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The experimental evaluation of the performance of a corrugated apron under free flow subcritical and submerged conditions was conducted, with a focus on scour patterns over the apron. Comparative analysis with a smooth rigid apron revealed an increase in scour depth upon the application of the corrugated apron under free and submerged jet flow conditions. The implementation of a corrugated apron resulted in a considerable reduction in scour depth and length compared to a smooth rigid apron. The maximum reduction in scour depth and length amounted to 79% and 83%, respectively, while the minimum reduction observed was 13% in scour depth and 11% in scour length. Additionally, investigations into velocity and turbulence characteristics over both smooth and corrugated aprons were conducted. It was observed that the rate of turbulence intensity increase within the scour hole due to the presence of a smooth apron surpassed that of the corrugated apron. Scour downstream of the corrugated apron exhibited distinct delineations, including regions of jet diffusion, transition, acceleration, and a recirculating zone near the bed of the scour hole. [ABSTRACT FROM AUTHOR]

The phenomenon of hydraulic jumps has been widely studied in laboratory flumes. However, few studies have been made to bridge the discrepancy encountered in the formulation of relations ascribing hydraulic jumps based on laboratory model studies and that occur in natural conditions. Most of the predictive formulae for sequent depth ratio and length of jump proposed in the literature have not been verified in the field. The present study attempts to link the field investigation data of hydraulic jump in a weir with laboratory channel flume observation for similar flow conditions. The hydraulic jump parameters were collected in the field using feasible technologies in the study weir. The weir selected for this study has geometric, kinematic and Froude similarities with the laboratory model. The comparison of laboratory model data and field measurements showed inconsistency. It is observed that the sequent depth ratio and length of the jump are inaccurately predicted by the laboratory relation compared to the field observations by the laboratory relation. A fieldvalidated-based relationship is suggested for the calculation of sequent depth and length of jump in a smooth rectangular channel for Froude numbers ranging from 4 to 10. [ABSTRACT FROM AUTHOR]

Flip bucket is a type of energy dissipator structure. Flip buckets can sometimes be improved by adding wedge-shaped deflectors. This research introduced the best height proportion of used deflector on the flip buckets to increase energy dissipation. It used 4 types of deflector series including 32, 45, 47 and 55 degrees toward horizon with two different regular and irregular layouts and 19 different heights from 2.31 to 5.6 cm and in different hydraulic condition and the results were compared with a flip bucket without a deflector. The characteristics of laboratory flume were: length= 7.5 m, width= 0.58 m and height= 1.6 m. The results illustrates that the energy dissipation in the model with deflectors increased from 11.83 to 19.38 percent as compared with model without a deflector. The greatest percentage of energy dissipation was 80.74% which observed at a deflector angle of 55° and a discharge of 10 L/s, at deflector’s ratio of n=0.8 and in non-uniform layout and in free hydraulic jump. Larger deflector angles and side lengths initially boosted energy dissipation, but this effect plateaued or even reversed at very large angles. For calculating energy dissipation and hydraulic jump length parameters, the regression relations were extracted in this research and results of this relations were compared with results of the gene expression programming (GEP), random forest (RF) and multivariate adaptive regression splines (MARS) methods. The results showed that the RF method is the most accurate method for calculating energy dissipation and hydraulic jump length parameters. [ABSTRACT FROM AUTHOR]

ABSTRACTGabion steps on stepped spillways can be a suitable alternative to solid impermeable steps due to their economic advantages, ease of implementation, stability through water pressure reduction, and energy dissipation. This study explores hydraulic jumps and the rate of energy dissipation downstream of gabion stepped spillways under different flow regimes. Six stepped spillway models, including a solid spillway with solid steps and five models with gabion steps, were made with different step arrangements in a 26.6° slope (1 V:2 H) facility. The results showed that in stepped spillways with gabion steps and in the nappe flow regime, as a result of seepage flow through the pores of the aggregate and overflow passing the gabion step, there is an increased energy dissipation associated with a smaller sequent depth ratio, the relative length of jumps, and roller length compared to solid and impermeable steps. The reduction in the hydraulic jump depends on the flow regime and the arrangement of the gabion steps. For skimming flows, smaller energy dissipation rates were measured downstream of the gabion step. On average, when gabion steps are placed on all steps, the sequent depth ratio, jump length, and roller length decrease by 3.34%, 8.61%, and 8.14%, respectively, compared to solid steps. The maximum energy dissipation was measured at the downstream end of the gabion steps with a value of 74.4%, which is 5.03% more than that with the solid steps. On the solid stepped spillway, the nondimensional residual head was 4.65, and for the same flow conditions, the average dimensionless residual head on the gabion steps was 4.21.

Intake structures are commonly used in drainage systems to redirect surface rainfall runoff into underground tunnels. The Hong Kong West Drainage Tunnel (HKWDT) system is designed to capture stormwater from steep upland catchments during periods of heavy rainfall, concurrently maintaining a minimal environmental flow downstream during dry weather. However, during heavy rainfall events, excess rainfall water is often directed into the drainage system, presenting a significant challenge to the urban drainage system. Undistorted Froude scale physical models and computational fluid dynamics (CFD) models are developed to investigate the flow performance. In this study, effects of various design parameters on water diversion performance are examined across a wide range of inflow conditions. Steeper channel bottom slopes leading to a larger proportion of water being directed downstream. Extending the length of the bottom rack effectively reduces adhering flow. Introducing a transverse barrier generates a hydraulic jump, which increases flow diversion into the LFC. With higher barrier heights, the hydraulic jump becomes stronger, facilitating greater water diversion into the downstream sewage system. The results indicate potential solutions to these challenges and provide valuable insights into optimizing flow diversion performance in intake structures, particularly in areas characterized by steep terrains and varying flow conditions. [ABSTRACT FROM AUTHOR]

Hydraulic jump is used to dissipate excessive flow energy in stilling basins to control erosion on the downstream side. The literature review revealed that the convergence of the side walls in a USBR type II stilling basin has enhanced energy dissipation by stabilizing the hydraulic jump. Taking this into account, a Computational Fluid Dynamics (CFD) model was created using CFD code to analyze the hydraulic efficiency of a USBR type III stilling basin with varying degrees of side wall convergence. Additionally, alterations were made to the standard Impact Blocks geometry to evaluate their effect on energy dissipation. The side walls of stilling basin were converged from 0.5° to 2.5° (with an increment of 0.5°). Study results indicated an increase in hydraulic jump efficiency from 1.6 to 14.5% due to increase in wall convergence. Modified Friction Blocks also enhanced the energy dissipation up to 2%. Post-jump Froude number values were found in acceptable range of 0.6 to 0.78. The optimal hydraulic performance of stilling basin was noted when wall convergence angle of 2.5° was used along with modified Friction Blocks. Hydraulic performance of modified stilling basin may be investigated during gated operation of the model. HIGHLIGHTS Walls convergence in stilling basin.; Navier–Stokes equations.; Computational Fluid Dynamics (CFD) code.;

Surfactants play a pivotal role in daily life owing to their commendable performance. The outbreak of the COVID-19 pandemic notably escalated surfactant usage. Upon entering building drainage systems with wastewater, surfactants profoundly influence hydraulic performance, an aspect that has garnered limited scholarly attention. This study employs an equally proportioned drainage test device to meticulously examine the variances in physical properties between surfactants, such as sodium dodecyl benzene sulfonate (SDBS) and alkyl ethoxylate-9 (AEO-9), and their repercussions on the hydraulic dynamics of building drainage horizontal main drains. Our findings reveal that the introduction of surfactants leads to the following: (1) an augmentation in water velocity and deposition distances of the solid simulant in the building drainage horizontal main drain with concentrations exacerbating this effect. The deposition distance of the solid simulation surged by up to 527% under experimental conditions compared to no surfactant; (2) there was a suppression of hydraulic jump and full degree of the horizontal main drain, with the concentration amplifying this suppression; and (3) an exacerbation of positive pressure in the horizontal main drain was found with increasing concentration, reaching a staggering 235.3% elevation compared to no surfactant. Moreover, SBDS foam outperformed AEO-9, demonstrating a 17.70–36.04% higher positive pressure in the horizontal main pipes. SBDS exhibits lower starting and ultimate viscosity, along with smaller colloid particle sizes, resulting in a 0.9–2.0% reduction in hydraulic jump and full degree. However, its inferior drag-reduction capability leads to a 17.48–36.44% decrease in the final deposition distances of solid simulant in the building drainage horizontal main drain compared to AEO-9. [ABSTRACT FROM AUTHOR]

Hydraulic jump pressure field analysis is essential to assess slab stability in dissipation basins. This study is aimed to modelling non-dimensional extreme pressure coefficients of the minimum pressure fluctuation (CP−) and maximum pressure fluctuation (CP+) using experimental data with three deep learning (DL) techniques. Pressure coefficients were estimated using Convolutional Neural Network (CNN), Gated Recurrent Unit (GRU), and Long Short-Term Memory (LSTM) methods. For the CP− coefficient related to the tested dataset, the correlation coefficient (CC)=0.894 and Willmott’s index of agreement (WI)=0.944 are achieved using the LSTM model, compared with 0.892 and 0.936 for CNN; and 0.892 and 0.943 for GRU. For the CP+ coefficient, CC=0.910 and WI=0.950 are attained using the LSTM model, compared with 0.903 and 0.941 with CNN; and 0.905 and 0.945 with GRU. The results indicate the excellent performance of the LSTM model for estimating pressure coefficients. With laboratory conditions and the experimental data domain framework used in this study, it is shown that the DL models have been successful for modelling very complex systems. Therefore, DL techniques are recommended for estimating extreme pressure coefficients with a reduction in the need to perform expensive experiments. [ABSTRACT FROM AUTHOR]

Assessing drag force and Reynolds stresses in turbulent flows is crucial for evaluating the stability and longevity of hydraulic structures. Yet, this task is challenging due to the complex nature of turbulent flows. To address this, physical models are often employed. Nonetheless, this practice is associated with difficulties, especially in the case of high sampling frequency where the inherent randomness of velocity fluctuations becomes mixed with the measurement noise. This study introduces a stochastic approach, which aims to mitigate bias from measurement errors and provide a probabilistic estimate of extreme stress values. To accomplish this, a simple experimental setup with a hydraulic jump was employed to acquire long-duration velocity measurements. Subsequently, a modified first-order autoregressive model was applied through ensemble simulations, demonstrating the benefits of the stochastic approach. The analysis highlights its effectiveness in estimating the uncertainty of extreme events frequency and minimizing the bias induced by the noise in the high-magnitude velocity measurements and by the limited length of observations. These findings contribute to advancing our understanding of turbulent flow analysis and have implications for the design and assessment of hydraulic structures. [ABSTRACT FROM AUTHOR]

In the stilling pool of the spillway and flushing tunnel, there are often problems such as unstable fluctuation range of hydraulic jump and even overtopping the side wall. In order to obtain a good energy dissipation and erosion prevention effect of the stilling pool, the fluid movement during the flood discharge process of the spillway and flushing tunnel was studied through a combination of numerical simulation and physical model testing, which was beneficial for gaining hydraulic dynamics of the flow field and the downstream riverbed erosion conditions . The hydraulic characteristics of water flow under different stilling pool body shape optimization schemes were analyzed, and those schemes were verified by physical experiments. The results show that the flow pattern is more stable under adding a rectangular tailgate at the stilling pool, the water surface fluctuation is reduced. At the same time, the maximum decrease of inlet and outlet velocity in the stilling pool is 7.66 m/s. The pressure distribution is uniform, no negative pressure is generated, and the energy dissipation rate reaches 80.60%. After the addition of the rectangular tailgate, the riverbed scour pit range of the design and verification conditions are reduced by 12.20 m and 13.30 m compared with the original scheme, and it' s maximum scour pit depth are reduced by 0.48 m and 1.00 m compared with the original scheme, respectively. The decrease of the riverbed scour pit range and the maximum scour pit depth shows that the addition of rectangular tailgate has obvious protective effect on the downstream. The research shows that the stilling pool body shape optimization scheme can effectively improve its energy dissipation. The flow field distribution of the optimized stilling pool body shape is uniform, which have great protection on the downstream river bed. The research results can provide reference for diversion and flood discharge and sand flushing projects. [ABSTRACT FROM AUTHOR]

Different flow characteristics namely sequent depth ratio, relative height of jump, relative energy loss, efficiency, relative length of jump and relative length of roller in suddenly expanding channel against inflow Froude number varying between 2 to 9 at different expansion ratios B1/B2 (0.4, 0.5, 0.6 and 0.8) as third variable are experimentally studied. Physical explanations of the variation of these characteristics with Froude number are discussed based on the results from experiments. Empirical models are proposed for all the six characteristics for rectangular and suddenly expanding channels using Buckingham π-method which gives quite satisfactory results when compared with other researchers result. Effectiveness of baffle blocks and sills (with different configurations) were also discussed in dissipating maximum energy. Due weightage has been given to Froude and Reynold's number in present study as reported literature as well. As a result, baffle block and sills caused a significant improvement in sequent depth ratio by an amount of 30%, reduction in relative length of jump ratio and relative length of the roller by an amount of 38% and 37% respectively. Hence, energy dissipation increases due to appurtenances. [ABSTRACT FROM AUTHOR]

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The present investigation delves into the intricate dynamics surrounding the incorporation of thresholds and their consequential impact on parameters associated with hydraulic jumps—a phenomenon critical to the efficient functioning of the gates. In the pursuit of a comprehensive understanding, the study employed experimental models of thresholds crafted from polyethylene. These models underwent meticulous examination, encompassing variations in dimensions, widths, and positions relative to the gate. The positions explored included beneath the gate, tangent to the gate upstream, and downstream, each contributing unique insights into the behavior of water flow and energy dissipation. An intriguing outcome emerged as thresholds were introduced at different locations. The energy dissipation for a given gate opening exhibited a discernible increase, shedding light on the intricate relationship between threshold placement and hydraulic performance. Notably, as the initial depth relative to the secondary depth increased, a consequential decrease in the ∆EAB/yA was observed, signaling a convergence between the initial and secondary depths. Further illuminating the findings, a comparative analysis of energy loss was conducted across all three threshold positions—beneath the gate, tangent to the gate upstream, and downstream. This scrutiny uncovered a distinct pattern, indicating a heightened energy dissipation in scenarios where the threshold was submerged, setting it apart from conditions where the threshold was positioned otherwise. In essence, the investigation not only accentuates the intricate interplay between sluice gates, thresholds, and hydraulic parameters but also underscores the importance of considering the placement of thresholds in optimizing the energy dissipation efficiency of these hydraulic structures. [ABSTRACT FROM AUTHOR]

The hydraulic jump occurs in open channels and downstream of hydraulic structures because these features change the flow regime from super-critical to sub-critical. To prevent downstream channel erosion and guarantee the construction of a hydraulic jump, a stilling basin is utilized. The effect of sand-roughened beds on hydraulic jump characteristics was investigated using an experimental study. After that, new machine learning models including Emotional neural network (EANN), Hammerstein Weiner model (HWM), Elman neural networks ENN, and Extreme learning neural networks (ELNN) were adopted to estimate the ratio of hydraulic jump length to initial water depth. Different evaluation criteria such as determination Coefficient (R2), Mean Square Error (MSE), Correlation Coefficient (R), and Rout Mean Square Error (RMSE), scatter plots, time series comparison, and Spiral plots have been used to evaluate the models' performance. The results revealed that the Elman NN model outperformed the other models in estimating the ratio of hydraulic jump length to the initial depth (Lj/y1), while the HWM model has a weaker performance than other models in estimating Lj/y1.

The experimental evaluation of the performance of a corrugated apron under free flow subcritical and submerged conditions was conducted, with a focus on scour patterns over the apron. Comparative analysis with a smooth rigid apron revealed an increase in scour depth upon the application of the corrugated apron under free and submerged jet flow conditions. The implementation of a corrugated apron resulted in a considerable reduction in scour depth and length compared to a smooth rigid apron. The maximum reduction in scour depth and length amounted to 79% and 83%, respectively, while the minimum reduction observed was 13% in scour depth and 11% in scour length. Additionally, investigations into velocity and turbulence characteristics over both smooth and corrugated aprons were conducted. It was observed that the rate of turbulence intensity increase within the scour hole due to the presence of a smooth apron surpassed that of the corrugated apron. Scour downstream of the corrugated apron exhibited distinct delineations, including regions of jet diffusion, transition, acceleration, and a recirculating zone near the bed of the scour hole.

Stilling basins are built in conjunction with dams, weirs, and gates to dissipate the high kinetic energy of incoming flow and prevent severe scouring of the downstream riverbed. Dissipation of this high energy can be achieved through forming a hydraulic jump. The hydraulic jump features, including the relative length, ratio of sequent depth, and energy dissipation, are utilized as criteria to evaluate the efficiency of the stilling basin operation. The present study involved conducting experimental and numerical tests to evaluate the performance of the USBR II stilling basin downstream of an ogee spillway using six upstream Froude numbers ranging between 6.37 and 14.97. Experiments were conducted for the Typified USBR II stilling basin. The results were used to perform mesh sensitivity for numerical simulation. The USBRII stilling basin with different rough beds was numerically simulated using FLOW-3D software. The rough beds were designed using three roughness intensities, 10%, 15%, and 22%, and three relative roughness heights: 1, 0.75. and 1. According to the numerical results, distributing staggered cubic elements in the bed of the USBR II stilling basin at 10% intensity and a relative roughness height of (1) enhanced the stilling basin performance compared to the smooth bed and other rough beds. In the case of the best roughness bed, the sequent depth ratio decreased by about 12.1%, and the energy dissipation enhanced by around 5.1% compared to the Typified basin.

Hydropower is an affordable, sustainable way to generate electricity. Research on hydraulic jumps focuses only on determining head loss across the jump, but there are no studies on generating power from the jump. This research aims to utilize energy dissipated from hydraulic jumps for power-generating purposes and further use this power in real-life applications. This research simulates ideal hydraulic conditions to identify the most stable hydraulic jumps, which will be used to generate power. The Seriakos barrage in Egypt was taken as a case study to simulate energy dissipated/power generated from hydraulic jumps generated downstream. This power is then used to simulate lighting up some streets in Egypt according to Egyptian power consumption standards. An Excel spreadsheet was used to mathematically model generated hydraulic jump types, energy dissipated, and generated power. The study found that submerged flow generates maximum power values from hydraulic jumps as opposed to free flow. The research concluded that energy produced by hydraulic jumps at the Seriakos barrage could light up 78 street light bulbs. Although this is a small amount of power, Egypt could meet a significant portion of its energy needs if hydraulic jumps from all its hydraulic structures were utilized for power generation. Doi: 10.28991/HEF-2024-05-01-06 Full Text: PDF

Hydraulic jump is a common physical phenomenon in the field of hydraulic engineering. The essence of hydraulic jump is the conversion and dissipation of a large amount of energy due to the interaction between vortex structures, mainly released in the form of turbulence and water waves. This process significantly reduces the kinetic energy of water flow, thereby mitigating downstream erosion and protecting hydraulic structures, which in turn extends their service life. As a crucial factor in the energy dissipation design of discharge structures, the length of the hydraulic jump is influenced by various factors, including flow velocity, upstream and downstream water depths, riverbed roughness height, and Froude number. In this study, we applied dimensional analysis to identify the key parameters influencing hydraulic jumps on the dataset provided by literature. We utilized a multi-task learning strategy, incorporating a shared feature extraction layer for characteristic modeling of hydraulic jumps within Physics-Informed Neural Networks (PINNs). Furthermore, we compared the performance of PINNs with other data-driven models such as Deep Neural Networks (DNNs), Convolutional Neural Networks (CNNs), and Transformers. The results demonstrated that these models are effective in estimating the length of hydraulic transitions and distinguishing between steady and unsteady hydraulic jump processes. Notably, the PINNs model exhibited better performance than other models, achieving an $\mathbf {R^{2}}$ score of $\mathbf {0.8818}$ , RMSE of 4.4627(cm), MAE of 3.3784(cm), precision of $\mathbf {0.9677}$ and recall of 0.9677 on the test set. These findings are significant for elucidating the characteristics and effects of hydraulic jumps in hydraulic structures, providing a scientific basis for the safe operation and design of practical hydraulic engineering projects.

Different flow characteristics namely sequent depth ratio, relative height of jump, relative energy loss, efficiency, relative length of jump and relative length of roller in suddenly expanding channel against inflow Froude number varying between 2 to 9 at different expansion ratios B1/B2 (0.4, 0.5, 0.6 and 0.8) as third variable are experimentally studied. Physical explanations of the variation of these characteristics with Froude number are discussed based on the results from experiments. Empirical models are proposed for all the six characteristics for rectangular and suddenly expanding channels using Buckingham π-method which gives quite satisfactory results when compared with other researchers result. Effectiveness of baffle blocks and sills (with different configurations) were also discussed in dissipating maximum energy. Due weightage has been given to Froude and Reynold’s number in present study as reported literature as well. As a result, baffle block and sills caused a significant improvement in sequent depth ratio by an amount of 30%, reduction in relative length of jump ratio and relative length of the roller by an amount of 38% and 37% respectively. Hence, energy dissipation increases due to appurtenances.

This study presents a comprehensive dataset comprising multiple data packages derived from laboratory experiments on steady and unsteady hydraulic jumps interacting with a large-scale Gaussian-shaped bed obstacle in an open-channel flume. The primary objective was to accurately measure the impact of hydraulic jump on the free surface and the bed pressure along the obstacle, ensuring the transferability of the results. A multi-process method was followed: designed experiments were recorded, images were postprocessed, and water level data were digitalized. For steady conditions, the bed pressure along the obstacle were measured by piezometers. The repository data are organized and provided in a single package, supplemented by a second package containing panoramas for each experimental time instant and graphical representations of the data, facilitating rapid evaluation of the outcomes. This study provides versatile data that can be utilized in various ways, particularly for fluvial model validation and studying turbulence-driven phenomena in open-channel flows. The detailed methodology presented herein can contribute to the advancement of enhanced laboratory techniques to study similar flow problems. [ABSTRACT FROM AUTHOR]

Sills and baffles are appurtenances used to stabilize hydraulic jump in a stilling basin. The force acting on these appurtenances are characterized by the drag coefficient (CD). This paper describes experimental methods carried out in a rectangular channel to analyze the drag characteristics of sill and baffles in free (unsubmerged) and submerged hydraulic jumps. The sills and baffles were designed as per the USBR type III stilling basin guidelines. A calibrated loadcell connected to an Arduino board was used to measure the drag force. Errors in measurements are limited to 1%. The drag co-efficient was obtained for different Froude numbers (F1=U1/√gy1) pertaining to strong jump (4.5–9) for different relative position of sills (xS/y2) and baffles (xb/y2) from the nozzle of the sluice gate. Both forced (unsubmerged) and submerged jumps were investigated. It is seen that the drag coefficient of appurtenances in submerged jumps were lower than those in free jumps. This may be attributed to the reduction in wake size in submerged jumps. Comparisons of the experimental results of the sill with the previous theoretical studies are reasonable. [ABSTRACT FROM AUTHOR]

With ever increasing integration density of electronic components, the demand for cooling solutions capable of removing the heat generated by such systems grows along with it. It has been shown that a viable answer to this demand is the use of direct liquid jet impingement. While this method can generally be scaled to the cooling of large areas, this is restricted by the necessity of coolant flow rate scaling. In this study, the benefits and restrictions of using increased nozzle pitch to remedy the increasing demand for overall flow rate are investigated. To this end, a model is validated against experimental findings and then used for computational fluid dynamics simulations, exploring effects of the pitch change for micro-scale nozzle diameters and nozzle-to-target spacings. It is found that while this method is efficient in adjusting the tradeoff between total coolant flow rate and pressure drop up to a certain pint, the occurrence of a hydraulic jump in the cavity causes a deterioration of its effect for large nozzle pitches. [ABSTRACT FROM AUTHOR]

The hydraulic jump is a natural phenomenon that occurs when the flow transitions from a supercritical flow to a subcritical flow within a short distance. The hydraulic jump is considered one of the most effective methods of dissipating energy through the stilling basin downstream of the control structures. The energy dissipation in the stilling basin contributes to protecting the area downstream of the control structures from erosion which may cause the collapse of the structure. The aim of this study is to calibrate the Flow 3D program using practical experiments. A three-dimensional numerical simulation was performed using the Flow 3D program to investigate the dissipation of energy due to a hydraulic jump through stilling basins with a negative step and compare the results of the study with the results of the practical experiments. (The simulated experiments in this paper using the Flow 3D program were performed at the National Centre for Water Research, Egypt.) It was clear from the comparison that the program has a high ability to simulate the phenomenon and to show results that are close to reality with an error of not more than 10%. [ABSTRACT FROM AUTHOR]

Twin tungsten electrode-wire electrode indirect arc welding (TTW-IAW) is a new welding method, in which the twin tungsten electrodes are connected to the power source together with the welding wire, while the base metal is not connected to the power source, so that the indirect arc is formed between the twin tungsten electrodes and the welding wire. Currently, only the arc characteristics and the droplet transition behavior have been studied, which limits the application of this process in practical welding. In this paper, the thin-plate butt welding process is applied for the first time in TTW-IAW, and the effects of process parameters on weld formation, microstructure, and its hardness are investigated. Additionally, the formation mechanisms of burn-through and hump defects are revealed by the static model and hydraulic jump model of the molten pool, respectively. The results show that TTW-IAW achieves stable weld formation at a maximum welding speed of 600 mm/min, a fourfold increase compared to conventional cold-wire single-TIG welding (conventional cold-wire STW), which reflects its advantages of large deposition rate and high welding efficiency. The degree of influence of the welding current on the penetration of base metal is greater than the welding speed, and the increase in welding current is conducive to the increase in the base metal penetration and the heat-affected zone (HAZ) width, while the increase in welding speed can reduce the convex height of the weld. However, excessive welding currents cause the downward component of arc force and droplet impact to be increased and the upward component of surface tension to be decreased, which results in destabilization of the molten pool, leading to the formation of burn-through defects. Excessive welding speed causes the flow rate of the liquid in the molten pool to be increased and the critical value for the occurrence of a hydraulic jump is exceeded, leading to the formation of a hump. [ABSTRACT FROM AUTHOR]

Free falling or controlled high velocity jets from diversion weirs or dams results in the scouring of downstream riverbeds. Monitoring and analysing scouring is a complex problem as it depends on several factors, such as the discharge characteristics from the reservoir, sediment concentration of the discharge, tail water levels, etc. Timely monitoring of dam apron scour helps in adjusting the channel capacity downstream. This paper aims to propose an experimental technique to monitor the scour at the downstream apron of free overflow spillway using piezoelectric patches. A lab-based hydraulic jump was made through an ogee spillway in the flume. A sand bed was constructed to simulate soil scour (in the actual scenario) caused due to hydraulic jumps. Piezoelectric patches were arranged in optimised distance and depth to monitor the onset and severity of scour during the jump. The experimental piezo-induced voltages were measured, which indicate the different stages of scour phenomena, and a normalised scour depth was plotted to highlight the efficiency of the proposed technique. A statistical based signal index has been proposed for better reliability of the proposed study. At last, frequency-based analysis was carried out to study piezo frequency deviations for scour phenomena. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally the changing of a hydraulic characteristic of combined hydraulic structure owing to the existence of dike structure. Different models of combined structures are used with rectangular gates and rectangular weirs, respectively. Also, the location of the dike structure is considered. A dike is located upstream, downstream, and on both sides of the combined hydraulic structure. Discharge quantity, average downstream water depth, discharge coefficient, and Reynolds number are adopted to describe the alteration in hydraulic behavior of a combined structure. While the relation between upstream Froude number and downstream Froude number, as well as the relation between downstream Froude number with distance, are employed to illustrate the interactive response between dike and combined structure, From the study, the relation between Froude number at downstream and non-dimensional downstream distance as well as the relation between non-dimensional downstream water depth and non-dimensional distance reveal how the dike location effects on water depth and flow velocity, which lead to a change in the type of flow. Here, the dike position is shared in the form of a hydraulic jump at downstream of the combined structure. The experimental data were statistically analyzed to ensure their validity and reliability. The importance of this study is concentrated on how the location of the dike structure is shared in the alteration in the hydraulic characteristics of the combined hydraulic structure, especially the rise in the water depth at downstream, in addition to the change in the hydraulic jump height and energy losses. [ABSTRACT FROM AUTHOR]

A hydraulic jump phenomenon is exciting in turbulent flow as it causes large-scale turbulence and high-energy loss. This paper investigates the hydraulic jump characteristics of right triangular prism rough beds. The renormalization group RNG k-ε turbulent model and the volume of fluid (VOF) method in a CFD model are utilized to simulate hydraulic jumps. A total of 210 numerical simulations of four new types of rough beds were performed with an initial Froude number (Fr1) ranging from 4.8 to 9.4, the non-dimensionless wave steepness values of 0.67 ≤ t/s ≤ 1.33, and the distances between roughness elements of 0 ≤ Ls/y1 ≤ 2.67. This study found that arranging the right triangular prism rough elements in a stilling basin increased bed shear stress and energy loss. At the same time, they reduced sequent depth and jump length by about 22% and 50% compared to a smooth bed, respectively. In addition, the entropy production rates are also used to analyze energy dissipation, which clearly shows that the characteristic shape of a rough bed significantly influences the hydraulic jump length. Equations and plots that specify the relationships between the hydraulic jumps and study parameters are helpful guidelines for defining the rough bed dimension when designing or repairing a stilling basin for low-head irrigation works and highway sewers. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for estimation of hydrodynamic loads acting on the bottom and at the walls of a stilling basin of a stepped chute with converging walls, based on the pressure measurements at the selected points of a scale model. This is the first study of hydrodynamic loads for this type of structure, and the first one of the loads on the stilling basin walls in general. For selected flow discharges, step heights and hydraulic jump submergence ratio, the hydrodynamic pressures were measured at a significant number of points, providing the spatio-temporal distribution of relevant hydrodynamic loads. The most influential effect proved to be a convergence angle of the chute walls. Based on these measurements, appropriate regression expressions were proposed for predicting hydrodynamic loads. These expressions show good agreement with measurements, offering a reliable tool for the structural design of stepped spillway stilling basins. [ABSTRACT FROM AUTHOR]

Weirs are often used in laboratories, industries, and irrigation channels to measure discharge. The discharge capacity of a structure is vital for its safety and plays an important role in the combined gate-weir flow, which is a complicated phenomenon in hydropower. This study carried out experiments on a combined hydraulic structure, which included a compound sharp-crested weir made up of two rectangles along with an inverted semicircular sharp gate. Installed on a straight channel, this structure served as a control instrument. The study aimed to investigate the downstream hydraulic jump characteristics of this combined structure, specifically, the sequent depth ratio (y2/y1), the hydraulic jump height ratio (Hj/y1), the energy loss ratio through the jump (EL/Eu), and the jump length ratio (Lj/y1). The width of the upper rectangle on the weir was set at 20 cm. The width of the lower rectangle (W2) was set at 5, 7, and 9 cm, while its depths (z) were fixed at 6, 9, and 11 cm. The gate's diameters varied between 8, 12, and 15 cm. These measurements were alternated with varying initial Froude numbers (Fn1) ranging between 1.32 and 1.5. The results showed that the dimensions of both the weir and the gate influenced the hydraulic jump characteristics. Empirical formulas were developed to predict y2/y1, Hj/y1, EL/Eu, and Lj/y1 based on the differing dimensions of the combined structure. The findings and analysis of this study are limited to the range of data that were tested.

Hydraulic jump is used for dissipation of kinetic energy downstream of hydraulic structures such as spillways, chutes, and gates. In the present study, the experimental measurements and numerical simulation of the free hydraulic jump by applying Flow-3D software in six different conditions of adverse slope, roughness, and positive step were compared. It should be noted that two turbulence models including k-ε and RNG were used for numerical simulation. Based on the results, simulation accuracy using the RNG model was more than the k-ε model. The statistical indices of NRMSE, ME, NS, and R2 for comparing the water surface profile were obtained at 34.3, 0.0052, 0.995, and 983 for the application of the RNG model, respectively. Also, using the RNG model, the values of these indices for the velocity profile were obtained at 14.92, 0.127, 0.9982, and 962, respectively. In general, the error of the simulated water surface and velocity profile were obtained at 5.31 and 12.4 percent, respectively. Moreover, the maximum error of the numerical simulation results of D2/D1, Lj/D2, and Lr/D1 was ±12, ±12, and 16%, respectively. Therefore, the use of Flow-3D software with the application of the RNG turbulence model is recommended for numerical simulation of the hydraulic jump in different situations.

This study reported and discussed turbulence characteristics, such as turbulence intensity, correlation time scales, and advective length scales. The characteristic air–water time scale, including the particle chord time and length and their probability density functions (PDFs), was investigated. The results demonstrated that turbulence intensity was relatively greater on a rough bed in the roller length, whereas further downstream, the decay rate was higher. In addition, the relationship between turbulence intensity and dimensionless bubble count rate reflected an increase in turbulence intensity associated with the number of entrained particles. Triple decomposition analysis (TDA) was performed to determine the contributions of slow and fast turbulent components. The TDA results indicated that, regardless of bed type and inflow conditions, the sum of the band-pass (Tu′) and high-pass (Tu″) filtered turbulence intensities was equal to the turbulence intensity of the raw signal data (Tu). Tu″ highlighted a higher turbulence intensity and larger vorticities on the rough bed for an identical inflow Froude number. Additional TDA results were presented in terms of the interfacial velocity, auto- and cross-correlation time scales, and longitudinal advection length scale, with the effects of low- and high-frequency signal components on each highlighted parameter. The analysis of the air chord time indicated an increase in the proportion of small bubbles moving downstream. The second part of this research focused on the basic properties of particle grouping and clustering.

A survey on bubble clustering in air–water flow processes may provide significant insights into turbulent two-phase flow. These processes have been studied in plunging jets, dropshafts, and hydraulic jumps on a smooth bed. As a first attempt, this study examined the bubble clustering process in hydraulic jumps on a pebbled rough bed using experimental data for 1.70

The stilling basin of the Taunsa barrage is a modified form of the United States Bureau of Reclamation (USBR) Type-III basin, which consists of baffle and friction blocks. Studies revealed uprooting of baffle blocks due to their vertical face. Additionally, the literature highlighted issues of rectangular face baffle blocks: less drag, smaller wake area, and flow reattachment. In contrast, the use of wedge-shaped baffle blocks (WSBBs) is limited downstream of open-channel flows. Therefore, this study developed numerical models to investigate the effects of USBR and WSBB basins on the hydraulic jump (HJ) downstream of the Taunsa barrage under lower tailwater conditions. Surface profiles in WSBB and modified USBR basins showed agreement with previous studies, for which the coefficient of determination (R2) reached 0.980 and 0.970, respectively. The HJ efficiencies reached 57.9 and 58.6% in WSBB and modified USBR basins, respectively. The results of sequent depths, roller length, and velocity profiles in the WSBB basin were found more promising than the modified USBR basin, which further confirmed the suitability of the WSBB basin for barrages. Furthermore, WSBB improved flow behaviors in the basin, which showed no fluid reattachment on the sides of WSBB, increased wake regions, and decreased turbulent kinetic energies. HIGHLIGHTS Investigation of hydraulic jumps in the WSBB basin at lower tailwater using FLOW-3D was studied.; Also, comparison of hydraulic jumps and energy dissipating index between WSBB and modified USBR baffle block basins was studied.; Performance assessment of different hydraulic parameters was carried out by employing regression analysis.;

This article focuses on the United States Bureau of Reclamation (USBR) Type II stilling basin, which has chute blocks, an end dentated sill, and a flat floor. USBR provides general design criteria to contain the hydraulic jump within the stilling basin. The sequent depth ratio, energy dissipation ratio, and stilling basin dimensions of the hydraulic jump are changed when the bed slope of USBR II stilling basins is changed. This study aimed to investigate the effects of adverse slope on the performance of USBR II stilling basin in terms of sequent depth ratio and energy dissipation. Six discharges ranging from 8 to 33 lps were applied to the USBR II stilling basin with bed slopes (S) of −0.085, −0.055, −0.035, and 0. Results demonstrated that for Q = 13 and 8 lps, the basin performs better than other models with S = −0.085, increasing energy dissipation by about 10% compared to a typical basin due to the formation of a free hydraulic jump downstream dentated end sill. On the other hand, the floor downstream of the dentated end sill needs more protection against this free jump, and this case becomes economically expensive. In other cases, the downstream jump was submerged, resulting in a counterintuitive current and reverse roller based on the submerged ratio, reducing the effectiveness of the stilling basin. In addition, the modified design of the stilling basin resulted in a shorter effective length that included the hydraulic jump downstream spillway, thereby reducing internal friction. As a result, the standard USBR II with a flatbed is less expensive and more efficient than the adverse slope basin.

This document is a summary of a special issue of the journal Metals titled "Advances in Molten Metal Refining Process." The issue includes ten articles that cover various aspects of molten metal refining processes, focusing on iron, steel, aluminum, magnesium, and titanium. The articles discuss topics such as the evolution of vortex structures in continuous casting molds, the excitation of micro-scale flow near the solid-liquid interface, the optimization of electrode insertion depths in magnesia furnaces, the behavior of hydraulic jumps during the continuous casting process, the bubble size distribution in single-snorkel furnaces, the refining process of slot-porous matched dual tuyeres, the desulfurization process in Kanbara reactors, the wear and efficiency of graphite rotors in aluminum refinement, and the prediction of bending forces in hot-rolled plates. The articles present mathematical models, numerical simulations, and experimental results to advance the understanding and optimization of molten metal refining processes. [Extracted from the article]

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Hydraulic structures, such as barrages, play an important role in the sustainable development of several regions worldwide. The aim of this novel study is to identify the critical hydraulic parameters (CHPs) of Taunsa Barrage, built on the Indus River. These CHPs, including free surface profiles, flow depths, Froude number, velocity profiles, energy dissipation and turbulence kinetic energy, were investigated using simulation via FLOW-3D numerical models. Incompressible Reynolds-averaged Navier–Stokes (RANS) equations on each computational cell were solved using the numerical methods available in FLOW-3D. The simulation results indicated that the locations of hydraulic jumps (HJs) were lower than that were reported in the previous one-dimensional study. Similarly, the distances of the HJs from the downstream toe of the glacis were reached at 2.97 m and 6 m at 129.10 m and 130.30 m tailwater levels, respectively, which deviated from the previous studies. In higher tailwater, the sequent depth ratio also deviated from the previous data. The maximum turbulent kinetic energies were observed in the developing regions of HJs, which were found to be decreased as the distance from the HJ was increased. The results of this research will be highly useful for engineers working in the field of design of hydraulic structures. [ABSTRACT FROM AUTHOR]

We present developments to the physical model and the open-source numerical code IMEX_SfloW2D (de' Michieli Vitturi et al., 2019). These developments consist of a generalization of the depth-averaged (shallow-water) fluid equations to describe a polydisperse fluid–solid mixture, including terms for sedimentation and entrainment, transport equations for solid particles of different sizes, transport equations for different components of the carrier phase, and an equation for temperature/energy. Of relevance for the simulation of volcanic mass flows, vaporization and entrainment of water are implemented in the new model. The model can be easily adapted to simulate a wide range of volcanic mass flows (pyroclastic avalanches, lahars, pyroclastic surges), and here we present its application to transient dilute pyroclastic density currents (PDCs). The numerical algorithm and the code have been improved to allow for simulation of sub- to supercritical regimes and to simplify the setting of initial and boundary conditions. The code is open-source. The results of synthetic numerical benchmarks demonstrate the robustness of the numerical code in simulating transcritical flows interacting with the topography. Moreover, they highlight the importance of simulating transient in comparison to steady-state flows and flows in 2D versus 1D. Finally, we demonstrate the model capabilities to simulate a complex natural case involving the propagation of PDCs over the sea surface and across topographic obstacles, through application to Krakatau volcano, showing the relevance, at a large scale, of non-linear fluid dynamic features, such as hydraulic jumps and von Kármán vortices, to flow conditions such as velocity and runout. [ABSTRACT FROM AUTHOR]

Turbulent diapycnal mixing is important for the estuarine circulation between basins of the Baltic Sea as well as for its local ecosystems, in particular with regard to eutrophication and anoxic conditions. While the interior of the basins is overall relatively calm, stratified flow over steep bathymetric features is known as a source of strong turbulent mixing. Yet, current in situ observations often cannot capture the spatio-temporal development of dynamic and intermittent turbulent mixing related to overflows over rough bathymetry. We present observational oceanographic data together with openly accessible high-resolution bathymetry from a prototypical sill and an adjacent deep channel in the sparsely sampled Southern Quark located in the Åland Sea, connecting the northern Baltic Proper with the Bothnian Sea. Our data were acquired during two 1-week cruises on R/V Electra in February–March 2019 and 2020. We collected high-resolution broadband acoustic observations of turbulent mixing together with in situ microstructure profiler measurements, and current velocities from acoustic Doppler current profilers. We found that a temporally reversing non-tidal stratified flow over the steep bathymetric sill created a dynamic and extremely energetic environment. The observed flow reversed during both cruises on timescales of a few days. Saltier, warmer, and less oxygenated deep water south of the sill was partly blocked, the reversing flow was at times hydraulically controlled with hydraulic jumps occurring on both sides of the sill, and high spatial variability occurred in the surface layer on small scales. Dissipation rates of turbulent kinetic energy, vertical turbulent diffusivities, and vertical salt flux rates were increased by 3–4 orders of magnitude in the entire water column in the vicinity of the sill compared to reference stations not directly influenced by the overflow with average dissipation rates near the sill between 10 -7 and 10 -6 W kg -1 , average vertical diffusivities of 0.001 m 2 s -1 in the halocline and up to 0.1 m 2 s -1 below the halocline, and average vertical salt flux rates around 0.01 g m -2 s -1 in the halocline and between 0.1 and 1 g m -2 s -1 below the halocline. We suggest, based on acoustic observations and in situ measurements, that the underlying mechanism for the highly increased mixing across the halocline is a combination of shear and topographic lee waves breaking at the halocline interface. We anticipate that the resulting deep- and surface-water modification in the Southern Quark directly impacts exchange processes between the Bothnian Sea and the northern Baltic Proper and that the observed mixing is likely important for oxygen and nutrient conditions in the Bothnian Sea. [ABSTRACT FROM AUTHOR]

This study aimed to assess the effect of time on local scour development downstream of parallel sluice gates in different operations. The results revealed that the time scale of local scour development is a function of symmetric and asymmetric operations of the gates. By reducing the gate opening to a channel width ratio, the maximum scour depth and accuracy of the power-law equation increase and decrease, respectively, compared with classic hydraulic jump conditions. Finally, a new equation with high accuracy is proposed. [ABSTRACT FROM AUTHOR]

Hydraulic jump is used for dissipation of kinetic energy downstream of hydraulic structures such as spillways, chutes, and gates. In the present study, the experimental measurements and numerical simulation of the free hydraulic jump by applying Flow-3D software in six different conditions of adverse slope, roughness, and positive step were compared. It should be noted that two turbulence models including k-ε and RNG were used for numerical simulation. Based on the results, simulation accuracy using the RNG model was more than the k-ε model. The statistical indices of NRMSE, ME, NS, and R² for comparing the water surface profile were obtained at 34.3, 0.0052, 0.995, and 983 for the application of the RNG model, respectively. Also, using the RNG model, the values of these indices for the velocity profile were obtained at 14.92, 0.127, 0.9982, and 962, respectively. In general, the error of the simulated water surface and velocity profile were obtained at 5.31 and 12.4 percent, respectively. Moreover, the maximum error of the numerical simulation results of D2/D1, Lj/D2, and Lr/D1 was ±12, ±12, and 16%, respectively. Therefore, the use of Flow-3D software with the application of the RNG turbulence model is recommended for numerical simulation of the hydraulic jump in different situations. [ABSTRACT FROM AUTHOR]

The performance of stilling basins including a negative step was analyzed addressing its effect on the energy dissipation efficiency, dimensions and structural properties of the hydraulic jump, streambed pressures and pressure fluctuations. Six different cases were simulated, considering two possible relative heights for the step and three possible Froude numbers. The results show that the step yields to lower subcritical depths, allowing smaller basin dimensions. Nevertheless, it tends to slightly increase the roller length of the jump. Concerning the relative energy dissipation, results confirm the improvement derived from the step presence. The internal flow occurring in the jump was also analyzed, and more specifically the subzones generated upstream and downstream the impingement point. The results prove the contribution of the negative step in the stabilization of hydraulic jumps in the stilling basin. In particular, a general decrease of the streambed pressure is observed. In addition, pressure fluctuations are significantly reduced due to the negative step size influence on the hydraulic jump. Furthermore, the effectiveness of the computational fluid dynamics (CFD) techniques to simulate stilling basin flows and to adequately characterize the hydraulic jump performance was confirmed. [ABSTRACT FROM AUTHOR]

Floating raft aquaculture has gradually become a mainstream aquaculture model in the waters of Changhai County, Dalian. To quantitatively describe the impact of floating raft aquaculture facilities on the hydrodynamic environment of nearby sea areas, in this study, we took a single floating raft aquaculture structure as the research object and built a numerical prediction model for water flows passing through the floating raft aquaculture structure using a six-degree-of-freedom VOF (volume of fluid) multiphase flow simulation method based on an overset moving mesh system. Then, we verified the numerical model by utilizing oblique hydraulic jumps and water flows passing through a submerged bar. As shown by the findings, the simulated values are in good agreement with the theoretical solutions and measured values, indicating that the model features high precision and great stability. The impact of the raft area on the hydrodynamic force was introduced into the source term of an equation for consideration. In order to further determine the hindering effect of the raft body on the water body, transport equations and the tracer method were used to simulate the impact of floating raft aquaculture facilities on the water exchange performance of nearby sea areas. This study shows that the VOF multiphase flow model can be easily and accurately applied to studies on floating raft aquaculture, which can greatly reduce the limitations of experiments that utilize pure hydraulic models, wherein the impacts of floating raft aquaculture facilities on hydrodynamic force are generally considered simply based on observations, water roughness or the secondary drag force coefficient, thereby effectively improving the scientific understanding of the physical mechanism involved in floating raft aquaculture. [ABSTRACT FROM AUTHOR]

Turbulence and pressure fluctuations are key elements in the bed protection design of hydraulic structures. However, their roles in a hydraulic jump are not yet fully understood, and the nature of their relationships are not conclusive. In order to better understand the relationships between pressure fluctuations and flow characteristics of a hydraulic jump downstream of a weir, detailed measurements of flow kinematics using the nonintrusive techniques of particle image velocimetry and bubble image velocimetry and pressure using voltage-type pressure gauges were carried out in this study. The physical modeling of the hydraulic jump was carried out using the simultaneous measurements of pressure and turbulent flow properties. The distributions of flow properties, such as water level and velocity, were assessed in each case. Based on the measurements, the correlations between the pressure fluctuations and the variables were investigated by coupling the statistical values of the variables at the same points. The analysis results show that the water level and turbulence intensity are the main factors influencing the pressure fluctuations in the hydraulic jump. Using these factors, an empirical formula and dimensionless numbers are proposed to show that the pressure fluctuations depend on the bubble flow behavior. [ABSTRACT FROM AUTHOR]

ABSTRACT Advancements in computational capabilities have enabled engineers and scientists to numerically model complex turbulent phenomena such as hydraulic jumps. This research assesses the capability of numerically simulating a hydraulic jump that occurs in the UHE Porto Colômbia's stilling basin at a flow rate of 4,000 m3/s. To achieve this, simulation results were compared with data from three hydraulic physical models (scales 1:32, 1:50, and 1:100) and full-scale measurements. The simulations employed the Ansys CFX solver, utilizing a Reynolds-Averaged Navier-Stokes (RANS) approach, the RNG κ-ε turbulence model, and the Volume of Fluid (VOF) method for air-water interactions. Various variables were analyzed, with satisfactory results for mean pressures, conjugated depths, roller length, water profile in less aerated areas, and mean velocity at the submerged hydraulic jump upstream section, with errors below 10%. However, the submerged hydraulic jump's start position and the representation of the water surface profile in the region near the jump toe yielded more disparate results. In conclusion, the methods and conditions applied in the simulations are apt for representing variables less impacted by aeration phenomena, establishing CFD simulations as a valuable tool for hydraulic jump analysis.

One of the most used hydraulic structures for energy dissipation of supercritical flow is the hydraulic jump stilling basin. From dimensional analysis, the sequent flow depth ratio of a hydraulic jump over the right-triangle basin is derived as a function of the inflow Froude number and relative length of the basin front. The proposed structure stabilized the hydraulic jump at the toe of the chute spillway and hydraulic jump characteristics were investigated for the Froude number ranging from 4.4 < F1 < 7. The results obtained from both numerical and experimental simulations yielded increased efficiency in the energy dissipation performance of this novel design. The modeling showed the formation of two large recirculation regions at the jump roller and jump bed at the beginning of the downstream channel, which resulted in intense energy dissipation in the right-triangle basin. The relative energy loss is approximately 37% higher for relative basin front lengths larger than three compared to the classic jump. Practitioners and academia on the usefulness of a right-triangle basin for hydraulic purposes and further experimental tests are needed to estimate the scalability and cost–benefit of this modified system for implementation. HIGHLIGHTS The right-triangle basin with the downstream horizontal channel, as a modified energy dissipation structure.; For this design, the frontal face of the basin is set perpendicular to the inflow direction and its end edge is at the same level as the downstream horizontal channel bed.; The results obtained from both numerical and experimental simulations efficiency in energy dissipation performance of this novel design.;

Water–air two-phase flow has been the theoretical basis of traditional building drainage systems. However, with the popularization of water saving devices, more research investigations need to be performed on the impact of solid waste on drainage systems. Through experiments under the solid waste scenario, the effects of drainage volume, diameter, and slope of the pipeline on the hydraulic performances of the horizontal main drain were investigated. The results showed that the drainage volume, diameter, and slope of the pipeline did not affect the location of the hydraulic jump on the horizontal main drain. The heights of the hydraulic jump were proportional to the discharge volumes and diameters of the pipeline, but inversely proportional to the slopes of the pipeline. The depth ratio was mainly responsible for the change of positive pressure value in the horizontal main drain. The depth ratios were proportional to the drainage volumes and inversely proportional to the diameters and slopes of the pipeline. The final deposition distances of solid wastes in the horizontal main drain were proportional to the discharge volumes and the pipeline slopes. The self-cleaning lengths of the clear water were 1.2∼1.6 times of the real final deposition distances of solid wastes. HIGHLIGHTS The change of depth ratio caused the variation of positive pressure in horizontal main drain.; The location of hydraulic jump was not affected by the drainage volume, the diameter or the slope.; The height of the hydraulic jump was affected by the drainage volume, the diameter and the slope.; The depth ratio was affected by the drainage volume, the diameter and the slope.; The final deposition distance of solid wastes was affected by the drainage volume, the diameter and the slope.;

Abstract The performance of stilling basins including a negative step was analyzed addressing its effect on the energy dissipation efficiency, dimensions and structural properties of the hydraulic jump, streambed pressures and pressure fluctuations. Six different cases were simulated, considering two possible relative heights for the step and three possible Froude numbers. The results show that the step yields to lower subcritical depths, allowing smaller basin dimensions. Nevertheless, it tends to slightly increase the roller length of the jump. Concerning the relative energy dissipation, results confirm the improvement derived from the step presence. The internal flow occurring in the jump was also analyzed, and more specifically the subzones generated upstream and downstream the impingement point. The results prove the contribution of the negative step in the stabilization of hydraulic jumps in the stilling basin. In particular, a general decrease of the streambed pressure is observed. In addition, pressure fluctuations are significantly reduced due to the negative step size influence on the hydraulic jump. Furthermore, the effectiveness of the computational fluid dynamics (CFD) techniques to simulate stilling basin flows and to adequately characterize the hydraulic jump performance was confirmed.

Hydraulic jump is of fast altering flow type, within which a critical flow transforms into a subcritical flow, and such alteration occurs within a relatively short path of the channel. In the present study, the impact of lateral angles of trapezoidal channel walls in the continuous form on the relative loss of hydraulic jump energy is investigated. For this purpose, the meta-heuristic harmony search algorithm is used for declaring the continuous lateral angles within the range of 45°–75°. With regard to the hydraulic definition for the hydraulic jump phenomenon, the harmony search algorithm, which is widely used for optimization and continuous problems, is considered as a simple concept of a useful algorithm. The results demonstrated the high efficiency of harmony search in the optimization of hydraulic problems. The highest value of jump energy loss up to 81% was recorded for the angle of 45°, implying the high efficiency of this section. As can be clearly seen in the results, the amount of destructive energy loss of hydraulic jump in the meta-heuristic algorithm is significantly higher than other previous methods. HIGHLIGHTS In the present study, the impact of lateral angles of trapezoidal channel walls in the continuous form on the relative loss of hydraulic jump energy is investigated. For this purpose, the meta-heuristic harmony search algorithm is used for declaring the continuous lateral angles with the range of 45°–75°.; Continuously assuming trapezoidal channel angles in this research has been one of the most impressive functions of this algorithm.; At the angle of 45 degrees, the highest amount of hydraulic jump energy loss has been shown compared to other responses obtained from the algorithm.;

Objective The Dupuit model of well flow is a classical steady-state well flow model for a homogeneous unconfined aquifer in a round island. However, it does not consider the widely existing infiltration recharge from precipitation, and is also inapplicable for stratified heterogeneous aquifer systems. Therefore, it must be modified to address these issues. Methods On the basis of the revised Dupuit well flow model which incorporates infiltration recharge, this study further extended its application to a stratified heterogeneous unconfined aquifer. The Girinskii's potential function was used to construct the differential equations for the radial groundwater flow according to the water balance principle, and the analytical solutions satisfying the boundary conditions are then obtained as formulas of the flow rate, water table and groundwater divide. Taking the bilayer structure as an example, typical groundwater level curves with respect to 30 scenarios of different parameter values were investigated. A special phenomenon was found in which the curves of different hydraulic conductivities intersect at a single point, which could also be proven in theory. This analytical model still adopted the Dupuit assumption and did not consider the "hydraulic jump" phenomenon on the wall of the pumping well. To check the impact of these constraints on the applicability of the analytical formulas, a two-dimensional numerical model for axially symmetric seepage was built for comparison. Results As indicated by the results, the relative error of the groundwater level estimated from the analytical solution is generally less than 4%, except for the zone near the pumping well. On the groundwater divide, where the Dupuit assumption is mostly invalid, the relative errors of the analytical solution to both the distance and height of the divide are smaller than 0.1%. Conclusion The Dupuit assumption does not significantly influence applicability of the analytical model.