characterise the thermal sensor precisely. The consistency of the parameters indicates that the performance of the thermal sensor keeps stable in water while driven by electricity. The R-squares in all calibrations exceed 0.995. The deviations between the predicted and the generated wall shear stress are about 5%.