The Influence of Finite Tailwater on The Characteristics of Plane Turbulent Wall Jets

This paper displays a laboratory study of plane turbulent wall jets on smooth boundaries with finite tailwater depth. The primary aim was to study the effect of changing Froude numbers on the behavior of plane turbulent wall jets with shallow tailwater depth. A series of four experiments, maintaining constant tailwater depth ratio of yt/bo = 22 and four values of Froude numbers (4, 6, 8, and 10), were conducted to observe and quantify the growth of the wall jet, the decay of the velocity scale, and the variations in discharge and momentum fluxes. The results from these experiments were compared with the classical wall jet. It was found that the characteristics of plane turbulent wall jets with shallow tailwater depth differ significantly from those of classical wall jets. The experimental results show that jets with shallow tailwater depth ratios experience faster maximum velocity decay and faster growth of the jet half width. In addition, there is an increased relative discharge with normalized longitudinal distance, but it decreases rapidly to a maximum value at the end of the eddy length. The momentum flux in the forward flow of the wall jet significantly diminishes with increasing distance from the nozzle. The decay is attributed to the entrainment of the return flow, which possesses negative momentum, and an increase in tailwater depth at a distance from the nozzle generates this return flow. This study enhances the understanding of the behavior of plane turbulent wall jets on smooth beds with finite tailwater depth.