A study on turbulent boundary layers on a smooth flat plate in an open channel

An experimental study was undertaken to investigate the characteristics of turbulent boundary layers developing on smooth flat plate in an open channe l flow at moderately high Froude numbers (0.25 < Fr <1.1) and low momentum thickness Reynolds numbers (800 < Re-theta< 2900). The low range of Reynold s numbers and the high Froude number range make the study important, as mos t other studies of this type have been conducted at high Reynolds numbers a nd lower Froude numbers (similar to0.1). Velocity measurements were carried out using a laser-Doppler anemometer equipped with a beam expansion device to enable measurements close to the wall region. The shear velocities were computed using the near-wall measurements in the viscous subregion. The va riables of interest include the longitudinal mean velocity, the turbulence intensity, and the velocity skewness and flatness distributions across the boundary layer. The applicability of a constant Coles' wake parameter (Pi = 0.55) to open channel flows has been discounted. The effect of the Froude n umber on the above parameters was also examined.