Abstract The stepped spillway is a hydraulic structure that uses steps to decrease the energy in the stilling basin, which can reduce the cost of maintenance and repair of the hydraulic structure that results from scouring issues. The study faced challenges such as unstable flow, complex turbulence, and difficulties in accurately measuring energy dissipation on stepped spillways with different baffle block layouts. Despite these challenges, new baffle distributions were developed that improved energy dissipation, reduced downstream scour, and enhanced overall hydraulic performance. The current study was based on laboratory test that aims to increase percentage of energy dissipation for uniform and non-uniform stepped spillways by using different baffle energy distributions. The methodology of the study was conducted by using uniform and non-uniform stepped spillways with 45o spillway angle with 5 and 10 steps to produce 16 cases of flowing. The results show that the hydraulic jump length was significantly reduced for a uniform five-stepped spillway after using baffles compared with other conditions. The study confirmed that burners that contain (baffled block) are more efficient in dissipating power than ordinary burners, as the models that contain one baffled block 5 step had the highest percentage of energy dissipation at the distance (B/2.5). The developed relationships can predict (∆E) with high accuracy. (R 2 ) 0.9857, (RMSE) 0.09, (MSE) 0.0083, and (MAE) 0.08.

Numerical analysis of flow characteristics through stilling basin at pump stations outlets

The updated flood guidelines in Sweden have led to higher design discharges for many existing dams. While the primary function of a spillway chute is to convey floodwater, roughness appurtenances are proposed for installation along the chute. The aim is to dissipate an extra portion of the flow’s energy before release into the tailwater. One straight and three labyrinth roughness configurations are designed and manufactured. Their effectiveness is assessed through model tests. The roughness leads to an increase in water depth and induces an undulating streamwise water-surface profile. Due to their lateral interaction with the flow, the labyrinth shapes exhibit less distinct contours of surface unevenness than the straight one. With an increasing water depth, the free surface becomes gradually smeared out. For all the shapes, the roughness effect on the surface flow almost disappears if the water depth exceeds 6.5–7.0 times the roughness height. Compared to the smooth chute, the straight elements augment the energy loss by a factor of 1.9–3.8; the labyrinth configurations outperform the straight ones by 16–35% more energy dissipation. The differences among the triangular, trapezoidal, and rectangular shapes are, however, minor. Introducing chute roughness is a complementary measure. If the chute is sufficiently long, an adequate number of roughness rows could replace the function of a stilling basin.

This study presents an investigation on the effects of introducing an abrupt drop immediately downstream of a modified USBR Type IV stilling basin. Conducted on 1:60 scaled model, this study explored various abrupt drop heights to assess their effects on energy dissipation and hydraulic performance. The discharge and Froude number ranged from 8.5 to 16 litre per second and 2.5 to 3.7 respectively. Results showed the energy dissipation enhanced by up to 19% compared to traditional configurations for relative drop heights of 0.5 to 1.5 and then reduced with increase in drop height. The presence of a drop downstream of the stilling basin reduced the sequent depth ratios, and compensated tailwater deficits by 20% to 37% compared to horizontal bed hydraulic jumps. Thus, an abrupt drop downstream of a stilling basin has shown to offer a promising solution for improving energy dissipation and addressing insufficient tailwater levels.

Many run-of-river hydropower plants built without stilling basins now experience progressive scour due to prolonged operation and increasingly frequent floods. The Chancy-Pougny dam on the Rhône River, constructed in the 1920s at the Swiss–French border, exemplifies this issue. Severe flow recirculation was identified as the main cause of erosion, with pressure fluctuations increasing between the original and current stilling basin. While earlier work developed scour protection measures through physical modelling and numerical predictions, the present study focuses on analyzing pressure measurements within the stilling basin to assess how fluctuations can be reduced to limit future scour. Effective mitigation strategies include: (1) raising the basin water level, (2) introducing a guidance wall to restore symmetrical flow, and (3) adding various configurations of half-cube concrete prisms to increase roughness and energy dissipation. A life cycle assessment of prism materials and construction methods further supports a sustainable approach to rehabilitating ageing hydraulic infrastructure.

Abstract This study evaluates the hydraulic performance of a number of stilling basins at the outlet of pumping stations focusing on improving energy dissipation using computational fluid dynamics CFD simulations through ANSYS Fluent. Three stilling basins of pump station designs were analyzed: Taziz Al-Taziz, Taziz Al-Lteefea, and East-Ghraaf. Each of these designs has unique geometric and operational configurations designed for specific flow conditions. High turbulence resulting from outflows from pumping stations represents a major challenge affecting the efficiency of energy dissipation and the stability of the infrastructure. Simulation of Taziz Al-Taziz basin design showed that the velocity decreased from 3.98 m s −1 in the basin to 1.4 m s −1 in the canal. Taziz Al-Lteefea velocity decreased from 2.514 m s −1 in the basin close to 0.9 m s −1 in the canal. While East-Ghraaf hydraulic performance reduced the outflow velocity to 0.5 m s −1 in the canal. Moreover, the result showed that the shear stress is largely concentrated inside the basin and on the sills. The shear stress of Taziz Al-Taziz showed that the largest value appears to be on the sill end of 98.870 Pa, while the highest value of Taziz Al-Lteefea is concentrated at the floor of the basin by 20.815 Pa. The shear stress of East-Ghraaf showed occur outside the basin area at the beginning of the canal, reach to 31.222 Pa. The efficiency of the basins was as follows: 89%,61.5%, and 30.7% for Taziz Al-lteefea, East-Ghraaf, and Taziz Al-Taziz, respectively. This shows the importance of the accuracy of the design of basins with the importance of the angle of inclination of the pumping pipes entering the basin and its importance in the dissipation of energy. Taziz Al-Lteefea is the most efficient of the designs studied, as it combines optimal geometry with its high ability to reduce flow disturbances, making it the ideal choice for improving hydraulic performance and energy dissipation in hydraulic infrastructure. Moreover, it was found that there is no negative pressure in all models, indicating that the pressures within the structures are stable and that values less than atmospheric pressure are not reached.

Abstract Controlling hydraulic jump is critical for maximizing energy dissipation, minimizing erosion, and improving the performance of stilling basins. This study presents the first comprehensive experimental investigation of the combined effects of transverse bed slope and surface roughness on hydraulic jump characteristics, energy dissipation, and free-surface flow dynamics in an asymmetrical trapezoidal channel. An innovative stilling basin configuration was implemented, featuring a transversely inclined rough bed (θ = 17°) with vertical sidewalls and three distinct roughness heights (14.32, 24.47, and 30.76 mm), tested across a wide range of Froude numbers (〖3.3<F〗_r1<9.4). The experimental setup allowed the exploration of previously unexplored three-dimensional flow structures, revealing pronounced secondary turbulence that contributed significantly to energy dissipation. The results demonstrated that increasing bed slope and roughness substantially altered hydraulic jump behavior, reducing the sequent depth ratio by approximately 31.16% and the secondary depth by nearly 18.6% compared to classical jump. Additionally, the roller length decreased by an average of 39.11%, while greater slope and roughness height increased relative energy dissipation by 9.53% compared to a classical jump. Beyond the experimental work, new empirical relationships were developed to predict key hydraulic jump parameters, achieving error margins of ±10% to ±20% and closely matching the observed data, offering practical guidance for the design of efficient and resilient stilling basins

The Pinglu Canal is a cross-basin canal project. The Qinjiang River, serving as a vital tributary of the Pinglu Canal, exhibits a significant elevation differential between its riverbed and the canal bed. This geomorphological disparity exerts a substantial influence on both hydraulic dynamics and navigational parameters within the confluence zone. This study investigates the effects of hydrodynamic conditions—specifically, flow velocity characteristics, lateral velocity distribution, and flow regime—at the confluence section of the tributary of the Qinjiang River. The aim is to ensure navigational safety in the connecting segment of the tributary inflow. Through a 1:50 scale river engineering model experiment, systematic optimization and comparative analyses are conducted using iterative combinations of energy dissipation configurations. This approach aims to address the identified deficiencies related to elevated transverse flow velocities and unstable hydrodynamic patterns in the preliminary design. Subsequent validation through a 1:100 scale undistorted physical model quantitatively confirms the recommended scheme’s efficacy in sediment flux interception at tributary confluences. The findings demonstrate that the implementation of stepped stilling basins and sedimentation basins in the confluent reach of the Qinjiang tributary achieves superior remediation efficacy. This engineering configuration enhances navigational flow conditions within the canal while concurrently provides substantial sediment interception capacity for the tributary. These results offer valuable insights for analogous confluence rehabilitation projects in fluvial systems.

The objective of this study was to assess the impact of stepped spillways on the dimensions of stilling basins. This goal can be reached by using the computational fluid dynamics code FLUENT, which works with the ANSYS software. The experiment’s results were used to test the code. The results from the code were identical to what the first results of the experiment showed. Then, the code was used on 45 different stepped spillways, each with three different step numbers: 20, 30, and 40 steps. Then, the code was used on each of the spillways. There are three different step slopes in this area: 0°, 6°, and 12°. There were five different flows: 0.16, 0.32, 0.48, 0.64, and 0.8 m3/s. The study found that stepped spillways with sloped steps needed a stilling basin that was 16% shorter. This was in contrast to stepped spillways featuring level steps.

Taziz Al-Taziz irrigation pumping station, within Al-Muthanna Governorate, Iraq, was studied, aiming at investigating the performance of its stilling basin in reducing the energy of the water out of the discharge pipes outlet. The study relied on the results of the physical model of the basic design of the stilling basin and the use of ANSYS Fluent 21.0 software to simulate both the basic design and the as-built stilling basin. The physical model was constructed and studied by the Center for Studies and Engineering Designs of the Iraqi Ministry of Water Resources. Simulations showed the variation in velocity within the basic design of Taziz Al-Taziz pumping station to be 3.98 m/s to 0.209 m/s in the basin, with an average velocity at the beginning of the canal of 1.4 m/s. For that, as built Taziz Al-Taziz, the velocity results showed a variation of 3 m/s to 0.209 m/s within the basin with an average velocity of 1m/s at the beginning of the canal. By converting the physical model's measured results to a prototype, the average velocity at the beginning of the canal is 1.28 m/s. The efficiency of the basic design stilling basin is 30.7%, while that for the as-built is 50.5 % and 36.7% for the physical model. This indicates the quality and efficiency of the as-built stilling basin in dispersing a significant percentage of water energy from the pipes. Moreover, it was found that no negative pressure is developed within the basins.

This study investigates the behavior of hydraulic jumps in compound rectangular channels with uniformly roughened beds, a configuration common in natural and engineered open-channel systems but underexplored in existing literature. While traditional research has focused on smooth or partially rough beds in prismatic channels, this work addresses the gap by experimentally analyzing roller length variations in channels featuring both major and minor flow sections roughened with consistent plastic elements. Conducted in a horizontal, closed-circuit flume, the experiments varied bed roughness (ε = 0–12 mm) and Froude numbers (F₁ ≈ 2–9) to replicate realistic flow conditions. Dimensionless parameters were used to derive empirical correlations between roller length and relative bed roughness, showing a consistent inverse relationship. Statistical regression confirmed strong linear trends between relative roughness and derived model coefficients for both bed types, with high determination coefficients (R² > 0.97). The findings demonstrate that full-bed roughness significantly enhances energy dissipation by reducing roller length, offering practical design implications for more compact and efficient stilling basins in compound channels.

Hydraulic jumps are characterized by intense turbulence and substantial energy dissipation in open channel flows or stilling basins. This study utilizes the Flow-3D hydraulic computational model, integrating the renormalization group k-ε turbulence model with the volume of fluid method, to investigate hydraulic jump behavior over rectangular prism rough beds. The findings reveal that these rough beds significantly influence hydraulic jump characteristics, leading to reductions of ∼17% in conjugate depth and 50% in jump length compared to classical hydraulic jumps. In addition, the vortex in hydraulic jumps is also used to clearly explain energy dissipation, which shows that the rough bed configuration significantly influences the hydraulic jump length. The results clarify the relationship between the hydraulic jump characteristics and the rough bed types studied. Moreover, this research provides valuable guidelines for choosing the geometrical features of the rough bed when designing or repairing the stilling basin for irrigation works and highway sewers downstream.

Hydraulic jumps are essential for dissipating the kinetic energy of high-velocity flows downstream of hydraulic structures such as spillways, drops, chutes, and gates. Effective energy dissipation is critical to prevent scouring and structural damage, and one of the most influential factors in enhancing this dissipation is the roughness of the stilling basin floor. This study investigates how varying bed roughness affects hydraulic jump characteristics in open channel flow. Five-bed conditions were tested, including a smooth surface and four different gravel bed roughness heights: 1.13 cm, 1.58 cm, 2.19 cm, and 2.72 cm. The investigation focused on key hydraulic jump parameters: the sequent depth ratio, relative energy loss, and relative jump length. The results revealed that increasing bed roughness significantly influences jump behavior. Specifically, it was observed that using a roughened bed leads to a marked reduction in both the height and length of the hydraulic jump. Higher initial Froude numbers also increased sequent depth ratios across all bed types. Quantitatively, energy dissipation improved by 7.54%, 21.26%, 25.74%, and 29.27% for the four roughness conditions, respectively, compared to the smooth bed scenario. This improvement in energy loss is accompanied by a considerable reduction in relative sequent depth, ranging from 32% to 66%. Similarly, the relative length of the hydraulic jump decreased by 50% and 29% for the highest roughness levels compared to the smooth condition. These findings confirm that rough beds in stilling basin designs can enhance energy dissipation efficiency while reducing energy dissipaters' spatial requirements and associated construction costs.

The elevation of the water surface by damming causes rapid flow downstream of the dam. To dissipate the energy in this flow, an energy dissipating structure, called a stilling basin, is needed. The purpose of this study is to analyze and select the flow characteristics of types of stilling basins between short, long vlughter, and sink bucket. The research method used is experimental, utilizing a circulating flume with dimensions of 7.5x24x491 cm and an ogee spillway with variations in the stilling basin: vlughter with a length of 5.7 cm (Short vlughter type), vlughter with a length of 19 cm (Long vlughter type), and sink bucket with a length of 11 cm (Sink bucket type). The results of this study show that the greater the discharge, the greater the specific energy after the hydraulic jump. The largest specific energy after the jump is found in the sink bucket type, followed by the long vlughter type, and the smallest in the short vlughter type. The conclusion is that the variation in shape and dimensions of the stilling basin can affect the output characteristics of the hydraulic jump, with specific energy after the jump being greater in the sink bucket type, followed by the short vlughter and long vlughter types, which are relatively the same but smaller, with the difference becoming more significant as the discharge increases.

Changing the water flow leads to significant fluctuations in the water levels of the spillway, resulting in substantial energy changes as the water passes through and risking its stability. Consequently, spillway design must include the design of a stilling basin as an energy reducer to decrease the effects of scour. The primary objective of this research is to explain the influence of the hydraulic behavior in the stilling basin on the depth of scour downstream of the spillway structure. The study was conducted using the replica of the Krueng Kluet Dam spillway at the Dr. Masimin Hydrotechnic Physical Model Laboratory within the Faculty of Engineering, Syiah Kuala University, Indonesia. A dimensional analysis design methodology was deployed to examine the correlation between hydraulic parameters, including Froude number, hydraulic jump characteristics, energy dissipation efficiency, and scour depth. The research results show a direct relationship between discharge and both Froude number and hydraulic jump magnitude, resulting in corresponding scour depth. In addition, a higher discharge corresponds to a reduced energy dissipation efficiency, which contributes to increased scour depth. An anomaly observed in the efficiency-scour depth relationship is attributed to the generation of thin flow and its significant impact on the baffle block.

The primary purpose of stilling basins in a hydraulic structure is to attenuate the kinetic energy of flowing water in order to prevent erosion downstream of the structure, which might potentially result in its failure. The USBR VI stilling basin is an early basin designed specifically for dissipating pipe outlet flow. This study assessed the impact of adding a sill to a type VI stilling basin on the dissipation of energy by evaluating eight distinct models. The purpose of adding the sill is to increase energy dissipation and thus reduce scouring at the downstream of the basin. The aim of this study, employing numerical modelling, was to enhance the efficiency of the USBR VI stilling basin in dissipating energy. This was achieved by investigating the impact of positioning the sill at various positions and identifying the optimal position that maximises energy dissipation. The study's findings indicate that model 2 exhibits the largest percentage of energy dissipation, reaching 86.5%. The addition of a sill at 4850 mm from the inflow pipe resulted in an improvement in the performance of the stilling basin, with the energy dissipation percentage increasing from 67.1% to 86.5%. The sill at this location produces lower pressure at the outlet section than the bench model and other models as a result of the increased fluctuations at the sills. Finally, the inclusion of adding a sill at 0.723 times the length of the basin from the inlet resulted in the highest percentage of dissipation.

The velocity at the toe of a spillway is a major variable when designing a stilling basin. Reducing this velocity leads to reduce the size of the basin as well as the required appurtenances which needs for dissipating the surplus kinetic energy of the flow. If the spillway chute is able to dissipate more kinetic energy, then the resulting flow velocity at the toe of spillway will be reduced. Typically, stepped spillway is able to dissipate more kinetic energy than that of a smooth surface. In the present study, the typical uniform shape of the steps has been modified to a labyrinth shape. It is postulated that a labyrinth shape can increase the dissipation of kinetic energy through increasing the overlap between the forests of nappe will circulating the flow that in turns leading to further turbulence. This action can reduce the jet velocities near the surfaces, thus minimizing cavitation. At the same time the increasing of circulation regions will maximize the opportunity for air entrainment which also helps to dissipate more kinetic energy. The undertaken physical models were consisted of three labyrinth stepped spillways with magnification ratios (width of labyrinth to width of conventional step) WL/W are 1.1, 1.2, and 1.3 as well as testing a conventional stepped spillway (WL/W=1). It is concluded that the spillway chute coefficient is directly proportional to the labyrinth ratio and its value decreases as this ratio increases.

The hydraulic characteristics of dams can be predicted with high precision and reliability of physical and numerical models depending on accurate hydraulic data. The model is operated and simulated to get a more efficient, optimized utilization of the dam. This research included a comprehensive overview and literature examination of the Makhool Dam which is considered one of the most important dams under construction in Iraq. Previous studies of the dam focused on different topics in the operation of the dam and analyses of its properties, part of which focused on the dam ability to manage flood and how it works best with other dams in critical times, and another part studied the properties of the stilling basin, velocity in the dam reservoir, pressure, seepage and other characteristics that affect the operating the dam. Despite this research and the variety of topics discussed, there is no well-established research on the operation of the bottom and emergency spillway of the dam by using computational fluid dynamics (CFD) simulation software. CFD is considered an essential tech because it has an important influence in determining the hydraulic properties of a spillway and studying its effectiveness under different operating conditions. Because the spillway is an important element in the dam body, the research highlighted the necessity of performing a simulation using appropriate CFD software for this part. This research has also reviewed previous research on CFD software and their ability to simulate previously constructed or under-construction dams to analysis of its hydraulic properties.

A stilling basin is a vital energy dissipator structure that transitions supercritical flow from a dam spillway into subcritical flow to protect downstream (ds) riverbeds from the scouring caused by high-velocity water. This study evaluates the impact of wall configurations and middle blocks on energy dissipation efficiency in stilling basins by modifying wall shapes and incorporating middle blocks. Five cases were tested: flat walls with middle blocks (Case 1), small zigzag walls without and with middle blocks (Cases 2 and 3), and large zigzag walls without and with middle blocks (Cases 4 and 5). A total of 55 experiments were conducted with discharges ranging from 0.010 m³/s to 0.020 m³/s. The average energy dissipation rates were 61.1%, 58.5%, 65.2%, 63.6%, and 64.9% for Cases 1, 2, 3, 4, and 5, respectively. Case 3, featuring small zigzag walls with middle blocks, demonstrated the highest energy dissipation efficiency, outperforming the other cases. This research highlights innovative designs for stilling basins, enhancing energy dissipation efficiency and mitigating the ds scouring effects.

Hydraulic jumps are widely used to dissipate excess energy in civil, ocean, and hydro-power engineering, particularly in high dams with large reservoirs. Different inflow and tailwater conditions lead to the occurrence of various types of hydraulic jumps. Among them, A-jumps are often preferred for stilling basin design, due to their high energy dissipation efficiency and favorable outflow patterns. This study numerically investigated the hydraulic characteristics of 75 critical A-jumps by adjusting tailwater levels, considering varying inflow conditions (flow depth, velocity, discharge, and Froude number) and stilling basin parameters (negative step height and incident angle), covering key parameter ranges from existing practical applications in high dam projects. Based on theoretical analysis and numerical simulations, estimation methods are proposed for the key hydraulic parameters of A-jumps, including the sequent depth ratio, roller length, reattachment length, and energy dissipation rate. A correction for the sequent depth ratio, incorporating the influence of the incident angle, is proposed for the first time. These estimation methods offer valuable insights for designing and optimizing negative step stilling basins in various practical engineering scenarios. To validate their applicability, a case study was conducted, showcasing the superior energy dissipation and stable outflow performance of the designed stilling basin, with the basin length shortened by 1.8% and the near-bottom velocity reduced by 42.4%, based on the proposed estimations, compared to the classical stilling basin.