Numerical and experimental assessment of the water discharge segment in a pumped-storage power station.

The discharge channel of the pumped storage power station has bidirectional flow characteristics. When the water flow from the conveyance tunnel diffuses to the reservoir through the discharge channel, the instantaneous velocity at the trash rack section varies greatly, and the fluctuation value exceeds twice the time-averaged value. As previously reported, only the time-averaged velocity parameter cannot fully represent instant flow effects. In this paper, the improved delayed detached eddy simulation (IDDES) is proposed to numerically simulate the velocity field inside the discharge channel. The laser doppler velocimetry (LDV) is used to measure the velocity along the segment inside the discharge channel. It is found that the instantaneous velocity of the trash rack section varies significantly with time, the fluctuating velocity is close to or even more than twice the time-averaged velocity, and the average turbulence intensity is 0.72. The probability density distribution of fluctuating velocity is found to be close to normal distribution. During the flow from the conveyance tunnel segment to the reservoir through the diffusion segment and the adjustment segment, the turbulence intensity initially increases and then decreases along the process. The fluctuating velocity in the conveyance tunnel segment is minor, and the average turbulence intensity is 0.27. The turbulence intensity of water flow at the diffusion segment increases by 4.55 times to 1.23, which explains the large fluctuation velocity and high turbulence intensity at the trash rack section. The research results could help to understand the flow characteristics of the discharge channel, optimize the shape parameters of the discharge channel, and analyze the cause of fatigue failure of the trash rack. • The fluctuating velocity characteristics at the trash rack section are demonstrated detailed. • The large fluctuating velocity and the turbulent intensity of the trash rack section are explained. • The improved delayed detached eddy simulation is used to simulate the field inside the discharge channel. • The laser doppler velocimetry is used to measure the velocity along the segment inside the discharge channel. [ABSTRACT FROM AUTHOR]