Journal of Fluid Mechanics   Pressure-gradient-dependent
logarithmic laws in sink flow turbulent boundary layers
Experiments were done on sink flow turbulent boundary layers
over a wide range of streamwise pressure gradients in order to
investigate the effects on the mean velocity profiles.
Measurements revealed the existence of non-universal logarithmic
laws, in both inner and defect coordinates, even when the mean
velocity descriptions departed strongly from the universal
logarithmic law (with universal values of the Kármán constant
and the inner law intercept). Systematic dependences of slope
and intercepts for inner and outer logarithmic laws on the
strength of the pressure gradient were observed. A theory based
on the method of matched asymptotic expansions was developed in
order to explain the experimentally observed variations of log-
law constants with the non-dimensional pressure gradient
parameter (Δp=(ν/ρU3τ)dp/dx). Towards this end, the system of
partial differential equations governing the mea