地下河川の流入立坑部の水理特性

Abstract

This paper deals with effects of shape of a dropshaft intake to energy dissipation and air transport control. First, free-surface swirling flows in vertical dropshafts are modeled and their solutions are derived. With these solutions, the energy dissipation effects of the dropshafts are examined by the vertical change of vertical momentum flux and kinematic energy, and some results of practical use are obtained. Next, the relations between the dropshaft shape and air entrainment are examined through dimensional analysis. Three types, that is, standard vortex flow dropshaft, helicoidal-ramp dropshaft and vortex flow dropshaft with contraction are analyzed. A hydraulic parameter influencing air entrainment is found and the excellence of the helicoidal-ramp dropshaft is clarified.