Experimental investigation on the unsteady flow fluctuation of a vertical pipe inlet/outlet of the pumped storage power station

Under the outflow condition (water from the inlet/outlet to the reservoir), the instantaneous velocity at the trash rack section of the inlet/outlet in a pumped storage power station varies greatly. Only the time-averaged velocity parameter cannot fully represent instant flow effects. Acoustic Doppler velocimetry is used to measure the velocity at the trash rack section. Under the outflow condition, the maximum instantaneous velocity is 3 times the time-averaged velocity. According to the instantaneous velocity, the trash rack section along the orifice height can be divided into a positive velocity zone, an alternating zone of positive and negative velocity, and an alternating zone of negative and positive velocity. The proportion of the zone height to the orifice height is 28 %, 52 %, and 20 %, respectively. According to the time-averaged velocity distribution, the trash rack section along the orifice height can be divided into a positive velocity zone and a negative velocity zone, with a proportion of 80 % and 20 %, respectively. Under the inflow condition (water from the reservoir to the inlet/outlet), the instantaneous velocity changes little, which is 0.9–1.1 times the time-averaged velocity. The research results will contribute to further optimizing the shape of the inlet/outlet.