Based on self-developed Venturi-type hydrodynamic cavitation device with different throat length-radius ratios L/R in Hydraulics Laboratory at Zhejiang University of Technology in China, 4 throat length-radius ratios L/R=10, 30, 60 and 100, and 4 raw water percentages V0/V=25%, 50%, 75%, and 100% were considered, Escherichia coli and total colony count were selected for indicator bacteria, effects of throat length-radius ratio, throat velocity, cavitation time, raw water percentage and cavitation number on inactivating pathogenic microorganism in raw water by hydrodynamic cavitation were experimentally studied. The results showed cavitation damage of cells of pathogenic microorganisms occurred by microjets and shock waves due to cavitation bubble collapse. The lower the flow cavitation number, the higher the killing rate of E. coli and total colony count. When flow velocity was lower or raw water percentage was higher, killing rate gradually increased with increase in throat length-radius ratio; when flow velocity was higher or raw water percentage was lower, killing rate was almost independent of throat length-radius ratio. Inactivated effect of pathogenic microorganisms can be further enhanced by increasing throat velocity or prolonging cavitation time. Hydrodynamic cavitation is a novel disinfection technique for drinking water without disinfection byproducts (DBPs) and no need to add disinfectant.

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.

An experimental investigation of the cavitation characteristics of high-velocity flow over an offset-into-flow with various heights and chamfers both in the presence and absence of aeration was conducted in a cavitation tunnel of the Hydraulics Laboratory, Zhejiang University of Technology in China. The 2- and 5-mm abrupt and sloping offsets into flows were employed to be models of surface irregularities. Cavitation phenomena of high-velocity flow over the various offsets were carefully observed. A range of air concentrations was considered. Variations of wall pressures downstream and upstream of the offset were measured in terms of the air concentration. The effects of air concentration and chamfer on the cavitation characteristics of the offsets were analysed. In addition, the cavitation cloud over the offset-into-flow and the turbulent boundary layer over a flat plate are compared.