Abstract: Heavy rainfall and fog disasters caused by flood discharge have a great impact on the safety of surrounding buildings and ecological environment. The buildings located within such rainfall areas (of rainfall intensity S ≥ 10 mm/h) should be avoided as much as possible. Aiming at the situation of the powerhouse at the Nazixia hydropower station located in the rainfall area of its flood discharge, this study conducts hydraulic scale-model tests to optimize the bucket types of spillway. Various parameters of different bucket types are compared: trajectory height, trajectory distance, impinging edge width of the jet nappe, downstream riverbed erosion pattern, nappe wind, weight of splashed water. Through optimization, we suggest a flip bucket of curved surface attached to the spillway left wall, and compare it with the original design in terms of various atomization characteristics under different discharges. For this bucket, its trajectory nappe is deflected rightward away from the spillway axis and far away from the powerhouse, thereby significantly reducing its weight of splashed water and nappe wind speed near the powerhouse under different working conditions. Thus the suggested bucket is obviously superior to the original design.

Key words: hydraulics test, trajectory nappe, flip bucket optimization, hydraulic characteristics, nappe wind, splash area