Flow Observations in Tall Plunging Flow Dropshafts

Abstract

Plunging flow dropshafts are commonly used in municipal drainage systems. In this Note, an exploratory study is reported on the physics of the flow and air demand in two dropshafts of 7.7 and 6.3 m drop height. The flow inside these dropshafts was controlled by the upstream conditions with no outlet control. The water flow distribution and flow velocities in the vertically falling section are presented, and the energy dissipation in plunge flow drop structures is analyzed. The air demand was measured, and an empirical relation is proposed to predict the air demand in these tall dropshafts.