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 The Effect of Inception Point on Dissipation Energy in Stepped Spillways Modeling

2019 ◽  
Vol 54 (3) ◽  
Author(s):  
Denik Sri Krisnayanti ◽  
Suhardjono ◽  
Very Dermawan ◽  
Djoko Legono
Keyword(s):  
Energy Loss ◽  
Relative Energy ◽  
Downstream Face ◽  
Stepped Spillway ◽  
Critical Depth ◽  
Roughness Factor ◽  
Flow Conditions ◽  
Dissipation Energy ◽  
Stepped Spillways ◽  
Inception Point

Stepped spillway is generally a modification on the downstream face of a standard ogee spillway. The steps increase significantly the rate of energy dissipation taking place along the chute and reduce the size of the need for a large energy dissipate at the toe of the spillway. In skimming flow conditions, the steps act as roughness factor which is great because most of the energy is lost to maintain horizontal vortices that develop beneath the pseudo bottom. This study aimed to investigate the effect of the inception point against the value of the relative energy loss on the stepped spillway in skimming flow regime. In this research, the models test of stepped spillway carried out with twelve configuration and variations of ratio (dc/h). The slope of stepped spillway (θ) is used 30˚ and 45˚, the number of steps (N) are 40 and 20, and two type of steps: flat steps and pooled steps. The critical depth to the height of steps (dc/h) is ranging from 0.700 < dc/h < 3.00 with the discharge per unit width 69.13 cm2/s < q < 707.65 cm2/s. The results showed that the relative energy loss can be analyzed to be a function of the inception points, the number of steps, and the slope of spillway, in the equation form of (ΔH/Hmax) = a (Li/ks)bNc(sin θ)d. The discharge which function of the Froude number and height of the step already include to the length of inception point parameters.

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 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.

scholarly journals Numerical study of energy dissipation and block barriers in stepped spillways

2020 ◽  
Author(s):  
Mehdi Karami Moghadam ◽  
Ata Amini ◽  
Ehsan Karami Moghadam
Keyword(s):  
Energy Dissipation ◽  
Numerical Study ◽  
Flow Simulation ◽  
Step Length ◽  
Energy Dissipation Rate ◽  
Relative Energy ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Using Data ◽  
Turbulent Models

Abstract In this research, the accuracy of the Flow-3D numerical model in the flow simulation in a stepped spillway was probed using data obtained from the physical model. In addition, the effects of block barriers on the energy dissipation rate were investigated. To adopt a proper turbulent model, Renormalization Group k-ε, RNG k-ε, and standard k-ε models were employed. Then, the Flow-3D was run in five discharges for nine spillways with the ratios of block length to step length (Lb/l) and block height to step height (Hb/h) as 0.3, 0.4, and 0.5. The results indicated that both turbulent models had almost similar outcomes though the run time of the RNG k-ε model was shorter. The blocks with a shorter length in low ratios of Hb/h and the lengthier blocks in high ratios of Hb/h undergo more relative energy dissipation relative to the no-block situation. For Hb/h = 0.3 and Lb/l equal to 0.3, 0.4, and 0.5, the relative energy dissipation climbed on average as 8.5, 6.5, and 4.5% respectively, compared with the no-block case. The most influence exerted on relative energy dissipation was obtained via the blocks with Hb/h = Lb/l equal to 0.3 and 0.5 with respective increases of 8.6 and 8.4%.

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 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 CFD Modelling of a Stepped Spillway with Various Step Layouts

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Shicheng Li ◽  
Qiulin Li ◽  
James Yang
Keyword(s):  
Kinetic Energy ◽  
Numerical Modelling ◽  
Energy Loss ◽  
Relative Energy ◽  
Secondary Flows ◽  
Stepped Spillway ◽  
Central Plane ◽  
Cfd Modelling ◽  
Flow Features ◽  
The Face

A traditional stepped spillway is prone to cavitation risks. To improve its hydraulic behaviors, distorted step faces and pool weirs are devised. By numerical modelling, comparative studies are conducted to look into the flow features. The pressures on step surfaces of the unconventional layouts exhibit 3D distributions. Pool weirs are essential in increasing both the min. and max. pressure loads. Pressures on the downstream bed show a unique pattern for V- and inverted V-shaped models, with the extreme pressures at the sidewalls for the former and at the central plane for the latter. Symmetrical secondary flows are formed in V- and inverted V-shaped cases with different patterns. Distributions of turbulent kinetic energy suggest differences in flow motions in all cases. Furthermore, the relative energy loss of flat setups is ∼5.4% lower than that of the pooled ones with the same step face angle; inverting the face angle does not give rise to noticeable change. The results provide reference for relevant projects.

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