This study aims to investigate the effect of rated flow rate and lateral distance on the risk of clogging in the button-type emitter during drip irrigation using high-sediment sediment-loaded water. Three rated flow rates (2, 4, and 8 L/h) of button-type emitters were subjected to the muddy water clogging tests, corresponding to the different lateral positions (lengths of branch pipe at the inlet of the lateral w, 2w, and 3w, respectively, with lateral spacing w=204 mm; referred to the inside, the middle, and the outside, in that order). A two-factor full-scale test was then carried out with a total of nine combinations. Three combinations were tested at one time, and three tests were conducted as one round, where a total of two rounds of tests were conducted to ensure the reliability. The results show that the rated flow rate of the emitter and the lateral distance posed the great impacts on the full cross-section mean flow rate in the lateral and the branch pipe, leading to the initiation of sediment deposition in the pipe, even in the process of emitter clogging. The emitter with the rated flow rate of 4 L/h presented the slowest decrease in the average relative flow rate and the coefficient of irrigation uniformity, indicating the best anti-clogging performance, and the highest number of effective irrigation times. The average service life increased by 11.84% and 49.11%, respectively, compared with the emitters with a rated flow rate of 2 and 8 L/h, respectively. The smaller the rated flow rate of the emitter was, the more significant the impact of the lateral distance on the service life of the emitter was. The lower the rated flow rate of the emitter was, the greater the mass of sediment retained in the lateral was, the greater the proportion of large-particle sediment deposited was, and the greater the tendency for the large-particle sediment to be retained in the lateral relative to small-particle sediment was. The emitter with the rated flow rates of 8, and 2 L/h shared the highest and lowest number of particles in the initiating motion of sediment deposited in the lateral, as well as the largest and smallest upper limit of particle size, respectively. The higher the rated flow rate of the emitter and the closer to the front of the installation on a single lateral were, the larger the sediment particle size it discharged. The initiation of sediment deposits in the lateral was the main cause of faster clogging of high-flow emitters. The amount of sediment entered the emitter, due to the too too-large rated flow rate of the emitter, the large velocity of water flow in the lateral, and the strong sand holding. The sediment particles then failed to discharge from the emitter in time to be easily deposited inside the emitter or flocculation and sedimentation by collision, leading to the emitter more susceptible to clogging. The clogging was easier to be washed away, due to the rated flow rate of the emitter for the 8 L/h of the flow channel cross-section dimensions (1.60 mm×1.08 mm) and the flow velocity of the muddy water within the channel is maximum. Repeated clogging was more likely to occur in the 8 L/h emitter than in the 4 and 2 L/h ones. The finding can provide a strong reference for the selection of a rated flow rate to prevent the emitter clogging in drip irrigation.

Y-type mesh filters have been widely used in the micro-irrigation systems. A better hydraulic performance is highly required for the stable operation during irrigation. In this study, the standard k-model was adopted to simulate the internal flow field of different filters using the computational fluid dynamics with multi-angle analysis. A series of simulation tests were carried out under three types of filter screen shapes (square, circular and diamond) and three angles of cylinder arc (0°, 15°, and 30°). Specifically, a systematic analysis was implemented on the hydraulic characteristics of the internal pressure drop coefficient, the flow distribution on the surface of the filter element, the internal flow field, and the pressure distribution. Physical tests were also conducted to verify the numerical simulation. The results show that: There was 9% average difference in the head loss coefficient between the physical test and the numerical simulation, indicating the better reliability of the numerical simulation. The head loss of the filter was concentrated on the outlet side of the screen, which was accounted for 85% of the total head loss. A stagnant zone of water flow was formed inside the plug, where the velocity was very low without the water flowing back. The smallest pressure was found in the center of the filter chamber from the center to the surrounding area. There was also an increase in the minimal pressure in a stepwise manner from the center to the periphery. Among them, the circular mesh filter shared the largest head loss coefficient, followed by the square mesh filter, and the smallest was found in the diamond mesh filter. The pressure dropped at the mesh, and the total pressure dropped to change, as the shape of the mesh changed. But there was no variation in the value and distribution of the maximum and minimum pressure in the chamber. It infers that the shape of the mesh posed a greater influence on the distribution of the overflow rate on the mesh surface of the filter. The highest proportion of medium-rate overflow area was 47.5% in the square mesh filters, followed by the circular shape, and the smallest medium-rate overflow area of diamond shape was only 26.5%. The head loss of the filter gradually decreased with the increase of the arc angle of the cartridge. The pressure drop coefficient at 35° decreased by 73.15%, compared with 0°. There was also the much more uniform distribution of the flow rate on the mesh surface with the increase of the angle, in which the area of the medium speed overflow area at 35° increased by 71.48%, compared with 0°, indicating the outstandingly improved hydraulic performance. There was the significant decrease in the internal and external pressure difference at the middle and upper section of the screen on the outlet side with the increase of the arc angle of the cartridge , particularly for the differences between 35° and 0°. The difference of the pressure drop between 35° and 0° was 2.97 times. Therefore, an optimal filter can be selected with a square cylinder arc angle of 30°in the actual micro-irrigation system, in order to improve the hydraulic performance and service life of the filter with the gentle internal flow field and uniform flow distribution on the mesh surface.