Hydraulic design of intake structures of deeply located underground tunnel systems

This paper deals with hydraulic effects of intake structures of underground storage or tunnel systems from the aspect of energy dissipation and entrained air control. First, through the literature reviews, the advantage of vortex-flow dropshaft type is confirmed. Next, with the analytical solutions of free-surface swirling flows in vertical dropshaft, the energy dissipation effects of vortex-flow dropshaft are examined and some results of practical use are obtained. Also, the relation between the dropshaft shape and air entrainment is studied and the excellent of the helicoidal-ramp dropshaft is clarified. Based on the above results, the directions of the hydraulic designs of drop structures are proposed.