Experimental study on the shape of the aeration facility in the 1# spillway tunnel of a certain hydro-junction

Abstract

The operating head of the 1~# spillway tunnel is as high as 83 m, with a maximum average flow velocity of over 35 m/s. Adopting a single slope with a bottom slope gradient of 0.81%. Three aerating facilities are designed with a combination of ridges and grooves. In order to verify the rationality of the design scheme of the aeration facility. Optimization research was conducted on the shape of the aeration facility through normal hydraulic model test with a scale of 1∶40. The result show that there is a significant negative pressure on the side wall of the diffusion section, with a negative pressure value of-86.6 kPa, and cavitation water flow is prone to occur at high speed water flow. The aeration facility has severe backflow in the cavity, intermittent blockage of the ventilation holes, small ventilation well area, and a maximum air-water flow ratio of 1.8%. The ratio of the 3~# aeration facility is only 0.6%. After experimental research, it is proposed to cancel the diffusion section, move the 1~# aeration facility forward and adjust its shape to a differential sudden expansion and drop form, and adjust the 2~# and 3~# aeration facilities to a differential form, and a steeper downstream bottom slope. The result show that the optimized body shape can meet the requirements of aeration, with an air-water flow ratio of over 4.2% at the flood control water level and over 7.0% above the normal high water level. The aeration effect is good, and it has important reference value for solving the aeration design of small bottom slopes in tunnels.

Keywords

spillway tunnel / aerator / sudden expansion and drop aerator / differential aerator