Reynolds-number scaling of the flat-plate turbulent boundary layer

Despite extensive study, there remain significant questions about the Reynolds-number scaling of the zero-pressure-gradient flat-plate turbulent boundary layer. While the mean how is generally accepted to follow the law of the wall, there is little consensus about the scaling of the Reynolds normal stresses, except that there are Reynolds-number effects even very close to the wall. Using a low-speed, high-Reynolds-number facility and a high-resolution laser-Doppler anemometer, we have measured Reynolds stresses for a hat-plate turbulent boundary layer from Re-theta = 1430 to 31 000. Profiles of (u'(2)) over bar, (v'(2)) over bar, and (u'v') over bar show reasonably good collapse with Reynolds number: (u'(2)) over bar in a new scaling, and (v'(2)) over bar and (u'v') over bar in classic inner scaling. The log law provides a reasonably accurate universal profile for the mean velocity in the inner region.