A possible reinterpretation of the Princeton superpipe data

In experiments recently performed at Melbourne, Pitot-tube mean velocity pr ofiles in a boundary layer disagreed with those obtained with hot wires. Th e standard MacMillan (1956) correction for the probe displacement effect an d a correction for turbulence intensity were both required for obtaining ag reement between the two sets of mean velocity data. We were thus motivated to reanalyse the Princeton superpipe data using the same two corrections. T he result is a plausible conclusion that the superpipe is rough at the high er Reynolds numbers and its data follow the Colebrook (1939) formula for co mmerical pipes rather well. It also appears that the logarithmic law of the wall is valid, with a Karman constant close to that found recently by Oste rlund (1999) from boundary layer measurements with a hot wire. The smooth r egime in the pipe gave almost the same additive constant for the log-law as Osterlund's. A comparison between the superpipe data and the pipe data of Perry, Henbest & Chong (1997) suggests that the conventional velocity defec t law may be valid down to lower Reynolds numbers than concluded by Zagarol a & Smits (1998).