Study of rotary and diffused flow in spillway tunnel with blocking.

Niu Zheng-ming, Sun Jing, Li Qi-long, HOU Yan-ping

Thursday 2 july 2015

12:57 - 13:00h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering, Poster pitches

Parallel session: Poster pitches: 11B. River Engineering

The rotary flow spillway tunnel with blocking was proposed for meeting the requirement of energy dissipation in high dam. Then the hydraulic characteristics of rotary and diffused flow in tunnel, such as the flow pattern, pressure, velocity, ventilation, aeration, energy dissipation and cavitaion, were analyzed by model test and numerical simulation. The results showed that the flow in vortex section was rotational flow with cavity and high wall pressure, which transformed to air-water two phase flow with high turbulent and negative pressure after the diffuser. The velocity of rotary flow could be kept down below 30 m/s. The disturbution of tangential velocity along radial was combined vortex approximately, and the axial velocity was symmetrical, but the radial velocity was low. Even under the submerged condition of the outlet, the good ventilation and exhale were obtained. The rotary flow was stable and the pressure in cavity was closed to atmosphere, but it was aerated sufficantly and no huge air sac exist after the diffuser. The cavitaion could not be happened in tunnel before the blocking, and sufficient water-air bleeding could reduce the possibility of cavitation with negative pressure significantly after the diffuser. Because of good cavitation resistance and high energy dissipation, the rotary flow spillway tunnel with blocking have a good application prospect in the flood discharge and energy dissipation in high dam.