Turbulence characteristics in a weir-orifice-slot combined fishway with an identical layout

Abstract

A combined fishway containing notched weir, central orifice and vertical slot with an identical layout was designed, and its turbulence characteristics were experimentally studied. An acoustic Doppler velocimetry (ADV) was used to measure three-dimensional velocity. Flow regime, average velocity, turbulence intensity, Reynolds stress, power frequency-spectrum, correlation function, turbulence scale were analysed. The experimental results showed the combined fishway was of remarkable three-dimensional flow structures. Longitudinal velocity exhibited obvious extreme value region on the horizontal plane. Extreme values of longitudinal turbulence intensity were concentrated mainly on the mixing region between weir flow and orifice jet, as well as the vertical slot wall jet region, extreme value region of transverse turbulence intensity occurred on the central plane of orifice jet, and extreme values of vertical turbulence intensity were scattered. Reynolds stress extreme value occurred mainly in the convergent zone of multiple jets. Dominant frequency of power frequency-spectrum was highest for notched weir and lowest for vertical slot. Longitudinal velocity fluctuation exhibited a correlation with time, which was characterised by dominant frequency. Turbulence scales showed eddy structures were related to flow zones.