Journal of Irrigation and Drainage Engineering

The gravity flow in sewer systems may change to partially pressurized flow for reasons including rapid filling, and maintenance and repair. During this alteration, air can be entrapped and becomes highly pressurized, and this air pressure can negatively impact the sewer system and hydraulic infrastructure. The available mathematical models in this field mostly overestimate the peak pressures and underestimate the attenuation. In partially pressurized transient flows following air-pocket entrapment, the frictional force, similar to other forces, can be affected by the unsteady behavior of the flow and by the air-pocket size. Therefore, using a constant steady-state friction factor for the numerical simulation is a simplistic approximation. In this study, an additional friction factor, which has the same form as the steady-state Darcy–Weisbach friction factor, is proposed using dimensional analysis and calibrated by experimental data. Two well-known mathematical models, the rigid column and the method of characteristics models, were used for the numerical simulation. It was found that, compared with a constant steady-state friction factor, the additional friction factor can improve the numerical results significantly, including the overestimation of the pressure peak values, and can predict the attenuation behavior.

Particle transport by fluid is probably one of the most difficult and involved subjects among fluid dynamics, with many important issues in this field still to be fully understood. The main purpose in this work was to advance the capabilities of the computational fluid dynamics (CFD) code caffa3d so to include effective numerical modeling of particle transport by turbulent fluid flow. An Eulerian mixture model was selected wherein particles are not addressed individually but rather as a whole, incorporating their effect by means of an effective local viscosity. Numerical simulation of local scour caused by a vertical impinging jet on a sand sediment bed was carried out. The nozzle velocity value were changed in order to analyze the influence of the erosion parameter in the equilibrium erosion value. The influence of internal friction angle and porosity were also analyzed. The results achieved show that the model adequately represents the different physical processes that drive the evolution of the fluid–particle mixture, reaching a good quantitative match with the results previously reported in the bibliography.

In this study, the performance of a vortex settling basin (VSB) with a clockwise circulation was experimentally evaluated. The inlet flow rate was in the range of $8–22\mathrm{L}/\mathrm{s}$. Based on the Taguchi and response surface methods, the effects of inlet flow ($Q_{\mathrm{in}}$), central orifice diameter ($d_o$), sediment particle diameter ($d_s$), end sill height ($S_{\mathrm{out}}$), and outlet weir height ($W$) were investigated. The orthogonal array, signal-to-noise ratio (SNR), and ANOVA were used to study the performance of the VSB. The inlet canal efficiency, trapping efficiency, water abstraction ratio, and total performance were measured and the SNR calculated. The total performance of the VSB was calculated based on the inlet canal efficiency, trapping efficiency, and water abstraction ratio. The factors $Q_{\mathrm{in}}$, $W$, $S_{\mathrm{out}}$, $d_o$, and $d_s$ were ranked first to fifth with respect to impact on total performance. Based on dimensional analysis and experimental data analysis, total performance receives direct influence from $Q_{\mathrm{out}}/Q_{\mathrm{in}}$ while being inversely affected by $S_{\mathrm{out}}/H_{\mathrm{in}}$, $W/H_{\mathrm{in}}$, and $d_o/H_{\mathrm{in}}$. The highest total performance was obtained for $S_{\mathrm{out}}/H_{\mathrm{in}}=0.265$, $W/H_{\mathrm{in}}=0.159$, $Q_{\mathrm{out}}/Q_{\mathrm{in}}=0.915$, $D_{50}/H_{\mathrm{in}}=0.0019$, and $d_o/H_{\mathrm{in}}=0.370$.

The curve-number method is reviewed and assessed using rainfall and runoff measurements at 80 well-instrumented experimental watersheds in the United States. Key results of the study show that the applicable curve number (CN) in design applications is not always independent of the rainfall amount, the uncertainty factors associated with CN can vary between watersheds, CN dependence on both rainfall duration and rainfall amount is detected for some catchments, and the characteristic infiltration rate of a catchment can be expressed as a function of CN. When the curve-number equation is used in estimating the runoff hydrograph, it is shown that implicit infiltration rates can sometimes exceed the realistic infiltration capacity of the catchment, and that not representing CN as a function of the rainfall amount can lead to substantial underestimation of the peak-runoff rate.

The World Food Studies (WOFOST) model’s performance in simulating different field maize (Zea mays L.) growth and productivity variables was evaluated using 6 years of field experimental data that were measured from the 2005–2010 maize growing seasons in south central Nebraska. Irrigation levels were rainfed (no irrigation), limited irrigation [50% full irrigation (FIT), 60% FIT, and 75% FIT] and full irrigation conditions. Different maize growth and developmental periods and the entire growing seasons were evaluated by comparing simulated leaf area index (LAI), aboveground biomass, grain yield, and soil water content (SWC). When the data for all growing seasons were pooled, the values of RMS error (RMSE) and normalized RMSE (NRMSE) between simulated and observed days to flowering were 3.7 and 4 days, respectively, which were considered very accurate. When all growing seasons’ data were combined, the values of RMSE and NRMSE between simulated and observed days to maturity were 7.5 and 5 days, respectively. There was acceptable agreement between predicted and observed LAI (${\mathrm{RMSE}}_n=13\%–24\%$, and $R^2=0.80–0.95$) and aboveground biomass (${\mathrm{RMSE}}_n=9\%–25\%$, and $R^2=0.91–0.99$). During the validation, there was no significant difference between the simulated and observed LAI values ($P>0.05$). The model simulated the rainfed and irrigated aboveground biomass reasonably well. There were no significant differences between model-estimated and measured grain yield. The $P_e$ of grain yields across the 2005–2010 growing seasons ranged from $-18\%$ to 31%. The RMSE between the observed and simulated grain yield ranged between 1.02 and 2.05 ton ${\mathrm{ha}}^{-1}$ and NRMSE ranged from 7% to 17%. The largest difference between yield potential and measured grain yield (yield gap) was observed in the rainfed treatment (9.97 ton ${\mathrm{ha}}^{-1}$) and the least gap was in the FIT (3.75 ton ${\mathrm{ha}}^{-1}$). The model’s performance in simulating SWC was considered to be poor to moderate, with a wide range $R^2$ values between the treatments, from 0.10 to 0.82. The mean difference between observed and simulated SWC ranged from 0.2 to ${0.4\mathrm{m}}^3{\mathrm{m}}^{-3}$. Although overall, the WOFOST model’s performance was considered to be good for some of the variables (i.e., plant phenology, LAI, and grain yield), its performance in simulating other variables (i.e., SWC) was marginal under these experimental conditions. Its performance declined substantially under water-limiting and rainfed conditions. Further research that identifies potential reasons for the poor performance and determining potential solutions to improve the model’s prediction accuracy is needed.

As hydraulic control structures, side weirs are generally employed for irrigation, drainage, and many other water regulation purposes. Researchers have studied the use of labyrinth geometry to increase the length of side weir crests while maintaining the same channel opening length. The present work proposes a novel inclined-bed triangular side weir design and evaluates its discharge characteristics. A total of 159 experimental tests were performed using different geometric designs and hydraulic variables. The experimental data were analyzed, and results were evaluated to develop a nonlinear equation for the discharge coefficient of the introduced side weir. An error analysis for the equation showed fairly acceptable accuracy, with most results falling within $\pm 7\%$ of the measured values. Final results demonstrate a significant improvement in efficiency of up to 78% and 39% for the discharge coefficient of the proposed design compared with conventional rectangular side weirs and orthogonal-bed triangular side weirs, respectively.

Conical central baffle flumes present an effective solution for temporary flow measurements in open channels. A conical central baffle flume consists of a cone-shaped obstruction, or a central baffle, oriented vertically at the center of an open channel. In the present study, a previously developed discharge prediction model for flow measurements in open channels using the conical central baffle flumes has been experimentally recalibrated for use in rectangular and trapezoidal channels to cover a wider application range. The proposed calibration equation has been validated for an extended range of flow and geometrical parameters using the results of computational fluid dynamics (CFD) simulations using Flow-3D. The simulation studies are carried out in two steps. The first step is the validation of the defined simulation problem set up by comparing the water surface profiles of the simulation and experiment flows for the same discharge and flow conditions. The second step is the validation of the proposed discharge prediction model for the extended range (0–0.50) of the dimensionless discharge and side slopes ($m_1=0$, 0.50, 1.00, and 1.50). It is found that for submergence less than 80%, the error in discharge prediction is always less than 10% with a mean value of nearly 3%. Based on the results of the CFD analysis, the use of the calibrated discharge prediction model has been recommended up to a submergence limit of 80%, beyond which the errors are found to be greater than 10%.