Effect of the flow regime on the hydraulic features governing the operation of vortex drop shafts with spiral inlets

Abstract

If the operation of existing vortex drop shafts should be verified, then it is essential to know the hydraulic performance of these special structures under both subcritical and supercritical flow regimes. The purpose of the present research consisted, then, in providing practical guidelines and recommendations for managing the hydraulic design and verification of subcritical and supercritical vortex drop shafts. The examination of various experimental results from physical model investigations allowed to show that the inlet channel and the spiral inlet behave differently depending on the energy approach flow content. The main dissimilarity lied, however, in the functioning of the vertical shaft and the dissipation chamber. The rotation of the falling flow along the vertical shaft was more evident for approach supercritical flows. Severe flow conditions in terms of water depths and bottom pressures could be observed in the dissipation chamber under a supercritical flow regime. The design of this special component must be carried with prudence compared with the subcritical flow regime because failure events as the chamber submergence and the crash of the bottom surface just under the shaft outlet may occur for approach supercritical flows.

Experimental investigation on the hazard of geyser created by an entrapped air release in baffle-drop shafts

“…Atrabi et al 18 also studied the motion regularities of entrapped air cavities in an inclined pipe. In addition, the hydraulic characteristics of different drop shafts were experimentally investigated by some scholars 19 – 21 . Many studies have demonstrated that previously entrapped air in water flows in deep tunnel drainage systems plays a crucial role in the formation of a geyser.…”