Correction to "Accounting for Uncertainty in the Analysis of Overlap Layer Mean Velocity Models" (original) (raw)

Power Law or Log Law for the Turbulent Boundary Layer?

2000

There has been considerable controversy during the past few years on the validity of the classical log law for the mean velocity profile in the canonical turbulent boundary layer. Alternative power laws have been proposed by George, Chorin and Barenblatt, to name a few. Advocates of either law typically have used selected data sets to foster their claims. In the present research, we analyze the experimental and DNS data from six independent groups. For the range of momentum thickness Reynolds numbers of 300 <= Re_theta <= 6200, we determine the best-fit values for the `constants' appearing in either law. Our strategy involves calculating the fractional difference between the measured/computed mean velocity and that calculated using either of the two respective laws. We bracket this fractional difference in the region ± 0.5%, so that an accurate, objective measure of the boundary and extent of either law is determined. It is found that while the extent of the power-law reg...

Is there a universal log law for turbulent wall-bounded flows?

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, 2007

The history and theory supporting the idea of a universal log law for turbulent wall-bounded flows are briefly reviewed. The original idea of justifying a log law from a constant Reynolds stress layer argument is found to be deficient. By contrast, it is argued that the logarithmic friction law and velocity profiles derived from matching inner and outer profiles for a pipe or channel flow are well-founded and consistent with the data. But for a boundary layer developing along a flat plate it is not, and in fact it is a power law theory that seems logically consistent. Even so, there is evidence for at least an empirical logarithmic fit to the boundary-friction data, which is indistinguishable from the power law solution. The value of kappa approximately 0.38 obtained from a logarithmic curve fit to the boundary-layer velocity data, however, does not appear to be the same as for pipe flow for which 0.43 appears to be the best estimate. Thus, the idea of a universal log law for wall-b...