Intrusive and non-Intrusive air-water measurements on stepped spillways with inclined steps: a physical study on air entrainment and energy dissipation

2021 ◽  
Author(s):  
Yvan Arosquipa Nina ◽  
Rui Shi ◽  
Davide Wuthrich ◽  
Hubert Chanson
Keyword(s):  
Energy Dissipation ◽  
Air Entrainment ◽  
Stepped Spillways ◽  
Physical Study

scholarly journals Numerical Study on the Hydraulic Properties of Flow over Different Pooled Stepped Spillways

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 710
Author(s):  
Amir Ghaderi ◽  
Saeed Abbasi ◽  
Silvia Di Francesco
Keyword(s):  
Energy Dissipation ◽  
Numerical Study ◽  
Air Entrainment ◽  
Computational Procedure ◽  
Maximum Pressure ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Pressure Distributions ◽  
Efficiency Performance ◽  
Inception Point

This work presents numerical simulations carried out to study the influence of geometric characteristics of pooled steps on the energy dissipation performance, flow patterns properties, velocity rates, and pressure distributions over a spillway. The localization of the inception point of air entrainment was also assessed, being a key design parameter of spillways. With this aim, different configurations of steps were taken in account, including flat, pooled, and notch pooled types. The computational procedure was first validated with experimental results from the literature and then used to test the hydraulic behavior derived from different geometric configurations. The flat step configuration showed the best energy dissipation performance as compared with other configurations. With the notched pooled step configuration, the efficiency performance of the pooled structure improved by about 5.8%. The interfacial velocities of the flat stepped spillway were smaller than those of the pooled structure. The pressure value at the beginning of the step in the pooled configuration was larger than the flat configuration, while for the notched pool the maximum pressure values decreased near the step pool. Pool configuration (simple or notched) did not have a significant influence on the location of air entrainment.

scholarly journals Numerical Analysis of Pressure Profiles and Energy Dissipation across Stepped Spillways Having Curved Risers

2022 ◽  
Vol 12 (1) ◽  
pp. 448
Author(s):  
Najam us Saqib ◽  
Muhammad Akbar ◽  
Huali Pan ◽  
Guoqiang Ou ◽  
Muhammad Mohsin ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Stokes Equations ◽  
Free Surface Flow ◽  
Air Entrainment ◽  
Surface Flow ◽  
Stepped Spillway ◽  
Flow Rates ◽  
Stepped Spillways ◽  
Pressure Profiles ◽  
Negative Pressures

In this study, curved risers stepped spillways models based on the increasing angle of suspension were tested to check for improvement in energy dissipation and pressure distributions. Four fourteen-steps stepped spillway models with a slope 1:0.84 were selected, using Froude’s number non-dimensional similarity. The risers of steps were made curved, based on three angles of suspensions, i.e., 30°, 60°, and 90°. The simulations were performed by FLOW 3D software and by the turbulence model Renormalization Group (RNG) for discharges between 0.020 and 0.068 m3/s followed by the model calibration. The 3D Reynolds-averaged Navier–Stokes equations were solved, which included sub-grid models for air entrainment, density evaluation, and drift–flux, to capture free-surface flow over the stepped spillway. It was estimated that curving the risers increases the energy dissipation up to three percent for lower flow rates, whereas it has no significant impact on energy dissipation for higher flow rates. It was found that in simply stepped spillway lower steps dissipate more energy as compared to curved risers stepped where energy dissipation is shifted to higher steps. On the other hand, curved risers stepped spillways showed lower values of negative pressures as compared to the simply stepped spillway. It was seen that a higher energy dissipating step as experienced more negative pressures as compared to the lower energy dissipating step.

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 Stepped spillway flows and air entrainment

1993 ◽  
Vol 20 (3) ◽  
pp. 422-435 ◽  
Author(s):  
Hubert Chanson
Keyword(s):  
Energy Dissipation ◽  
Flow Characteristics ◽  
Air Entrainment ◽  
Stepped Spillway ◽  
Calculation Methods ◽  
Stepped Spillways ◽  
Popular Method ◽  
Roller Compacted Concrete ◽  
Construction Techniques ◽  
Recent Developments

Stepped spillways have become a popular method for handling flood releases. The steps significantly increase the rate of energy dissipation taking place on the spillway face and reduce the size of the required downstream energy dissipation basin. The compatibility of stepped spillways with roller compacted concrete and gabion construction techniques results in low additional cost for the spillway. This paper presents a review of recent developments for the design of stepped spillways, provides a discussion of the effects of air entrainment, and presents new calculation methods that take into account the effects of flow aeration on the flow characteristics and the rate of energy dissipation. Key words: stepped spillway, air entrainment, dam, spillway, energy dissipation.

scholarly journals Energy dissipation efficiency as a new variable in the empirical correlation of total dissolved gas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jingying Lu ◽  
Xiaolong Cheng ◽  
Zhenhua Wang ◽  
Ran Li ◽  
Jingjie Feng ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Standard Error ◽  
Air Entrainment ◽  
Empirical Equations ◽  
Generation Process ◽  
Field Observations ◽  
Dissolved Gas ◽  
Total Dissolved Gas ◽  
Future Work ◽  
Hydropower Stations

AbstractTotal dissolved gas (TDG) supersaturation, which occurs during dam spilling, may result in fish bubble disease and mortality. Many studies have been conducted to identify the factors pertaining to TDG generation, such as the spilling discharge and tailwater depth. Additionally, the energy dissipation efficiency should be considered due to its effect on the air entrainment, which influences the TDG generation process. According to the TDG field observations of 49 cases at Dagangshan and Xiluodu hydropower stations, the TDG was positively related to the energy dissipation efficiency, tailwater depth and discharge per unit width. A correlation between the generated TDG level and these factors was established. The empirical equations proposed by the USACE were calibrated, and the TDG level estimation performance was compared with the established correlation for 25 spillage cases at seven other dams. Among the considered cases, the standard error of the TDG estimation considering the energy dissipation efficiency was 5.7%, and those for the correlations obtained using the USACE equations were 13.0% and 10.0%. The findings indicated that the energy dissipation efficiency considerably influenced the TDG level, and its consideration helped enhance the precision of the TDG estimation. Finally, the generality of this approach and future work were discussed.

scholarly journals An improved air entrainment model for stepped spillways

2021 ◽  
Author(s):  
Silje Kreken Almeland ◽  
Timofey Mukha ◽  
Rickard E. Bensow
Keyword(s):  
Air Entrainment ◽  
Stepped Spillways

NUMERICAL SIMULATION OF AIR ENTRAINMENT ON STEPPED SPILLWAYS

2019 ◽  
Author(s):  
ZONGSHI DONG ◽  
JUNXING WANG ◽  
DAVID FLORIAN VETSCH ◽  
ROBERT MICHAEL BOES ◽  
GUANGMING TAN
Keyword(s):  
Numerical Simulation ◽  
Air Entrainment ◽  
Stepped Spillways

Prediction of Air Entrainment in Skimming Flow over Stepped Spillways Using Numerical Methods

2019 ◽  
Author(s):  
JACOB VAN ALWON ◽  
DUNCAN BORMAN ◽  
JORGE MATOS ◽  
NIK KAPUR ◽  
ANDREW SLEIGH
Keyword(s):  
Numerical Methods ◽  
Air Entrainment ◽  
Stepped Spillways

scholarly journals Experimental Characterization of the Hydraulic Jump Profile and Velocity Distribution in a Stilling Basin Physical Model

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1758
Author(s):  
Juan Macián-Pérez ◽  
Francisco Vallés-Morán ◽  
Santiago Sánchez-Gómez ◽  
Marco De-Rossi-Estrada ◽  
Rafael García-Bartual
Keyword(s):  
Free Surface ◽  
Energy Dissipation ◽  
Velocity Distribution ◽  
Physical Model ◽  
Hydraulic Jump ◽  
Surface Profile ◽  
Air Entrainment ◽  
Stilling Basin ◽  
Free Surface Profile ◽  
Stilling Basins

The study of the hydraulic jump developed in stilling basins is complex to a high degree due to the intense velocity and pressure fluctuations and the significant air entrainment. It is this complexity, bound to the practical interest in stilling basins for energy dissipation purposes, which brings the importance of physical modeling into the spotlight. However, despite the importance of stilling basins in engineering, bibliographic studies have traditionally focused on the classical hydraulic jump. Therefore, the objective of this research was to study the characteristics of the hydraulic jump in a typified USBR II stilling basin, through a physical model. The free surface profile and the velocity distribution of the hydraulic jump developed within this structure were analyzed in the model. To this end, an experimental campaign was carried out, assessing the performance of both, innovative techniques such as the time-of-flight camera and traditional instrumentation like the Pitot tube. The results showed a satisfactory representation of the free surface profile and the velocity distribution, despite some discussed limitations. Furthermore, the instrumentation employed revealed the important influence of the energy dissipation devices on the flow properties. In particular, relevant differences were found for the hydraulic jump shape and the maximum velocity positions within the measured vertical profiles, when compared to classical hydraulic jumps.

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.

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