Turbulence Structure in Plane Couette Flow

Turbulent flow between two plane surfaces in relative shearing motion has been studied with air in a belt-type apparatus with one fixed surface. Mean velocities, turbulence intensities, scales and energy spectra measured in this flow indicate two regions of appreciably different characteristics. A wall region near the plane surfaces is found to occur with flow characteristics close to those found near walls of other turbulent shear flows when these are expressed in terms of the wall similarity parameters. A core region, of width at least three-eights the distance between the planes, appears away from these evidencing the characteristics of the homogeneous turbulence predicted by von Karman. The mean velocity has a linear gradient in this region and the turbulence intensity and scales are essentially constant; in fact, homogeneity is strongly suggested. For a more than two-fold range in flow Reynolds numbers (center line velocity 15 fps to 35 fps) the microscale is found to be constant, the macroscale increases linearly and the relative intensity is constant.