Journal of Irrigation and Drainage Engineering

Y-type screen filters are widely used in microirrigation systems. Their good hydraulic performance and working life are the premise to ensure the normal and stable operation of microirrigation systems. In addition to the particle impurities in the fluid affecting the performance of the filter, the energy loss of the vortex in the flow field is also an important factor. This study explored the flow field, vortex characteristics, and wear of a Y-type screen filter under various operating conditions and design parameters. In particular, the fluid mechanics discrete-element method was used to numerically simulate the flow characteristics and wear characteristics of five Y-type screen filter inlet velocities (0.5, 0.75, 1, 1.25, and $1.5\mathrm{m}/\mathrm{s}$) and five Y-junction angles (35°, 40°, 45°, 50°, and 55°) using computational fluid dynamics. The numerical simulation results were experimentally verified. With increased inlet velocity, the strong vortex extended from the filter screen to the outlet pipe. At a maximum velocity of $1.5\mathrm{m}/\mathrm{s}$, the vorticity degree rose by 51.49% compared with that at a minimum velocity of $0.5\mathrm{m}/\mathrm{s}$, and the helicity distribution slightly changed. With the increased angle of the Y-section, the vorticity in the filter also increased. The increase of the Y-junction angle from a minimum value of 35° to a maximum of 55° angle resulted in a vorticity degree rise by only 10.64%. The positive vortex area of the outlet pipe decreased with the filter angle. The $Q$-criterion vortex identification method revealed that high-intensity vortices were mainly distributed on the mesh of the filter screen. Through numerical simulation prediction and experimental verification by wear tests, it was found that the parts with the largest wear depth were the outlet side filter screen and shell cover area, and the wear depth increased with the flow rate. At 2 s, the wear depth at the maximum flow rate significantly exceeded that at the minimum one. After a certain period of time, the wear depth of the Y-type screen filter increased with the Y-junction angle. In practical applications, the filter with an angle of 35° was selected for operating at low flow rates below $1\mathrm{m}/\mathrm{s}$. Hence, its internal flow field was more moderate, and its hydraulic performance improved, reducing the filter screen wear and prolonging its service life.

Canal controllability is an open and significant topic that addresses the unreliability/uncertainty in water delivery, efficiency, and modernization in the irrigation system. The study developed an analysis tool for canal controllability to estimate controllable performance and reduce the uncertainty of water delivery under steady and unsteady flow. We designed a linear quadratic control algorithm and applied it to the Nongchang test canal to verify the tool reliability and improve efficiency of water utilization. Finally, the effects of hydraulic variables on canal controllability were quantified. The numerical model of unsteady flow showed satisfactory predictions of water level (correlation coefficient, root mean square error, and mean absolute percentage error were 0.929%, 0.293%, and 12.86%, respectively). The Nongchang test canal was rather controllable (controllability indicator 0.265 to 0.279), implying that linear quadratic control algorithm was appropriate. The algorithm performed well under all conditions tested; the maximum absolute error was 3.66%–8.65%. The water level remained stable (deviation usually less than 0.05 m) and water delivery met user demands in terms of flow rate (the measure of performance relative to adequacy was 92.51%–98.94%) with relatively small gate movements. The bottom slope and roughness were the principal contributors to controllable performance, explaining approximately 46% of the variance. Specifically, controllability was highest when the bottom slope was low, and the roughness and side slope were high. We offer a reliable and flexible tool for assessment of canal controllability. Study results demonstrated that stakeholders benefit when conventional canal operation is modernized. The work will guide automation and upgrading of canal hardware as irrigation becomes optimized.

Various grate inlets are commonly used for different purposes. Since the grate inlets’ water-catching capacity depends on many factors, defining the best option is crucial for a sustainable drainage system. In this study, four cases with the same length, width, and void area but different geometries have been numerically studied to establish to which extent the design difference in the grate inlet affects the water-catching capacity. It has been determined how much of the approaching flow is caught by the grate inlets placed on the road with constant transverse and longitudinal slopes. The most efficient case is examined in more detail to determine the effect of the void area location on the water-catching capacity. The numerical results are discussed by comparing them with the analytical results. It has been confirmed that the location and shape of the void areas have an essential effect on the efficiency of grate inlets. Even though the void area is equal, it is concluded that the continuous void areas are more effective than the discontinuous areas. According to the results, choosing the most suitable grate among the alternative inlet designs is possible, or developing a more effective new design using numerical results provides the opportunity to compare the designs.

Abstract

This study used a large-scale ASTM International D6459 rainfall simulator to evaluate performance of various types of erosion control products used in construction. Rolled erosion control products (RECPs), hydraulic erosion control products (HECPs), and soil amendments were tested and compared based on Cover factor (C factor), a parameter between 0 and 1 where 0 represents perfect erosion protection and 1 represents bare soil. All products behaved statistically similarly at the lowest rainfall intensity [$5.1\mathrm{cm}/\mathrm{h}$ ($2\mathrm{in.}/\mathrm{h}$)] with an average C factor of 0.03. At the next intensity of $10.2\mathrm{cm}/\mathrm{h}$ ($4\mathrm{in.}/\mathrm{h}$), RECPs had significantly lower C factors than HECPs (0.11 and 0.41, respectively). Among the HECPs, Type 2 had worse C factors than other products, but all deteriorated at the highest $15.2\mathrm{cm}/\mathrm{h}$ ($6\mathrm{in.}/\mathrm{h}$) intensity, reaching an average C factor of 0.48. Most (88%) products met their industry minimum specifications at the lowest rainfall intensity, but only 25% met them by the highest intensity. The soil amendments did not have published C factors, so their performance was compared to traditional products. Gypsum statistically matched the RECPs while Polyacrylamide (PAM) statistically matched the HECPs. Preliminary testing was performed on thee straw applications, but due to sampling differences only a soil loss ratio, or simple ratio of soil lost on the bare plot to soil lost on the treated plots, was calculated. A cost estimate obtained though local professionals revealed that the straw treatments appeared to be the most economical in terms of total dollars spent per reduction in sediment loss, and that the cost of premium hydraulic mulches did not appear to translate into improved performance. This study is useful because large-scale simulations more accurately reflect field erosion performance, but they are seldom performed due to time and cost considerations. In addition, varying intensities revealed performance differentiations, many product types were compared, and using an industry standard allows for confident comparison to other results.

Practical Applications

This study used a large-scale ASTM D6459 rainfall simulator to evaluate sediment loss performance of four types of erosion control products used on construction sites: rolled erosion control products (RECPs), hydraulic erosion control products (HECPs), straw mulch, and soil amendments. Under a $5.1\mathrm{cm}/\mathrm{h}$ intensity, all products tested behaved statistically identically. As rainfall intensity increased to 10.2 and $15.2\mathrm{cm}/\mathrm{h}$, gypsum and RECPs performed better than polyacrylamide (PAM) and HECPs. Of the seven products that had available manufacturer specifications, all fell short of advertised performance. Preliminary results suggest that straw may be the most cost-effective erosion control measure of the methods tested. This study suggests that more adherence to nationally and internationally recognized testing standards is needed in the field of rainfall simulation. It also suggests that erosion performance data from large-scale simulators is more reliable than data obtained from small-scale simulators.

Trapezoidal profiled weirs and barrages are employed extensively in agrarian countries like India and Pakistan for diverting river water for canal-fed irrigation. The downstream slope of a weir is designed as $1\mathrm{V}:3\mathrm{H}$, although in some older structures, slopes as mild as $1\mathrm{V}:5\mathrm{H}$ are noticed. Downstream slopes of $1\mathrm{V}:5\mathrm{H}$ also exist for the barrages on the Nile in Egypt and in the standard Crump weir used in the UK and some European countries. This study explores the effect of the downstream slope of a short-crested trapezoidal weir on its flow hydraulics and conveyance properties. Irrigation barrages and weirs, apart from diverting water to a canal, also help in measuring the discharge of a river, which is a function of the up- and downstream water levels. For large discharges during floods, the gates of a barrage are withdrawn to ensure an uncontrolled flow that may either be free or submerged, depending on the downstream water level. Although past studies on uncontrolled flows have recognized the effect of the upstream slope of a weir on the coefficient of discharge, $C_d$, this study establishes that it is also influenced by a weir’s downstream slope. An equation of $C_d$ for free flows and a flow reduction factor for submerged flows are proposed considering both weir-face angles. For free flows, $C_d$ is seen to increase with the steepness of a weir’s downstream slope; for submerged flows, the discharge reduction factor is observed to improve as the slope becomes milder, leading to a greater conveyance. Data from our own laboratory experiments, past publications, and results derived from a 2D RANS-VOF multiphase computational fluid dynamics model are used in arriving at the conclusions reported in the study.