| Cavitation is a key problem of the outlet works. There are many cases of cavitation erosion in gate slots in actual water control project. Many scholars have studied it, but those studies focus on overhaul gate slots or accident gate slots, not on service gate slots. By means of depression model test,this paper researches cavitation characteristics of service gate slots for middle outlet works of Jishixia hydropower station.The water head of the middle outlet works is 56m, and it has discharge of 2310 m3/s .Because of geological characteristics, the middle outlet works can not uses routine arch service gate, but applies flat gate. So, cavitation problem on gate slots must be solved. In order to measure cavitation noise, this test uses the 8103 hydrophone and the 3560C PULSE multi-spectrum analysis system which is produced by B&K Company in Denmark.By analysis of ultrasonic noise spectrum in different reservoir levels and gate openings, cavitation characteristics are obtained for the gate slots in different ratio of width to depth. Then configuration of gate slots is got which can solve cavitation problem. It is obvious that gate opening is main factor, cavitation characteristic in 0.8 of gate opening is less than other gate opening and the service gate ought to use non- 0.8 gate opening firstly.Cavitation characteristics are related closely to pressure on wall. The hydraulic model arranges 70 piezometers to measure pressure distribution in different reservoir levels and gate openings. This paper summarizes laws of pressure and pressure coefficient, which is that gate opening is main factor, elevation is secondary factor and elevation is tiny factor. The minimum pressure appears in the condition of minimum gate opening; the maximum pressure is in 0.2~0.5 gate opening. In the scope of this test, pressure changes with reservoir level but it changes less than 10% in same point. Pressure coefficient varies greatly with gate opening, but it almost does not vary with reservoir level.
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