Measurements of wall shear stress of a turbulent boundary layer using a micro-shear-stress imaging chip

Measurements of wall shear-stress streaks of a turbulent boundary layer in the channel flow were carried out using a MEMS-based micro-shear-stress ima ging chip, which contains about 100 sensors. The chip is designed and fabri cated by surface micromachining technology. One array of 25 micro-shear-str ess sensors in the chip that covers a length of 7.5 mm is used to measure t he instantaneous spanwise distribution of the surface shear stress. The sta tistics of high shear-stress streaks were established. Based on the measure ment, the physical quantities associated with the high shear-stress streaks , such as their length, width and peak shear-stress level, were obtained. W e found out that a high correlation exists between the peak shear-stress le vel and front-end shear-stress slope of a high shear-stress streak. This im portant property is currently being applied to the design of a rear-time fl ow control logic. (C) 1999 The Japan Society of Fluid Mechanics and Elsevie r Science B.V. All rights reserved.