Irrigation Emitters Research Articles

Mechanism of intermittent fluctuated water pressure on emitter clogging substances formation in drip irrigation system utilizing high sediment water

Emitter clogging is one of the bottlenecks that restricts the application and promotion of drip irrigation technology. Applying intermittent fluctuated water pressure is regarded as an effective way to overcome drip irrigation emitter clogging when using high sediment water. Therefore, a drip irrigation experiment using Yellow River water was carried out at Deng Kou County, Inner Mongolia, China, to study emitter clogging controlling effects of three fluctuation patterns. The control group (CG) operation pressure was 40 kPa, and three intermittent fluctuated water pressure modes were 40 kPa + fluctuating water pressure for 1 h (FP1 h), 2 h (FP2 h), and 4 h (FP4 h), respectively. The system was fluctuated once every 16 h, and the amplitude of the fluctuating water pressure was 80–100 kPa with a cycle of 40 s. The characteristics of the sediment size and mineral components of clogging substances found in emitters and laterals were also analyzed. The results showed that intermittent fluctuated water pressure not only directly changed the flow velocity distribution in the emitter flow path to reduce the deposition of clogging substances, but also controlled the formation of clogging substances inside the laterals to avoid enhanced emitter clogging by transporting into the emitter. The intermittent fluctuated operating pressure could effectively reduce contents of emitter clogging substance in drip irrigation, and the longer period it was applied, the better controlling effect was observed. Comparing with the CG, applying intermittent fluctuated water pressure with constant period of 4 h would reduce the total clogging substance contents by 26%. The clay and powder particles were reduced by 56% and 34%, respectively. Meanwhile the quartz, silicate, calcium magnesium and carbonate in the clogging substances decreased by 36%, 35%, and 11%, respectively. Thus, the discharge ratio variation coefficient (Dra) and Christiansen Uniformity coefficient (CU) increased by 10.1–16.7% and 8.9–14.2%, correspondingly. These results could provide references for the application and promotion of drip irrigation technology using water with high sediment load.

Composite fouling of drip emitters applying surface water with high sand concentration: Dynamic variation and formation mechanism

Drip irrigation applying surface water with high sand concentration leads to a higher risk of composite fouling, which is the most complex material type of clogging. Thus, understanding the dynamic variation and formation mechanism of composite fouling is the prerequisite for controlling clogging substance and establishing rational anti-clogging method to promote high-sand surface water for drip irrigation. In this paper, the components of the composite fouling were studied through the emitter composite fouling experiment under three drip irrigation frequencies. The results indicated that the particulate fouling composition (solid particle, SP), crystallization fouling composition (CaCO3 and MgCO3 precipitate, C-MP), and biofouling composition (extracellular polymeric substance, EPS, and microbial activity, MA) grew as the system operated. Significant positive linear correlations were obtained among different compositions (R2>0.82, p < 0.01), and the microorganism attached on the surface of SP and continuously secreted EPS mutually promoted the formation of biofouling and particulate fouling. The condensation of microcrystals formed by C-MP with SP promoted the formation of crystallization and particulate fouling, and phosphorus anions enhanced flocculation and agglomeration between particles. Thus, physical-chemical-biological reactions occurred to promote mutual growth, which ultimately led to composite fouling formation. Meanwhile, various components in the composite fouling increased gradually with higher operating frequency, which could aggravate the emitter clogging and decrease the relative discharge of the drip irrigation emitters (Dra) and the uniformity coefficient (CU).

Hydraulic performance and energy dissipation effect of pit structure flow channel emitter

In this paper, a drip irrigation emitter with new pit flow channels such as shunt, sharp turn, and confluence was constructed by the pit structure in the water transporting tracheid of bionic plant xylem. In order to study the hydraulic performance and energy dissipation effect of the pit flow channel, the geometric parameters of the pit flow channel were combined by simulation prediction and orthogonal test. The 25 sets of test schemes were carried out to test the hydraulic characteristics, and the Bernoulli equation was used to solve the structural loss coefficient. At the same time, the orthogonal test results were analyzed by the range and variance, and the regression model of geometric parameters and flow index was established. The results showed that the flow index of the emitter was 0.462~0.496, and its hydraulic performance was good. The structural loss coefficient under the pressure head of 5~25 m was 2120~6321, which showed that the energy dissipation effect was obvious. The order of influence of each geometric parameter on the flow regime was T>B>S>D>A, and the optimal scheme was T0.18B2.2S2.2D0.2A4. The regression coefficient of the model was significant. The value of the F statistic was 16.670, corresponding to the significance level Sig.=0<0.05, and the error of the experimental and simulated values of the flow index was less than 5%, which proved the accuracy and reliability of the regression model. This paper provides a new idea for agricultural drip irrigation control technology.

Composite clogging characteristics of emitters in drip irrigation systems

This study investigated the characteristics of emitter clogging substance in 16 kinds of drip irrigation emitters using 3 kinds of water sources that could typically induce composite clogging in the Yellow River irrigation area. The research results indicate that there was remarkable randomness in the behavior of composite clogging substances in a single emitter, and peak randomness ( $$\Delta F_{Q}^{t}$$ ) values were 19.5–20.8%, 20.5–22.4% and 25.9–28.2% higher than that with physical, chemical and biological clogging, respectively. Clogging in a single emitter also exhibited recoverability ( $$R_{Q}^{{{\text{CD}}}}$$ ) which would be lost when the clogging degree reached 60–75%, and recoverability ( $$R_{Q}^{{{\text{CD}}}}$$ ) showed the opposite variation rule to randomness ( $$\Delta F_{Q}^{t}$$ ). Though clogging in a single emitter was associated with certain randomness and recoverability, the overall variation of the micro-irrigation system's average discharge variation ratio (Dra) and Christiansen’s uniformity (CU) was not affected. Instead, the two showed relatively consistent dynamic variation of mild fluctuation followed by acute descending. The fluctuation trend during the earlier stage lasted from 128 to 660 h, and descending branch slopes of Dra and CU during the later stage were 0.09–0.12 and 0.13–0.21, respectively. In terms of various types of emitters, $$\Delta F_{Q}^{t}$$ generally demonstrated dynamic variation for a tape emitter (highest), a single-side labyrinth emitter (slightly lower), a cylindrical emitter (even lower) and a flat emitter (lowest). However, the dynamic variation of $$R_{Q}^{{{\text{CD}}}}$$ , Dra and CU were inverse. As far as various water sources were concerned, mixing water had the highest $$\Delta F_{Q}^{t}$$ , followed by Yellow River water, and surface lake water had the lowest $$\Delta F_{Q}^{t}$$ , while variation characteristics of $$R_{Q}^{{{\text{CD}}}}$$ , Dra and CU among the three water sources were inverse. The present study could provide reference for revealing the characteristics of composite clogging in emitters, thus constructing effective clogging control methods.

Water-Use Efficiency of Potted Pakchoi in Yunnan Laterite with Root Infiltration Irrigation and Anticlogging Emitter

AbstractA method is developed to calculate crop water consumption based on the water balance principle. An independently designed emitter resistant to clogging caused by negative pressure (EK) is a...

An in-situ accelerated experimental testing method for drip irrigation emitter clogging with inferior water

Emitter clogging has become a bottleneck in the application and promotion of inferior water drip irrigation technology. Understanding the detailed emitter clogging process is the precondition and basis for solving clogging issue. However, the existing indoor simulated experiments have the disadvantages in unnecessary effect on the results, and the in-situ experimentation is difficult due to the long experiment period. Therefore, this paper proposed an in-situ accelerated (ISA) experimental testing method for studying the emitter clogging behaviors in drip irrigation systems with inferior water source. Its feasibility was verified in Dengkou in Inner Mongolia, and a comparative study was performed to examine the differences and correlations between the ISA method and the normal intermittent (NI) method for drip irrigation using Yellow River water (YRW) and brackish water (BRW). The results indicated that the drip irrigation emitter clogging behaviors via the ISA method were relatively conservative. The values of randomness of clogging occurrence (△FQt), emitter clogging degree (EC), emitter discharge variation (qvar), clogging substance on the internal laterals (CSL) and clogging substance inside emitters (CSE) were lower than those of the NI method by 24–57, 64–110, 58–121, 16–38 and 14–32%, respectively. The average discharge variation ratio (Dra), Christiansen coefficient of uniformity (CU) and statistical uniformity coefficient (Us) were 7–13, 15–23 and 17–39% higher than those of the NI, respectively. Besides, the experimental results under the two modes (ISA and NI) had significant linear correlation (0.98 > R2 > 0.75). Thus, the ISA experimental results could be converted into those under NI mode using the linear model, without considering the effects of emitter type nor the water quality. This result indicated that the ISA method could accurately reflect the clogging behaviors of the drip irrigation emitter.

Chemical Clogging Behavior in Drip Irrigation Systems Using Reclaimed Water

Abstract. Reusing reclaimed water in agricultural irrigation has become an effective way to alleviate water shortages in agriculture. However, the multiple substances in reclaimed water and their coupling effects easily lead to emitter clogging when using drip irrigation technology. The microorganisms present in reclaimed effluents secrete extracellular substances and absorb large amounts of solid particles, ions, nutrients, and organic matter and thus become the main part of the clogging substance. Meanwhile, traditional drip irrigation systems converted from irrigation to both irrigation and fertilization and the water-fertilizer coupling effects result in more chemical precipitation. Determining whether the chemical process has a significant impact on clogging and understanding the mechanism of this process was considered a difficult and important research question. For this reason, an indoor experiment, under a controllable environment, for drip irrigation emitter clogging using both reclaimed water with three Ca2++Mg2+ concentrations and groundwater was carried out. Several precise testing methods, such as x-ray diffraction, were applied to identify the mineral components in the clogging substances, and their characteristics and impacts on clogging were systematically explored. The results indicated that the emitter clogging characteristics were coincident under different treatments when using reclaimed water, and chemical precipitates were found in all treatments. Higher Ca2++Mg2+ concentrations led to more serious emitter clogging. The discharge ratio variation and Christiansen coefficient of uniformity for the reclaimed water treatments were lower than those for the groundwater treatment. Meanwhile, the total weights of the clogging substances were 5.6% to 58.8% higher. There were sufficient mineral components in the clogging substances, and they were identified as quartz, silicate, carbonate, and salt. Their contents all showed significant linear correlations with the degree of emitter clogging (R2 &amp;gt; 0.64, p &amp;lt; 0.05), which indicated that mineral components increased as the system continued operation. Among them, salt and silicate were linearly correlated to quartz contents, as they mainly originated from the water used for drip irrigation. However, carbonate contents increased in an exponential pattern with quartz contents (R2 &amp;gt; 0.67, p &amp;lt; 0.01), which demonstrated that carbonate was the main mineral component formed during the clogging process and the key component that increased clogging. The results obtained in this study provided insights into the chemical clogging process and the targeted chemical precipitates to be dealt with when using reclaimed water for drip irrigation. Keywords: Chemical precipitation, Emitter, Microirrigation clogging, Reclaimed water application.

三角形灌水器形状参数对其水力性能的影响

三角形灌水器形状参数对其水力性能的影响

Shape and Form Optimization of On-Line Pressure-Compensating Drip Emitters to Achieve Lower Activation Pressure

This study presents the design and validation of on-line pressure-compensating (PC) drip irrigation emitters with a substantially lower minimum compensating inlet pressure (MCIP) than commercially available products. A reduced MCIP, or activation pressure, results in a drip irrigation system that can operate at a reduced pumping pressure, has lower power and energy requirements, requires a lower initial capital cost, and facilitates solar-powered irrigation systems. The technology presented herein can help spread drip irrigation to remote regions and contribute to reducing poverty, particularly in developing countries. The activation pressures of drip emitters at three flow rates were minimized using a genetic algorithm (GA)-based optimization method coupled with a recently published fluid–structure interaction analytical model of on-line PC drip emitter performance. The optimization took into account manufacturing constraints and the need to economically retrofit existing machines to manufacture new emitters. Optimized PC drip emitter designs with flow rates of 3.3, 4.2, and 8.2 lph were validated using precision machined prototype emitters. The activation pressure for all was ≤0.2 bar, which is as low as 16.7% that of commercial products. A limited production run of injection molded 8.2 lph dripper prototypes demonstrated they could be made with conventional manufacturing techniques. These drippers had an activation pressure of 0.15 bar. A cost analysis showed that low MCIP drip emitters can reduce the cost of solar-powered drip irrigation systems by up to 40%.

Effects of microbial community variation on bio-clogging in drip irrigation emitters using reclaimed water

Drip irrigation emitter clogging is one of the key barriers to the development and application of reclaimed water drip irrigation technology. Reclaimed water typically contains large amounts of bacteria, and their excretions, the sticky extracellular polymeric substances (EPS). Indeed, different amounts and types of microorganisms affect drip irrigation emitter clogging, especially bio-clogging process, via excretive EPS. Therefore, it is important to study the dynamic microbial community structure and its effect on the emitter bio-clogging process. In this paper, a drip irrigation experiment using reclaimed water was carried out. Phospholipid fatty acids (PLFAs) in biofilm (bio-clogging substance) were taken as the biomarker of microbial community inside emitters, and the dynamic variation of microbial community in drip irrigation emitter and its effect on the clogging process were studied. The results showed that the microbial growth of biofilms inside 9 types of drip irrigation emitters could enhance emitter clogging, and the PLFAs showed S-shaped pattern with emitter clogging degrees (R2>0.95, p<0.01), which was closely associated with the variation of microbial community. There were 3–7 types of PLFAs commonly in biofilms within drip irrigation emitters, among which gram positive bacteria (i15:0, 16:0 and 18:0) were dominant in amounts, with the close contents of 24.4%–34.2%, 24.8%–37.2% and 24.2%–39.0%, respectively, and their total proportion exceeding 76.3%. The Pseudomonas (16:0) was found to be the most critical bacteria to affect emitter clogging as it performed better to decompose and utilize organic matters, and showed the best relation with clogging degrees, along with significant relations with other types of bacteria. Therefore, controlling gram positive bacteria, especially Pseudomonas was the most effective way to relieve emitter clogging. Their variation also changed the microbial community structure, and the diversity index (H), evenness index (J) and dominance index (D) of microbial community in biofilms varied within 1.08–1.53, 0.75–1.11 and 0.65–0.75. The diversity index and dominance index both decreased as the amounts and types of microorganisms increased. The total amount of the gram positive bacteria increased after their decrement, and resulted in the similar variation of the microbial community evenness index. The results of this study will establish a theoretical basis for exploring the effects of microbial community variation on emitter bio-clogging, and provide insight into the emitter clogging mechanisms and possible mitigation strategies.

Evaluation of numerical simulation accuracy for two-ways mixed flow drip irrigation emitter based on CFD

Evaluation of numerical simulation accuracy for two-ways mixed flow drip irrigation emitter based on CFD

Manipulation of Soil Texture to Remove Salts from a Drip‐Irrigated Root Zone

Core Ideas Root zone soil texture manipulation improved leaching efficacy for drip irrigation. Manipulation consists of coarse medium, with roots within, surrounded by fine medium. Capillary barrier between coarse and fine media prevents salt return to roots. Study results may contribute to the practice of irrigation with salty water Drip irrigation is a useful method for the application of low‐quality water because it does not wet the foliage and limits the spread of contaminants. Nevertheless, when using water containing high levels of dissolved salts, drip irrigation may be insufficient for leaching and can lead to soil salinization. A new conceptual model was tested experimentally and numerically to examine if manipulation of the distribution of soils with different textures could promote the removal of salts from the root zone and increase leaching efficiency. The manipulated root zone consisted of a volume of coarse soil, located under a drip irrigation emitter, surrounded by finer texture soil. We hypothesized that the differences in hydraulic properties between the two soils and the capillary barrier developed at their interface would generate a one‐directional flow path of the salty water from the location of irrigation to the fine soil. This would enforce salt accumulation beyond the root zone. The concept was tested in a series of lysimeter and Hele–Shaw chamber experiments, together with a two‐dimensional flow model created in HYDRUS‐2D. Results showed preferential salt accumulation beyond the coarse segment of the manipulated soil, providing a volume of leached soil sufficient to support a healthy root system. Under conditions of homogenous soil texture, a notable buildup of salinity was observed in the central root zone, whereas under the manipulated texture conditions, such salt buildup was not observed.

Modeling the future of irrigation: A parametric description of pressure compensating drip irrigation emitter performance.

Drip irrigation is a means of distributing the exact amount of water a plant needs by dripping water directly onto the root zone. It can produce up to 90% more crops than rain-fed irrigation, and reduce water consumption by 70% compared to conventional flood irrigation. Drip irrigation may enable millions of poor farmers to rise out of poverty by growing more and higher value crops, while not contributing to overconsumption of water. Achieving this impact will require broadening the engineering knowledge required to design new, low-cost, low-power drip irrigation technology, particularly for poor, off-grid communities in developing countries. For more than 50 years, pressure compensating (PC) drip emitters—which can maintain a constant flow rate under variations in pressure, to ensure uniform water distribution on a field—have been designed and optimized empirically. This study presents a parametric model that describes the fluid and solid mechanics that govern the behavior of a common PC emitter architecture, which uses a flexible diaphragm to limit flow. The model was validated by testing nine prototypes with geometric variations, all of which matched predicted performance to within R2 = 0.85. This parametric model will enable irrigation engineers to design new drip emitters with attributes that improve performance and lower cost, which will promote the use of drip irrigation throughout the world.

Controlling mechanism of chlorination on emitter bio-clogging for drip irrigation using reclaimed water

Drip irrigation using reclaimed water or polluted surface water involves a higher risk of bio-clogging, which is the most typical and the most complex type of clogging, and the clogging of drip irrigation emitters limits the use and spread of drip irrigation technology. Due to its strong oxidizing effect, chlorination has been considered as the most effective method of controlling emitter bio-clogging. However, the detailed controlling mechanism has remained unclear until now. Meanwhile, there have been no unified standards established for chlorination to refer to. Therefore, field experiments were carried out in a sewage treatment plant, where the reclaimed water after secondary treatment was treated with the Cyclic Activated Sludge System (CASS) process that had been incorporated to the drip irrigation system to study the controlling mechanism and impacts on non-pressure-compensating emitter bio-clogging. There were three chlorination treatments studied, which included 2.5mg/L×2h (low concentration, long duration), 5.0mg/L×1h (moderate concentration and duration), and 10mg/L×0.5h (high concentration, short duration). The results showed that the chemical chlorination could control the microbial growth in the bio-clogging substances effectively, with the microbial phospholipid fatty acids (PLFAs) decreased by 8.3%–36.1%, the number of microbial species decreased by 2–3, the microbial activity decreased by 2.6%–23.2%, and the secretion of extracellular polymeric substances (EPS) decreased by 19.8%–43.4%. Thus, the bio-clogging substances were well controlled, and the contents of solid particles (SD) content decreased by 4.8%–48.2% compared to the non- chlorinated treatment, while the discharge ratio variation (Dra) and Christiansen uniformity coefficient (CU) increased by 14.7%–22.8% and 6.77%–19.9%, respectively. However, the effects of different chlorination modes varied significantly. Chlorination with a low concentration and a long contacting duration decreased microbial activity, and better controlled emitter bio-clogging. Thus, the chlorination treatment of 2.5mg/L×2h was recommended in the drip irrigation system using reclaimed water treated with CASS technology.

Anti-clogging evaluation for drip irrigation emitters using reclaimed water

Emitter clogging has a direct impact on the required operating time and benefit of a drip irrigation system, especially when using reclaimed water. Thus, accurately evaluating its anti-clogging ability is important to select an appropriate emitter under specific conditions. In his paper, a drip irrigation emitter clogging experiment was carried out, and the dynamic outflows of 14 emitter types using 3 kinds of reclaimed water and the groundwater in the experiment station in Tongzhou, Beijing, were tested. Then, the drip irrigation emitter anti-clogging ability evaluation index (Ia) was proposed, based on the measured emitter clogging characteristics. Ia ranked in consistent with average discharge variation rate (Dra) among different types of emitters. Thus, Ia is a valid performance indicator to evaluate anti-clogging ability, and an emitter with a relatively large value of Ia has a better anti-clogging ability. According to the calculated Ia, the same type of emitter showed better anti-clogging ability with the groundwater than with the reclaimed water, while cylindrical emitters were more likely to clog than flat emitters. Additionally, Ia was mainly affected by flow path length (L), flow path width/depth ratio (RW/D) and average near-wall water shear force (τ), as Ia increased with shorter L, smaller RW/D and larger τ. Furthermore, the quantitative estimating model of Ia was established through dimensional analysis and was predicted by an emitter’s rated outflow (Q) and flow path geometrical parameters (L, W and D).

Effects of Flow Path Geometrical Parameters on Flow Characteristics and Hydraulic Performance of Drip Irrigation Emitters

AbstractIn this paper, 13 fractal flow paths were designed and the effects of flow path geometric parameters on the internal flow characteristics and hydraulic performance explored. The results showed as the flow path width increased from 0.9 to 1.3 mm, the flow velocity followed from 1.83 to 2.43 m s−1. There was significant difference in the turbulence intensity. The flow velocity (about 2.14 m s−1) and turbulence intensity distribution (5.6–48.1%) in flow paths with different depths were approximately the same. Different flow path lengths would obviously affect the values of the flow characteristics, while the distributions were similar. The length increased from 128 to 256 mm, the flow velocity decreased from 2.52 to 1.84 m s−1 and the maximum turbulence intensity dropped from 55.6 to 40.1%. As for hydraulic performance, the flow regime indexes were all about 0.49. The flow coefficient was obviously positively related to flow path width and depth, but very negatively correlated with flow path length and a prediction model of flow coefficient was constructed (R2 = 0.94). After comprehensive consideration, the optimized flow path width was about 1.0 mm, the length should be less than 224 mm, and a series of emitters with different flow rates could be developed by changing the depth. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Water and salt movement in different soil textures under various negative irrigating pressures

This study examined the effect of different negative pressures and soil textures on water and salt movement to improve the efficiency of negative pressure irrigation (NPI). Four soil textures of varying fineness (Loamy Sand, Loam, Silty Loam, and Sandy Loam) and three negative pressure values (0, –5, and –10 kPa) were used. As irrigation time increased, wetting front movement speeds decreased, and as negative pressure increased, wetting front size decreased. Coarse soils had the smallest wetting front under greater negative pressure. Next, water infiltration rate decreased as irrigation time increased, and coarse soils had the lowest average infiltration rate under greater negative pressure. Finally, salt content increased with distance from the irrigation emitter and with increased negative pressure. Further, coarse soils were found to have decreased desalination under greater negative pressure. Thus, soil texture has a strong effect on NPI efficiency. However, by adjusting pressure values in accordance with soil texture, soil water content can be controlled and maintained. These findings are important to the improvement of NPI systems, increasing their practicality for agricultural use.

Use of Dehydrated Agar to Estimate Microbial Water Quality for Horticulture Irrigation.

Petrifilms are dehydrated agar culture plates that have been used to quantify colony forming units (CFU) mL of either aerobic bacteria (Petrifilm-AC) or fungus (Petrifilm-YM), depending on substrate composition. Microbes in irrigation systems can indicate biofilm risk and potential clogging of irrigation emitters. The research objective was to compare counts on Petrifilms versus traditional, hydrated-agar plates using samples collected from recirculated irrigation waters and cultures of isolated known species. The estimated count (in CFU mL) from a recirculated irrigation sample after 7 d of incubation on Petrifilm-YM was only 5.5% of the count quantified using sabouraud dextrose agar (SDA) with chloramphenicol after 14 d. In a separate experiment with a known species, Petrifilm-YM did not successfully culture zoospores of . Isolates of viable zoospores were cultured successfully on potato-dextrose agar (PDA), with comparable counts with a vegetable juice medium supplemented with the antibiotics pimaricin, ampicillin, rifamycin, pentochloronitrobenzene and hymexazol (PARP-H). The quantification of pv. Begoniaceae on Petrifilm-AC was not significantly different ( < 0.05) than on PDA, but was lower than on Reasoner and Goldrich agar (R2A) or with a hemocytometer. The current formulation of Petrifilm-YM is unlikely to be a useful monitoring method for plant pathogens in irrigation water because of the inability to successfully culture oomycetes. However, Petrifilm-AC was an effective method to quantify bacteria and can provide an easy-to-use on-farm tool to monitor biofilm risk and microbial density.

Chemical Clogging of Emitters and Evaluation of Their Suitability for Saline Water Drip Irrigation

AbstractDrip irrigation with saline water is one of the most effective methods to ease the current worldwide water shortage. However, there are more ionic compositions in saline water, resulting in easy clogging of drip irrigation emitters. In this study, we selected five common emitters as study subjects and conducted a saline water drip irrigation experiment in the Hetao Irrigation District (Inner Mongolia, China). The results showed that, as the running time increased, the discharge ratio variation (Dra) and coefficient of uniformity (CU) both declined. The Dra and CU of cylindrical emitters decreased gently, while those of flat emitters showed a 'slow–fast' downward trend. The Dra of the five different emitters decreased to 46.3–78.6% and the CU dropped to 23.5–85.0% over the course of the experiment. Cylindrical emitters with higher flow showed better anti‐clogging capacity. The temporal and spatial distribution of clogging materials within emitters differed. Specifically, the dry weights (DW) of clogging materials in different positions occurred in the order of DWhead &lt; DWmiddle &lt; DWend laterally, and clogging materials accumulated gradually with time. The average clogging materials distribution density showed a significant negative linear relationship with Dra and CU (R2 = 0.81 and 0.88). It indicated that as the clogging materials accumulated, the anti‐clogging capacity of emitters degraded. The chemical constituents of the clogging materials in the different emitters were the same (Ca + Mg carbonate, quartz, silicate and litter sodium chloride). The amounts of Ca + Mg carbonate showed a strong positive correlation with Dra and CU (R2 = 0.93 and 0.92), while the amounts of quartz showed a remarkable negative linear relationship with Dra and CU (R2 = 0.85 and 0.87). The main material responsible for emitter clogging was calcium carbonate deposits, which accounted for &gt;88.1% of the total. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Effects of flow path boundary optimizations on particle transport in drip irrigation emitters

AbstractA modified digital particle image velocimetry (DPIV) was used to test particles' moving characteristics in cylindrical fractal M‐geometries flow paths with three optimized boundaries. Taken the vorticity and characteristics of streamlines distribution in the central area and the velocity field near the boundary into consideration, it was found that the fractal M‐type flow path would be optimized with a design such that the radius of an arc in tooth‐root facing‐water zone, tooth‐tip backing‐water zone and facing‐water zone was half width of the flow path. Moreover, the radius of the arc in the tooth‐root backing‐water zone was desired to be the same with the width of the flow path. This optimization was attributed to two reasons. Firstly, with a large radius arc in the tooth‐tip backing‐water zone and facing‐water zone, the velocity in the central domain and near boundary area was improved. And the following performance of particles near the boundary was suppressed. Secondly, adoption of a small arc in the tooth‐root facing‐water zone could improve the velocity, vorticity and self‐cleaning capability near wall. In conclusion, when optimizing the boundary, the distribution characteristics of vortices should be fully considered to enhance vortices development in the flow path. Copyright © 2016 John Wiley &amp; Sons, Ltd.