Outflow Characteristics from Circular Pipe

The characteristics of jets issued by partially filled pipes are studied. The main flow features of such jets are specified, based on systematic observations and accounting for the Froude similarity. The end depth ratio, i.e., the depth at the section of issue normalized to the approach flow depth is predicted with the momentum equation. Further, an expression for the drawdown curve, from the approach flow to the end section is presented. Then, the lower and the upper trajectories of the jet issued into the atmosphere are studied, and expressions are given for the lower trajectory and the axial jet thickness. The analysis accounts for a novel dimensionless axial coordinate in which effects of approach filling and approach Froude number are included. The dimensionless coordinate in the streamwise direction may be considered as the expansion of a familiar term known in hypercritical plane flow. Additional data refer to the modular limit of pipe outflows and to submergence effects. Photographs illustrate the flow features.