The invention provides a
rotational flow spillway tunnel for reducing flow velocity of an outlet of a
rotational flow tunnel. The
rotational flow spillway tunnel comprises a
sluice gate chamber, a diversion tunnel, a
volute chamber, a vertical shaft, an expansion body connecting section, a stilling
pool and a flow guiding tunnel; the upstream of the diversion tunnel is connected with the
sluice gate chamber; the downstream of the diversion tunnel is connected with the
volute chamber through a transition section; a water division partition wall is arranged in the transition section; the lower end of the
volute chamber is connected with the vertical shaft through a vertical shaft connecting section; the lower part of the vertical shaft communicates with the flow guiding tunnel through the expansion body connecting section; one end of the flow guiding tunnel is blocked; a flow dividing
pier is arranged in the expansion body connecting section; and the stilling
pool is arranged at the bottom of the vertical shaft.
Water flow passes through the transition section and the water division partition wall, so that the thickness of rotating
water flow in the volute chamber is increased, the altitude of a water surface is greatly reduced, and the water surface
height difference of the rotating
water flow in the volute chamber is also reduced. After the
water flow reaches the stilling
pool for stilling, the damming phenomenon of hydraulic jump is weakened and an energy dissipation space of pressure flow vortex rolling is enlarged through the expansion body connecting section.