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Hubert Chanson - One of the best experts on this subject based on the ideXlab platform.
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discussion of cavitation potential of flow on stepped Spillways by k warren frizell floriana m renna and jorge matos
Journal of Hydraulic Engineering, 2015Co-Authors: Hubert ChansonAbstract:The authors presented a very interesting contribution to the topic of stepped spillway hydrodynamics. Based on a water-tunnel study, they presented some detailed flow features, for example, in terms of the strain rate, which are valuable to designers. The authors stated that “stepped Spillways have no documented damage.” It is partially correct. Indeed no cavitation damage and sign of cavitation pitting were reported on stepped Spillways after more than 3,000 years of operation, but there were documented damages and failures of stepped spillway systems (Marsh 1957; Jansen 1983; Pravdivets 1993; Chanson 1995b, 2000, 2001a). In this discussion, a number of prototype stepped spillway tests are reviewed and the operational experiences are discussed with a focus on the stepped chute performances. Several prototype stepped spillway tests were conducted in China, Russia, Germany, the United Kingdom, and Africa. Some extensive tests were performed on the Dachaoshan rollercompacted concrete (RCC) Dam spillway in 2002 with discharge per unit width up to 72 m=s (Lin and Han 2001; K. Lin, personal communication, 2002, 2012). Detailed inspections after each series of test indicated no damage or any sign of pitting. A series of tests conducted at the Dnieper hydroplant were performed with discharges per unit width up to 59.4 m=s, velocities up to 23 m=s, a step height of 0.405 m, and water depths between 0.5 and 3 m (Grinchuk et al. 1977). No damage was reported. Full-scale tests were undertaken in the Sorpe Dam spillway in 2002–2003 to investigate some jump-wave instabilities (P. Kamrath, personal communication, 2003). Some field tests were conducted successfully on the Brushes Clough Dam spillway in the United Kingdom up to 1 m=s, although for a short duration (Baker 1994). Some inspection of the M’Bali RCC Dam stepped spillway after a wet season operation showed no sign of damage and pitting (Bindo et al. 1993). Further, a number of prototype overflow events were documented worldwide (Chanson 1995b, 2001b). In China, the
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effects of step pool porosity upon flow aeration and energy dissipation on pooled stepped Spillways
Journal of Hydraulic Engineering, 2014Co-Authors: Stefan Felder, Hubert ChansonAbstract:AbstractThe hydraulics of stepped Spillways with flat steps has been studied for the last three decades, including for embankment dam slopes, but studies of alternative stepped designs are limited. In this study, a pooled stepped spillway was investigated in a relatively large-size facility, and three different pool wall porosities were tested. The flow patterns, the macro- and microscopic air-water flow properties, and the energy dissipation performances were recorded; the results were compared with the flat stepped spillway design for the same chute slope (θ=26.6°). The investigations highlighted a close agreement between air-water flow properties on the configurations in terms of void fraction, turbulence levels, bubble count rate, and chord sizes. The interfacial velocity distributions showed larger interfacial velocity on the pooled step configurations of approximately 5–10% linked with a reduced flow depth. On the porous pooled stepped Spillways, the interfacial velocities within the cavity highligh...
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aeration flow instabilities and residual energy on pooled stepped Spillways of embankment dams
Journal of Irrigation and Drainage Engineering-asce, 2013Co-Authors: Stefan Felder, Hubert ChansonAbstract:AbstractAir-water flow experiments were conducted on some flat and pooled stepped Spillways with slopes of 8.9° and 26.6° in transition and skimming flows. The study comprised the observations of the flow patterns, characteristic air-water flow properties, and energy dissipation performances. The air-water flow properties showed some differences in terms of interfacial velocity, bubble count rate, and turbulence intensity between the stepped chutes for the two channel slopes. These differences were also reflected in the residual energy data, highlighting a better energy dissipation rate for the pooled stepped spillway with slope of 8.9°. However, the aerated flows on the pooled stepped Spillways exhibited some hydrodynamic instabilities, and a safe operation must be tested in physical models. The flat stepped spillway appeared to be the preferable design in terms of energy dissipation and flow stability.
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Flow patterns in nappe flow regime down low-gradient stepped chutes. Reply by the authors
Journal of Hydraulic Research, 2009Co-Authors: Luke Toombes, Hubert ChansonAbstract:To date, most studies on stepped Spillways were conducted with flat horizontal steps in prismatic rectangular channels. The contribution provides some insight into the hydraulics of stepped Spillways with pooled steps. Indeed the ddition of end sills or end walls at the downstream step end modifies substantially the flow pattern. Altogether, this is a timely reminder of our limited expertise in stepped spillway hydrodynamics, especially for non-conventional designs like the pooled steps.
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Hydraulics of stepped Spillways : current status
Journal of Hydraulic Engineering, 2000Co-Authors: Hubert ChansonAbstract:H. CHANSON Department of Civil Engineering, The University of Queensland, Brisbane QLD 4072, Australia Email : h.chanson@mailbox.uq.edu.au Stepped-channel Spillways, staircase waste waterways, stepped Spillways, or stepped chutes have been used for more than 3,000 years (Fig. 1). In recent years they are experiencing renewed attention. The present forum article discusses briefly the current status of stepped Spillways, and it draws attention to a recent workshop on the subject. A significant number of dams were built with overflow stepped Spillways during the 19th century and early 20th century, before such Spillways became outdated by progresses in hydraulic jump stilling basins (Fig. 2). Recent advances in technology (e.g. RCC, polymer-coated gabion wire) have however triggered a regain of interest for stepped Spillways. Unfortunately, though, much expertise had been lost in the past 60 years. Research on stepped spillway hydraulics has been active for the past ten years (Fig. 3). During the period 1985-2000, the international database Science Citation Index (The Web of Science) lists fourteen papers and twenty-one discussions and closures on stepped spillway, or stepped chute, hydraulics, all but two were published between 1990 and 2000. A 1985 paper (
Kem C Kadavy - One of the best experts on this subject based on the ideXlab platform.
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Inception Point for Embankment Dam Stepped Spillways
Journal of Hydraulic Engineering, 2013Co-Authors: Sherry L Hunt, Kem C KadavyAbstract:AbstractRetrofitting embankment dams with stepped Spillways has become a common design practice, particularly for those dams that change hazard classification from low to high. For embankment dams retrofitted with stepped Spillways, the chute length is often insufficient for developing aerated flow or an inception point. The inception point is a key spillway design parameter used in energy dissipation, flow depth, and air entrainment prediction relationships. Original research for developing an inception-point relationship for stepped Spillways was based on primarily gravity (θ≥26.6°) stepped Spillways, with the majority having an ogee crest control section. The resulting, inception-point relationship tends to overestimate the inception-point location for broad-crested weir stepped Spillways (θ≤26.6°) when the Froude surface roughness (F*) is less than 10. Consequently, research on broad-crested weir stepped Spillways retrofitted for embankment dams has been conducted to provide an optimized inception-poi...
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converging stepped Spillways simplified momentum analysis approach
Journal of Hydraulic Engineering, 2012Co-Authors: Sherry L Hunt, Kem C Kadavy, Darrel M Temple, Steven R Abt, Greg J HansonAbstract:AbstractRoller compacted concrete (RCC) stepped Spillways are growing in popularity for providing overtopping protection for aging watershed dams with inadequate auxiliary spillway capacity and for the construction of new dams. Site conditions, such as limited right-of-way, topography, and geological formations, often dictate that these Spillways converge. Convergence increases the flow depth near the training walls and alters the stilling basin design requirements as compared with traditional straight Spillways. A simplified control volume momentum analysis is presented for predicting the minimum vertical training wall height necessary to prevent wall overtopping in converging stepped Spillways. An expression is developed to predict vertical training wall height as a function of centerline flow depth, centerline velocity, chute slope, and convergence angle. A three-dimensional 3(H):1(V) sloping stepped spillway model with an ogee crest and convergence ranging from 0–70° was constructed to verify this rel...
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energy dissipation on flat sloped stepped Spillways part 1 upstream of the inception point
Transactions of the ASABE, 2010Co-Authors: Sherry L Hunt, Kem C KadavyAbstract:In recent years, hazard classifications for many existing embankment dams have changed because hydrologic conditions have been altered. Consequently, many of these dams no longer provide adequate spillway capacity according to state and federal dam safety regulations. Stepped Spillways are a popular choice for providing increased spillway capacities to existing embankment dams. Stepped Spillways in these applications are typically placed over the existing embankment or auxiliary spillway; thereby, the chute slope is the same as the downstream embankment face or auxiliary spillway slope. Design guidelines and literature in general for these stepped Spillways are very limited, so further research on these stepped Spillways is warranted. A two-dimensional, physical model was constructed to evaluate the inception point, velocities, and energy dissipation in a 4(H):1(V) spillway chute having 38 mm (1.5 in.) high steps. Model unit discharges ranging from 0.11 m3 s-1 m-1 (1.2 cfs ft-1) to 0.82 m3 s-1 m-1 (8.8 cfs ft-1) were tested. Water surfaces, bed surfaces, and velocities were collected during the tests. An inception point relationship provided by H. Chanson may be used to determine the inception point for slopes as flat as 4(H):1(V) when F* ranges between 10 and 100. The velocity profiles transition from uniform at the crest to approaching a one-sixth power law distribution at the inception point for all tested flows. Energy losses increase in a linear fashion from near zero at the crest to approximately 30% near the inception point for all tested flows. This research will assist engineers with the design of stepped Spillways applied on relatively flat embankment dams.
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inception point relationship for flat sloped stepped Spillways
2009 Reno Nevada June 21 - June 24 2009, 2009Co-Authors: Sherry L Hunt, Kem C KadavyAbstract:Many small earthen embankments are faced with hazard classification changes due to urban encroachment. As a result, some embankments have inadequate spillway capacity. To bring the dam into compliance with state and federal dam safety laws, rehabilitation of the dam is often required. RCC stepped Spillways are becoming a popular choice for addressing these issues. However, design guidelines for RCC stepped Spillways applied to small earthen dams are scarce, especially for Spillways with slopes flatter than 2(H):1(V).
M. El-fooly - One of the best experts on this subject based on the ideXlab platform.
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Improving energy dissipation on stepped Spillways using breakers
Ain Shams Engineering Journal, 2018Co-Authors: Gamal M. Abdel Aal, M. Sobeah, Esam Helal, M. El-foolyAbstract:Abstract Stepped Spillways have many applications in dam structures, and river engineering. Moreover, stilling basins can be constructed with lower costs as energy dissipation by adding appurtenances to these stilling basins. This study aims to investigate the over-flow, through-flow, and under-flow breakers in stepped Spillways and to evaluate their effect on energy dissipation. For this purpose, physical models of four steps were carried out on stepped Spillways. Breakers were installed over the steps of spillway; the energy dissipation can be increased by different quantities, according to the characteristics of the breakers (height, width, arrangement of breaker heights and perforated holes). So studying the effect of the breaker on stepped spillway on the energy dissipation is very important issue. The dimensional analysis was used to correlate the different parameters affecting the studied phenomena. Comparison of flow energy dissipation over the toe of stepped spillway with breakers and classical stepped spillway shows that the stepped spillway with breakers type had dissipated more energy than the classical stepped spillway type.
Sherry L Hunt - One of the best experts on this subject based on the ideXlab platform.
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Inception Point for Embankment Dam Stepped Spillways
Journal of Hydraulic Engineering, 2013Co-Authors: Sherry L Hunt, Kem C KadavyAbstract:AbstractRetrofitting embankment dams with stepped Spillways has become a common design practice, particularly for those dams that change hazard classification from low to high. For embankment dams retrofitted with stepped Spillways, the chute length is often insufficient for developing aerated flow or an inception point. The inception point is a key spillway design parameter used in energy dissipation, flow depth, and air entrainment prediction relationships. Original research for developing an inception-point relationship for stepped Spillways was based on primarily gravity (θ≥26.6°) stepped Spillways, with the majority having an ogee crest control section. The resulting, inception-point relationship tends to overestimate the inception-point location for broad-crested weir stepped Spillways (θ≤26.6°) when the Froude surface roughness (F*) is less than 10. Consequently, research on broad-crested weir stepped Spillways retrofitted for embankment dams has been conducted to provide an optimized inception-poi...
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converging stepped Spillways simplified momentum analysis approach
Journal of Hydraulic Engineering, 2012Co-Authors: Sherry L Hunt, Kem C Kadavy, Darrel M Temple, Steven R Abt, Greg J HansonAbstract:AbstractRoller compacted concrete (RCC) stepped Spillways are growing in popularity for providing overtopping protection for aging watershed dams with inadequate auxiliary spillway capacity and for the construction of new dams. Site conditions, such as limited right-of-way, topography, and geological formations, often dictate that these Spillways converge. Convergence increases the flow depth near the training walls and alters the stilling basin design requirements as compared with traditional straight Spillways. A simplified control volume momentum analysis is presented for predicting the minimum vertical training wall height necessary to prevent wall overtopping in converging stepped Spillways. An expression is developed to predict vertical training wall height as a function of centerline flow depth, centerline velocity, chute slope, and convergence angle. A three-dimensional 3(H):1(V) sloping stepped spillway model with an ogee crest and convergence ranging from 0–70° was constructed to verify this rel...
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energy dissipation on flat sloped stepped Spillways part 1 upstream of the inception point
Transactions of the ASABE, 2010Co-Authors: Sherry L Hunt, Kem C KadavyAbstract:In recent years, hazard classifications for many existing embankment dams have changed because hydrologic conditions have been altered. Consequently, many of these dams no longer provide adequate spillway capacity according to state and federal dam safety regulations. Stepped Spillways are a popular choice for providing increased spillway capacities to existing embankment dams. Stepped Spillways in these applications are typically placed over the existing embankment or auxiliary spillway; thereby, the chute slope is the same as the downstream embankment face or auxiliary spillway slope. Design guidelines and literature in general for these stepped Spillways are very limited, so further research on these stepped Spillways is warranted. A two-dimensional, physical model was constructed to evaluate the inception point, velocities, and energy dissipation in a 4(H):1(V) spillway chute having 38 mm (1.5 in.) high steps. Model unit discharges ranging from 0.11 m3 s-1 m-1 (1.2 cfs ft-1) to 0.82 m3 s-1 m-1 (8.8 cfs ft-1) were tested. Water surfaces, bed surfaces, and velocities were collected during the tests. An inception point relationship provided by H. Chanson may be used to determine the inception point for slopes as flat as 4(H):1(V) when F* ranges between 10 and 100. The velocity profiles transition from uniform at the crest to approaching a one-sixth power law distribution at the inception point for all tested flows. Energy losses increase in a linear fashion from near zero at the crest to approximately 30% near the inception point for all tested flows. This research will assist engineers with the design of stepped Spillways applied on relatively flat embankment dams.
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inception point relationship for flat sloped stepped Spillways
2009 Reno Nevada June 21 - June 24 2009, 2009Co-Authors: Sherry L Hunt, Kem C KadavyAbstract:Many small earthen embankments are faced with hazard classification changes due to urban encroachment. As a result, some embankments have inadequate spillway capacity. To bring the dam into compliance with state and federal dam safety laws, rehabilitation of the dam is often required. RCC stepped Spillways are becoming a popular choice for addressing these issues. However, design guidelines for RCC stepped Spillways applied to small earthen dams are scarce, especially for Spillways with slopes flatter than 2(H):1(V).
B. Sakaa - One of the best experts on this subject based on the ideXlab platform.
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THE NON-RECTILINEAR SPILLWAY DUG SYMMETRICALLY AND THE RECTILINEAR SPILLWAY (EXPERIMENTAL STUDY)
Journal of Fundamental and Applied Sciences, 2018Co-Authors: A. Noui, B. SakaaAbstract:It is clear that the role of spillway is ensured the safety of dams. It is characterized by its different geometric configurations such as rectilinear spillway and non-rectilinear spillway. The present work was interested in the experimental comparison between the non-rectilinear Spillways dug symmetrically (by different depths of hollowing of the alveoli) and the rectilinear Spillways in thin wall of the same width, in order to compare the evacuation performance between them. This study showed that the performance of non-rectilinear Spillways symmetrically excavated, is greater than the discharge capacity of rectilinear Spillways in thin wall in all phases of hydraulic loads.
