Statistical analysis on wall shear stress of turbulent boundary layer in a channel flow using micro-shear stress imager

Abstract

Abstract Measurements of wall shear stress of turbulent boundary layers in the channel flow were carried out using a micro-electro-mechanical-system (MEMS)-based micro-shear stress imaging chip. The study was carried out in a turbulent channel flow facility. One array of 25 micro-shear stress sensors in the chip that covers a length of 7.5 mm is used to measure the instantaneous span-wise distribution of the surface shear stress. The characteristics of high shear stress area (streaks) were described with statistics. Based on the measurement, the physical quantities associated with the high shear stress streaks, such as their length, width with the high shear stress level, were obtained. To further explore the relationship between the shear stress slope and the peak shear stress, the probability density function (PDF) of the ratio of peak shear stress to shear stress slope at different Reynolds number Re is examined. As for the distribution of PDF, it was found that the distribution concentrated towards a certain value in each Re . This result is extremely important because it points to the possibility of predicting the peak shear stress level based on the shear stress distribution at the leading edge of the streaks.