Estimation of Energy Dissipation of Flow Over Stepped Spillways | Chapter 8 | Engineering Research: Perspectives on Recent Advances Vol. 2

Stepped spillways have been used since ancient times, about 3500 years ago. In a stepped spillway, the spillway face is provided with a series of steps from near the crest to the toe. This type of spillway is attractive for water resource management because it dissipates energy that is within the flow. When energy is dissipated by the steps, it reduces the energy reduction that otherwise must occur at the toe of the spillway. Air entrainment inflates the water flow over stepped spillways; the bulking of water due to high air entrainment forces designers to use a greater height for sidewalls in stepped spillways and for the downstream stilling basins. The purpose of this research is to investigate the energy dissipation rate in spillways with different slopes. In the present study, nine physical stepped spillway models with slopes of 15, 25, and 45 degrees and with a number of steps varying from 5 to 50 have been constructed. The crest of the spillways has standard Ogee profiles and a constant slope extends from the crest to the spillway toe. Two different-sized flumes were used in the experiments (25 and 50 cm wide). Several physical models have been constructed in order to measure the energy dissipation. The result revealed that the two most important dimensionless factors influencing energy dissipation are the Froude number and q²/(gH_dam³). Here q is the discharge per unit width of the spillway (m³/s/m), H_dam is equal to the height of the spillway and g is the acceleration of the Earth's gravity equal to 9.81 m/s2. The results showed that slope alone is not an effective factor for energy dissipation and should be used in combination with other factors. The spillway slope and step number have less impact on the rate of energy dissipation. But for a constant discharge over a stepped spillway, increasing the spillway slope, and increasing the number of steps will increase the energy dissipation. Using multiple regressions, some useful relations for determination energy dissipating are obtained.

 

Author (s) Details

 

Farzin Salmasi
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.

 

John Abraham
University of St. Thomas, Minnesota, School of Engineering 2115 Summit Avenue St. Paul, Minnesota 55105, USA.

 

Please see the book here:- https://doi.org/10.9734/bpi/erpra/v2/3975

New Perspectives on the Design of Stilling Basins | Chapter 5 | Theory and Applications of Engineering Research Vol. 6

In the design of hydraulic structures, the water velocity should be maintained at acceptable levels. The high velocity of water in an earthen channel or a natural river causes erosion of the channel bed and walls, which may cause irreparable damage to the facilities adjacent to the river. Also, in many cases, factors such as the steep slope of the channel floor, the large energy difference between two sections, the free fall of water, or the kinetic energy of the water flow is more than expected. This inevitably requires designing structures to reduce the kinetic energy. Such hydraulic facilities are called energy dissipation structures. Different types of energy dissipaters are available, the most common of which are stilling basins. With stilling basins, the flow energy is depleted by the hydraulic jump and the creation of strong turbulence in the stilling basin. For a better understanding of the energy available in the water velocity at the toe of the spillway, we can refer to the Grand Coulee dam. This dam was built on the Columbia River in America. The designed discharge of the dam spillway is 28,320 m3/s and the upstream and downstream water levels for this discharge are 393.8 and 308.23 m, respectively. If it is assumed that the energy loss on the spillway is insignificant, the energy of the water downstream of the spillway is equal to 23 GW according to the relation E=pgQH, where H is the difference in water level between the upstream and downstream sections. If the energy is not restrained properly, even the best conditioned downstream stone protection will undergo severe erosion. The design and construction of stilling basins downstream of dam spillways are one of the most common methods of water energy control and is the subject of this study.

Author(s) Details:

Farzin Salmasi,
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz- Iran.

John Abraham,
University of St. Thomas, Minnesota, School of Engineering 2115 Summit Avenue St. Paul, Minnesota 55105, USA.

Please see the link here: https://stm.bookpi.org/TAER-V6/article/view/13373

Exploring Two-Phase Flow Dynamics: Experimental Investigations and Computational Modeling in Smooth and Stepped Chutes | Chapter 6 | Theory and Applications of Engineering Research Vol. 2

 Cavitation damage to hardened structures is coarse in dam spillways. Cavitation can lead to cracks on the actual surface which further increases the risk of damage to hardened by means of sulfate attack, freeze-unfreeze, alkali-silica response, and others. Cavitation damage happens on concrete surfaces when discontinuities or irregularities are met in the path of speedy water flow. Stepped spillways are acceptable, economic alternatives for high-volume depository dams that require meaningful energy amusement, for structural reworking to roller-compressed concrete dams, and to advance spontaneous flow aeration. In this place study, numerical analysis of the hydraulic traits for the skimming flow government of over the stepped chute of the Zirdan Dam is carried out. A corresponding between the flow traits for stepped and smooth spillways is given. By preparing numerical models utilizing the k-ε RNG turbulence model and the multiphase combination method, a hydraulic reasoning of the flow was completed. To validate the performance of the mathematical model, field data was composed and used for confirmation. The results show that the presence of steps along the chute cause a significant decline in the length of the perimeter layer and faster aeration happens. In a stepped chute, the cavitation index is higher than the fault-finding limit along the whole length of the spillway. So, the risk of cavitation and destruction is insignificant. On the other hand, accompanying a smooth spillway, the likelihood of cavitation may happen. This negative effect (negative pressures) occurs 56 m from the ridge of the spillway on the coming after side. For the design discharge, the difference in energy wantonness for the stepped and smooth chute is 47%.

Author(s) Details:

Farzin Salmasi,
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.

John Abraham,
School of Engineering, University of St. Thomas, Minnesota, USA.

Please see the link here: https://stm.bookpi.org/TAER-V2/article/view/12949

Two New Equations for Energy Dissipation down a Stepped Spillway with Channel Slopes between 3.4∘ and 26.6∘ | Chapter 2 | Techniques and Innovation in Engineering Research Vol. 8

 A skipped spillway is a hydraulic building provided at storage and confinement dams to release flood water that cannot be retained harmlessly in reservoirs. Its purpose is to increase the strength dissipation that would have caused hazardous scour in the everyday channel below the hydraulic makeup. Several studies in the literature highlight the hurtful effects of the moving power of water falling on the type water channel. However, only a few of these studies considered the impact of strength losses developing from stepped spillways accompanying channel slopes of 3.4∘ and 26.6∘. Additionally, the existing model for predicting strength dissipation in danced spillways features a limit, the friction factor, f, that is difficult to estimate absolutely, thereby bestowing rise to its emotional estimation by those complicated with the design of treaded spillways. The authors resolve these issues by reviewing researchers' advertisements on horizontal tiptoed spillways with dam slopes 'tween 3.4∘ ≤ � ≤ 26.6∘ conducted in transition and grazing flows in large-diameter facilities accompanying phase-detection obtrusive probes. They obtain dossier sets from them, that they reanalyzed to develop two new energy disappearance models without the limit, f (the frictional factor) that govern change and skimming flows over a off-course range of operating conditions. The dossier sets from these new models compare favourably with the calculated data sets, accompanying coefficients of correlation varying from 0.95 to 0.99. These models are simple to use and produce more accurate results than the current model.

Author(s) Details:

Okechukwu Ozueigbo,
Department of Civil Engineering, Faculty of Engineering, University of Nigeria, Nsukka, Nigeria.

J. C. Agunwamba,
Department of Civil Engineering, Faculty of Engineering, University of Nigeria, Nsukka, Nigeria.

Please see the link here: https://stm.bookpi.org/TAIER-V8/article/view/9384

Flow Characteristics of Skimming Regime Flow over Stepped Spillways with Attention to Optimum Step Size | Chapter 3 | Current Overview on Science and Technology Research Vol. 6

 With an overflow chute, the stepped design increases the energy dissipation rate of the slide itself and reduces the size of the downstream energy dissipator. Here, a study was conducted to better understand the flow behavior in a stepped chute with scraper flow. In this work, we used different experimental setups and large-scale models previously obtained from other researchers. The current results lead to a new practical design method for step overflow with scoop flow. The design methodology includes several important aspects not foreseen in previous studies. The results apply to a variety of downcomer geometries and flow conditions typical of embankment slides. A step channel hydraulic layout drawing is provided. From these figures, the optimal number of stages is determined for maximum energy dissipation, allowing the size of downstream energy dissipators to be reduced. The method provides parameters such as the optimal number of stages, typical flow depth, average velocity at the edge of the stepped channel, sidewall height, and distillation tank type to maximize energy dissipation. Easy to implement for designers who want to

Author(s) Details:

Farzin Salmasi,
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.

John Abraham,
School of Engineering, 2115 Summit Avenue St. Paul, University of St. Thomas, Minnesota - 55105, USA.

Please see the link here: https://stm.bookpi.org/COSTR-V6/article/view/8413

Energy Loss at the Base of a Free Straight Drop Spillway | Chapter 2 | Current Overview on Science and Technology Research Vol. 6

 Vertical drop or free overflow is a common feature of both natural and man-made canals. Natural drips are formed by bed erosion, while artificial drips are incorporated into irrigation systems to reduce canal slopes to design slopes. A gradual overflow results in greater energy loss. Greater energy dissipation is caused by the jet mixing with the pool at the downstream end of each droplet. As a result, this accounts for the reduced energy dissipation commonly present in drop chips and gradual overflows. In this work, we investigate the energy dissipation of linear droplets through the creation of a physical model. Effective geometric and hydraulic parameters were determined and three drops of different heights were made from plexiglass. These physics models were installed in his two existing channels at the Hydropower Laboratory at Tabriz University, Iran. Several runs of the physical model were performed to determine the key parameters for determining energy dissipation. The results show that droplet energy dissipation is affected by droplet height and ejection. The predicted relative energy dissipation varied from 10.0% (for yc/h = 0.94) to 94.3% (for yc/h = 0.02). Energy loss due to falling is primarily due to mixing of the jet with the pool behind the jet, which entraps air bubbles in the flow. A statistical model was developed to predict the energy dissipation of droplets that exhibits nonlinear correlations between effective parameters. Comparing this work with the results of his Moore, Rand, White, Rajaratnam and Chamani, White's model overestimates the droplet energy dissipation and Rand's model underestimates the droplet energy dissipation. I understand. Others can predict energy dissipation similarly to the proposed statistical model. The length of the downstream calm basin predicted by White is 20% shorter than the others.

Author(s) Details:

Farzin Salmasi,
Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.

John Abraham,
University of St. Thomas, Minnesota, School of Engineering 2115 Summit Avenue St. Paul, Minnesota 55105, USA.

Please see the link here: https://stm.bookpi.org/COSTR-V6/article/view/8412

Hydraulic Characteristics of Fish-passes on Inclined Drops with Multifarious Configurations: An Experimental Study| Chapter 7 | Research Developments in Science and Technology Vol.4

With environmental and economic concerns, this study shows how to enhance the energy dissipation of flow along an inclined drop. The goal of this research is to develop a novel way for evaluating aquatic health on inclined drops, as well as a mechanism for dissipating surplus flow energy utilising fish-pass components. Three varieties of basic inclined drops and inclined drops without fish-pass features were used in 81 distinct studies with a flow rate of 200-600 lit/min. The researchers discovered that when the relative critical depth grows, the energy dissipation values increase and the downstream Froude number decreases. The metrics of relative downstream depth, relative duration of the hydraulic jump, and relative aeration length all climb when the relative critical depth rises. Model F7 dissipates the most energy, whereas Model F2 has the longest flow aeration duration and relative downstream depth. The employment of fish-pass components decreases the downstream Froude number greatly, in addition to boosting aeration and dispersing the destructive force of the flow. As a result, these components may be useful for scouring the bed and channel walls, as well as strengthening the stability of downstream structures. Non-hole fish-pass components were also shown to be useful for enhancing energy dissipation, but hole elements are more efficient for designs with environmental goals.

Author(s) Details:

Rasoul Daneshfaraz,
Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, East Azerbaijan, Iran.

Ehsan Aminvash,
Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, East Azerbaijan, Iran.

John Abraham,
School of Engineering, University of St. Thomas, St Paul, MN, USA.

Please see the link here: https://stm.bookpi.org/RDST-V4/article/view/6855