Abstract: Cavitation and cavitation erosion under high flow velocity and gate seal under high water head are two problems that high-head outlet structure is facing with in operation. To further understand the hydraulic and cavitation characteristics of aerators with sudden lateral enlargement and bottom drop, we took a hydraulic project’s flood discharge tunnel with orifices as research object and through a local hydraulic model with scale of 1:20, we analyzed the physical hydraulic parameters (wind velocity of ventilation hole, flow pattern, pressure, air concentration) of the middle lock chamber’s ventilation system and the aerator with sudden lateral enlargement and bottom drop. Furthermore we compared the test results with prototype observation results. Results showed that this project had good aeration effect. The test values of wind speed change with gate opening in ventilation pipe, flow aeration concentration, pressure and its fluctuation were consistent with prototype result. Prototype observation and practical operation both validate that the sudden enlargement layout meets practical demand, so it is safe and feasible. It is also an effective measure to solve gate seal and air entrainment to alleviate cavitation under high water head.

Key words: sudden lateral enlargement and bottom drop, cavitation and cavitation erosion, gate seal, aerator, pressure, air concentration