Study on the Aerator of Spillway Tunnel in One Large-scale Project

This paper studied the hydraulic characteristics of the spillway tunnel in one large scale hydroelectric project through 1: 50 and 1: 30 scaled hydraulic model tests. The water surface profile, flow speed, time averaged pressure along the tunnel were measured and the cavitation numbers were calculated. The results show the flow velocity may exceed 30m/s and the cavitation number may be smaller than 0.3 in the last 60 similar to 70m section before the outlet, which means cavitation damadge may occur in this range. Based on these results, an aerator was designed and set at the end of the quadratic curve section in the open channel of the tunnel. Experiments on the spillway tunnel with aerator showed that steady cavity was formed behind the aerator and the downstream flow was well aerated, which proved that the aeration effect was fine and cavitation damage could be successfully avoided.