| Gill-piece separation device(GPSD)is an energy-saving and environmental protection water-sediment separation device,mainly used to deal with muddy water containing high concentration of viscous sediment.In this paper,based on the research results of the GPSD under static water and dynamic water conditions,the two-phase flow field of water-sediment and separation efficiency of the GPSD under dynamic water condition were studied from macro and micro perspectives by physical model experiments and numerical simulation.The research results provide theoretical and technical support for the application of the GPSD in municipal water treatment and drip irrigation system.The main work and conclusions of this paper are as follows:(1)Physical model experiments were carried out to the GPSD and common tube with different gill-piece spacing(d=5cm,d=8cm,d=11cm).①The water-sediment separation efficiency of the GPSD under different gill-piece spacing is higher than that of the common tube.②In the GPSD under different gill-piece spacing,the water-sediment separation efficiency changes with time includes three stages,which are slow increase,rapid increase and slow increase.③When the time is 10～125min,the water-sediment separation efficiency of gill-piece spacing d=5cm is 7.87～35.1 2%,which is 1.25～1.43 and 1.37～1.77 times that of gill-piece spacing 8 and 11cm.(2)The mixture model and four turbulence models were used to simulate the two-phase flow field of water-sediment in the GPSD.It was found that the coupling of Mixture Model and RNG k-ε model is more suitable for simulating the two-phase flow field of water-sediment in the GPSD,and the relative error of the results of physical experiment and numerical calculation is only 1.77%.(3)Numerical simulation is carried out to the two-phase flow field of water-sediment in the GPSD at different gill-piece spacing(d=5cm,d=8cm,d=11cm),different inlet positions of muddy water(4 positions)and different length-width ratios(1:1,2:1,3:1,4:1).①The phenomenon of double density flow exists in the GPSD with the different gill-piece spacing,the inlet position and the length-width ratio,that is the transverse density flow generated by water and sand around the upper and lower surface of the gill-piece and the vertical density flow generated by water and sand around the sediment channel and clear water channel of the GPSD,which is conducive to the separation of water and sand.②The smaller the spacing between gill-piece,the more stable the double density flow in the GPSD,the higher the volume fraction of sediment on the upper surface of the gill-piece,and the lower the volume fraction of sediment at the clean water outlet.The water-sediment separation efficiency is highest when gill-piece spacing d=5cm.③When the inlet is located at the bottom of the GPSD,the flow field of the GPSD is less affected by water flow,and the water-sediment separation efficiency at this location is the highest,reaching 72.45%.④With the increase of the length-width ratio,the influence of turbulent flow generated by the inlet at the bottom of the GPSD on the flow field is smaller,and the range of high concentration in the gill-piece passage is smaller,and the thickness of the top clear water layer is larger.The water-sediment separation efficiency at the GPSD with the length-width ratio of 4:1 is the highest,which is 90.40%. |
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