Water And Sediment Movement Of Y-type Screen Filter Based On CFD-DEM

As a common filter in the field of irrigation,the performance of the mesh filter affects the whole micro-irrigation system.The performance of mesh filter can be divided into hydraulic performance,filtering accuracy and anti-blocking ability.In screen filter,uneven flow field leads to local clogging whose distribution is influenced by flow rate,particle diameter,streamlines and etc.This paper aims to simulate and analyze the particles'motion and distribution under different flow rates and diameters by adopting CFD-DEM method,which reflects the resistance characteristics of mesh.?1?There are back flow,vortex and stagnation zone inside the filter,which results in uneven flow velocity on each filter surface,highest flow velocity at the outlet side and lowest flow velocity at the inlet side,with a difference of 39%.The head loss of the filter accounted for77%of the total head loss.The maximum flow rate(8.21L/h^-1)is at the top of the outlet side filter and the minimum flow rate(1.71L/h^-1)is at the center of the inlet side filter.The former is5.9 times higher than the latter.?2?With the change of time,the flow field in the filter changes obviously.Sand accumulation occurs on the lower end face of the outlet side,the upper end face of the outlet side,the lower end face of the inlet side and the upper end face of the inlet side in turn,and eventually fills the whole filter core.Among the four filter surfaces of the filter element,the upper surface of the outlet has a higher velocity of flow while the sand accumulation is the least,and the upper surface of the inlet has a smaller velocity and the largest accumulation.Thus,the upper surface of the outlet side has a better filtering performance,which can properly improve the filtration efficiency of the hydraulic performance.?3?For the particles?d<190?m?passing through the filter,the higher the inlet velocity is,the more concentrated the particles passing through the filter.For the intercepted particles,when the particle size is close to the pore size?190?m?,the particles adhere to the filter steadily,and increasing the inlet velocity makes the particles accumulate to the side of the filter and cause local blockage.When the particle size is twice larger than the pore size,the particles move continuously in the inner chamber,and it is difficult to adhere to the filter steadily.Reducing the inlet flow rate will improve the uniformity of the particle distribution.High uniformity of particle distribution can prolong the high efficiency period of the filter and reduce the difficulty of flushing.The sand water numerical simulation shows that with the increase of flow velocity,the impact force of circulating flow increases,the sediment captured on the net surface decreases,and the sediment quantity and particle size in the plug head increases,which results in the concentration of sediment distribution on the filter surface,the increase of the cleanliness of the filter surface,the improvement of anti-clogging performance,local blockage and filtration performance.Comprehensive analysis shows that there is no significant difference in the performance of filters above 0.5m/s,so 0.5m/s is the most economical flow rate.In total,because the blockage of mesh filter is affected by water and sediment movement,while the movement of water and sediment is also affected by the particle size of sediment and the filtration speed.More smooth transition structure should be adopted to avoid dead space and centralized flow.Appropriate filtration speed should also be selected according to the demand and the operation of equipment in actual production.