Turbulent plane-Couette flow between smooth and rough walls

All turbulent wall shear flows have a region close to the wall where the viscous stress is negligibly small compared with its turbulent counterpart and, hence in which the total stress may be assumed to be essentially constant. This layer is called 'constant stress layer', or also the 'logarithmic layer'. Although important, the constant stress layer is usually difficult to investigate experimentally because it constitutes only 10-15% of the overall thickness of a wall and shear flow. This paper describes an experimental facility where the walls are rigid, thereby making it possible to study both smooth and rough wall conditions