In turbulent flow near a flat wall, the local velocity u varies only with distance y from the wall, wall shear stress τw, and fluid properties ρ and μ. The following data were taken in the University of Rhode Island wind tunnel for airflow, ρ = 0.0023 slug/ft3, μ = 3.81E−7 slug/(ft•s), and τw = 0.029 lbf/ft2:
y, in 0.021 0.035 0.055 0.080 0.12 0.16
u, ft/s 50.6 54.2 57.6 59.7 63.5 65.9
(a) Plot these data in the form of dimensionless u versus dimensionless y, and suggest a suitable power-law curve fit. (b) Suppose that the tunnel speed is increased until u = 90 ft/s at y = 0.11 in. Estimate the new wall shear stress, in lbf/ft2.