Further observations on the mean velocity distribution in fully developed pipe flow

The measurements by Zagarola & Smits (1998) of mean velocity profiles in fully developed turbulent pipe flow are repeated using a smaller Not probe to reduce the uncertainties due to velocity gradient corrections. A new static pressure correction (McKeon & Smits 2002) is used in analysing all data and leads to significant differences from the Zagarola & Smits conclusions. The results confirm the presence of a power-law region near the wall and, for Reynolds numbers greater than 230 x 10(3) (R+ > 5 x 10(3)), a logarithmic region further out, but the limits of these regions and some of the constants differ from those reported by Zagarola & Smits. In particular, the log law is found for 600 < y(+) < 0.12R(+) (instead of 600 < y(+) < 0.07R(+)), and the von Karman constant kappa, the additive constant B for the log law using inner flow scaling.. and the additive constant B* for the log law using outer scaling are found to be 0.421 +/- 0.002, 5.60 +/- 0.08 and 1.20 +/- 0.10, respectively, with 95% confidence level (compared with 0.436 +/- 0.002, 6.15 +/- 0.08, and 1.51 +/- 0.03 found by Zagarola & Smits). The data also confirm that the pipe flow data for Re-D less than or equal to 13.6 x 10(6) (as a minimum) are not affected by surface roughness.