Numerical Simulation of Flow over Stepped Spillways with Varying Step-Angle

In the present study, the flow over the stepped spillway was numerically investigated by using Flow3D model. The effect of step angle on different properties of Nappe flow regime such as the water surface profile, location of free-surface aeration inception, Froude number at the spillway’s toe, and pressure, flow velocity, air concentration and cavitation index were evaluated. The realizable k–ε was applied as the turbulence model, and Volume of Fluid (VOF) model was used to determine the free surface flow profiles of the spillway. The model was verified using experimental data. In order to investigate the different characteristics of Nappe flow regime, 17 numerical runs was designed, in which,four step angles, four flow discharge were considered to investigate the flow characteristics over the stepped spillway. The results indicated that the numerical model is well suited with the experimental data over the stepped spillway (RMSE = 0.147 and ARE = 6.9%). In addition, with increasing the step angles, the aeration inception point is generally moved downstream. By increasing the step angles from zero to 10 degrees, the Froude number does not change significantly, however, at the angle of 15 degrees, the Froude number decreases by about 42 percent

Numerical Simulation of Hydraulic Jump over Rough Beds

In this study, the hydraulic jumps over rough beds are numerically simulated. In order to calibrate the numerical model, the experimental data were used, which performed in a rectangular flume in various roughness arrangements and different Froude numbers. The effect of the distance (s) and the height (t) of the roughness on different characteristics of the hydraulic jump, including the sequent depth ratio, water surface profile, jump’s length, roller’s length, and velocity distribution were evaluated and compared. The results showed that the numerical model is fairly well able to simulate the hydraulic jump characteristics. The results also showed that the height and distance of roughness slightly reduced the sequent depth ratios for all Froude numbers. Also, the hydraulic jump length is reduced at the presence of the rough bed. Velocity profiles in different experiments were similar and there was a good agreement between simulated and measured results. Also, increasing the distance and the height of the roughness will slow down the velocity near the bed, increase the shear stress, and increase the gradient of the velocity distribution near the bed

Estimation of wind drift and evaporation losses of sprinkler irrigation systems using dimensional analysis

Wind Drift and Evaporation Losses (WDEL) critically determine the application efficiency of sprinkler irrigation systems. In specific conditions, even half of the irrigation water can evaporate or drift out of the irrigated area. The purpose of this study was to develop a WDEL estimation equation based on dimensional analysis (Buckingham's π method), considering a wide set of independent variables. An equation was sought that could be used for various sprinkler technologies and meteorological conditions in semiarid areas. Our research used experimental data from the literature, obtained in northeastern Spain and northwestern Iran. The complete data set consisted of 153 WDEL observations obtained at different operating pressures, nozzle diameters, irrigation durations, day and night irrigations, elevations from the soil surface and meteorological conditions. The experiments involved solid-sets and moving laterals, impact sprinklers, gear driven sprinklers and rotating spray plate sprinklers. The equation developed in this research included four technical independent variables (main nozzle diameter, auxiliary nozzle diameter, operating pressure and nozzle elevation) and four meteorological independent variables (air temperature and relative humidity, wind speed and solar radiation). The equation resulted in improved estimation respect to the equations previously derived from part of the experimental data set. The proposed equation was calibrated using 70% of the experimental data and validated using 30% of the experimental data. When the proposed equation was applied to the complete experimental data set, the determination coefficient was 0.81 and the root mean square error was 3.49%. The proposed equation represents a clear improvement respect to the equations reported in the literature in terms of the number and range of the independent variables and the predictive capacity

Physical modeling of the effect of shape, blockage, and flow variability on scour in culvert outlets.

The widespread use of culverts has prompted researchers to focus on developing precise designs to prevent their failure caused by scouring at the culvert outlet. This study employed physical modelling to investigate alternation in culvert outlets under different conditions, including variations in culvert shape, blockage, and flow discharge during steady and unsteady flow conditions. Box and circular culverts were examined with 0%, 15%, and 30% blockage rates at the culvert inlet. For unsteady flow conditions, two hydrographs were generated, each with nine distinct flow discharges, while for steady flow conditions, flow rates of up to 14 l/s and 22 l/s were used. The sediment and flow conditions were carefully selected to ensure clear water throughout the experiments. According to the study results, the scour profile exhibited more growth in the circular culvert compared to the box culvert across all cases. Furthermore, an increase in flow rate led to an increase in the scour hole dimension, and the scouring increased with a rise in hydrograph stepwise. However, when the degree of blockage was increased, a strictly proportional increase in scour depth was not observed across all cases. The results and data presented in this research can be used by other researchers in addition to being used by hydraulic designers

Experimental and computational assessment of wetting pattern for two-layered soil profiles in pulse drip irrigation: Designing a novel optimized bidirectional deep learning paradigm

One of the most important parameters in the design and implementation of drip irrigation systems is the accurate prediction of the wetting dimensions pattern around the emitters, which leads to the precise determination of the distance between the emitters and the drippers. This search provides a comprehensive experimental and computational investigation to predict accurate wetting patterns (dimensions and area) in the layered-textural soil profiles under pulse drip irrigation. To achieve this first 1217 sets of experiments, including the physical and hydrometric properties of two-layered soil profiles under plus drip irrigation, were carried out at Kurdistan University, Iran. Then, a new hybrid deep learning (DL) approach comprised of Boruta extreme gradient boosting (Boruta-XGB) feature selection incorporated with the bidirectional gated recurrent unit (Bi-GRU) scheme was designed to predict the diameter of horizontal distribution (D), downward vertical distribution (V), and wetting area below the emitter (A). For each scenario, the most influential predictors in terms of input combinations (C1, C2, and C3) were extracted among nine available inputs using Boruta-XGB, employed in the Bi-GRU model. The multilayer perceptron neural network (MLP) and adaptive boosting tree (Aadaboost) were also developed as benchmark comparing models based on several metrics (e.g., correlation coefficient (R), root mean square error (RMSE), and Kling-Gupta efficiency (KGE) and various infographic analyses. The outcomes demonstrate that the C3 combination includes the elapsed time, emitter outflow rate (Q), initial soil moisture rate (θ1/θ2), saturated hydraulic conductivity ratio (Ks1/Ks2), the ratio of irrigation time in a cycle to the entire cycle time (Tirr/Ttot), and the ratio of silt (Silt1/Silt2) with Bi-GRU yielded better accuracy in terms of (R = 0.994, RMSE = 1.295 cm, and KGE = 0.989) for D-scenario, (R = 0.995, RMSE = 1.489 cm, and KGE = 0.992) for V-scenario, and for A-scenario (R = 0.996, RMSE = 76.624 cm2, and KGE = 0.976) than MLP and Adaboost models

Hydraulic Performance of Howell–Bunger and Butterfly Valves Used for Bottom Outlet in Large Dams under Flood Hazards

Floods control equipment in large dams is one of the most important requirements in hydraulic structures. Howell–Bunger valves and butterfly valves are two of these types of flow controls that are commonly used in bottom outlet dams. The optimal longitudinal distance (L) between the two Howell–Bunger and butterfly valves is such that the turbulence of the outlet flow from the butterfly valve should be dissipated before entering the outlet valve. Subsequently, the flow passing through the butterfly valves must have a fully developed flow state before reaching the Howell–Bunger valve. Therefore, the purpose of this study was to evaluate the optimal longitudinal distance between the Howell–Bunger and butterfly valves. For this purpose, different longitudinal distances were investigated using the Flow-3D numerical model. The ideal longitudinal distance obtained from the numerical model in the physical model was considered and tested. Based on the numerical study, the parameters of flow patterns, velocity profiles and vectors, turbulence kinetic energy, and formation of flow vorticity were investigated as criteria to determine the appropriate longitudinal distance. In addition, the most appropriate distance between the butterfly valve and the Howell–Bunger valve was determined, and the physical model was evaluated based on the optimal distance extracted from the numerical simulation. A comparison of the results from the numerical and the laboratory models showed that the minimum distance required in Howell–Bunger valves and butterfly valves should be equal to four times the diameter of the pipe (L=4D) so as not to adversely affect the performance of the bottom outlet system

Hydraulic Performance of Howell–Bunger and Butterfly Valves Used for Bottom Outlet in Large Dams under Flood Hazards

Floods control equipment in large dams is one of the most important requirements in hydraulic structures. Howell–Bunger valves and butterfly valves are two of these types of flow controls that are commonly used in bottom outlet dams. The optimal longitudinal distance (L) between the two Howell–Bunger and butterfly valves is such that the turbulence of the outlet flow from the butterfly valve should be dissipated before entering the outlet valve. Subsequently, the flow passing through the butterfly valves must have a fully developed flow state before reaching the Howell–Bunger valve. Therefore, the purpose of this study was to evaluate the optimal longitudinal distance between the Howell–Bunger and butterfly valves. For this purpose, different longitudinal distances were investigated using the Flow-3D numerical model. The ideal longitudinal distance obtained from the numerical model in the physical model was considered and tested. Based on the numerical study, the parameters of flow patterns, velocity profiles and vectors, turbulence kinetic energy, and formation of flow vorticity were investigated as criteria to determine the appropriate longitudinal distance. In addition, the most appropriate distance between the butterfly valve and the Howell–Bunger valve was determined, and the physical model was evaluated based on the optimal distance extracted from the numerical simulation. A comparison of the results from the numerical and the laboratory models showed that the minimum distance required in Howell–Bunger valves and butterfly valves should be equal to four times the diameter of the pipe (L=4D) so as not to adversely affect the performance of the bottom outlet system