Abstract
Direct numerical simulation of a fully-developed open-channel flow has been carried out for a range of subcritical Froude numbers at a fixed friction-velocity Reynolds number of 180. The effects of the free-surface fluctuations on the quantities important in understanding and improving turbulence models have been studied. The amplitude of the free-surface fluctuation increases as the square of the Froude number. The free-surface fluctuation has no directionality and its scale is larger than the viscous scale. Statistical quantities involving the vertical velocity component are most influenced by the Froude number but only in the region close to the free surface. The pressure fluctuation is influenced over much wider region.
