ABSTRACT
A fluid flowing past a boundary exerts normal and tangential stresses on it. Normal stresses or pressures are readily measured by connecting a small hole on the surface to a manometer. Consequently, numerous studies have been made of the pressure distribution on solid surfaces in contact with a flowing fluid. The measurement of the tangential or shear stresses is much more difficult. However, the extra effort needed to obtain such data is rewarding, since information about the variation of the wall shear stress is, often, quite useful in analyzing a flow field. The six principal methods developed for measuring the local wall shear stress, aside from the extrapolation of direct velocity measurements, are
The Stanton tube [1]
Direct measurement [2]
Thermal method [3]
The Preston tube [4]
The sublayer fence [5, 6]
The electrochemical technique [7, 8]
