Journal of Irrigation and Drainage Engineering

Vortex drop structure is used to convey water through underground conduits in urban sewers and drainage systems. During the plunge, a large volume of air is entrained into the water and then is released from the drop shaft downstream. Basically, volume of entrained air is comparatively hard to measure. In this research, a physical model was constructed to understand the mechanism of air circulation through vortex structure. In fact, experiments were tested to investigate effects of variables on the air circulation. Through the experiments, results of dimensional analysis results indicated that the approach flow Froude number ($F_r$), drop total height to shaft diameter ratio ($L/D$), and sump depth to shaft diameter ratio ($H_s/D$) had significant influences on the relative air discharge ($\beta$). To express the role of each independent variable on relative air discharge ($\beta$) in terms of regression analysis, response surface methodology, based on central composite face-entered design (RSM-CCFD) was examined. Hence, a regression-based-equation in form of quadratic polynomial was proposed to estimate $\beta$ variable. Additionally, experimental design was to investigate simultaneous effects of $F_r$, $L/D$, and $H_s/D$ on the $\beta$. Results of experimental study indicated that $\beta$ variable had upward trends with an increase in $F_r$ variable and $L/D$ ratio. Analysis of variance for the proposed regression model demonstrated that simultaneous effect of $L/D$ and $H_s/D$ on $\beta$ variable remained statistically significant, whereas other interaction effects of variables were insignificant. Ultimately, the optimum location for installation of air vent pipe ranged from $D$ to $2.25D$ in a way that air vent pipe had the most satisfying level of air outlet flow performance.

This study investigates the relationship between the curve number and regional rainfall characteristics, and also determines the extent to which intrastorm application of the curve number method is likely to generate infiltration rates that exceed the infiltration capacities of catchment soils. It is shown that there is a sufficiently strong relation between the curve number and regional rainfall characteristics in the US that precludes translating curve numbers between locations based only on land cover, land use, and hydrologic soil group. It is also shown that intrastorm application of the curve number method is valid only for relatively high curve numbers, thereby limiting the application of the curve number method for calculating intrastorm runoff rates.

PhiX174 (or $\mathrm{\Phi }\mathrm{X}174$) is a spherical single-stranded DNA bacteriophage used as a surrogate to study viral enteric pathogens in the environment. The resuspension of viral pathogen from bed sediment in irrigation canals impairs the quality of overlaying water and can result in the contamination of produce. We conducted a series of laboratory experiments to evaluate the resuspension of PhiX174 from bed sediment in an open channel flume. Different flow conditions (e.g., flow rate, velocity, shear stress) and three types of sediment mixtures (i.e., loam, sand, sandy loam) were investigated. Results revealed that the resuspension rate increases with the dimensionless bed shear stress. Based on these results, for the first time, we proposed two models to correlate the concentration of PhiX174 with the dimensionless bed shear stress for different sediment. One model was proposed for sandy loam and loam, was verified favorably by the experimental data, and yielded a Nash-Sutcliffe efficiency coefficient (NSE) of 0.71 and $R^2$ value of 0.72. The other model was proposed for sand, with NSE of 0.20 and $R^2$ of 0.26. The application of these models also indicated viruses are more easily resuspended from sand than sandy loam or loam sediments. The models shed a light for studying the correlation between the viruses in water and sediment and will benefit the management of irrigation water quality.

The Samani, Magallanez, Baiamonte, Ferro (SMBF) flume is a simple and inexpensive instrument for indirect discharge measurement that was originally proposed for use in a horizontal channel and then also applied in sloping channels. The contraction of the flow cross section, aimed at establishing a critical flow condition, is simply obtained by applying two half cylinders to the walls of a rectangular cross section. In this paper a theoretical approach previously proposed for a horizontal SMBF flume is first extended to a sloping SMBF flume and a new stage-discharge relationship is deduced. Then, this equation is experimentally tested using laboratory measurements from literature for different values of the contraction ratio and flume slope, and its reliability is compared to the reliability of the equation originally proposed in the literature.

The supercritical flow over a side weir is a type of spatially varied flow with decreasing discharge. Most studies of side weir flows are limited to the estimation of the discharge coefficients, and less attention has been paid to the characteristics of the water surface profile. This paper investigated the characteristics of the supercritical water surface profile along the side weir. Based on the characteristics of the general flow profile, a dimensionless quadratic function is proposed for the variations of the flow depth along the main channel which depends on the geometric and hydraulic parameters of the side weir. Using an experimental study, the equation of water surface profiles was derived. Following the determination of the flow depth and investigation of the velocity variations along the side weir, variations of the discharge along the main channel were investigated, and a new equation of the main-channel discharge along the side weir is proposed. Using the proposed equations, the flow depth and discharge in the main channel are estimated at any section of the side weir. Comparison of the predictions of the proposed equations with different sets of existing experimental data showed that these equations can predict the water surface profile and the flow discharge with good accuracy, and are of design relevance.

A hybrid programming methodology was proposed to derive a simple empirical formulation for the estimation of the required pipe diameter in the sizing problems (Type 3) of pipe distribution systems. The model was derived based on multiple regression-based analysis using the Richardson’s extrapolation approach and the Levenberg–Marquardt algorithm with double precision. The proposed formulation was developed using a total of 300,000 different data points within the framework of MATLAB and DataFit scientific software. The application of the model was explored for a wide range of five fundamental pipeline design variables [absolute roughness of the pipe wall ($\epsilon =0–9\mathrm{mm}$), water temperature ($T=5°\mathrm{C}–100°\mathrm{C}$), pipe length ($L=5–500\mathrm{m}$), flow rate ($Q=0.01–1{\mathrm{m}}^3/\mathrm{s}$), and head loss ($\mathrm{\Delta }h=1–30\mathrm{m}$)] and tested against a total of 10,000 additional computational scenarios and the available models reported in the literature. The uncertainty prediction of the proposed formula was quantified and compared with those of existing prediction models. For the new empirical equation, the mean prediction errors between the estimated and the theoretical diameter values (calculated from the numerical solution of the Colebrook–White equation) were significantly smaller than those of existing models. Moreover, the narrowest uncertainty bands, the lowest 95% confidence prediction error intervals, and the lowest amounts of expanded uncertainty (U95) were achieved for the proposed model. Other statistics (e.g., mean absolute relative error, absolute relative error, coefficient of variation of root mean squared error, determination coefficient) also corroborated that the proposed empirical model produced realistic estimations that were superior to those obtained from other well-known explicit models in the literature. The findings of this study concluded that the computational analysis yielded a simple mathematical structure to be easily and accurately used for educational and practical purposes.

The current state of the art on how the circular cross-section shape of a rigid boundary channel affects the incipience of sediment entrainment is not well investigated in the literature. Moreover, the incipience of sediment entrainment studies via artificial intelligence is very limited so far. The studies for rigid boundary channels to date have yielded different incipient motion data depending on the cross-sectional shape. Also, most of the existing works were proposed for rectangular cross-sectional channels. Conversely, this study investigated the effects induced by a circular cross-sectional shape on critical dimensionless shear stress by experimental procedures under smooth flow conditions. It was found that the circular cross-sectional channel shape significantly altered the conditions in favor of reducing the critical shear stress for the incipient sediment entrainment. This implies that the circular cross-sectional channel shape exhibits the advantage of self-cleansing open channel design. For a circular cross-sectional channel and smooth flow conditions, a new critical shear stress formula is proposed based on the obtained experimental data. Ninety-seven experimental observations were performed under hydraulically transitional flow conditions with a grain shear Reynolds number (${\mathrm{Re}}^{*}$) range of 5.2–41.17. Most of the experiments were performed with ${\mathrm{Re}}^{*}>10$. The new proposed equation is an empirical approach to express the governing equations of incipient motion in rigid boundary channels. Furthermore, a novel hybrid-geno-fuzzy inference system (GENOFIS) and the adaptive neural fuzzy inference system (ANFIS) approaches were developed using experimentally obtained data to predict the incipient motion of sediment entrainment. The performance of the quantitative results of the novel GENOFIS, ANFIS, and empirical equations were evaluated via the root mean square error (RMSE), $F$-test, and the coefficient of efficient (CE) model evaluation criteria. The GENOFIS is a novel attempt to revolutionize the prediction of complicated nonlinear phenomena such as incipient motion. The results show that prediction of the incipient motion of sediment via the GENOFIS approach yielded more accurate results than those of ANFIS for hydraulically transitional flow conditions.

Sediment deposition in irrigation systems results in the disruption of water distribution and thereby high maintenance costs. The vast majority of studies on the behavior of cohesive and noncohesive sediments have been done in rivers and estuaries. Modeling studies on sediments in irrigation systems have mainly dealt with noncohesive sediments mostly using one-dimensional (1D) models. In practice, irrigation systems diverting from natural rivers often face a mix of cohesive and noncohesive sediments. Sediment deposition is usually asymmetric, especially around offtakes and structures, and cannot be resolved using 1D models. Therefore, the authors used Delft3D version 4.02.03—a two- and three-dimensional (2D/3D) model commonly applied to rivers and estuaries—adapting it for use in irrigation canals to test different scenarios of uniform and mixed cohesive and noncohesive sediments of varying concentration and water discharge. The authors found that the model was able to provide additional insights into the behavior of cohesive and noncohesive sediments in irrigation canals, thus showing the importance of using 2D/3D models. Also, they found that cohesive sediments are more sensitive to variations in discharge and velocity compared with noncohesive sediments. Simulations revealed that where noncohesive sediments are present in a mixture with cohesive sediments, deposition is slower than in the case of pure noncohesive sediments of the same concentration.