scholarly journals Evaluation of step�s slope on energy dissipation in stepped spillway

2014 ◽  
Vol 3 (4) ◽  
pp. 501
Author(s):  
Ali Heidari ◽  
Poria Ghasemi
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Dissipative Structures ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Flow Energy ◽  
Hydraulic Behaviour ◽  
Basin Geometry ◽  
And Performance ◽  
Mean Kinetic Energy

Stepped spillways are kind of dissipative structures used in rivers with steep slopes to reduce the flow energy and also the scouring potential of water. This dissipation is caused through diffusion along the spillway. The reduction of energy also leads to optimize the still basin geometry and performance downstream, and thus make the project more economic. In this paper, the hydraulic behaviour of stepped spillway is investigated based on kinetic energy. The results show that the average mean kinetic energy decreases upon an appraise in stepss slope. Finally, horizontal steps are proposed. Keywords: Stepped Spillway, Mean Kinetic Energy, Dissipation, and Stepss Slope.

FLOW AND ENERGY DISSIPATION OVER ON FLAT AND POOLED STEPPED SPILLWAY

2016 ◽  
Vol 78 (8) ◽  
Author(s):  
Denik Sri Krisnayanti ◽  
Soehardjono Soehardjono ◽  
Very Dermawan ◽  
Mohammad Sholichin
Keyword(s):  
Energy Dissipation ◽  
Energy Loss ◽  
Froude Number ◽  
Relative Energy ◽  
Stepped Spillway ◽  
Dissipation Energy ◽  
Stepped Spillways ◽  
Flow Energy ◽  
Physical Study ◽  
Roughness Elements

The stepped spillway has increasingly become effective energy dissipation. The stepped spillway has been accepted to be the most powerful hydraulic structure to dissipate large flow energy downstream from spillway crest. The steps act as roughness elements significantly increase the dissipation energy rate. The physical study has performed on flat and pooled stepped spillways with a slope spillway    (θ = 45˚) and number of steps (N): 20 and 40. The experiments were conducted for ten Froude number (Fr) run ranging from 1.117 to 9.909 with 0.700<yc/h<3.00. The focus of research to investigate the relationship between relative energy losses in skimming flow performance against Froude number on various stepped. The effect of number of steps is evident when the relative energy loss increases with the number of steps. In addition, the relative energy loss of flow on pooled steps is dissipating more energy than flat steps.

scholarly journals Numerical Study to Evaluate the Performance of Nonuniform Stepped Spillway Using ANSYS-CFX

2020 ◽  
Vol 10 (2) ◽  
pp. 1-9
Author(s):  
Shawnm M. Saleh ◽  
Sarhang M. Husain
Keyword(s):  
Energy Dissipation ◽  
Numerical Study ◽  
Energy Dissipation Rate ◽  
Step Height ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Flow Discharge ◽  
Flow Energy ◽  
Ansys Cfx ◽  
Inception Point

The main features that attract hydraulic engineers for designing stepped spillways are their ability to lose a large portion of the flow energy and add or increase aeration to the flow naturally. Hence, smaller size stilling basin and no aeration device may require. This study aims to find the amount of energy dissipation rate and the location of inception point over non-uniform stepped spillway. The numerical 2D ANSYS-CFX code is applied to generate and run thirty-two models of different configurations using two different moderate slopes (1 V:2 H and 1 V:2.5 H) as most of the downstream slopes designed for moderate slope, and two different step heights (hs= 0.08 m and hs= 0.016 m) under skimming flow discharge for different (dc/hs) ranging from dc/hs= 1–2.2, in which dc is the critical flow deptho n the crest. The volume of fluid is implemented and the renormalized group of k-ɛ turbulence model is activated. The computational results demonstrated that the amount of energy dissipation increases with decreasing the flow discharge, chute slope, and step height. In addition, it is observed that the length of the inception point is directly proportional to the discharge and inversely proportional to both the chute slopes and step height. Moreover, for the design point of view, the results revealed that configuration B can be considered as the optimal one amongst the others examined herein.

scholarly journals Uniform flow and energy dissipation of hydraulic-jump-stepped spillways

2020 ◽  
Vol 20 (4) ◽  
pp. 1546-1553
Author(s):  
Yu Zhou ◽  
Jianhua Wu ◽  
Fei Ma ◽  
Jianyong Hu
Keyword(s):  
Energy Dissipation ◽  
Water Flow ◽  
Hydraulic Jump ◽  
Flow Region ◽  
Uniform Flow ◽  
Stepped Spillway ◽  
Flow Depth ◽  
Clear Water ◽  
Air Concentration ◽  
Stepped Spillways

Abstract In skimming flow, a uniform flow can be achieved and the flow depth, velocity and air concentration remain constant if a stepped spillway is sufficiently long. In this study, physical model experiments were performed to investigate the uniform characteristics and energy dissipation of a hydraulic-jump-stepped spillway, which is a new type of stepped spillway for increasing the unit discharge capacity and energy dissipation. Based on the redefinition of uniform flow, experimental results show that at a given stepped spillway slope, a smaller height for the beginning of the uniform flow region, a greater uniform aerated flow depth and a greater uniform equivalent clear water flow depth can be obtained as compared with the traditional stepped spillway due to strong aeration in the aeration basin. Under the condition of uniform flow, the energy dissipation rate of stepped spillways can be estimated by the equivalent clear water flow depth with given inflow conditions. Compared with the traditional stepped spillway, the uniform flow over the hydraulic-jump-stepped spillway has a smaller specific energy, revealing that the hydraulic-jump-stepped spillway is more advantageous for dissipating energy, especially at large unit discharges.

scholarly journals Genetic algorithms for optimizing stepped spillways to maximize energy dissipation

2021 ◽  
Author(s):  
Farzin Salmasi ◽  
John Abraham
Keyword(s):  
Water Management ◽  
Genetic Algorithm ◽  
Energy Dissipation ◽  
Objective Function ◽  
Relative Energy ◽  
Stepped Spillway ◽  
Construction Time ◽  
Stepped Spillways ◽  
Decision Variables ◽  
West Azerbaijan

Abstract Stepped spillways are important water-management structures that are used for energy dissipation. Use of these spillways has increased in recent decades, they can reduce construction time and they are effective for reducing the flow's downstream kinetic energy. In this study, the width and height of the steps as well as the slope and height of the overflow spillway were considered as variables. Due to the large number of variables, non-linearity of the objective function and constraints, and the lack of an explicit relationship between decision variables, a genetic algorithm (GA) was used. A stepped spillway with optimal dimensions was proposed as a replacement of the smooth spillway of Sarogh Dam located in West Azerbaijan province, Iran. The proposed steps increase energy dissipation; for constant discharge and varying slopes, the changes in the optimal height of the steps were insignificant. Sensitivity analysis using the objective function showed that the relative energy dissipation for a constant discharge is independent of the optimal height of the steps and decreases with increasing spillway slope. In addition, for fixed slopes, increasing the flow rate leads to a decrease in relative energy dissipation and an increase in the optimal height of the steps.

scholarly journals Stepped Spillways and Energy Dissipation: A Non-Uniform Step Length Approach

2019 ◽  
Vol 9 (23) ◽  
pp. 5071
Author(s):  
Abdelwanees Ashoor ◽  
Amin Riazi
Keyword(s):  
Energy Dissipation ◽  
Step Length ◽  
Maximum Energy ◽  
Stepped Spillway ◽  
Constant Number ◽  
Stepped Spillways ◽  
Interference Region ◽  
Different Types ◽  
Stepped Chute

A stepped spillway, which is defined as a spillway with steps on the chute, can be used to improve the energy dissipation of descending water. Although uniform stepped spillways have been studied comprehensively, non-uniform stepped spillways need more attention. In the interest of maximum energy dissipation, in this study, non-uniform stepped spillways were investigated numerically. To this end, within the range of skimming flow, four different types of non-uniform step lengths, including convex, concave, random, and semi-uniform configurations, were tested in InterFOAM. To evaluate the influence of non-uniform step lengths on energy dissipation, the height and number of steps in all models were fixed and equal to a constant number. The results indicated that in semi-uniform stepped spillways, when the ratio between the lengths of the successive steps is 1:3, a vortex interference region occurs within the two adjacent cavities of the entire stepped chute, and as a result, the energy dissipation increases by up to 20%.

scholarly journals Numerical Investigation on the Hydraulic Properties of the Skimming Flow over Pooled Stepped Spillway

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1478 ◽  
Author(s):  
Shicheng Li ◽  
Jianmin Zhang
Keyword(s):  
Energy Dissipation ◽  
Transverse Direction ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Energy Dissipation Rate ◽  
Spanwise Direction ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Aeration Efficiency ◽  
Horizontal Step

Pooled stepped spillway is known for high aeration efficiency and energy dissipation, but the understanding for the effects of pool weir configuration on the flow properties and energy loss is relatively limited, so RNG k − ε εturbulence model with VOF method was employed to simulate the hydraulic characteristics of the stepped spillways with four types of pool weirs. The calculated results suggested the flow in the stepped spillway with staggered configuration of` two-sided pooled and central pooled steps (TP-CP) was highly three dimensional and created more flow instabilities and vortex structures, leading to 1.5 times higher energy dissipation rate than the fully pooled configuration (FP-FP). In FP-FP configuration, the stepped spillway with fully pooled and two-sided pooled steps (FP-TP) and the spillway with fully pooled and central pooled steps (FP-CP), the pressure on the horizontal step surfaces presented U-shaped variation, and TP-CP showed the greatest pressure fluctuation. For FP-TP and FP-CP, the vortex development in the transverse direction presented the opposite phenomenon, and the maximum vortex intensity in TP-CP occurred at Z/W = 0.25, while FP-FP illustrated no significant change in the transverse direction. The overlaying flow velocity distribution in the spanwise direction demonstrated no obvious difference among FP-FP, FP-TP, and FP-CP, while the velocity in TP-CP increased from the axial plane to the sidewalls, but the maximum velocity for all cases were approximately the same.

scholarly journals Hydraulic Model Investigation on Stepped Spillway's Plain and Slotted Roller Bucket

2019 ◽  
Vol 9 (4) ◽  
pp. 4419-4422
Author(s):  
A. S. Kote ◽  
P. B. Nangare
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Hydraulic Model ◽  
Physical Models ◽  
Stepped Spillway ◽  
Stilling Basin ◽  
Discharge Water ◽  
Energy Dissipater ◽  
Low Head ◽  
High Head

In ogee spillway, the released flood water from crest to toe possesses a high amount of kinetic energy causing scour and erosion on the spillway structure. The dam projects normally have a stilling basin as an energy dissipater which has specific energy dissipation limitations. The stepped spillway is a better option to minimize kinetic energy along the chute and safely discharge water in the river domain. The Khadakwasla dam is situated in Pune, Maharashtra (India), and has scouring and erosion issues on the chute of ogee spillway and on the stilling basin. The present study develops a physical hydraulic model for the dam spillway with steps, plain and slotted roller bucket as per IS Code 6934 (1998) and IS Code 7365 (2010). Experiments were performed at heads of 4m (low head) and 6m (high head) on the developed physical models, namely on the plain and slotted roller bucket model for the ogee spillway and the plain and slotted roller bucket model for the stepped spillway. It was found that the plain roller bucket of ogee spillway dissipates 81.26% of energy at the low head, whereas the stepped spillway with slotted roller bucket dissipates the 83.86% of the energy at the high head.

scholarly journals Predicting the Flow Velocity at the Toe of a Labyrinth Stepped Spillway

2021 ◽  
Vol 18 (1) ◽  
pp. 20-25
Author(s):  
Jaafar S. Maatooq
Keyword(s):  
Kinetic Energy ◽  
Flow Velocity ◽  
Smooth Surface ◽  
Air Entrainment ◽  
Physical Models ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Stilling Basin ◽  
Major Variable ◽  
Jet Velocities

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.

scholarly journals Energy dissipation performance of the trapezoidal stepped spillway

2021 ◽  
Author(s):  
Erdinc Ikinciogullari ◽  
Keyword(s):  
Energy Dissipation ◽  
Dissipation Rate ◽  
Energy Dissipation Rate ◽  
Stepped Spillway ◽  
Base Length ◽  
Stepped Spillways

Stepped spillways are a more effective type of spillway in energy dissipation than conventional chute channels. Therefore, the dimensions of the energy breaker at the downstream of the stepped spillways are lower. It is an alternative especially for the downstream pool that cannot be built in sufficient length due to the terrain conditions. In this study, the energy dissipation performance of the trapezoidal stepped spillways was investigated numerically by using Flow3D software. Four different models and three different discharges were utilized for this aim. According to the results, the trapezoidal stepped spillway is more effective up to 30% than classical stepped spillways in energy dissipation. The depth of the trapezoidal step and the bottom base length of the trapezoid significantly affected the energy dissipation rate for the trapezoidal stepped spillway.

Sign in / Sign up

Export Citation Format

Share Document