In a recent paper, work of Jordan [1] has pointed out that “measurements of Lueptow et al. [2] did not confirm the empirical expression $δ/a=0.45(x/a)0.746$ proposed by Afzal and Singh [3], but however supports the general consensus that the log-layer parameters converged to those of the flat plate as $δ/a$ regardless of the specific flow conditions.” Lueptow et al. [2] also pointed out that the boundary layer thickness does not grow according to the law $δ/a=0.045(x/a)0.746$ proposed by Afzal and Singh [3]; see also Lueptow [4]. The discussion arose without any comparison with the data [1,2,4], who also ignored the fact that...