Abstract: Under outflow conditions, flows in a side inlet/outlet are in the diffusion mode and produce large velocity fluctuations in the trash rack section. In this work, a test facility for typical inlet/outlet flows is used for an experimental study with flow velocity measured using a laser doppler velocimetry and an acoustic doppler velocimetry. The results show large velocity fluctuations occur at the cross section of the trash rack installed near the exit of the diffuser, with the fluctuating components reaching up to 1.8 times of the mean velocity and an average turbulence intensity of 0.724. The probability density of the fluctuations basically follows a normal distribution. Turbulent intensity shows a streamwise trend of first increasing and then decreasing along the flow starting from the diffuser inlet, through the diffusion section, adjustment section, and anti-vortex section, and to the reservoir. Velocity fluctuations are small in the upstream tunnel section and become relatively large in the diffusion and adjustment sections. Large velocity fluctuations at the trash rack cross section are explained. The results provide a theoretical basis for optimization of the inlet/outlet parameters and analysis of the vibration damage to trash racks.

Key words: inlet/outlet, acoustic Doppler velocimetry, laser doppler velocimetry, fluctuating velocity, diffusion section, turbulent intensity