Experiments on the swirling flow of water in a vertical pipe and a bend

Abstract

A vertical Perspex pipe was fixed to the bottom of an open circular tank and supplied with water possessing various amounts of swirl. At a low swirl photographs were obtained of the collapse of the thin air core. At a higher swirl the core was steady, and significant volumes of air were not entrained until a 90° bend and a horizontal tail pipe were attached to the foot of the vertical pipe. The airflow was measured and the complicated motion in the bend examined. Some of the water had its swirl reversed by its passage through the bend, and an approximate theory is put forward to explain this effect. The experiments were repeated after the piping had been moved to a closed tank, from which a supply at higher pressure could be obtained. A narrow axial core formed in the vertical pipe was distorted into a helical shape on the downstream side of the bend.