The use of a vertical pipe as an overflow for a large tank

This paper describes small-scale experiments made on the flow of water from a large tank through a vertical pipe projecting upwards through the bottom for A considerable distance. Under these conditions the discharge is greatly affected by the type of flow existing at the entrance to the pipe, and at certain heads considerable volumes of air are carried down the pipe with the water. Th e literature of the subject appears at present to be scanty. The classical researches of Lord a (1766), which are described in text-books on hydraulics, were carried out on uniform pipes projecting inwards for a short distance only. He distinguished two types of how from the bottom of a tank in which the water was sensibly at rest: (a) free flow, in which a vena contracta was formed at entrance to the pipe and the jet was steady and of the same diameter as the vena contracta; (b) full how, in which the stream, after passing the vena contracta, expanded to till the pipe and issued as a turbulent jet. Later writers— e. g. Bilton (1908), Smith and Walker (1923)— have determined experimentally the coefficients of discharge and contraction for varying pipe diameters and heads.