The Clauser plot
The so–called Clauser–plot technique is used to determine the wall shear stress in a turbulent boundary
layer from the mean velocity profile, in conditions where an accurate, direct determination of the
velocity gradient at the wall is not possible (which is the common situation for turbulent boundary
layers).
The table given below represents the measured velocity profile, such as determined e.g. by means of a
traverse with a pitot tube or a hot–wire probe. As a function of the distance y from the wall (measured
in mm), the velocity is given in non–dimensional form as u/Ue, where u is the local (mean) velocity in
the boundary layer, and Ue the velocity in the external flow.
a. Determine the value of the skin friction coefficient Cf by means of a curve fit of the law of the
wall to (the lower part of) the velocity profile.
b. Determine also the strength of the ‘wake–component’ of the velocity profile. For a measured
profile, this is defined as the maximum difference between u(y) and the law of the wall
expression