Plane Turbulent Wall Jets in Shallow Tailwater

Abstract

This paper presents a theoretical and laboratory study of plane turbulent wall jets with finite tailwater depth. The main objective was to show that, when the depth of tailwater is finite, the momentum flux of the forward flow in the wall jet decays appreciably with the distance from the nozzle. This decay is due to the entrainment of the return flow, which has negative momentum that requires a depression of the water surface near the gate housing the slot. An extensive set of experiments, with different Froude numbers and tailwater depth ratios, was used to observe and quantify the growth of the wall jet, the decay of the velocity scale and the momentum flux, and the variation of the volume flux. Also, experiments were conducted to measure the length of the surface eddy and the drop in the water surface elevation at the gate. This study contributes to an understanding of the behavior of plane turbulent wall jets when the ambient fluid has a limited extent.