  The Virk asymptote is shown to be similar in nature to the Karman buffer
layer profile and does not represent a new log-law with a modified
mixing-length. It is simply part of the wall layer velocity profile but is
extended because of the increase in wall layer thickness in drag reduction
flows. The friction factors at the maximum drag reduction asymptote correspond
to velocity profiles consisting of a wall layer and a law of the wake
sub-region. Maximum drag reduction results in the suppression of the law of the
wake and full relaminarisation of the flow.
