Flip Buckets Research Articles

Experimental investigation on local scour downstream of stepped chutes with a flip bucket

Stepped chutes and flip buckets are the most prevalent energy dissipators in emergency spillways at dams. Given the impact that scour depth has on the stability and safety of these structures, the effects of stepped and smooth chutes on the local scour process downstream of a flip bucket for various hydraulic and geometric conditions were experimentally investigated in the present study. Experiments were conducted for 1:1 and 1:2 chute slopes (V: H), bucket exit angles of 15° and 30°, and a ratio of critical flow depth to step height (yc/h) between 0.53 and 0.97. The comparison of results revealed that installing steps over the chute profile reduced the maximum scour depth downstream in range of 15–51 percent, compared to smooth chute. By changing chute slope from 1:1 to 1:2, the maximum scour depth was reduced by an average of 16 and 25 percent for smooth and stepped chutes, respectively.

Investigation of Hydraulic Conditions and Shape of Flip Bucket Spillways on Cavitation Phenomenon by Considering Dynamic Pressures

Abstract Cavitation is one of the destructive phenomena which occurs in hydraulic structures and can cause considerable damage to them. This phenomenon is likely to take place in parts of hydraulic structures where the flow velocity is high and water pressure is below the water vapor pressure, thereby leading to the formation of cavitation bubbles. Dynamic pressures may, frequently and in short time periods, reduce flow pressure to below the vapor pressure of water and form cavitation bubbles as a result. Taking dynamic pressures into account, this study examines the potential for the occurrence of cavitation in flip bucket spillways. This research is based on experimental studies and it focuses on the cavitation phenomenon by measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. Measurements of dynamic and statics pressures on three different models of flip buckets were made within a range of different Froude numbers. Using statistical analyses on pressure fluctuations, this study has obtained the equivalent pressures of the 0.1% incidence probability, which, in turn, have been used, along with static pressures, for calculating the cavitation. Results show that as the Froude number increases (from nearly five to almost ten), the cavitation index decreases, and after that, the trend of cavitation index is reversed and starts to rise. Also, it is demonstrated that the cavitation probability on inlet and outlet scope of the flip bucket is higher than the middle part. Hence, cavitation incidence probability increases while the ratio of width to radius of the bucket rises.

Hydraulics of Wedge-shaped Flip Bucket to Investigate Flow Pattern with Retracted Bottom Plate

This study analyzed the flow pattern of a wedge-shaped flip bucket with a retracted bottom plate (WFB-R) that is quite different from conventional flip buckets. The flow pattern of the free jet release from WFB-R is determined by the relationship between water depth at the exit and wedge height. If the water depth is less than or equal to the wedge height, the free jet appears narrow and long, whereas if the water depth is greater, the free jet appears like a hammer. Hence, WFB-R offers the advantage of extending the free jet longitudinally, but its longitudinal length can be controlled, which allows it to avoid hitting the bank of the plunge pool. The experimental results indicate that, compared to constant-width flip buckets with retracted bottom plates (CFB-R), WFB-R reduces the maximum impact pressure on the plunge pool bottom to 70–86% of what it originally was. In addition, the flow structure of free jets issued from WFB-R was modeled using the k-ε turbulence model. The numerical results show that in the case of WFB-R, the shrinkage ratio should be less than or equal to a critical shrinkage ratio (0.63 for the present case) in order to stretch a free jet longitudinally. The length of the retracted bottom plate affects the longitudinal extension of the free jet. The longer the retracted bottom plate, the better the longitudinal stretching effect. The flow pattern is determined by the relationship between water depth at the exit of WFB-R and wedge height. Based on the projectile theory, a novel method was developed to predict the trajectory of free jets released from WFB-R by incorporating the average velocity, takeoff velocity coefficient, and takeoff angle coefficient. The Yangfanggou high dam project illustrates the application of WFB-R.

A Concise Method to Predict the Mean Dynamic Pressure on a Plunge Pool Slab

Hydrodynamic pressure exerted on a plunge pool slab by jet impingement is of high interest in high dam projects. The present study experimentally investigated the characteristics of pressure induced by a jet through a constant width flip bucket (CFB) and a slit flip bucket (SFB). A pressurized plane pipe was employed in the flume experiments to control the inlet velocities in the flip buckets. A concise method is proposed to predict the mean dynamic pressure field. Its implementation is summarized as follows: First, the position of the pressure field is determined by the trajectories of free jets, and to calculate its trajectories, an equation based on parabolic trajectory theory is used; second, the maximum mean dynamic pressure is obtained through dimensional analysis, and then the pressure field is established by applying the law of Gaussian distribution. Those steps are integrated into a concise computing procedure by using some easy-to-obtain parameters. Some key parameters, such as takeoff velocity coefficient, takeoff angle coefficient, and the parameter , are also investigated in this paper. The formulas of these coefficients are obtained by fitting the experimental data. Using the proposed method, the easy-to-obtain geometric parameters and initial hydraulic conditions can be used to calculate the maximum mean dynamic pressure on the slab. A comparison between experimental data and calculated results confirmed the practicability of this model. These research results provide a reference for hydraulic applications.

Dynamic Pressure at Flip Buckets of Chute Spillways: A Numerical Study

Dynamic Pressure at Flip Buckets of Chute Spillways: A Numerical Study

Hydrodynamic Performance of A‐Jacks Concrete Armor Units in Riverbeds around Downstream in Flip Buckets

The jet flipped from flip buckets hits the dam’s downstream side as a free jet with an immense amount of energy, leading to bed erosion. Erosion of river bed materials downstream of dams could affect the performance of dams or power plants by altering the tailwater depth, rendering proper designs of controlling structures or erosion reduction methods highly indispensable in this regard. Hence, the hydrodynamic performance of A‐Jacks concrete armor units in controlling scour was examined in this study. A‐Jacks armors are applicable as a flexible protection without environmental risks often for bed erosion control. The desirable functionality of A‐Jacks armors depends on the flow hydrodynamic parameters such as velocity profile variations (U/UB), the Reynolds stresses ( and τv′w′), and the skin friction coefficient (Cf) created as a consequence of using A‐Jacks armors on beds. The size of A‐Jacks elements can have a role in increasing the flow turbulence to a certain depth so that after the impact of the flow with A‐Jacks armor, the vortices’ intensity as well as the shear stress affecting the bed gradually decreases. The results of the numerical model suggest that the surge in the flow turbulence energy dissipation downstream of flip buckets significantly mitigates the underlying conditions of scouring phenomena, which is evidence of A‐Jacks armors’ acceptable performance in scaling down scour depths.

Prediction of the dynamic pressure distribution in hydraulic structures using soft computing methods

Prediction of dynamic pressure distribution ( $$ P^{*} $$ ) is a subject of great importance in the design and operation of the hydraulic structures. Flip buckets, using as hydraulic structures for dissipation of the excess energy outflow, are usually constructed at the end of the chute of the spillways. In this research, based on experimental studies of large hydraulic models, five well-known soft computing methods including artificial neural networks (ANN), gene expression programming (GEP), classification and regression trees (CART), M5 model tree (M5MT), and multivariate adaptive regression splines (MARS) approaches are examined. Mathematical expressions are obtained by these methods to predict $$ P^{*} $$ in flip buckets. Compared to ANN and GEP expressions, explicit formulas derived by CART, M5MT, and MARS demonstrated more straightforward calculations. In addition, linear and nonlinear equations are generated for better comparison with the outcomes of the proposed soft computing methods. The obtained results showed the high performance of the suggested soft computing methods for the prediction of $$ P^{*} $$ in flip buckets. It is found that the GEP approach culminated in more accurate results than other proposed soft computing methods and conventional linear and nonlinear regression techniques. Error measures in the testing stage showed that the formula provided by GEP with root mean square error (RMSE = 0.095), scatter index (SI = 13%), and mean absolute error (MAE = 0.073) has the best accuracy among the other predictive equations.

On the Effect of Block Roughness in Ogee Spillways with Flip Buckets

In this study, the effect of the presence of bed-block roughness in an ogee spillway on energy dissipation and jet length is investigated. A series of experimental and numerical tests were conducted using an ogee spillway with block roughness on the bed without a flip bucket and with a flip bucket at different take-off angles (32 °C and 52 °C). To model the free-flow surface, the volume-of-fluid (VOF) method and turbulence model from RNG k–ε were used. Results indicated that the numerical model is fairly capable of simulating a free-flow surface over an ogee spillway; using block roughness on the spillway chute without a bucket, relative energy dissipation increased by 15.4% compared to that in the spillway with a smooth bed, while for the spillway with 32 °C and 52 °C buckets, it increased by 9.5%. The jet length for a spillway with a flip bucket and roughened bed decreased by 8% to 58% compared to that in a smooth bed. Lastly, the relationships for the estimation of relative energy dissipation and jet length are presented.

Investigation of Supercritical Flow and Shape of Flip Bucket Spillways on Coefficients of Dynamic Pressure

Abstract Pressure fluctuation is one of the major turbulent flow characteristics. It may cause crucial problems for hydraulic structures. This research is based on experimental studies, and it focuses on the measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. The function of the flip bucket spillway is discharging floods from reservoir dams which are energy storage source measurements of dynamic pressures on three different models of flip buckets that were performed for this investigation. Pressure fluctuation of the flip buckets have been measured within a range of Froude numbers from 5 to 13 (Fr = u/gy, where u is the flow speed, y is the depth, and g is 9.81 m/s2). Statistical characteristics of pressure fluctuations, the location, and the values of maximum and minimum fluctuations have also supplemented the study. The results show that the coefficients of pressure fluctuations (Cp = RMS/(0.5(u2/g)) where RMS is the root-mean-square of pressure fluctuation, u is the flow speed, and g is 9.81 m/s2) reduce as the Froude number (Fr) of flow increases, except a maximum Froude number. Pressure coefficients increase along the flip bucket with incremental mutations in the transformation area of the flip bucket. In the middle part of the flip bucket spillway, pressure coefficient values decrease. Additionally, as B/r (B is the width of the flip bucket and r is the radius of the flip bucket) ratio increases, pressure coefficients become larger and this process continues along the flip bucket.

Experimental Modeling and Evaluation Sediment Scouring in Riverbeds around Downstream in Flip Buckets

Flip buckets are a common configuration for side channel spillways. Similar to other spillways, the flip bucket or ski jump has its disadvantages, among which the scour hole downstream due to the flip bucket jet is the most important. The structure safety and stability may be influenced by the scour holes generated at the downstream side of bucket type energy dissipators. This study has employed an experimental model in order to examine the sediment scour created at the end of flip bucket energy dissipators at various flow rates and tail water depths. A total of 45 experiments were performed under different conditions. The experimental invistigation was conducted at the hydraulic laboratory of Shahid Chamran University in Iran. The main objective of this research was to identify the maximum depth of sediment scour ( ) and the maximum distance of sediment scour hole ( ) from the structures. The results showed that the maximum depth of scour and its distance from the structure increased by increasing discharge. The results of experimental models show that, at the downstream depths ( ) of 0.2 and 0.3 m, the stack was formed by the scouring at the upstream side of the hole, and at a depth of 0.1 m, this stack was transferred to the area after the scour hole. This could be explained by the fact that at downstream depths of 0.2 and 0.3 m, the rolling flow moved from the bottom upwards in the opposite direction of the water flow and sequestrated the sediments upstream. According to Equation Mean Absolute Relative Error(MARE) proposed relation based on laboratory studies has MARE of about 34.2%.

Experimental investigation on the effect of different slot shapes and configurations on scour dimension downstream of flip buckets

Flip buckets at the end of a spillway can dissipate the flood discharge energy. Compared to other energy dissipators, this is a cost-effective structure. The formation of a scour hole downstream of a flip bucket is a topic of interest among hydraulic engineers. The current study investigated scouring downstream of a flip bucket under two major scenarios: (i) free conditions, and (ii) slotted conditions with rectangular and triangular slots configured differently under four different discharge rates. In total, 20 experiments were conducted in this study. Results showed that the use of a deflector slot greatly affected the scour extent and depth, resulting in a greater scour reduction (53%) in the labyrinth rectangular slotted bucket compared to the solid bucket. The results were compared to empirical equations, and a high correlation was observed between them. In comparison, the Taraimovich equation produced more accurate results in control experiments, and the Damle-A and Damle-B equations produced more accurate results in experiments corresponding to labyrinth rectangular and triangular slotted buckets.

Stability of A-Jack concrete block armors protecting the riverbeds

Flip buckets are among one of the most common types of energy dissipaters, especially for dams. The scouring phenomenon occurs when falling jets hit the river bed, and A-Jack concrete block armors can be used as an effective way to control such a phenomenon. The main purpose of this study is to investigate the stability of sediment particles using A-Jack concrete block armors. In this regard, the general form of the incipient motion and incipient failure of A-Jack armor were extracted based on dimensional analysis and particle stability analysis. In these analyses, the dimensionless parameter of stability number denoted by SN is a function of other variables. The results of different physical models for different hydraulic conditions and sediment sizes are evaluated. Variability of SN related to each variable is considered, and linear and non-linear models for prediction of breakage conditions of the A-Jack block are derived. Using the experimental results, several empirical relations were developed to predict the incipient motion and incipient failure for different protection alternatives under different conditions of A-Jack block. By defining the bed scour as a criterion for the stability of A-Jack block, a design relation was also proposed to determine the required block size. Other topics investigated and discussed in this paper include effects of size and type of A-jacks as well as criteria for a gravel filter.

Experimental investigation of energy dissipation on flip buckets with triangular deflectors

ABSTRACT Flip buckets are commonly used to discharge flow from a hydraulic structure to the downstream as ski jump when flow velocity is large. Deflectors can be used to increase the efficiency of energy dissipation by flip buckets. This wedge-shaped structure deflects a portion of the flow by splitting it on the bucket. In this study, the effect of triangular deflectors which are used continuously across the channel, on energy dissipation by a flip bucket was experimentally investigated. For this purpose, a triangular deflector with three side lengths (3, 6 and 9 cm) and seven angles equal to 12°,17°, 22°, 27°, 32°, 37° and 42° was tested under different hydraulic conditions and the results were compared with a flip bucket without a deflector. The experiments were carried out in a laboratory flume with a length of 15 m, a width of 0.3 m and a height of 0.5 m. The results indicate that the model with a deflector increased energy dissipation by 8.2 to 22.7 percent as compared to that without a deflector. Increasing the deflector angle and side length initially increased energy dissipation, but then decreased it at large angles and lengths. An optimum angle of 27° to 32° was obtained with an optimal deflector length (L) to the Reynolds number (R) ratio of 0.46. A correlation was proposed to predict energy dissipation by the flip bucket with a triangular deflector using multivariate nonlinear regression.

Research on the Optimization Design of Abnormal Flip Buckets

This study constructs an optimization model to address ski-jump energy dissipation problems in different reservoir environments. The multiobjective genetic algorithm is herein applied as the calculation method. In the process of changing the ski-jump flow model, the runoff of ski-jump flow is changed (especially the abnormal flip bucket). Water flow might go from having a single falling point to multiple falling points. Optimization is only performed after the stabilization of the fall of the water because the fall of the water from the starting point to the ground is not stable over a short period. Only a stable flow can reduce the computation time for optimization. The optimal overflow width and height of the flip bucket were calculated through optimal computation, which can minimize the scouring force of the water flow as it falls to the ground. The results obtained provide theoretical references for practical engineering and reduce the potential safety hazards. The energy in flip buckets following the optimization of the water flow can be fully dissipated, creating an ecosystem where water can flow unobstructed. Guiding a water flow to water-deficient areas is of great significance in ensuring the long-term protection of environments and ecosystems.

Performance of Hydrodynamics Flow on Flip Buckets Spillway for Flood Control in Large Dam Reservoirs

Flip buckets are usually used in high head dams to dissipate the destructive energy of high speed jets. These structures are fixes at the end of the outlet conduits to direct the moving jet into the atmosphere. The process of energy dissipation also resumes, while the jet entering into its downstream plunge pool. Although studies of flow over flip buckets turn back to many years ago, but still there are uncertainties regarding the flow behaviour over these structures with various geometries and flow conditions. In this study, experimental measurements of static and dynamic pressures and their distribution over these structures are investigated. Measurements were made along two different simple flip buckets with various Froude numbers to determine the effects of the geometry and flow characteristics on pressure field. Maximum pressures are also presented and the results are compared with those of other investigations. The results of this study can be used to increase the safety of large dams that remain sustainable in the process of exploitation such as irrigation, human consumption, industrial use, aquaculture, and navigability. Doi: 10.28991/HEF-2020-01-01-05 Full Text: PDF

Flow regime and energy dissipation of SFS-type flip buckets

In the present work, a slot-type flip bucket with separated flows, called SFS-type flip bucket, is developed, and flow regime and energy dissipation are experimentally investigated. Comparing with the circular-shaped or slot-type flip bucket buckets, the present SFS-type flip bucket has better flow regime and larger energy dissipation since the three branches of the flows are separated through the outlet of the flip bucket. Meanwhile, the energy dissipation for this flip bucket is estimated.

Evaluation and modeling scouring and sedimentation around downstream of large dams

Flip buckets are often used at the end of chute spillways to dissipate energy and direct flow to submergence plunge pool and especially in large dams. Flip buckets with central deviation also are a specific and new design of these buckets that have a transverse slope and are mixed in plan with a curvature. In this paper, the experimental and numerical simulation study of sediment scouring in such flip bucket has been targeted. Extensive experimental data are obtained from physical model studies conducted at Water Research Institute, Iran. The flow field with various flood discharges in a range of Froude numbers (Fr = $$V/\sqrt {gh}$$ : 3.5–7.5) in Flow3D model was compared to experimental results obtained from a similar model. Analyzing the simulated models in the Flow3D model and comparing the results with the experimental model, the hydraulic parameters of the pressure, velocity and depth of flow are determined. Considering the accuracy of the numerical model in simulating bed scouring, this model can be used for similar cases in large dams. The results of the simulation model compare well with the experimental results in parameters of the maximum scour depth, profile scouring and the ridge height which accumulates around downstream of the scour hole. This investigation improves the understanding of bed topography effects of downstream dams in high-velocity jet impact based on experimental observations and simulation analysis.

Energy dissipation of slot-type flip buckets

The energy dissipation is a key index in the evaluation of energy dissipation elements. In the present work, a flip bucket with a slot, called the slot-type flip bucket, is theoretically and experimentally investigated by the method of estimating the energy dissipation. The theoretical analysis shows that, in order to have the energy dissipation, it is necessary to determine the sequent flow depth h1 and the flow speed V1 at the corresponding position through the flow depth h2 after the hydraulic jump. The relative flow depth h2 / ho is a function of the approach flow Froude number Fro, the relative slot width b/Bo, and the relative slot angle θ/β. The expression for estimating the energy dissipation is developed, and the maximum error is not larger than 9.21%.

Experimental investigation of pressure fluctuation on the bed of compound flip buckets

In this study, pressure fluctuation and also the effect of entrance flow conditions on the pressure fluctuation on the bed of compound flip buckets used in the Gotvand dam in Iran are investigated experimentally. For this purpose, Pressure fluctuations on the buckets are measured in the entrance flow Froude number range of 3.5–7.5. Results show that mean of pressure decreases and pressure fluctuation increases when depth and discharge of the entrance flow increase or Froude number decreases. Furthermore, mean of pressure is maximum at the beginning and also minimum at the end of the buckets. The pressure fluctuation is maximum at the beginning and end of the buckets. In contrast, the pressure fluctuation is minimum at thalweg of the buckets. Therefore, this can be concluded that deflection of the flow streamlines is on the effect of the changing of the buckets bed and also impact of high-speed water flow at the beginning of the buckets can cause that the maximum value of mean and fluctuation of pressure occurred at the beginning of the buckets.

Head Loss Estimation for Water Jets from Flip Buckets

Head Loss Estimation for Water Jets from Flip Buckets