Viscous Sublayer and Adjacent Wall Region in Turbulent Pipe Flow

The boundary-layer research facility utilizing the highly viscous fluid, glycerine, was constructed to permit detailed experimental investigation of the viscous sublayer. At a pipe Reynolds number of 8700 the sublayer thickness corresponding to a nondimensional distance from the wall of yuτ/ν = 5.00 was 0.110 in. Detailed measurements of the streamwise fluctuating velocities were obtained with hot-film anemometers within the viscous sublayer as well as in the transition region between the linear and logarithmic mean velocity profiles. These data were used to form the space-time correlation function of the streamwise fluctuating velocities. An eigenfunction decomposition of the streamwise fluctuating velocity into a sum of products of eigenfunctions in the inhomogeneous coordinate direction, with random coefficients dependent on the homogeneous and stationary variables, was obtained from the correlation data. One dominant eigenfunction with a structure nearly identical to the mean velocity in the wall region was found. The dominant large scale structure of the flow in the wall region, obtained with the aid of a mixing length approximation, consisted of randomly distributed counterrotating eddy pairs of elongated streamwise extent.